Progress and Future Challenges in Designing High-Performance Ni/CeO2 Catalysts for CO2 Methanation: A Critical Review

Carbon Neutralization REVIEW Progress and Future Challenges in Designing High‐ Performance Ni/CeO 2 Catalysts for CO 2 Methanation: A Critical Review Kun Liu 1 | Muhammad Asif Nawaz 2 | Guangfu Liao 3 1 School of Resources and Environment, Nanchang University, Nanchang, Jiangxi, China | 2 Department of Inorganic Chemistry and Material Sciences Institute of Seville (ICMSE), University of Seville‐CSIC, Seville, Spain | 3 College of Materials Engineering, Fujian Agriculture and Forestry University, Fuzhou, China Correspondence: Kun Liu ([email protected]) | Guangfu Liao ([email protected]) Received: 11 November 2024 | Revised: 30 November 2024 | Accepted: 15 December 2024 Funding: The authors are grateful for financial support from the National Natural Science Foundation of China (grant no. 52203110) and the Natural Science Foundation of Fujian (grant no. 2024J01403). Keywords: CO 2 methanation | high activity and stability | low‐temperature activity | Ni/CeO 2 catalyst ABSTRACT The Ni/CeO 2 catalyst stands out among various solid metal oxide catalysts for its exceptional catalytic proficiency, positioning it as a prime candidate for the industrialization of methanation processes. This review thoroughly examines the prevalent challenges associated with Ni/CeO 2 in methanation reactions, compiles current strategies to overcome these hurdles, and presents novel perspectives. The review elucidates the structural characteristics of Ni/CeO 2 and its applications in catalytic reactions, discusses various synthesis methods and their respective merits and demerits, explores catalytic reaction systems at both laboratory and industrial scales, and clarifies the underlying reaction mechanisms. Furthermore, it underscores the mainstream approaches to enhance the low‐temperature activity of Ni/CeO 2 in methanation and to mitigate activity decrement due to Ni agglomeration. The review concludes by proposing future directions for improving low‐temperature methanation activity and preventing catalyst deactivation, encompassing the development of innovative catalyst architectures, integrating in‐ situ characterization with theoretical calculations, and investigating photothermal methanation catalytic systems. Undoubtedly, scientific researchers will persistently strive to develop Ni/CeO 2 catalysts with high activity across a broad temperature range and robust stability, driving the industrialization of CO 2 methanation technology in the foreseeable future. 1 | Introduction Since the Industrial Revolution, fossil fuel depletion has driven up CO 2 emissions. By 2024, levels surpassed 421 ppm, a 50% jump from preindustrial times [1–8]. CO 2 , a potent greenhouse gas, heavily influences the global environment [8–22]. As a recyclable C 1 resource, it is also crucial for converting into high‐value chemicals [13, 23, 24]. Using CO 2 from industrial waste and H 2 from renewables, products like methane (CH 4 ) and methanol (CH 3 OH) can be made. CH 4 and CH 3 OH are preferred targets, but converting CO 2 to methanol is inefficient (18.87% at 300°C, 5.0 MPa), needing multiple cycles and energy‐intensive processes. In contrast, CH 4 yield from CO 2 hydrogenation under mild conditions (250°C, 0.1 MPa) can exceed 80% [25]. CO 2 methanation offers: (i) Safe, eco‐friendly methane transport via gas pipelines; (ii) Clean fuel and key industrial raw material; (iii) Crucial for enclosed systems like submarines, providing fuel & water for defense & aerospace [26]. Thus, CO 2 methanation is a potential and feasible reaction for CO 2 utilization and a core reaction in the “Power‐to‐Gas This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2025 The Author(s). Carbon Neutralization published by Wenzhou University and John Wiley & Sons Australia, Ltd. 1of35Carbon Neutralization, 2025; 4:e190 https://doi.org/10.1002/cnl2.190 (P2G)”carbon neutrality cycle (Figure 1). Developing highly active catalysts for this process is crucial for advancing the P2G cycle, making in‐depth study of CO 2 methanation significant in energy and environmental fields [27]. The reaction of CO 2 catalytic hydrogenation to form methane was discovered by Paul Sabatier and Jean–Baptiste Senderens in 1902 [28]. The methanation of CO 2 is a volume‐decreasing and exothermic reaction (ΔG 298 K =–164 kJ/mol), with the reaction equation given as follows: →G C O + 4H CH + 2H O, Δ=−164kJ/mol . 2 2 4 2 298K From a thermodynamic perspective, conditions of low temperature and high pressure, H 2 /CO 2 = 4 are favorable for the progression of this reaction. The conversion of CO 2 into CH 4 through complete reduction requires the acquisition of eight electrons, a process that poses significant kinetic limitations. Therefore, highly active catalysts are essential to achieve rapid reaction rates and high CH 4 selectivity at low temperatures [29]. Vannice et al. [30] reported the activity order for metal catalysts in CO 2 methanation: Ru > Ni > Co > Rh > Pd > Pt > Ir. Catalyst support also matters, with CeO 2 ≈Y 2 O 3 >Al 2 O 3 > MgO. Notably, Ni/CeO 2 stands out with exceptional performance. In comparison with Ni/Al 2 O 3 ,Ni/MgO,Ni/TiO 2 ,andRu/CeO 2 ,theNi/CeO 2 catalyst exhibits remarkable cost‐effectiveness, low CO 2 activation energy, and high selectivity [31–41]. The non‐noble metal nature of Ni and the low cost of CeO 2 collectively reduce the preparation cost of Ni/CeO 2 . Meanwhile, the redox properties and oxygen storage capacity of CeO 2 , combined with the catalytic activity of Ni, effectively enhance the adsorption and activation efficiency of CO 2 [32–52]. Furthermore, Ni/CeO 2 demonstrates excellent selectivity under harsh conditions, efficiently converting CO 2 while minimizing byproduct formation. Therefore, Ni/CeO 2 presents broad application prospects in CO 2 ‐related reactions [32–52]. While previous methanation reviews concentrate on catalyst synthesis, mechanisms, and adjustments [53–65], thermodynamic hurdles are frequently overlooked. Addressing these is vital for industrial applications. Developing Ni/CeO 2 catalysts with remarkable low‐temperature activity is a key strategy. To obtain CO 2 methanation catalysts with excellent activity, stability, and selectivity, numerous chemical and engineering researchers have dedicated their efforts to improving catalysts through various strategies, including regulating the interface effects between active metals and oxide supports, optimizing preparation methods, adjusting metal loadings, controlling metal grain sizes, adding promoters, and forming metal alloys [28, 66]. Currently, extensive research has been conducted on Ni/CeO 2 catalysts due to their cost‐ effectiveness and superior activity [38, 39]. CeO 2 stands out due to its oxygen vacancies (OVs) and oxygen storage capacity, distinguishing it from other metal oxides, showing significantly enhanced CO 2 activation. From 1998 to 2022, conducting a search on the Web of Science database with the keywords “ceriaRef,”“methane,”“conversion of CO 2 to methane,”and “oxygen deficiency”resulted in the identification of 309 research papers. By analyzing these with the VOs viewer, we created a network visualization map with 231 items (Figure 2)[59]. In recent years, notable advancements have been made in the research of this catalyst, yet challenges still remain (Figure 3), these hurdles impede the widespread commercial adoption of CO 2 methanation [59, 67]. Numerous researchers are actively engaged in the development of CO 2 methanation catalysts, and technological advancements are continuously being made. However, this reaction has not yet entered the industrialization stage. As the catalyst with the greatest potential for industrialization, Ni‐based catalysts currently face two major challenges: poor low‐temperature activity and deactivation due to sintering and carbon deposition during long‐term operation [50, 68, 69]. Adopting reasonable measures to reduce the reaction temperature is crucial for this reaction. On the one hand, high temperatures are detrimental to the methanation reaction, leading to decreased conversion rates and selectivity, while the generation of numerous byproducts complicates product separation and increases production costs. On the other hand, high‐ temperature operating environments can easily cause catalyst sintering and carbon deposition, resulting in rapid deactivation. Therefore, the focus is on developing low‐temperature, high‐ efficiency catalysts for CO 2 methanation. FIGURE 1 | A conceptual schematic of the Power‐to‐Gas (P2G) process and the pathway for achieving a carbon‐neutral cycle. Reproduced with permission: Copyright 2023, Elsevier [27]. 