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A1117
A no el pe spec i e on accele a ed deg ada ion s udies
o p o on exchange memb anes
S en Jo ano ic* (1), Robe Rameke (1,2), Jean-Pie e Poc (1,3), E a Joda (1),
And e Ka l (1), Rüdige A. Eichel (1,3), Jose G anweh (1,2)
(1) IET-1, Fo schungszen um Jülich GmbH, Jülich/Ge many;
(2) ITMC, RWTH Aachen Uni e si y, Aachen/Ge many;
(3) IPC, RWTH Aachen Uni e si y, Aachen/Ge many;
*Con ac co esponding au ho s: www.EFCF.com/Con ac Reques
Abs ac
Accele a ed deg ada ion s udies a e widely applied in esea ch on p o on exchange
memb anes (PEMs) o he in es iga ion o he o igins and mechanisms o pe o mance loss
o elec olysis o uel cell applica ions. In a nu shell, i is epo ed in li e a u e ha
deg ada ion in PEMs commonly occu s ollowing Fen on-like eac ions, whe e in si u o med
H2O2 eac s wi h ansi ion me al ca ions o p oduce adicals. These adicals hen al e he
ionome on a chemical le el by a acking pa icula ly i s pola side chains, causing a loss o
unc ional moie ies o p o on anspo [1]. Fas deg ada ion s udies mimic and p omo e
hese condi ions by subjec ing PEMs o high concen a ions o H2O2 and Fe2+ ca ions a
ele a ed empe a u es. Howe e , hese s udies o en exhibi disc epancies when compa ed
o deg ada ion occu ing du ing long- e m ope a ion [2].
The p esen ed wo k a emp s o elucida e hese disc epancies by i) add essing
inconsis encies in accele a ed deg ada ion and es ing p ocedu es, ii) s udying he
dependence o deg ada ion on PEM chemis y and s uc u e and iii) u ilizing bo h NMR
spec oscopy and SEM mic oscopy among o he echniques o a comp ehensi e pic u e.
He eby, solid-s a e magic angle spinning (MAS) NMR spec oscopy p o ides in o ma ion on
bo h chemical and local s uc u al ans o ma ions o he PEM, while SEM o e s conc e e
insigh s in o s uc u al changes on a mic oscopic scale.
The Fen on-like accele a ed deg ada ion expe imen s we e op imized o homogenei y and
e ec i eness by in oducing he ca aly ic i on cen e s in o he PEMs. Addi ionally,
in e e ences in he analy ical echniques we e minimized by ca e ul emo al o excess
eac an s a e accele a ed deg ada ion. The combined analy ical echniques e eal ha
chemical deg ada ion in PEMs is signi ican ly less p onounced han sugges ed in li e a u e,
al hough di e ences we e obse ed depending on he ype o PEM ma e ial. Mo eo e ,
o ganic adicals ha o m du ing Fen on-like eac ions could no be de ec ed by EPR
spec oscopy. Howe e , all samples expe ienced signi ican changes in he local s uc u e,
as indica ed by NMR elaxome y, and mic oscopic s uc u e, as illus a ed by SEM
echniques. Thus, ins ead o chemical deg ada ion, he PEM may be a ec ed on a s uc u al
le el by mechanical s ess due o mic oscopic gas pocke s and mac oscopic bubbles
o ming inside he gas impe meable ma e ial.
[1] L. Ghassemzadeh e al., J. Am. Chem. Soc. 135, 8181–8184 (2013).
[2] J. Mališ e al., In . J. Hyd ogen Ene gy 41, 2177–2188 (2016).
EFCF 2025: Low-Temp. Fuel Cells, Elec olyse s & H2 P ocessing 1 – 4 July 2025, Luce ne Swi ze land
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In oduc ion
G een hyd ogen is p edic ed o be a c i ical esou ce in a shi owa ds CO2-neu al economy,
bo h as an ene gy ca ie and an educ o he chemical and s eel indus y [1]. P oduc ion o
g een hyd ogen needs o be clean, e icien and scalable, hus ion exchange memb ane
wa e elec olysis u ilizing enewable ene gy sou ces a e conside ed a p omising echnology
[2]. While anion exchange memb ane wa e elec olyze s o e an encou aging pe spec i e
due o hei non- eliance on noble-me al ca alys s, hei cu en echnology- eadiness-le el
is no su icien o indus ial implemen a ion [3]. Al e na i ely, p o on exchange memb ane
wa e elec olyze s (PEMWE) o e he mos compelling combina ion o ma u i y,
pe o mance and e iciency. Howe e , he indi idual componen s o PEMWEs, such as
bipola pla es, ca alys s and p o on exchange memb anes (PEMs) a e associa ed wi h a
high CAPEX, and he e o e, a high du abili y o hese ma e ials is desi able [4]. As a cen al
piece o his echnology, a la ge numbe o du abili y s udies a e ocused on PEMs
hemsel es [5]. This s udy aims o e isi he accele a ed deg ada ion expe imen s on PEM
by co ela ing a ious analy ical echniques, o e ing bo h insigh s on memb ane chemis y
and s uc u e.
