IR Nanospectroscopy Mapping of Facet-Dependent Sulfur Poisoning and Thermal Regeneration on Platinum Nanocrystals

IR Nanospectroscopy Mapping of Facet-Dependent Sulfur Poisoning and Thermal Regeneration on Platinum Nanocrystals Lihi Rikanati, Yehonatan Hovav and Elad Gross* Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University, Jerusalem 91904, Israel *Email: [email protected] Abstract Sulfur poisoning critically limits the activity and durability of Pt catalysts, yet the nanoscale structure-reactivity relationships that govern sulfate adsorption and its thermal desorption remain poorly resolved. Using infrared nanospectroscopy, we directly map the spatial distribution, adsorption geometry, and temperature-dependent evolution of sulfate species on individual Pt nanocrystals (NCs) with well-defined facets. At room temperature, SOx species preferentially accumulate at defect-rich inter-facet regions, edges, and open Pt(100)-like facets, in which bidentate adsorption dominates. Flat Pt(111) terraces exhibit lower SOx coverage and a larger contribution from tridentate species. Mild annealing (50-200 °C) induces selective desorption from undercoordinated sites and drives a structural transition from bidentate to tridentate coordination as species migrate toward highly coordinated terrace regions. At 300 °C, most sulfate species desorb from edges and side facets, whereas thermally robust tridentate species persist at the NC interior. These results provide a facet-resolved picture of sulfur adsorption and regeneration pathways, revealing how local surface structure dictates the stability and thermal evolution of poisoning species on Pt catalysts. Introduction Catalyst poisoning results in deactivation caused by the strong and often irreversible adsorption of molecular or atomic species to active metal sites.1 Sulfur-containing compounds (e.g., sulfuric acid and its derivatives), carbon monoxide, and halide ions are among the most potent poisoning agents.2,3 The consequences of surface poisoning include reduced catalytic efficiency, lower product yields, and, ultimately, the need for catalyst replacement or regeneration.3–5 Poisoners such as sulfur form strong bonds with Pt surface atoms, saturating active sites and preventing reactant adsorption. Chemical reactions between the poisoning species and the catalyst can also generate new surface compounds that may either desorb from the surface or further block catalytic sites.3 Strongly bound poisoners, such as SOx-Pt species, often require harsh treatments for removal and restoration of catalytic activity.3,6–8 Therefore, analyzing the adsorption and desorption patterns of SOx species on Pt nanoparticles is essential for understanding the mechanisms of catalyst poisoning and guiding regeneration strategies. The interaction between sulfuric acid and Pt depends strongly on the arrangement and coordination of the surface atoms and on the chemical properties of the SOx species.9 Sulfate is mainly adsorbed in a bidentate or tridentate coordination modes and the adsorption geometry directly influences the adsorption strength, and thermal stability of the poisoning species.10–12 On Pt(111), sulfate predominantly adopts a well-ordered, bidentate or tridentate geometry stabilized by the close-packed terrace arrangement.13 On Pt(100), which is characterized with higher density of bridge sites, sulfate binds more weakly and often in a tilted bidentate configuration.14,15 The natural interand intra-particle structural heterogeneity of catalytic nanoparticles16–20 makes it challenging to directly probe how different surface sites influence SOx poisoning and its removal. Resolving these site-dependent effects requires both experimental techniques capable of providing nanoscale chemical information and model catalysts with well-defined surface structures. Recent advances in high