2of35 Carbon Neutralization, 2025 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License This comprehensive review delves deeply into the latest advancements in Ni‐based catalysts for CO 2 methanation, with a particular emphasis on the performance factors of Ni/CeO 2 catalysts. It exhaustively examines the structural properties and diverse applications of Ni/CeO 2 in catalytic reactions. The review offers an in‐depth analysis of numerous synthesis methods, detailing their respective strengths and weaknesses. Furthermore, it discusses both experimental and industrial catalytic reaction systems, and presents an in‐depth exploration of the mechanisms underlying these catalytic reactions. The focus also encompasses mainstream strategies aimed at enhancing low‐temperature activity in methanation reactions, as well as countermeasures to address catalyst deactivation caused by Ni agglomeration. In addition, the review provides valuable insights into future research directions, such as the development of novel catalysts through the integration of in‐ situ characterization and theoretical calculations, and the exploration of photothermal methanation systems to prevent catalyst deactivation. These insights offer fresh perspectives and guidance for the research and application of Ni/CeO 2 catalysts, encouraging researchers to design catalysts that exhibit superior efficiency and stability at low temperatures. Ultimately, this will help to accelerate the industrialization of CO 2 methanation. 2 | Properties, Application, and Synthesis of Ni/CeO 2 Catalysts 2.1 | Structure of CeO 2 Ceria, or cerium oxide (CeO 2 ), stands as a versatile functional material with extensive applications across various domains, including catalysis [70], oxygen sensing [71], fuel cells [72], electronics [73], magnetic materials [74], glass polishing [75], and biotechnology/biomedicine [76]. Its benefits include a high abundance, cost‐efficiency, minimal toxicity, and strong chemical and structural stability, along with distinctive characteristics like oxygen vacancy defects, substantial oxygen storage capabilities, ion conductivity, and reversible oxidation state transitions between trivalent and tetravalent states. With over 28,000 publications since the first paper on “ceria”in the 1950s, CeO 2 ‐based materials have become pivotal in industrial processes like automotive emissions control [77], the elimination of three‐way automotive toxic exhaust gases [78], the water gas shift reaction [79], and numerous organic reactions [80]. FIGURE 2 | A network visualization map depicting the connections among 231 research items on CeO 2 ‐based catalysts, based on comprehensive publication records spanning from 1998 to 2022. Reproduced with permission: Copyright 2023, Elsevier [59]. FIGURE 3 | The process of CO 2 methanation encounters a range of critical and additional challenges that must be tackled for its successful implementation and widespread commercial adoption. Reproduced with permission: Copyright 2023, Elsevier [59]. 3of35 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License Consequently, CeO 2 continues to attract significant academic and industrial interest. CeO 2 displays a fluorite configuration characterized by a face‐centered cubic (f.c.c.) lattice unit within the Fm‐3m space group arrangement (a= 0.541134 nm, JCPDS 34‐394), as illustrated in Figure 4a. Typically, nonstoichiometric CeO 2−x (0 ≤x≤0.5) forms due to the release of oxygen and the conversion of Ce(IV) to Ce(III), oxygen vacancies emerge within the crystal lattice concurrently. Each cerium cation is surrounded by eight oxygen anions, and its electronic configuration of [Xe] 4f1 5d1 6s2 enables the transition of charges FIGURE 4 | (a) The crystal structure of both non‐stoichiometric (left) and stoichiometric ceria (right), alongside its distinctive physical and chemical attributes. In the left‐hand cube, two Ce 4+ ions are substituted by Ce 3+ ions (depicted as blue spheres), resulting in an oxygen vacancy (marked by a small empty sphere). Reproduced with permission: Copyright 2019, Wiley [81]. (b) The ideal lattice arrangement of CeO 2 . Reproduced with permission: Copyright 2021, American Chemical Society [82]. (c) The crystal structure of CeO 2 features one oxygen vacancy, accompanied by the formation of two Ce 3+ species. Reproduced with permission: Copyright 2021, American Chemical Society [82]. (d) Schematic approaches employed for the characterization of oxygen vacancies. Reproduced with permission: Copyright 2023, Elsevier [59]. (e) Unique attributes of CeO 2 micro/nanostructures and their importance across diverse applications. Reproduced with permission: Copyright 2019, Wiley [81]. 4of35 Carbon Neutralization, 2025 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License between the Ce 4+ and Ce 3+ states in a reversible manner (as illustrated in Figure 4b)[83, 84]. Consequently, the formation of Ce 3+ cations often aligns with the occurrence of oxygen deficiencies both on the exterior surface and within the interior bulk (Figure 4c)[84]. These oxygen vacancy defects (e.g., CeO 2−x ) enhance oxygen adsorption, activation, and self‐ diffusion within the lattice of non‐stoichiometric ceria, significantly boosting redox processes and reactions. Factors like thermal treatment temperature, oxygen partial pressure, doping elements and their concentrations, synthesis techniques, surface tension, and electric fields can regulate the creation of oxygen vacancies. The creation of an oxygen defect leads to the localization of electrons in Ce 4f states, forming two Ce 3+ ions. Notably, the ceria structure can withstand significant reduction without phase transition, especially at higher temperatures. Even with substantial doping, it maintains its highly symmetric cubic structure through the creation of defects like Ce 3+ and oxygen vacancies [85]. And these vacancies can be observed through various methods, including STM, ESR, Raman spectroscopy, X‐ray absorption spectroscopy (XAS), XRD, Mott‐ Schotty analysis, and numerous other techniques [50, 52, 59, 86–109]. By examining the diverse electrical and structural alterations illustrated in Figure 4d, it becomes possible to visualize the presence of oxygen vacancies. Previous extensive experimental and theoretical research has shown that ceria's potential in catalysis, energy conversion, and other applications stems primarily from its intrinsic oxygen‐ vacancy defects [83], which significantly influence its electronic and chemical properties [110]. Efforts have focused on increasing defect concentrations within CeO 2 structures. One approach involves preparing doped CeO 2 ‐based materials by incorporating redox‐active cations into the CeO 2 lattice to form solid solutions (M y Ce 1−y O 2−x )[111]. This increases oxygen vacancy concentrations due to structural strain caused by ionic radius differences [112] or electron loss to maintain electrostatic balance [98]. Another strategy is to design CeO 2 micro/nanostructures with specific morphologies [113], which, as particle size decreases, leads to higher densities of interfaces and grain boundaries, substantially reducing the energy required for defect formation and enhancing nonstoichiometry and electronic carrier generation [114]. Ceria nanoparticles (NPs) exhibit increased oxygen vacancy formation and Ce 4+ to Ce 3+ ion conversion near the surface, altering Ce‐O bond lengths and lattice parameters [115]. However, NPs are less stable and prone to sintering or dissolution in practical applications. Micro/nanostructured CeO 2 composed of NPs offers enhanced stability, reusability, and easier processing while retaining advantages like improved redox and transport properties and a larger surface‐to‐volume ratio derived from the basic units. CeO 2 is renowned for its exceptional catalytic properties, serving as catalysts [116], cocatalysts [117], additives [118], and supports [119]. Hollow CeO 2 structures offer notable advantages in catalysis, including expanded surface areas, increased exposure of active sites, improved electron transport, decreased mass transfer resistance, and improved shielding of the reactive species, coupled with a restricted spatial influence that aids in the distinct separation of catalytic processes, as shown in Figure 4e. Therefore, the construction of CeO 2 hollow structures represents an effective strategy for advancing catalytic performance. 2.2 | Ni/CeO 2 Catalyst CeO 2 is a basic oxide capable of adsorbing sufficient CO 2 .Dueto the oxygen vacancies present on the CeO 2 ,CO 2 can be readily reduced, allowing Ce to effortlessly switch between the +3 and +4 valence states. The Ni/CeO 2 catalyst consists of the active metal Ni and the support CeO 2 . Herein, Ni, serving as the active metal, plays a pivotal role in catalyzing the reaction. Meanwhile, CeO 2 , functioning as the support, not only offers excellent dispersion and support properties but also positively influences catalytic performance attributed to its abundant surface oxygen vacancies and high oxygen retention capacity [52]. The Ni/CeO 2 catalyst demonstrates distinct superiority in the CO 2 methanation reaction, outperforming other catalysts like Co/CeO 2 , Fe/CeO 2 , Ru/CeO 2 , and Ni‐based catalysts with different supports (Ni/Al 2 O 3 , Ni/ZrO 2 , Ni/MgO) [28, 53]. These advantages primarily stem from the close electronic interaction between Ni and CeO 2 , where Ni donates electrons to the 4 f orbital of CeO 2 , facilitating the reduction of Ce 4+ to Ce 3+ and forming favorable frustrated Lewis pair (FLP) structures [44, 59, 81, 120]. Notably, in Ni/CeO 2 nanorod catalysts, the FLP structures synergize with the steric hindrance effect of CeO 2 (110) facets and oxygen vacancies (OVs), effectively activating and converting CO 2 . Furthermore, the redox properties and abundant surface oxygen vacancies of CeO 2 provide favorable conditions for CO 2 activation and enhance the oxygen storage capacity of the catalyst, maintaining its high activity during the reaction [44, 59, 81, 120]. Consequently, the Ni/CeO 2 catalyst demonstrates high CO 2 conversion and CH 4 selectivity, particularly at low temperatures, while exhibiting excellent sintering resistance and carbon deposition resistance, ensuring long‐term stability and durability of the catalyst. Compared to noble metal catalysts, Ni/CeO 2 offers higher cost‐effectiveness, and in comparison to other Ni‐based catalysts, it exhibits superior performance in CO 2 activation, catalytic efficiency, selectivity, and durability, making Ni/CeO 2 a preferred material for CO 2 methanation reactions (Figure 5a–f)[9, 39, 49, 52]. The Ni/CeO 2 catalyst demonstrates high activity in various catalytic reactions, such as CO 2 methanation and the reverse water‐gas shift reaction. This is primarily attributed to the interaction between Ni and CeO 2 , as well as effective activation of CO 2 . During catalytic reactions, the Ni/CeO 2 catalyst can selectively catalyze the formation of target products while minimizing the generation of by‐products. For instance, in the CO 2 methanation reaction, this catalyst exhibits high selectivity toward methane production [52, 121]. In the process of CO 2 methanation, CeO 2 is commonly utilized as a support or an electronic promoter due to its merits of inhibiting coking, enhancing thermal stability, promoting metal dispersion, and altering the electronic properties of metals through strong metal–support interactions (SMSI) by transforming into CeO 2 and Ce 2 O 3 under oxidizing and reducing conditions, respectively [122]. Some research efforts have focused on combining CeO 2 with other mixed oxides to prevent the coking and sintering of Ni [123]. Zhou et al. [41] discovered that after H 2 reduction, CeO 2 can form surface oxygen vacancies, which can reduce CO 2 molecules to generate active CO species, thereby facilitating the methanation of CO 2 . Ye et al. [39] produced a nanostructured Ni/CeO 2 ‐SGM catalyst, synthesized through a 5of35 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License straightforward sol–gel method, attaining a conversion efficiency of 80.5% for CO 2 at a temperature as low as 250°C (Figure 5e,f), and the activity of this catalyst showed no declining trend during the 100‐h stability test. The superior low‐ temperature performance of this catalyst is primarily attributed to the formic acid pathway via the *CHO intermediate, as well as the notable synergistic effects of small‐sized Ni nanoparticles effectively decomposing H 2 and the CeO 2 support exhibits robust adsorption and effective activation of CO 2 . Shohei Tada et al. [124] conducted an investigation into the catalytic efficiency of nickel‐based catalysts supported on diverse substrates, including CeO 2 , titania, Al 2 O 3 , and magnesia, for the methanation of CO 2 . Ni/CeO 2 demonstrated superior CO 2 conversion rates in comparison to catalysts such as Ni/Al 2 O 3 , particularly with near‐unity methane selectivity at low temperatures. The coverage of CeO 2 surfaces by species derived from CO 2 and the partial reduction of cerium oxide surfaces may collectively contribute to the high CO 2 conversion observed for Ni/CeO 2 . Moreover, the Ni/CeO 2 exhibits exceptional CO 2 methanation activity, resulting in elevated CH 4 selectivity. Ni/CeO 2 not only exhibits comparable a CH 4 selectivity but also demonstrates a high CO 2 conversion rate, approaching equilibrium values (at 300°C). By estimating the H 2 consumption based on TPR results, it was found that both Ni species and CeO 2 underwent reduction at 600°C. CO 2 ‐TPD indicates that the quantity of CO 2 adsorbed on Ni/CeO 2 is significantly greater than that on Ni/Al 2 O 3 . 2.3 | Synthesis of Nanostructured Ni/CeO 2 For Ni/CeO 2 ‐based catalysts in CO₂methanation, synthesis methods serve as a pivotal factor in defining the catalyst's activity, stability, and resistance to sintering and carbon deposition [44, 59, 81, 120]. The structure, dispersion, and interaction of Ni with the CeO₂support are particularly important, as they impact both FIGURE 5 | (a) Quantifying the lattice capacity of CeO 2 for accommodating Ca 2+ cations involves initially determining this capacity through the XRD extrapolation method. Specifically, the lattice of CeO 2 exhibited a Ca/(Ca + Ce) molar ratio of 11%, indicative of its Ca 2+ lattice capacity. Reproduced with permission: Copyright 2024, Royal Society of Chemistry [9]. (b) The CO 2 methanation performance over Ni/Ca x Ce 1−x O y catalysts. Reproduced with permission: Copyright 2024, Royal Society of Chemistry [9]. (c) The comprehensive XRD analysis of the M 0.1 Ce 0.9 O x support includes both the full spectrum and partially enlarged patterns. Reproduced with permission: Copyright 2020, Elsevier [52]. (d) The CO 2 methanation performance over Ni/M 0.1 Ce 0.9 O x catalysts. Reproduced with permission: Copyright 2020, Elsevier [52]. (e) A schematic illustration of the preparation process for the Ni/CeO 2 ‐SGM catalyst. Reproduced with permission: Copyright 2020, Elsevier [39]. (f) A comparison of CO 2 methanation capabilities across various Ni‐based catalysts [39]. 6of35 Carbon Neutralization, 2025 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License low‐temperature activity and long‐term stability [44, 59, 81, 120]. Current synthesis approaches focus on achieving fine control over Ni particle size, strong metal–support interactions, and enhanced oxygen vacancy formation in CeO₂,allofwhicharecrucialforCO₂ adsorption and activation [44, 59, 81, 120]. Catalysts crafted from identical active metals and supports but through distinct synthesis methodologies can exhibit widely divergent performance profiles. A multitude of catalyst preparation techniques exist, and the judicious choice of a method, taking into account factors such as reaction type, frequently results in catalytic materials with unexpectedly superior performance capabilities (as evidenced in Table 1, Statistical Results). Traditional approaches to synthesizing Ni‐Ce‐ based catalysts encompass impregnation, “one‐pot”synthesis, precipitation, sol–gel, and so on. Each preparation method yields catalysts with unique attributes, underscoring the paramount importance of exploring and refining catalyst preparation techniques (as highlighted in Table 2). The impregnation methods including incipient wetness and wet impregnation, are simple and scalable but face challenges in achieving highly dispersed, small Ni particles. While suitable for large‐scale applications, these methods often yield larger particles, which can reduce low‐temperature activity. In contrast, co‐precipitation method offers better dispersion and stronger metal–support interactions but may lack reproducibility in achieving optimal particle sizes [131, 140, 141]. The sol–gel synthesis and hydrothermal methods enable more uniform distribution of Ni on CeO₂and promote a high density of oxygen vacancies, beneficial for low‐temperature applications [49, 52, 121, 131]. These methods yield catalysts with enhanced stability and activity, making them effective for lab‐to‐pilot scale production. Although they offer excellent catalytic performance, they require precise process control, which can be complex for scaling. Flame spray pyrolysis (FSP) method is particularly promising for industrial applications, as it produces Ni‐CeO₂with high dispersion, stability, and scalability [142]. FSP can effectively create catalysts with high surface areas and oxygen vacancies, essential for CO₂ activation at low temperatures. Meanwhile, atomic layer deposition (ALD) method provides the highest control over Ni distribution and particle size, achieving very strong metal–support interactions. ALD is highly effective for low‐temperature methanation but more costly and complex, making it better suited to research or high‐ value applications [143]. In summary, sol–gel and hydrothermal methods excel in lab‐to‐ pilot applications due to their balance of activity, stability, and manageable scale‐up. FSP is best suited for large‐scale production, while ALD offers precision for advanced studies on catalyst structure–performance relationships, despite its complexity and cost. Therefore, it is crucial to select an appropriate method for constructing Ni/CeO 2 catalysts that possess unique oxygen vacancies, crystallinity, surface area, morphology, structure, as well as a high dispersion of active components, appropriate strong metal–support interactions, and desirable physicochemical properties. Additionally, the synthesis method should be simple, cost‐effective, environmentally friendly, and safe. TABLE 1 | The merits and demerits associated with the preparation techniques of Ni/CeO 2 ‐based catalysts. Preparation method Merits Demerits Impregnation (i) Simple to operate, (ii) economical and practical, (iii) high flexibility. (i) Active metal distribution is uneven, (ii) loading control is hard. Coprecipitation (i) Simple preparation, (ii) economical and practical, (iii) uniform particle size. (i) Difficulties in settlement and filtration, (ii) prone to agglomeration. Mechanical