spatial resolution spectroscopy have enabled nanoscale investigations of catalytic nanoparticles,20–35 and were also utilized for analysis of SOx distributions on catalytic nanoparticles.7,36 In particular, infrared nanospectroscopy measurements37,38 have shown that the types and adsorption geometries of SOx species vary significantly due to morphological and structural heterogeneity among individual nanoparticles.7,36 Using a similar approach, we have mapped the distribution and adsorption strength of surface ligands on Au nanocrystals with well-defined facets.39 In this work, we employ atomic force microscopy infrared (AFM-IR) measurements to map the distribution of SOx species on Pt nanocrystals (NCs) with well-defined facets. We find that the majority of SOx species is adsorbed at a bidentate adsorption mode and reside on the more open facets and at inter-facet regions, whereas only a minority of SOx occupy the flat (111) facets. Annealing to 200 °C led to desorption from edge sites, accompanied by transition from bidentate into tridentate adsorption mode. Further annealing to 300 °C led to desorption of most of the SOx species, leaving residues near the center part of the nanocrystals, in which the SOx is strongly adsorbed in a bidentate mode. Experimental Pt NCs preparation: 15 nm thick Pt film was evaporated on a sapphire crystal (c-plane oriented, Gavish). NC were prepared by annealing the Pt-coated sapphire to 1000 °C for 2 minutes under N2 atmosphere. The sample was then immersed in 10 Mm solution of H2SO4 for 1 h at room temperature. Afterward, the sample was transferred to a vial on a hot plate pre-heated to 100 °C for 10 minutes in order to remove physiosorbed residues. Nano-IR measurements: AFM-IR measurements were performed at tapping mode using a nanoIR-3 (Bruker) setup equipped with a Bruker Hyperspectral QCL laser source (790-1950 cm−1), gold-coated Si probes with a nominal diameter of ~25 nm, resonance frequencies of 75±15 kHz, and spring constants of 1-7 N m−1. Averaged spectral acquisition time was 5 sec per spectrum with a spectral resolution of 2 cm−1. Focused-ion beam (FIB): Dual Beam FIB instrument (FEI Helios) was employed for lamella extraction and the resulting lamella was analyzed by high-resolution scanning-transmission electron microscopy (STEM) operated at 300 kV. X-ray photoelectron spectroscopy (XPS) measurements: Measurements were performed using Kratos AXIS Supra spectrometer (Kratos Analytical) with Al Kα monochromatic X-ray source (1486.6 eV). XPS spectra were acquired with a takeoff angle of 90° (normal to analyzer), pass energy of 20 eV and step size of 0.1 eV; vacuum condition in the chamber was 2·10-9 Torr. The binding energies were calibrated according to the C1s XPS peak position (B.E. = 285.0 eV). Results and discussion To identify the sensitivity of different atomic facets in Pt particles to sulfur poisoning, we focused our study on analyzing the adsorption and desorption of SOx species on Pt nanocrystals (NCs) with well-defined Wulff-like structures. The NCs were prepared by annealing a sapphire crystal coated with a 15 nm thick Pt film to 1000 °C for 2 minutes under an N2 atmosphere. The resulting NCs were then exposed to H2SO4 to induce surface poisoning, following recently published procedures.7,36 AFM topography images reveal NCs with lateral dimensions of 200-400 nm and height of up to 100 nm (Figure 1a). Exposure to H2SO4 did not lead to noticeable morphological changes. Two main NC morphologies were observed: elongated, hexagon-like NCs with distinctly longer opposing sides, yielding a more rectangular appearance (highlighted with a yellow circle in Figure 1a), and equilateral-like NCs resembling a rhombic structure (highlighted with a red circle in Figure 1a).40 To identify the crystallographic facets of the NCs, a lamella was extracted from the sample using focused