mixture (i) Flexible raw material selection, (ii) simplified process. (i) Catalysts are prone to damage and have low dispersion and adherence. Rigid template (i) The size and morphology can be rigorously controlled. (i) Structure is homogeneous, (ii) with cumbersome and costly preparation. Sol–gel (i) Ni exhibits high dispersion, leading to enhanced catalyst performance and stability. (i) The raw materials are costly, (ii) necessitating substantial use of organics. Hydrothermal (i) The catalyst features aggregation, (ii) high purity, (iii) excellent dispersion, and well‐defined crystallinity. (i) Demands rigorous production equipment and high pressure. Electrospinning (i) Simple operation (i) Short and long fibers are difficult to separate, (ii) and nanofibers exhibit low strength. Ion exchange (i) Active components are uniformly distributed in the catalyst and (ii) controllable by ion exchange conditions. (i) The preparation process requires strict control of ion exchange conditions, as the selection and regeneration of ion exchangers can impact catalyst performance and cost. Plasma (i) Enhanced Ni‐support interaction results in smaller catalyst particle size and (ii) improved Ni dispersion. (i) Demands rigorous operating conditions. Vapor deposition (i) High‐purity, (ii) active catalyst films can be tailored by adjusting deposition conditions. (i) Requires high‐temperature and vacuum conditions, (ii) involves complex and costly equipment. 7of35 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License TABLE 2 | Statistical results of CO 2 methanation using Ni/CeO 2 catalysts prepared over different synthesis methods. Entry Catalyst Preparation method Ni content (wt%) S BET (m 2 /g) m cat (mg) P(bar) T(°C) WHSV (mL/(g h)) CO 2 Con. (%) CH 4 Sel. (%) Reference 1 Ni/mpCeO 2 Impregnation 10 131 —1 250 60000 70 99 [125] 2 Ni/CeO 2 Impregnation 50 —300 1 250 4200 83 99 [126] 3 Ni/CeO 2 Impregnation 10 93.4 300 1 350 60000 85 98 [46] 4 Ni/CeO 2 Impregnation 5 ——1 400 —72 98 [127] 5 Ni/CeO 2 Impregnation 10 51.9 40 1 350 45000 71 95 [128] 6 Ni/CeO 2 Impregnation 10 56 100 1 250 36000 70 96 [129] 7 Ni/CeO 2 ‐ Al 2 O 3 Wetness impregnation 25 144 300 1 350 —85 —[130] 8 Ni/CeO 2 Wetness impregnation 10 —300 1 300 10000 90 94 [124] 9Ce‐Ni‐CN Wetness impregnation 10 51.5 50 1 250 300000 53.4 97 [131] 10 Ni/CeO 2 Wetness impregnation 10 ——1 250 14000 42 99 [132] 11 Ni/CeO 2 Wetness impregnation 5—100 1 250 24000 23.5 99 [3] 12 Ni/CeO 2 Hard template 10 —100 1 340 22000 91.1 —[41] 13 Ni/ CeO 2 ‐NCT Hard template 10 —50 1 360 45000 91.1 92 [133] 14 Ni/ CeO 2 ‐NCP Hard template 10 —50 1 360 45000 65.2 99 [133] 15 Ni/ CeO 2 ‐ZrO 2 Ammonia distillation 10 85.4 150 1 275 12000 55 99 [32] 16 NiCeO 2 / MCM Sedimentation 20 307 1000 1 380 3000 85.6 98 [134] 17 Ni/CeO 2 Sol–gel 20 11 300 1 250 10000 82.5 99 [135] 18 Ni/CeO 2 Sol–gel 5.7 19 300 1 305 10000 75 72 [135] 19 Ni/CeO 2 Hydrothermal 8 72 200 1 250 30000 30 23 [136] 20 Ni/CeO 2 ‐R Hydrothermal 8.92 89.8 —1 325 20000 84.2 98 [137] 21 Ni/CeO 2 Co‐precipitation 7.4 117 100 1 220 29000 30 92 [138] 22 Ni/CeO 2 ‐SG Co‐precipitation 10 —100 1 300 300000 72 —[139] 8of35 Carbon Neutralization, 2025 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 3 | Fundamentals of CO 2 Methanation 3.1 | Thermodynamics and Kinetics of Methanation The conversion of CO 2 into methane is a spontaneous exothermic reaction at ambient temperature from a thermodynamic perspective, resulting in high equilibrium conversion rates at temperatures ranging from 25°C to 400°C [144–147]. Despite its thermodynamic favorability, CO 2 is a stable and inert small molecule with a significant kinetic energy barrier. Converting fully oxidized carbon to CH 4 entails an eight‐electron transfer process, which is characterized by significant kinetic constraints. Four primary reactions occur during this process: CO 2 methanation, the reverse water‐gas shift (Equation 1), CO methanation (Equation 2), and dry reforming reversal (Equation 3). The reverse water‐gas shift reaction (RWGS) is endothermic, while the other three reactions are highly exothermic, generating a relatively large amount of heat during the process. Under these reaction conditions, besides the main CO 2 methanation reaction, other side reactions such as the reverse Boudouard reaction (Equation 6), carbon formation (Equation 5), and CO 2 reforming with methane (Equation 6) can occur at higher operating temperatures and on Ni‐based catalysts. Therefore, achieving high methane selectivity and stability under exothermic conditions is crucial and heavily depends on the selection of appropriate reaction conditions and catalysts: ↔H C O+H CO+HO, Δ= 41.2kJ/mol 2 2 2 298K (1) ↔H C O + 3H CH + 2H O, Δ=−206kJ /mol 2 4 2 298K (2) ↔H 2 CO + 2H CH + H O, Δ=−247kJ /mol 2 4 2 298K (3) ↔H C O + C 2CO, Δ= 172.4kJ/mol 2 298K (4) ↔H C O + 2H C + 2H O, Δ=−90.1kJ/mol 2 2 2 298K (5) ↔H C O + CH 2CO + 2H O, Δ= 247.3kJ/mol 2 4 2 298K (6) Ghaib et al. [35] employed the Van't Hoff equation to calculate the relationship between the equilibrium constant (K)ofthereactions and temperature, as illustrated in Figure 6[144]. It is evident from the figure that, apart from the CH 4 decomposition reaction, the equilibria of the reactions generating carbon are suppressed as the temperature rises. The maximum possible conversion rate of the reverse water‐gasshift(RWGS)reactiondecreaseswith decreasing temperature. However, by consuming CO through other reactions, the overall CO yield can be enhanced via the RWGS reaction. Due to the higher Kvalues, CH 4 can be produced at a high conversion rate at lower temperatures. In contrast, the Boudouard reaction, which forms undesirable carbon byproducts, has a K curve that falls between these two extremes. 3.2 | Reactor Technologies for CO 2 Methanation CO₂methanation is a highly exothermic reaction, requiring careful reactor design to manage temperature, optimize conversion, and maintain catalyst stability. Based on recent literature and industry insights, the following reactor configurations and designs are emerging as suitable options (Figure 7) [25, 148–154]: 3.2.1 | Fixed‐Bed Reactors Fixed‐bed reactors are common for CO₂methanation due to their simplicity and scalability [150, 151]. They allow for high contact between gas and catalyst, making them efficient in terms of conversion rates. However, heat management is challenging, and excessive temperatures may cause catalyst sintering or deactivation [150, 151]. To improve temperature control, multitubular fixed‐bed reactors are sometimes used, where heat can be removed more effectively across multiple tubes. 3.2.2 | Fluidized‐Bed Reactor In the realm of fluidized‐bed reactors (FBRs), while their application offers numerous advantages, a careful examination reveals several notable disadvantages that cannot be ignored [155–158]. A primary concern lies in the nonuniform contact between the gaseous and solid phases, which may hinder the achievement of optimal reaction efficiency, thereby undermining the overall productivity [155–158]. Additionally, the propensity for solid particles to undergo fragmentation during the fluidization process exacerbates equipment wear and tear, while simultaneously augmenting the intricacy and expenditure associated with subsequent treatment procedures. Moreover, the separation of solids from gases within FBRs presents a formidable challenge, significantly impacting product purity and recovery rates, and consequently, the market competitiveness of the resultant products. Despite their capacity to facilitate superior mixing and heat transfer, particularly in large‐scale applications and for exothermic reactions where they contribute to maintaining a stable temperature profile and FIGURE 6 | The temperature‐dependent natural logarithms of the equilibrium constants for potential reactions involved in the methanation process. Reproduced with permission: Copyright 2016, Wiley [144]. 9of35 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License oxygen storage capacity (OSC) [187]. During the reduction process, oxygen atoms are extracted from the lattice, leaving behind oxygen vacancies that play a crucial role [188, 189]. Leveraging its redox properties, CeO 2 can facilitate a repetitive sequence involving the adsorption, activation, and dissociation of CO 2 molecules. This process ultimately leads to the formation of adsorbed CO species, which undergo further hydrogenation to produce CH 4 in the context of CO 2 methanation. The term OSC specifically refers to the quantity of oxygen lattice sites incorporated within the CeO 2 structure [190]. The morphology, shape, defects, and OSC characteristics of CeO 2 nanoparticles at the nanoscale are significantly influenced by the chosen preparation method [191]. Nanoscale material fabrication techniques offer unique qualities that cater to a diverse range of applications [192]. Beyond traditional methods, the creation of vacancies in ceria can also be achieved through a multitude of chemical processes [50, 52, 86–108]. These processes provide additional avenues for tailoring the properties of CeO 2 to meet specific requirements in various technological fields (Figure 12). 