ion beam (FIB) milling, and transmission electron microscopy (TEM) images of both the hexagonaland rhombic-like NCs were acquired (Figure 1c and 1d, respectively), along with their corresponding electron diffraction patterns (inset, Figure 1c and 1d). The hexagonal Pt nanocrystal exhibited a dominant (111) plane with adjacent (110) facets (Figure 1c). The smaller rhombic NC displayed multiple crystallographic orientations, including prominent (111), (001), and (113) planes (Figure 1d). The formation of these two distinct NC types is attributed to variations in local growth rates along different crystallographic directions, likely driven by subtle differences in the local defect density that influence facet stability. It is expected that these structural changes will impact the adsorption pattern of SOx.41–46 AFM-IR mapping was performed at 1100 cm−1 (Figure 1b), correlated to the S-O vibration of sulfate anion,47 on the same area imaged by AFM (Figure 1a). The IR signal intensity varied across the NCs, with higher signals detected at edges, steps, and the more open facets, while weaker signals appeared on the inner, flat (111) facets. These variations provide evidence for facet-dependent adsorption behavior and show the dominant role of nanocrystal structure in governing the local surface density of SOx species. Single NC analyses, including localized IR spectral measurements and AFM-IR mapping, were conducted to obtain high-resolution, sub-particle information on SOx adsorption, distribution, and desorption (Figure 2). An AFM topography image of a hexagon-like NC is shown in Figure Figure 1. Characterization of Pt NCs. (a) AFM topography image of Pt NCs following sulfur poisoning. Representative hexagonand rhombic-like NCs are circled in yellow and red, respectively. (b) AFM-IR map at 1100 cm−1, that was acquired on the same area that was imaged by AFM. HRTEM imaging of a cross section of hexagon NC (c) and rhombic NC (d), with their corresponding diffraction pattern (inset). 2a(i). IR spectra were acquired at the edge and the center of the NC (measurement positions are indicated by red and black colored dots in Figure 2a(i)), and are presented in redand blackcolored spectra, respectively, in Figure 2a(ii). The spectra exhibit a broad feature spanning at 1000-1280 cm−1. The spectrum acquired at the center of the NC shows a stronger contribution in the 1000-1100 cm−1 region. Figure 2. AFM-IR analysis of hexagon NC. AFM topography (i), localized IR spectra (ii) and AFM-IR mapping at 1100 cm−1 (iii) and 1200 cm−1 (iv), following surface poisoning by H2SO4. Measurements were conducted at room temperature (a(i)-a(iv)), after annealing to 50 °C (b(i)-b(iv)), 200 °C (c(i)-c(iv)) and 300 °C (d(i)-d(iv)). AFM topography images are shown in a(i), b(i), c(i) and d(i). IR spectra were acquired from the center (black-colored spectrum) and edge (red-colored spectrum) of a Pt NC and are shown in a(ii), b(ii), c(ii) and d(ii). The locations in which the IR measurements were acquired are indicated by black and red circles in the AFM topography images. The AFM images following annealing were acquired in different areas of the sample, and therefore different NCs were analyzed following each thermal treatment. Scale bar represents 200 nm. Sulfuric acid adsorbs on Pt primarily through bidentate and tridentate binding modes.7,48,49 The bidentate (2-fold) adsorption mode is energetically favored at undercoordinated sites such as edges, steps, and defects.44,50–53 Tridentate (3-fold) adsorption occurs when the sulfate species coordinates with three adjacent Pt atoms, a geometry which is mostly realized on atomically flat, close-packed terraces.7,11,36 It was demonstrated that sulfate is adsorbed on Pt(100) and Pt(110) with 2-fold geometry (C2v symmetry) and induce two IR bands around 1100 and 1200 cm−1, assigned to the stretching vibration of S-O bond in SO42− coordinated to Pt atoms and that of the uncoordinated S-O bond, respectively. Sulfate adsorption on Pt(111) gives a single IR band at around 1200 cm−1, which is assigned to the S-O stretching vibration of a 3-fold adsorption geometry.47 The spectrum measured at the edge of the NC showed a higher signal at ~1100 cm−1, correlated to a dominant presence of sulfuric acid with a bidentate adsorption geometry on this site (red colored spectrum, Figure 2a(ii)). The IR signal that was acquired at the center of the NC showed a similar amplitude at 1000-1250 cm−1, indicative that both bidentate and tridentate binding modes of sulfuric acid coexist on these sites (black colored spectrum, Figure 2a(ii)). AFM-IR maps were acquired at 1100 and 1200 cm−1 (Figures 2a(iii) and 2a(iv), respectively) to identify the spatial distribution of bidentate and tridentate adsorption modes across the facets of the NCs. The IR map at 1100 cm−1 (Figure 2a(iii)) shows strong signal intensities at the nanocrystal edges and on the side Pt(110) facets, with reduced intensity at the NC center. AFMIR mapping at 1200 cm−1 (Figure 2a(iv)) exhibits weaker signals, that were primarily localized at inter-facet regions and edge sites. The IR mapping support the results obtained in the localized IR spectra and show that there is a preference toward a 2-fold adsorption geometry at sites with low-coordinated surface atoms. Integration of the IR mapping and spectroscopy data reveals that the surface structure of Pt NCs governs the surface distribution of SOx. The spectral signature associated with the 2-fold (bidentate) adsorption mode of sulfate (~1100 cm−1) was detected across most regions of the NCs, with high signal variability across the NC. Higher signal intensity was observed on the side facets and at inter-facet regions, whereas lower intensity appeared on the flat Pt(111) terraces. The spectral signature corresponding to the 3-fold (tridentate) adsorption mode (~1200 cm−1) was weaker, and was characterized with local enhancement at inter-facet and the more open (110) facets. To obtain a quantitative measure of the spatial distribution of SOx species, the NC was segmented into concentric rings at increasing radial distances from its center. The IR signal amplitude within each ring was averaged and the averaged IR intensities, analyzed from the IR maps at 1100 and 1200 cm−1, were plotted as a function of the radial distance of each concentric ring from the NC center (Figures 3a and 3b, respectively). This analysis revealed a detectable spectral contribution at the NC center for the IR signal at 1100 cm−1 (black-colored curve, Figure 3a) and a pronounced ~50% enhancement in the IR intensity at a radial distance of approximately 75 nm, corresponding to inter-facet regions where SOx species preferentially accumulate. Quantitative analysis of the IR mapping at 1200 cm−1 (black-colored curve, Figure 3b) showed a lower and much more homogeneous signal, with a relatively small increase at the particle's rim. These results show that the distribution of SOx species at a tridentate binding mode is more consistent on the NC's surface, in comparison to the dominant bidentate mode that was mainly probed at inter-facets and side facets. Analysis of the IR signal at room temperature reveals a clear preference for SOx adsorption at bidentate adsorption mode on edge sites and on more open facets. The bidentate mode was consistently more prominent than the tridentate mode, and more heterogeneous in its dispersion on the NC surface. This indicates competitive adsorption at identical surface sites, with the energetically less demanding bidentate configuration dominating under ambient conditions. Figure 3. Quantitative analysis of AFM-IR maps. The AFM-IR maps shown in Figure 2 were analyzed by dividing each nanocrystal into concentric rings originating