4.1.2 | Oxygen Vacancies‐Mediated CO 2 Methanation The influence of oxygen vacancies on CO 2 methanation is multifaceted, with one notable effect being the facilitation of CO 2 adsorption and activation, serving as an effective strategy to enhance low‐temperature activity [52, 121]. Wang et al. [104] investigated the catalytic process of CO 2 methanation employing Ru/CeO 2 and Ru/α‐Al 2 O 3 (Figure 13a). They found that oxygen vacancies in Ru/CeO 2 catalyze the rate‐limiting step of formate dissociation to methanol, while Ru acts as the primary catalytic site promoting the CO pathway in Ru/α‐Al 2 O 3 . Liu et al. [52] utilized the sol–gel technique to prepare CeO 2 , which is incorporated with alkaline earth elements, such as Mg, Ca, Sr, and Ba. By analyzing the relationship between oxygen vacancies, alkaline centers, and activity, it was discovered that surface oxygen vacancies create a moderately strong alkaline center due to oxygen deficiency. The alkaline centers arising from oxygen vacancies can significantly enhance low‐ temperature activity (Figure 13b). During the reduction process of CeO 2 , oxygen atoms are removed from the crystal lattice and replaced by oxygen vacancies [188]. CeO 2 undergoes a cyclic process involving the adsorption, activation, and subsequent cleavage of CO 2 molecules, subsequently creating adsorbed CO species during the CO 2 methanation process and further hydrogenating them into CH 4 due to their redox properties. According to reports, in comparison to other oxides Ni catalysts supported on CeO 2 , as well as other oxides, such as TiO 2 , MgO, and Al 2 O 3 exhibit higher activity and specificity in favor of CH 4 production during the methanation of CO 2 [46]. The distinctive attribute of CeO 2 lies in its ability to generate oxygen vacancies and its exceptional capacity for storing and releasing oxygen, distinguishing it from other metal oxides. The oxygen vacancies on the surface of metal oxides are considered active centers for CO 2 activation [197]. These oxygen vacancies could function as binding sites for surface‐adsorbed species or sites for exciting charges. Surface oxygen vacancies can provide additional electrons, which possess the capability to adsorb CO 2 molecules and activate them, representing another mechanism by which these vacancies facilitate successful charge transfer processes and reduce the activation energy of CO 2 . The catalyst exhibiting the greatest catalytic activity is the one that creates oxygen vacancies with minimal energy expenditure; the activation of CO 2 on oxygen vacancies constitutes the critical step that governs the reaction rate [198]. Hu et al. [193] prepared and optimized a Ni/CeO 2 ‐Co 3 O 4 catalyst that exhibits excellent CO 2 adsorption and activation performance. The mechanism analysis is illustrated in Figure 13c. The results indicate that Co 3 O 4 can adsorb and convert a portion of CO 2 , while the presence of oxygen vacancies in CeO 2 ‐Co 3 O 4 significantly boosts its CO 2 adsorption capacity, validating the promotional role of CeO 2 in facilitating CO 2 adsorption. However, the formation of CO still dominates, suggesting that Co 3 O 4 does not promote the generation of CH 4 . In‐situ CO 2 adsorption and DFT results reveal that CeO 2 ‐Co 3 O 4 exhibits stronger adsorption compared to Co 3 O 4 , attributed to the enhanced interaction with CO 2 facilitated by the vacancies in CeO 2 . Zhang et al. [194] successfully synthesized nickel‐ based catalysts supported on La‐doped flower‐like hollow CeO 2 microspheres. Among all the catalysts, the catalyst composed of La‐doped CeO 2 exhibited superior catalytic efficiency in the methanation of CO 2 , primarily due to its abundant oxygen vacancies, which play a pivotal role in methane formation. Upon adsorption onto the surface of Ni/CeO 2 ‐La‐600, CO 2 molecules react with the oxygen vacancies (active O* sites) at the Ni/CeO 2 ‐ La interface, resulting in the production of OCO 2 . This process repeats until the desired quantity of OCO 2 is generated (Figure 13d). Subsequently, the dissociated H* species can undergo a reaction with the newly formed OCO 2 * intermediate, leading to the formation of bicarbonate, which further converts into CH 4 through various intermediate species. Zou et al. [195] reported that incorporating Mo into the CeO 2 lattice significantly enhances the concentration of surface oxygen vacancies, as illustrated in Figure 13e. Utilizing Mo‐doped CeO 2 as a support not only inhibits the growth of NiO but also strengthens the metal–support interaction, thereby shortening the path for active H species to reach adsorbed CO 2 molecules. DRIFTS analysis indicated that CO 2 methanation on Ni/MoCe primarily proceeds through a rapid HCOO* pathway involving *CO. The surface oxygen vacancies favor the formation of bidentate FIGURE 12 | Various methods are employed to generate oxygen vacancies (OVs) in catalysts based on CeO 2 . Reproduced with permission: Copyright 2023, Elsevier [59]. 16 of 35 Carbon Neutralization, 2025 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License carbonates, which hydrogenate faster compared to monodentate carbonates on Ni/CeO 2 . Zhang et al. [196], as shown in Figure 13f, discovered that an abundance of H atoms promotes the creation of oxygen vacancies, further accelerating the hydrogenation of (bi)carbonates and formates derived from activated CO 2 over basic sites. Notably, our findings reveal that both the formate and CO pathways operate concurrently over the Ni/CeO 2 ‐EDA catalyst. Therefore, well‐dispersed Ni particles combined with adequate surface oxygen vacancies synergistically enhance the reactivity of CO 2 hydrogenation. FIGURE 13 | (a) Schematic representation of the reaction mechanism for CO 2 methanation over the Ru/CeO 2 catalyst, highlighting the formate route facilitated by oxygen vacancy active sites. Reproduced with permission: Copyright 2016, American Chemical Society [104]. (b) Schematic illustration of alkaline earth metal‐modified CeO 2 creating oxygen vacancies for low‐temp CO 2 methanation. Reproduced with permission: Copyright 2023, Elsevier [52]. (c) Proposed reaction pathways of CO 2 methanation of catalysts, less and more represented the amount of CO 2 adsorption. Reproduced with permission: Copyright 2023, Elsevier [193]. (d) Scheme illustration of the primary reaction pathway for CO 2 methanation utilizing the Ni/CeO 2 ‐La‐600 catalyst. Reproduced with permission: Copyright 2022, Elsevier [194]. (e) Scheme illustration of molybdenum doping enhancing surface oxygen vacancies in CeO 2 to boost low‐temperature CO 2 methanation efficiency on Ni/CeO 2 catalysts. Reproduced with permission: Copyright 2024, Elsevier [195]. (f) Schematic illustration of the proposed reaction pathways for CO 2 methanation on Ni/CeO 2 ‐EDA and Ni/CeO 2 catalysts, respectively. Reproduced with permission: Copyright 2021, American Chemical Society [196]. 17 of 35 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 4.2 | Engineering for Active Site Modification 4.2.1 | Single Active Site For Ni‐based catalysts in CO 2 methanation, metallic Ni serves as the active metal and is pivotal to the catalytic reaction. Tata et al. [101] examined the active sites responsible for CO 2 methanation on Ni/CeO 2 catalysts, which were synthesized through the wet impregnation method. They proposed that the rate of CO 2 conversion is not directly linked to the number of oxygen vacancies (Ce−V ox −Ce) on CeO 2 , but rather it correlates with the abundance of Ni−V ox −Ce sites (Figure 14a). Therefore, the formation of Ni−V ox −Ce centers (producing CO via RWGS) and the exposure of metallic Ni centers (methanation of the resultant CO) are crucial for CO 2 methanation. Catalytic behavior is associated with the contact between NiO and CeO 2 ; hence, the reduction ratio of Ni 0 sites and the intimate contact between NiO and CeO 2 are relevant. Introducing Ni before synthesizing the CeO 2 structure leads to a significant amount of NiO in intimate contact with CeO 2 , thereby creating numerous active sites and enhancing the decomposition of CO 2 . Cárdenas‐ Arenas et al. demonstrated through research that achieving maximum CO 2 conversion requires an optimal ratio of two sites: approximately 25% of the Ni 0 surface catalyzes the dissociation of H 2 , whereas 75% of the NiO–CeO 2 interface is responsible for the dissociation of CO 2 (Figure 14b)[42]. 4.2.2 | Bicentric Active Site In the field of CO 2 methanation, bimetallic catalysts typically refer to catalysts composed of two different metals supported on a carrier surface, possessing dual active sites. Due to the distinct chemical properties and electronic structures of the two metals, there is considerable potential for developing these catalysts in terms of design, catalytic activity, and product selectivity regulation. According to current reports, bimetallic catalysts used in CO 2 methanation reactions often feature Ru or Ni as the primary catalyst, with another metal from Group VIIIB or IB, which exhibits CO 2 hydrogenation activity, serving as the cocatalyst. Among these, Ru‐Ni bimetallic catalysts have been the most extensively studied. For instance, Su et al. reported a tandem catalyst (Ru1Ni/CeO 2 ) with dual active sites consisting of Ru single atoms (Ru1) and Ni nanoparticles. At 325°C, this catalyst demonstrated a remarkable CO 2 conversion rate of approximately 90%, coupled with a CH 4 selectivity of nearly 99%, outperforming both the Ru1/CeO 2 and Ni/CeO 2 catalysts in these respects. Through experimental and theoretical calculations, the authors elucidated that Ru1 dissociates CO 2 into CO and desorbs it, while the desorbed CO adsorbs at the Ni nanoparticle site for hydrogenation to produce CH 4 . This tandem reaction process provides a valuable reference for the subsequent design of bimetallic catalysts (Figure 15a)[199]. Additionally, Su et al. [200] reported another Ru1Ni/SiO 2 single‐atom alloy catalyst, clarifying that the Ru1Ni single‐atom alloy interface site is the intrinsic active site, which aids in the direct dissociation of CO 2 into CO and lowers the energy requirement for hydrogenating the CO* intermediate, thereby promoting the hydrogenation of CO 2 to CH 4 (Figure 15b). Goula et al. [61] loaded a series of noble metals (Ru, Pt, Pd, Rh, Ir) and Ni onto the surface of Pr‐doped CeO 2 and compared their catalytic activity for CO 2 methanation. Ru was the only noble metal that significantly improved catalytic activity. The optimal RuNi bimetallic catalyst achieved a CO 2 conversion rate of about 80% and a CH 4 selectivity of about 99.5% at 325°C. They also drew a similar conclusion: the addition of Ru facilitated the dissociation of CO 2 into CO (Figure 15c). Zhang et al. [201] synthesized Ni‐Co/MgO materials for CO 2 methanation and observed an interesting phenomenon. The robust interaction between Ni and Co facilitated electron transfer from Ni to Co, enhancing Co with an electron‐rich state (Co δ‐ ) that promoted the adsorption and activation of CO 2 , leading to the formation of monodentate carbonate intermediates, thereby displacing the initial bidentate carbonates (Figure 15d). Ding et al. [202] prepared Ni‐Fe bimetallic catalysts supported on CeO 2 and Al 2 O 3 for the CO 2 methanation reaction, observing an intriguing phenomenon. For CeO 2 , which is rich in basic FIGURE 14 | (a) The schematic depiction highlights that the conversion rate of CO 2 does not correlate with the number of oxygen vacancies present on CeO 2 (denoted as Ce–V ox –Ce), but rather it is linked to the abundance of Ni–V ox –Ce sites. Reproduced with permission: Copyright 2021, American Chemical Society [101]. (b) The investigation has delved into the roles of various active sites on Ni/CeO 2 catalysts during the CO 2 methanation process. Two distinct categories of active sites have been pinpointed: one at the NiO–ceria interface facilitating CO 2 chemisorption and dissociation, and another on Ni 0 entities promoting H 2 dissociation. These active site proportions have undergone optimization to enhance the overall catalytic efficiency. Reproduced with permission: Copyright 2020, Elsevier [42]. 18 of 35 Carbon Neutralization, 2025 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License FIGURE 15 | (a) A schematic representation of the acceleration of CO 2 conversion into CH 4 facilitated by distinct reactive sites (Ru1 and Ni). Reproduced with permission: Copyright 2023, Elsevier [199]. (b) A schematic illustration showcasing the enhancement of CO 2 methanation through the alloying of single‐atom Ru with Ni nanoparticles. Reproduced with permission: Copyright 2020, Wiley [200]. (c) Schematic representation of Ni‐noble metal bimetallic catalysts for enhanced low‐temperature CO 2 methanation. Reproduced with permission: Copyright 2024, Elsevier [61]. (d) Illustration of the reaction sequence for CO 2 methanation and a plausible reaction route over Ni‐Co‐MgO catalyst. Reproduced with permission: Copyright 2024, Elsevier [201]. (e) An in‐depth exploration of the mechanism by which the non‐precious metal Fe promoter influences CO 2 methanation. Reproduced with permission: Copyright 2022, American Chemical Society [202]. (f) The promotional impact of Fe on Ni‐supported catalysts in CO 2 methanation entails accelerating the activation and conversion of CO 2 via the formation of HCOO. Furthermore, the NiFe alloy enhances the reaction mechanism of CO 2 methanation by facilitating the formate pathway. Reproduced with permission: Copyright 2020, Elsevier [203]. 19 of 35 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License sites, the incorporation of Fe surprisingly blocked the basic sites on the catalyst surface, thereby inhibiting the performance of the originally basic‐site‐rich catalyst. In contrast, for the weakly basic support Al 2 O 3 , the introduction of Fe did not have any adverse effects on the catalyst but rather enhanced its basicity through the Fe 3+ /Fe 2+ redox system, further boosting the catalyst's CO 2 methanation performance (Figure 15e). Yu et al. [203] synthesized Ni–Fe bimetallic catalysts via a hydrotalcite precursor, exhibiting high catalytic performance. During the reduction process, particles of the NiFe alloy were formed in a small size. The authors employed in‐situ DRIFTS and DFT theoretical calculations to demonstrate that the addition of Fe facilitated the activation of CO 2 to form formate intermediates, and the hydrogenation of formate to methane possessed a relatively low energy barrier (Figure 15f). 4.2.3 | Dispersion of Active Site It is generally acknowledged that the particle size of Ni correlates with its dispersion, which in turn influences the active centers of catalysts [204]. Liu et al. [51] prepared Ni/CeO 2 catalysts with extremely fine Ni particles (~1.2 nm), exhibiting a large hydrogen uptake capacity and abundant oxygen vacancies, thereby facilitating the activation of CO 2 (Figure 16a). Lin et al. [205] prepared a 2% Ni/CeO 2 on a high‐surface‐area CeO 2 support, featuring uniform Ni particles of 2, 4, and 8 nm in size (Figure 16b). The results showed that the 8 nm catalyst exhibited a methanation activity that was 10 times greater than the 4 nm catalyst and 70 times higher than the 2 nm catalyst. This can be attributed to the effective promotion of the hydrogenation reaction of surface formate intermediates by larger Ni particles (8 nm) supported on CeO 2 . Varvoutis et al. examined the sensitivity of Ni particles (ranging from 10 to 25 nm) supported on CeO 2 nanorods to the process of CO 2 methanation. The corresponding sample exhibited the highest activity when the Ni particle size was 20 nm (Figure 16c)[206]. Analysis of the structural sensitivity of the CO 2 methanation on Ni/CeO 2 catalysts showed that neither the accessible Ni surface area nor the overall perimeter of Ni/CeO 2 exhibited a direct correlation with catalyst activity. Despite the inevitable reduction in the perimeter of the Ni/CeO 2 interface with larger Ni particles, the site‐time yield expressed per individual Nickel crystallite size and the intrinsic reaction rate normalized by the total FIGURE 16 | (a) A schematic illustration outlines how Ni particle size and the occurrence of oxygen vacancies affect the efficacy of Ni/CeO 2 and Ni/SiO 2 catalysts in CO 2 methanation. Reproduced with permission: : Copyright 2022, Elsevier [51]. (b) A schematic visualization of how Ni particle dimensions impact the production of renewable methane from CO 2 utilizing a Ni/CeO 2 . Reproduced with permission: Copyright 2021, Elsevier [205]. (c) A schematic representation illustrating the process of elucidating the impact of Ni particle size and the perimeter of the nickel–ceria interface on the highly efficient CO 2 methanation reaction over exceptionally active Ni/CeO 2 . Reproduced with permission: Copyright 2021, Elsevier [206]. 20 of 35 Carbon Neutralization, 2025 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License Ni/CeO 2 perimeter peaked at approximately 20 nm, which aligns fully with the experimental catalytic results. 4.3 | Morphology Engineering 4.3.1 | Shape‐Controlled Formation Mechanism and Synthetic Strategies Considering nanocrystal formation, managing size and morphology is crucial [207–209]. Crystal formation involves nucleation and growth processes, where controlling their rates determines the final size and shape [210–212]. Nucleation, the initial stage, can be heterogeneous (at preferential sites) or homogeneous (spontaneously). Heterogeneous nucleation is easier due to reduced free energy barriers, while homogeneous nucleation often requires superheating or supercooling [210, 213, 214]. Growth follows nucleation, spreading outwards and reaching a metastable equilibrium until stepwise advancement occurs [215–217]. Particle growth may introduce defects, catalyzing structural transformation [211, 218]. Crystal growth occurs swiftly, with the regulation of particle size hinging on the interplay between nucleation and growth rates. These rates are, in turn, influenced by various reaction conditions, including pH levels, pressure, temperature, precursor concentration, and the choice of solvent [215, 219]. Achieving size uniformity is vital and relies on separating nucleation and growth, often through controlled precursor addition and reaction conditions, as illustrated in Figure 17a [223, 224]. Organic ligand molecules can restrict the growth process and prevent agglomeration, leading to the formation of small, finely dispersed nanocrystals. Controlling shapes involves stabilizing higher surface energy planes with additives to optimize desired facets [225]. Regarding synthetic strategies, various methods can be employed to fabricate CeO 2 nanomaterials, including the precipitation technique, such as precipitation method [226], sol–gel method [227, 228], hydrothermal or solvothermal method [212, 229], surfactant‐assisted method [230], electrochemical deposition [231, 232], and so on. Furthermore, the creation of CeO 2 nanomaterials sometimes involves the integration of two or more fabrication techniques (Figure 17b,c). 