from its center. The AFM-IR signal within each ring was extracted and averaged to obtain the mean intensities at 1100 cm−1 (a) and 1200 cm−1 (b) as a function of the radial distance of the ring from the nanocrystal center. This analysis was performed for IR maps that were acquired at room temperature (black-colored curves), after annealing to 50 °C (red-colored curves), 200 °C (blue-colored curves) and 300 °C (green-colored curves). Diketone-Derived Surface Species. ACS Catal 2024, 14 (3), 1480–1493. https://doi.org/10.1021/acscatal.3c04774. (3) Chen, W.; Cao, J.; Fu, W.; Zhang, J.; Qian, G.; Yang, J.; Chen, D.; Zhou, X.; Yuan, W.; Duan, X. Molecular-Level Insights into the Notorious CO Poisoning of Platinum Catalyst. Angewandte Chemie - International Edition 2022, 61 (16). https://doi.org/10.1002/anie.202200190. (4) Kim, K. J.; Lee, Y. L.; Hong, G. R.; Ahn, S. Y.; Kim, B. J.; Lee, S. S.; Jeon, Y.; Roh, H. S. A Study on the Activity Recovery Behavior of Noble Metal Catalysts against Sulfur Poisoning. Catal Today 2024, 425. https://doi.org/10.1016/j.cattod.2023.114361. (5) Liu, S.; Wang, T.; Wu, X.; Li, J.; Liu, S.; Ran, R. Sulfur Poisoning and Thermal Regeneration of Silica-Alumina Supported Platinum Catalyst for Soot Oxidation. Surfaces and Interfaces 2025, 68. https://doi.org/10.1016/j.surfin.2025.106732. (6) Awad, M. I.; Saleh, M. M.; Ohsaka, T. Impact of SO2 Poisoning of Platinum Nanoparticles Modified Glassy Carbon Electrode on Oxygen Reduction. J Power Sources 2011, 196 (8), 3722–3728. https://doi.org/10.1016/j.jpowsour.2010.12.080. (7) Say, Z.; Kaya, M.; Kaderoğlu, Ç.; Koçak, Y.; Ercan, K. E.; Sika-Nartey, A. T.; Jalal, A.; Turk, A. A.; Langhammer, C.; Jahangirzadeh Varjovi, M.; Durgun, E.; Ozensoy, E. Unraveling Molecular Fingerprints of Catalytic Sulfur Poisoning at the Nanometer Scale with Near-Field Infrared Spectroscopy. J Am Chem Soc 2022, 144 (19), 8848– 8860. https://doi.org/10.1021/jacs.2c03088. (8) Wilburn, M. S.; Epling, W. S. Formation and Decomposition of Sulfite and Sulfate Species on Pt/Pd Catalysts: An SO 2 Oxidation and Sulfur Exposure Study. ACS Catal 2019, 9 (1), 640–648. https://doi.org/10.1021/acscatal.8b03529. (9) Gaudin, L. F.; Kang, M.; Bentley, C. L. Facet-Dependent Electrocatalysis and Surface Electrochemical Processes on Polycrystalline Platinum. Electrochim Acta 2023, 450. https://doi.org/10.1016/j.electacta.2023.142223. (10) Ungerer, M. J.; Van Sittert, C. G. C. E.; De Leeuw, N. H. Behavior of S, SO, and SO3on Pt (001), (011), and (111) Surfaces: A DFT Study. Journal of Chemical Physics 2021, 154 (19). https://doi.org/10.1063/5.0043501. (11) Hoshi, N.; Sakurada, A.; Nakamura, S.; Teruya, S.; Koga, O.; Hori, Y. Infrared Reflection Absorption Spectroscopy of Sulfuric Acid Anion Adsorbed on Stepped Surfaces of Platinum Single-Crystal Electrodes. Journal of Physical Chemistry B 2002, 106 (8), 1985–1990. https://doi.org/10.1021/jp012456o. (12) Mostany, J.; Herrero, E.; Feliu, J. M.; Lipkowski, J. Thermodynamic Studies of Anion Adsorption at Stepped Platinum(Hkl) Electrode Surfaces in Sulfuric Acid Solutions. Journal of Physical Chemistry B 2002, 106 (49), 12787–12796. https://doi.org/10.1021/jp026561p. (13) Aoki, M.; Shishido, T.; Morooka, T.; Nakanishi, T.; Masuda, T. Electrochemical Oxidative Desorption of Adsorbed Sulfur Species on (111) Surfaces of Single Crystals of Pure Pt and Pt-Based Bimetallic Alloys. Journal of Physical Chemistry C 2025, 129 (4), 2122–2131. https://doi.org/10.1021/acs.jpcc.4c06652. (14) Hossain, M. J.; Rahman, M. M.; Jafar Sharif, M. Preference for Low-Coordination Sites by Adsorbed CO on Small Platinum Nanoparticles. Nanoscale Adv 2020, 2 (3), 1245–1252. https://doi.org/10.1039/c9na00499h. (15) Rhee, C. K.; Kim, B. J.; Ham, C.; Kim, Y. J.; Song, K.; Kwon, K. Size Effect of Pt Nanoparticle on Catalytic Activity in Oxidation of Methanol and Formic Acid: Comparison to Pt(111), Pt(100), and Polycrystalline Pt Electrodes. Langmuir 2009, 25 (12), 7140–7147. https://doi.org/10.1021/la900204c. (16) Van Loon, J.; Kubarev, A. V.; Roeffaers, M. B. J. Correlating Catalyst Structure and Activity at the Nanoscale. ChemNanoMat. 