4.3.2 | Morphology‐Assisted Engineering The structure of Ni/CeO 2 is a primary factor influencing their performance in CO 2 methanation. The morphology of CeO 2 significantly affects the preferred exposed crystal planes of the catalysts, leading to variations in oxygen vacancy concentration and metal dispersion, thereby enhancing the catalysts' low‐ temperature activity. Zhou et al. [133]. synthesized Ni/CeO 2 using CeO 2 as the support, which was synthesized through hard templating, soft templating, and precipitation methods (named NCT, NCS, and NCP catalysts, respectively). Among NCT, NCS, and NCP, the NCT catalyst displayed superior CO 2 methanation FIGURE 17 | (a) The approach for synthesizing metal oxide nanocrystals involves utilizing an organic‐ligand‐facilitated supercritical hydrothermal method. Reproduced with permission: Copyright 2007, Wiley [220]. (b) A schematic representation depicting the transformation from nanorods to nanocubes. Reproduced with permission: Copyright 2008, American Chemical Society [221]. (c) A microwave‐assisted approach for synthesizing ceria hollow spheres. Reproduced with permission: Copyright 2010, American Chemical Society [222]. 21 of 35 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License performance, primarily due to its high specific surface area coupled with a well‐organized mesoporous structure. Bian et al. [33] employed a hydrothermal method to synthesize cerium oxide nanorods (NR) and nanocubes (NC), loaded with 5 wt% Ni (Figure 18a). An investigation into the impact of CeO 2 support morphology on CO 2 methanation revealed that Ni/ CeO 2 ‐NR exhibited superior catalytic activity in comparison to Ni/CeO 2 ‐NC, attributed to its elevated surface Ce 3+ concentration. Ma et al. [36] utilized a hydrothermal approach to prepare CeO 2 nanorods (CeO 2 ‐nrs), CeO 2 nanocubes (CeO 2 ‐ncs), and CeO 2 nanopolyhedra (CeO 2 ‐nps), and deposited NiO microcrystals on these supports via precipitation for CO 2 methanation (Figure 18b). Similar to the aforementioned results, the Ni/ CeO 2 ‐nrs catalyst exhibited excellent metal dispersion and a higher oxygen vacancy concentration, playing a key role in boosting its catalytic efficiency for CO 2 methanation. Zhang et al. [235] prepared three different morphologies of CeO 2 catalysts—flower‐like, nanowire, and bulk—using the impregnation method. Among them, the Ni/CeO 2 nanowire catalyst demonstrated the highest CO 2 conversion rate, attributed to its heightened oxygen vacancy concentration and optimized adsorption capabilities for CO 2 . Jomjaree et al. [233] employed a hydrothermal/wet impregnation method to synthesize Ni‐loaded CeO 2 catalysts with various morphologies such as nanorods (NR), nanoparticles (NP), nanocubes (NC), and nanopolyhedra (PH) (Figure 18c). An investigation was conducted into the catalytic performance of the prepared catalysts for the methanation of CO 2 at low temperatures. Among the diverse forms of CeO 2 , the Ni/CeO 2 ‐ NR stood out due to its substantial specific surface area and exceptional reduction capability, alongside notable oxygen vacancy and oxygen storage capacity (OSC) characteristics. However, the strong metal–support interaction (SMSI) between Ni and Ce in the Ni/CeO 2 ‐NR catalyst, as determined by H 2 ‐ TPR, adversely affected the low‐temperature conversion of CO 2 . In contrast, the Ni/CeO 2 ‐PH, featuring a single‐crystalline CeO 2 nanostructure morphology with a size of approximately 7.4 nm, exhibited a high specific surface area and superior reduction capability. Therefore, the Ni/CeO 2 ‐PH catalyst demonstrated excellent activity for low‐temperature CO 2 methanation. García‐Moncada et al. [34] have crafted a Ni catalyst supported on CeO 2 nanorods, exhibiting both high stability and activity. Under various reaction conditions, this catalyst outperforms FIGURE 18 | (a) A schematic representation showcasing the influence of Ni/CeO 2 morphology on its catalytic properties during CO 2 methanation. Reproduced with permission: Copyright 2020, Elsevier [33]. (b) Ni catalysts supported on CeO 2 nanorods (CeO 2 ‐nrs), CeO 2 nanocubes (CeO 2 ‐ ncs), and CeO 2 nanopolyhedrons (CeO 2 ‐nps) were evaluated for their effectiveness in CO 2 methanation. The findings revealed a direct correlation between the oxygen vacancy content and the catalyst's specific surface area. Reproduced with permission: Copyright 2022, Elsevier [36]. (c) A schematic depiction highlighting the performance of Ni catalysts, supported by CeO 2 in various morphological forms, specifically engineered for enhancing CO 2 methanation at lower temperatures. Reproduced with permission: Copyright 2021, Elsevier [233]. (d) Methanation of CO 2 utilizing Ni‐based catalysts supported on nano‐CeO 2 with diverse morphological characteristics. Reproduced with permission: Copyright 2023, Elsevier [234]. 22 of 35 Carbon Neutralization, 2025 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License commercial CeO 2 (octahedral) catalysts in CO 2 methanation reactions. The exceptional performance of this catalyst is attributed to the creation of oxygen vacancies, improved mobility, and optimized interaction and dispersion of Ni on the support. Bian et al. [234] have synthesized a variety of CeO 2 supports with unique morphologies, encompassing nanorods, nanocubes, nano‐octahedrons, and nanosized particles. They further developed Ni‐based CO 2 methanation catalysts employing the impregnation technique. The catalyst supported on nano‐CeO 2 particles (NPs) demonstrated superior catalytic activity and stability compared to those supported on alternative CeO 2 morphologies. This superiority is attributed to factors, such as abundant oxygen vacancies, balanced basic sites, optimal metal–support interaction, robust reduction abilities, and additional favorable characteristics (Figure 18d). Furthermore, on Ni‐based catalysts where the CeO 2 support exposes its crystal planes, the hydrogenation of CO 2 to carbonate species is dominant. In contrast, on Ni‐based catalysts with CeO 2 supports exposing {1 0 0} and {1 1 0} crystal planes, the reductive dissociation of CO 2 to CO holds a slight advantage. 4.4 | Surface Tuning Engineering 4.4.1 | Strong Metal–Support Interaction (SMSI) The interaction between metal active centers and supports can influence the performance, which is associated with metal– support interaction (MSI), charge transfer, interfacial perimeter, nanoparticle morphology, chemical composition, and strong metal–support interaction (SMSI) (Figure 19)[236]. These phenomena are commonly interconnected and contingent upon different catalysts and chemical reactions. Within the realm of catalysis, specifically heterogeneous catalysis, regulating MSI FIGURE 19 | A schematic depiction of metal–support interactions Reproduced with permission: Copyright 2019, Springer Nature [236]. 23 of 35 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License offers direction for designing catalysts. In recent years, methods for modulating MSI have continually advanced to augment the catalytic efficiency of metal catalysts supported on various substrates. MSI can induce charge transfer in metal nanoparticles [237, 238] and support‐induced reorganization of metal nanoparticles [239]. Therefore, MSI can be regulated by adjusting the properties of supports (composition, morphology, and reducibility [240], etc.) and metals (size and composition [241]), as well as altering pretreatment conditions (heat treatment, reduction‐oxidation cycles, adsorbate mediation, etc. [242]). SMSI significantly improves the catalytic performance of metal/oxide catalysts, prevents the sintering of supported metal nanoparticles, and enhances catalyst stability by encapsulating the supported metal nanoparticles. Numerous literature reports have highlighted the pivotal role of metal–support interaction in catalysts on methanation activity. Cárdenas‐Arenas et al. [43] conducted studies on the mechanism of CO 2 methanation over Ni/CeO 2 and Ni/Al 2 O 3 through isotopic labeling and in‐situ DRIFTS, revealing that Ni/CeO 2 generates a higher number of interfacial NiO sites due to metal–support interaction. These interfacial NiO and Ni 0 work synergistically to activate CO 2 and H 2 , thereby enhancing the methanation activity on Ni/CeO 2 .Alcalde‐Santiago et al. [243] synthesized Ni/LnO x (Ln = La, Ce, Pr) catalysts and discovered that Ni/CeO 2 showed the highest efficiency in catalyzing CO 2 methanation. They attributed this to the formation of more reactive intermediates at the interface between Ni 2+ and cerium oxide, coupled with the lowest stability of adsorbed CO 2 and H 2 O on its surface. Zhang et al. [244] reduced the Ru/TiO 2 catalyst at various temperatures under a reducing atmosphere and found that as the reduction temperature increased, TiO 2 was concurrently reduced to form TiO x species that epitaxially grew on the metal surface. This encapsulation effect enhanced the strong metal–support interaction (SMSI) between the metal and the support, thereby boosting the catalyst's activity. Parastaev et al. [245] manipulated the metal–support interaction by altering the particle size of the ceria‐zirconia support. Their findings revealed that when ceria‐zirconia was used as the support, larger support particles led to a stronger metal–support interaction, which paradoxically resulted in better dispersion of cobalt on the support surface. Consequently, the conversion rate of CO 2 hydrogenation was also higher. In recent research, Lin et al. [50] impregnated Ni onto CeO 2 and regulated the metal–support interaction (MSI) by altering the reduction atmosphere and conducting oxidation– reduction cycles (Figure 20a). This approach was employed to investigate effective means of enhancing the catalytic performance of the catalyst. Highly dispersed Ni nanoparticles in Ni/CeO 2 are in contact with the (111) and (100) crystal planes of CeO 2 , exhibiting a greater content of surface oxygen vacancies and a more suitable MSI. The presence of numerous weakly basic centers thereby enhanced the adsorption and activation properties of reactant molecules. Pu et al. [246] (Figure 20b) prepared CeO 2 supports with various morphologies and investigated the strong metal–support interaction (SMSI) on Ni/CeO 2 catalysts. The Ni nanoparticles supported on CeO 2 with different morphologies exhibited distinct surface structures. The encapsulation degree of Ni particles induced by SMSI followed an order from the strongest to the weakest: Ni/CeO 2 ‐(1 1 1), Ni/CeO 2 ‐(1 0 0), and Ni/CeO 2 ‐(1 1 0 + 1 0 0), which aligned with the catalysts' performance sequence. The encapsulation degree of Ni particles was closely related to the ability to form oxygen vacancies, which can activate CO 2 at low temperatures. In summary, metal–support interaction modifies the catalyst's electronic structure and active surface components, impacting nanoparticle size, interfaces, and charge transfer. Consequently, this interaction enhances or diminishes the adsorption of certain key species on the catalyst surface and the number of active sites, ultimately controlling CO 2 conversion and methane selectivity during methanation. 4.4.2 | Composite Support CeO 2 support material, an alkaline oxide, has proven its aptitude for the methanation process involving CO 2 .CeO 2 exhibits not just a large specific surface area, which facilitates metal dispersion but also possesses the capacity to store and release oxygen. This dual functionality not only fosters an environment favorable for electron transfer but also acts as a catalyst for CO 2 activation [247]. However, CeO 2 is prone to sintering and requires optimization through doping with other metal oxides. Studies have shown that the addition of zirconia can enhance the catalytic activity of ceria. In recent years, mixed oxides composed of CeO 2 and ZrO 2 have emerged as a promising support option for CO 2 methanation. Owing to their impressive capacity for storing and discharging oxygen and their ability to activate CO 2 , they have demonstrated remarkable efficacy in both activity and stability. FIGURE 20 | (a) The catalytic performance of Ni/CeO 2 with varying metal–support interactions (MSI), treated under different reduction atmospheres. Reproduced with permission: Copyright 2021, Elsevier [50]. (b) A schematic depiction illustrating the dependence of CO 2 methanation on the robust metal–support interaction for Ni/CeO 2 catalysts supported on a substrate. Reproduced with permission: Copyright 2019, Springer Nature [246]. 24 of 35 Carbon Neutralization, 2025 27693325, 2025, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/cnl2.190 by Readcube (Labtiva Inc.), Wiley Online Library on [05/03/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License According to previous reports [248], incorporating ZrO 2 into CeO 2 enhances its oxygen storage capacity, redox performance, and thermal stability. This improvement, along with the exhibition of catalytic activity at reduced temperatures, is attributed to the formation of a solid solution through partial substitution of Ce 4+ by Zr 4+ in the ceria lattice. The results suggest that zirconia contributes to controlling the structure or position of ceria crystals [249]. The method of preparation has a considerable influence on the structural and chemical properties of CeO 2 –ZrO 2 mixed oxides [248]. Techniques such as hydrothermal synthesis [250], sol–gel method [251], surfactant‐assisted routes [252], and reverse microemulsion [252] have been conducted on the preparation of CeO 2 ‐ZrO 2 composites. However, the most straightforward method is co‐precipitation, due to its simplicity and ease of industrial application. Cerium‐zirconium mixed oxides (Ce‐Zr) exhibit superior oxidation–reduction characteristics and resilient metal–support interplays, making them widely applicable in processes, such as steam reforming of hydrocarbons, methane oxidation, and hydrogenation reactions during CO 2 methanation. The CeO 2 component aids in the adsorption of CO 2 and strengthens the interaction between Ni 2+ /Ni 0 and the Ce support. Furthermore, the incorporation of zirconia enhances the redox characteristics of ceria, thereby boosting its catalytic activity. Zhu et al. [253] investigated how varying Ce/Zr ratios influenced the activity of CO 2 methanation. They discovered that a Ce/Zr ratio of 0.25:0.75 yielded the best results. Catalysts rich in zirconium, specifically Ce‐Zr catalysts with this ratio, were found to effectively drive the activation of CO 2 . Furthermore, as the Zr content rises, both the oxygen mobility within the Ce‐Zr lattice and the rate of vacancy formation increase. As the Zr content rises, there is an increase in oxygen mobility within the Ce‐Zr lattice. Additionally, the process of forming vacancies becomes more prevalent, facilitating easier reduction of the catalyst [254]. The incorporation of a third metal (such as Ni) into the Ce‐Zr lattice can enhance oxygen storage capacity. Zonetti et al. [255] investigated the addition of Ni into the Ce‐Zr lattice. They confirmed that, compared to traditional Ni impregnation on Ce‐Zr catalysts, this catalyst enhances its reducibility and increases the count of oxygen vacancies. Additionally, increasing the Ni content further elevates both the activity and stability of the catalyst. However, cerium‐rich Ce‐Zr solid solutions, due to their high Ce 3+ content, exhibit better oxygen storage capacity but have limited application in catalysts due to poor thermal stability [256]. Therefore, improving the thermal stability of Ce‐Zr materials remains one of the research focuses [257]. The crystalline phase and grain size of solid solutions significantly affect their high‐temperature thermal stability and redox properties. Specifically, grain size plays a crucial role in determining the tendency for particle agglomeration, where smaller crystalline particles, despite possessing a large specific surface area, exhibit heightened sintering kinetics. Furthermore, achieving a uniform grain size distribution in materials contributes to enhancing the thermal stability of Ce‐Zr solid solutions at high temperatures. Zhang et al. [258]discoveredthat enhancing the grain size of freshly prepared samples can hinder further grain growth and augment the thermal stability of the utilized samples. Numerous studies indicate that the CeO 2 grain size influences its redox properties, with smaller grains leading to reduced formation energies for oxygen vacancies. Consequently, optimizing both grain size and its distribution emerges as a potent strategy to enhance both the thermal stability and redox characteristics of Ce‐Zr solid solutions. Ashok et al. [32] synthesized various nickel catalysts supported on Ce x Zr 1−x O 2 (CZ) through ammonia evaporation (AE), impregnation (IMP), and deposition‐precipitation (DP) methods. The outcomes of the CO 2 methanation reaction demonstrated that the Ni/CZ‐AE catalyst surpassed the performance of Ni/CZ catalysts prepared by impregnation and deposition‐ precipitation techniques (Figure 21). Specifically, the Ni/CZ‐AE catalyst demonstrated a higher CO 2 conversion rate at 275°C, which was attributed to an improved interaction between Ni and Ce species, as confirmed by H 2 /CO‐TPR and XPS analyses, which showed the highest number of reducible centers below 450°C for Ni/CZ‐AE. Additionally, the surface oxygen/hydroxyl species in Ni/CZ‐AE were more mobile. DRIFTS experiments indicated that CO 2 methanation occurred via formate species rather than CO. These formate intermediates undergo transformation into formaldehyde‐like compounds, subsequently evolving into methoxy species, which ultimately undergo dissociation to yield CH 4 . The catalyst's performance was influenced by metal–support interactions, favoring methane formation over CO. In conclusion, the Ni/CZ catalysts synthesized through the AE method hold promise for utilization in various thermodynamically governed exothermic reactions that necessitate metallic activity at reduced temperatures. 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