2018, pp 6–14. https://doi.org/10.1002/cnma.201700301. (17) Groot, I. M. N. Investigation of Active Catalysts at Work. Acc Chem Res 2021, 54 (23), 4334–4341. https://doi.org/10.1021/acs.accounts.1c00429. (18) Choi, J. I. J.; Kim, T. S.; Kim, D.; Lee, S. W.; Park, J. Y. Operando Surface Characterization on Catalytic and Energy Materials from Single Crystals to Nanoparticles. ACS Nano. American Chemical Society 2020, pp 16392–16413. https://doi.org/10.1021/acsnano.0c07549. (19) Xu, W.; Kong, J. S.; Yeh, Y. T. E.; Chen, P. Single-Molecule Nanocatalysis Reveals Heterogeneous Reaction Pathways and Catalyticdynamics. Nat Mater 2008, 7 (12), 992–996. https://doi.org/10.1038/nmat2319. (20) Roeffaers, M. B. J.; De Cremer, G.; Libeert, J.; Ameloot, R.; Dedecker, P.; Bons, A. J.; Bückins, M.; Martens, J. A.; Sels, B. F.; De Vos, D. E.; Hofkens, J. Super-Resolution Reactivity Mapping of Nanostructured Catalyst Particles. Angewandte Chemie - International Edition 2009, 48 (49), 9285–9289. https://doi.org/10.1002/anie.200904944. (21) Dery, S.; Friedman, B.; Shema, H.; Gross, E. Mechanistic Insights Gained by High Spatial Resolution Reactivity Mapping of Homogeneous and Heterogeneous (Electro)Catalysts. Chemical Reviews. American Chemical Society 2023, pp 6003– 6038. https://doi.org/10.1021/acs.chemrev.2c00867. (22) Rikanati, L.; Dery, S.; Gross, E. AFM-IR and s-SNOM-IR Measurements of Chemically Addressable Monolayers on Au Nanoparticles. Journal of Chemical Physics 2021, 155 (20). https://doi.org/10.1063/5.0072079. (23) Mao, X.; Liu, C.; Hesari, M.; Zou, N.; Chen, P. Super-Resolution Imaging of NonFluorescent Reactions via Competition. Nat Chem 2019, 11 (8), 687–694. https://doi.org/10.1038/s41557-019-0288-8. (24) Wu, C. Y.; Wolf, W. J.; Levartovsky, Y.; Bechtel, H. A.; Martin, M. C.; Toste, F. D.; Gross, E. High-Spatial-Resolution Mapping of Catalytic Reactions on Single Particles. Nature 2017, 541 (7638), 511–515. https://doi.org/10.1038/nature20795. (25) Dery, S.; Mehlman, H.; Hale, L.; Carmiel-Kostan, M.; Yemini, R.; Ben-Tzvi, T.; Noked, M.; Toste, F. D.; Gross, E. Site-Independent Hydrogenation Reactions on Oxide-Supported Au Nanoparticles Facilitated by Intraparticle Hydrogen Atom Diffusion. ACS Catal 2021, 11 (15), 9875–9884. https://doi.org/10.1021/acscatal.1c01987. (26) Li, Z.; Kurouski, D. Plasmon-Driven Chemistry on MonoAnd Bimetallic Nanostructures. Acc Chem Res 2021, 54 (10), 2477–2487. https://doi.org/10.1021/acs.accounts.1c00093. (27) Friedman, B.; Giloni, L.; Gazit, O. M.; Gross, E. Nanoscale Chemical Imaging of Basic Sites Distribution on Catalytically Active Mg–Al Mixed Oxide Particles. Chemical and Biomedical Imaging 2025, 3 (8), 560–568. https://doi.org/10.1021/cbmi.5c00017. (28) Karreman, M. A.; Buurmans, I. L. C.; Geus, J. W.; Agronskaia, A. V.; Ruiz-Martínez, J.; Gerritsen, H. C.; Weckhuysen, B. M. Integrated Laser and Electron Microscopy Correlates Structure of Fluid Catalytic Cracking Particles to Brønsted Acidity. Angewandte Chemie - International Edition 2012, 51 (6), 1428–1431. https://doi.org/10.1002/anie.201106651. (29) Dery, S.; Kim, S.; Feferman, D.; Mehlman, H.; Toste, F. D.; Gross, E. Site-Dependent Selectivity in Oxidation Reactions on Single Pt Nanoparticles. Physical Chemistry Chemical Physics 2020, 22 (34), 18765–18769. https://doi.org/10.1039/d0cp00642d. (30) Dery, S.; Kim, S.; Haddad, D.; Cossaro, A.; Verdini, A.; Floreano, L.; Toste, F. D.; Gross, E. Identifying Site-Dependent Reactivity in Oxidation Reactions on Single Pt Particles. Chem Sci 2018, 9 (31), 6523–6531. https://doi.org/10.1039/c8sc01956h. (31) Ruiz-Martínez, J.; Beale, A. M.; Deka, U.; O’Brien, M. G.; Quinn, P. D.; Mosselmans, J. F. W.; Weckhuysen, B. M. Correlating Metal Poisoning with Zeolite Deactivation in an Individual Catalyst Particle by Chemical and Phase-Sensitive X-Ray Microscopy. Angewandte Chemie - International Edition 2013, 52 (23), 5983–5987. https://doi.org/10.1002/anie.201210030. (32) Kox, M. H. F.; Domke, K. F.; Day, J. P. R.; Rago, G.; Stavitski, E.; Bonn, M.; Weckhuysen, B. M. Label-Free Chemical Imaging of Catalytic Solids by Coherent Anti-Stokes Raman Scattering and Synchrotron-Based Infrared Microscopy. Angewandte Chemie - International Edition 2009, 48 (47), 8990–8994. https://doi.org/10.1002/anie.200904282. (33) Busch, O. M.; Brijoux, W.; Thomson, S.; Schüth, F. Spatially Resolving Infrared Spectroscopy for Parallelized Characterization of Acid Sites of Catalysts via Pyridine Sorption: Possibilities and Limitations. J Catal 2004, 222 (1), 174–179. https://doi.org/10.1016/j.jcat.2003.11.002. (34) De Cremer, G.; Bartholomeeusen, E.; Pescarmona, P. P.; Lin, K.; De Vos, D. E.; Hofkens, J.; Roeffaers, M. B. J.; Sels, B. F. The Influence of Diffusion Phenomena on Catalysis: A Study at the Single Particle Level Using Fluorescence Microscopy. In Catalysis Today; 2010; Vol. 157, pp 236–242. https://doi.org/10.1016/j.cattod.2010.04.035. (35) Bergwerff, J. A.; Visser, T.; Leliveld, B. R. G.; Rossenaar, B. D.; De Jong, K. P.; Weckhuysen, B. M. Envisaging the Physicochemical Processes during the Preparation of Supported Catalysts: Raman Microscopy on the Impregnation of Mo onto Al 2O3 Extrudates. J Am Chem Soc 2004, 126 (44), 14548–14556. https://doi.org/10.1021/ja040107c. (36) Kostan-Carmiel, M.; Theodoridis, A.; Eisenberg, H. R.; Stein, T.; Langhammer, C.; Gross, E. Nanoscale Analysis of Sulfur Poisoning Effects on Hydrogen Sorption in Single Pd Nanoparticles. ACS Nano 2025, 19 (42), 36969–36981. https://doi.org/10.1021/acsnano.5c08917. (37) Dazzi, A.; Prater, C. B. AFM-IR: Technology and Applications in Nanoscale Infrared Spectroscopy and Chemical Imaging. Chemical Reviews. American Chemical Society 2017, pp 5146–5173. https://doi.org/10.1021/acs.chemrev.6b00448. (38) Kurouski, D.; Dazzi, A.; Zenobi, R.; Centrone, A. Infrared and Raman Chemical Imaging and Spectroscopy at the Nanoscale. Chemical Society Reviews. Royal Society of Chemistry 2020, pp 3315–3347. https://doi.org/10.1039/c8cs00916c. (39) Rikanati, L.; Shema, H.; Ben-Tzvi, T.; Gross, E. Nanoimaging of Facet-Dependent Adsorption, Diffusion, and Reactivity of Surface Ligands on Au Nanocrystals. Nano Lett 2023, 23 (12), 5437–5444. https://doi.org/10.1021/acs.nanolett.3c00250. (40) Zhang, B.; Wang, D.; Hou, Y.; Yang, S.; Yang, X. H.; Zhong, J. H.; Liu, J.; Wang, H. F.; Hu, P.; Zhao, H. J.; Yang, H. G. Facet-Dependent Catalytic Activity of Platinum Nanocrystals for Triiodide Reduction in Dye-Sensitized Solar Cells. Sci Rep 2013, 3. https://doi.org/10.1038/srep01836. (41) Wongbua-ngam, P.; Veerasai, W.; Wilairat, P.; Kheowan, O. U. Model Interpretation of Electrochemical Behavior of Pt/H2SO4 Interface over Both the Hydrogen Oxidation and Oxide Formation Regions. Int J Hydrogen Energy 2019, 44 (23), 12108–12117. https://doi.org/10.1016/j.ijhydene.2019.03.076. (42) Huang, M. H.; Rej, S.; Hsu, S. C. Facet-Dependent Properties of Polyhedral Nanocrystals. Chemical Communications 2014, 50 (14), 1634–1644. https://doi.org/10.1039/c3cc48527g. (43) Han, B. C.; Miranda, C. R.; Ceder, G. Effect of Particle Size and Surface Structure on Adsorption of O and OH on Platinum Nanoparticles: A First-Principles Study. Phys Rev B Condens Matter Mater Phys 2008, 77 (7). https://doi.org/10.1103/PhysRevB.77.075410. (44) Hoshi, N.; Kuroda, M.; Ogawa, T.; Koga, O.; Hori, Y. Infrared Reflection Absorption Spectroscopy of the Sulfuric Acid Anion Adsorbed on Pd(S)-[n(111) × (111)] Electrodes. Langmuir 2004, 20 (12), 5066–5070. https://doi.org/10.1021/la036149g. (45) Zeng, X. M.; Huang, R.; Shao, G. F.; Wen, Y. H.; Sun, S. G. High-Index-Faceted Platinum Nanoparticles: Insights into Structural and Thermal Stabilities and Shape Evolution from Atomistic Simulations. J Mater Chem A Mater 2014, 2 (29), 11480– 11489. https://doi.org/10.1039/c4ta01731e. (46) Mastronardi, V.; Magliocca, E.; Gullon, J. S.; Brescia, R.; Pompa, P. P.; Miller, T. S.; Moglianetti, M. Ultrasmall, Coating-Free, Pyramidal Platinum Nanoparticles for High Stability Fuel Cell Oxygen Reduction. ACS Appl Mater Interfaces 2022, 14 (32), 36570–36581. https://doi.org/10.1021/acsami.2c07738. (47) Hoshi, N.; Sakurada, A.; Nakamura, S.; Teruya, S.; Koga, O.; Hori, Y. Infrared Reflection Absorption Spectroscopy of Sulfuric Acid Anion Adsorbed on Stepped Surfaces of Platinum Single-Crystal Electrodes. Journal of Physical Chemistry B 2002, 106 (8), 1985–1990. https://doi.org/10.1021/jp012456o. (48) Zhang, I. Y.; Zwaschka, G.; Wang, Z.; Wolf, M.; Campen, R. K.; Tong, Y. Resolving the Chemical Identity of H2SO4 Derived Anions on Pt(111) Electrodes: They’re Sulfate. Physical Chemistry Chemical Physics 2019, 21 (35), 19147–19152. https://doi.org/10.1039/c9cp03397a. (49) Gossenberger, F.; Juarez, F.; Groß, A. Sulfate, Bisulfate, and Hydrogen Co-Adsorption on Pt(111) and Au(111) in an Electrochemical Environment. Front Chem 2020, 8. https://doi.org/10.3389/fchem.2020.00634. (50) Groppo, E.; Rojas-Buzo, S.; Bordiga, S. The Role of In Situ/Operando IR Spectroscopy in Unraveling Adsorbate-Induced Structural Changes in Heterogeneous Catalysis. Chemical Reviews. American Chemical Society 2023, pp 12135–12169. https://doi.org/10.1021/acs.chemrev.3c00372. (51) Xia, Y.; Nelli, D.; Ferrando, R.; Yuan, J.; Li, Z. Y. Shape Control of Size-Selected Naked Platinum Nanocrystals. Nat Commun 2021, 12 (1). https://doi.org/10.1038/s41467-021-23305-7. (52) Lee, H.; Habas, S. E.; Kweskin, S.; Butcher, D.; Somorjai, G. A.; Yang, P. Morphological Control of Catalytically Active Platinum Nanocrystals. Angewandte Chemie - International Edition 2006, 45 (46), 7824–7828. https://doi.org/10.1002/anie.200603068. (53) Yeh, K. Y.; Restaino, N. A.; Esopi, M. R.; Maranas, J. K.; Janik, M. J. The Adsorption of Bisulfate and Sulfate Anions over a Pt(1 1 1) Electrode: A First Principle Study of Adsorption Configurations, Vibrational Frequencies and Linear Sweep Voltammogram Simulations. Catal Today 2013, 202 (1), 20–35. https://doi.org/10.1016/j.cattod.2012.03.011. (54) Chen, C. H.; Halford, A.; Walker, M.; Brennan, C.; Lai, S. C. S.; Fermin, D. J.; Unwin, P. R.; Rodriguez, P. Electrochemical Characterization and Regeneration of Sulfur Poisoned Pt Catalysts in Aqueous Media. Journal of Electroanalytical Chemistry 2018, 816, 138–148. https://doi.org/10.1016/j.jelechem.2018.03.015. (55) Smirnov, M. Y.; Kalinkin, A. V.; Pashis, A. V.; Prosvirin, I. P.; Bukhtiyarov, V. I. Interaction of SO2with Pt Model Supported Catalysts Studied by XPS. Journal of Physical Chemistry C 2014, 118 (38), 22120–22135. https://doi.org/10.1021/jp5069126. (56) Aoki, M.; Shishido, T.; Morooka, T.; Nakanishi, T.; Masuda, T. Electrochemical Oxidative Desorption of Adsorbed Sulfur Species on (111) Surfaces of Single Crystals of Pure Pt and Pt-Based Bimetallic Alloys. Journal of Physical Chemistry C 2025, 129 (4), 2122–2131. https://doi.org/10.1021/acs.jpcc.4c06652. (57) Lee, A. F.; Wilson, K. Sulfate-Enhanced Catalytic Destruction of 1,1,1-Trichlorethane over Pt(111). Journal of Physical Chemistry B 2006, 110 (2), 907–913. https://doi.org/10.1021/jp054658g. (58) Chen, C. H.; Halford, A.; Walker, M.; Brennan, C.; Lai, S. C. S.; Fermin, D. J.; Unwin, P. R.; Rodriguez, P. Electrochemical Characterization and Regeneration of Sulfur Poisoned Pt Catalysts in Aqueous Media. Journal of Electroanalytical Chemistry 2018, 816, 138–148. https://doi.org/10.1016/j.jelechem.2018.03.015.