1. Scien i ic App oach
In li e a u e, deg ada ion o pe luo ina ed sul onic acid (PFSA) PEMs is assumed o occu
ia Fen on o Fen on-like eac ions. The e, H2O2 o med in si u a he ca hode due o oxygen
di usion eac s wi h ansi ion me al ions such as Fe2+/Fe3+ o o m adicals by educ i e
spli ing [6]:
Fe2+ +H2O2→Fe3+ +OH−+OH•
HOO• can hen o m by eac ion o he OH• adical wi h ano he H2O2, while H• occu due o
homoly ic spli ing o H2 a he pla inum ca alys o by eac ion o hyd ogen gas wi h o he
adicals ( ig. 1a). These adicals can hen a ack he PEM, pa icula ly a side chains,
b anching poin s and chain ends, causing a loss o unc ional moie ies ha a e esponsible
o p o on anspo . In accele a ed deg ada ion s udies hese eac ions a e mimicked by ex
si u exposu e o he PEMs o Fen on’s eagen s, i.e. an aqueous solu ion o Fe sal s and
H2O2 a ele a ed empe a u es ( ig 1b). Compa ed o in si u condi ions, he concen a ions
o ansi ion me al ions and hyd ogen pe oxide a e signi ican ly highe , and hus, accele a ed
eac ion a es a e p esumed o occu , deg ading he PEM in hou s o days as opposed o
mon hs and yea s [7].
An impo an di e en ia ion o PEM Fen on s udies in li e a u e is he me hod o in oducing
Fe ca ions. Fe sal s can be sol a ed in he aqueous solu ion wi h H2O2, hus o ming he
adicals bo h in he solu ion i sel and in he ea ed memb ane [8]. Al e na i ely, he sul onic
acid -SO3H g oups o he PEM can be exchanged wi h i on sal be o ehand, hus
accumula ing all i on cen e s inside he memb ane i sel [9]. Subsequen addi ion o aqueous
H2O2 solu ion will only lead o he o ma ion o adicals in he PEM i sel . The e o e, his la e
me hod o e s a mo e sophis ica ed, con olled, and p ecise Fen on deg ada ion echnique.
While mos accele a ed deg ada ion s udies a e pe o med on Na ion, a long-side-chain
ionome ( ig. 1c), indus ial applica ions a o sho -side-chain ionome s such as Aqui ion
( ig. 1d). Aqui ion is conside ed o be mo e du able compa ed o Na ion, as i s sho e side
chain o e s less oppo uni ies o adicals o a ack, ye p o iding lowe p o on conduc i i y
[10].
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Figu e 1: Schema ic o he p oposed Fen on eac ion mechanism in a PEMWE (a) and in
an ex -si u Fen on expe imen (b). A ow wid hs indica e he ela i e a es o he
associa ed anspo and chemical eac ions. Chemical s uc u e o Na ion (c) and
Aqui ion (d), whe e p oposed adical a ack poin s a e highligh ed in ed.
Published Fen on s udies on PEMs u ilize a wide a ie y o analy ical ools o in es iga e
deg ada ion occu ing in memb anes. A common me hod is he de e mina ion o luo ine
elease a es, o en by op ical emission spec oscopy, which p o ides in o ma ion abou
luo ine anions in he Fen on solu ion, as hese mus o igina e om he chemical deg ada ion
o he PFSA memb ane [11]. Howe e , while his echnique enables a semi-quan i a i e
e alua ion o he deg ee o deg ada ion, de ails on i s mechanisms and impac a e lacking.
The e o e, spec oscopic echniques such as solid s a e NMR, in a ed o Raman
spec oscopy a e exploi ed in o de o p o ide in o ma ion on he chemis y o he occu ing
eac ions [12,13]. In pa icula , all men ioned echniques enable he s udy o p e e en ial
poin s o adical a acks by de e mina ion o ela i e signal in ensi ies o -OCF2, -SO3H o
o he unc ional g oups. Howe e , epo s in li e a u e u ilizing hese spec oscopic me hods
exhibi dispa i ies on p e e en ial deg ada ion mechanisms o a es. In case o NMR, he
emaining i on ca ions in he PEM a e Fen on ea men in some s udies con ibu e o hese
unce ain ies, as hei pa amagne ic p ope ies signi ican ly a ec he NMR esponse o he
sample [12]. Mic oscopy, in pa icula scanning elec on mic oscopy (SEM), a e ano he
powe ul ool o he examina ion o PEMs a e accele a ed deg ada ion es s. [14] He e, all
epo s ag ee on he se e e mo phological changes o memb anes a e Fen on ea men ,
wi h he o iginally smoo h su aces becoming oughened by he de elopmen o ea s o
pinholes. The ex en o hese mo phological changes s ongly depends on he deg ada ion
p o ocol. While hese e ec s a e a ibu ed o he desc ibed adical a ack mechanisms, o
ou knowledge no co ela ed s udy linking hese obse a ions o spec oscopic da a is
published.
This wo k aims o p o ide a new pe spec i e on Fen on based accele a ed deg ada ion
s udies o PEMs by es ablishing a b oad and co ela ed ange o analy ical esul s including
spec oscopy, mic oscopy, di ac ion and elec ochemical me hods, and by e alua ing he
e ec i eness o Fen on expe imen s o he pu pose o p obing PFSA PEM deg ada ion.
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2. Expe imen s/Calcula ions/Simula ions
Fen on deg ada ion expe imen s
The p is ine Na ion 115 memb anes we e pu chased om Fuma ech BWT GmbH
(Bie igheim-Bissingen, Ge many). The Aqui ion E98-15S memb anes we e pu chased om
MSE Supplies LLC (Tucson, A izona, USA). Fo p e ea men , he samples we e exposed
o 0.5 M H2SO4 solu ion o 5 h a 80 °C. Fo neu aliza ion, he samples we e hen ea ed
wice o 1 h in deionized wa e (DI) wa e a 80 °C. A e each ea men s ep, he su ace
o he samples was insed wi h DI wa e .
Fo he accele a ed s ess es , he samples we e i s moun ed in a home-build sample
holde and hen ea ed in 1 N H2SO4 solu ion wi h 1 M FeSO4 o 5 h a 80 °C. The sample
holde and he su ace o he memb ane we e hen ca e ully insed wi h DI wa e and
ans e ed in o a 80 °C H2O2 solu ion (30 % / in wa e ) o he speci ied Fen on eac ion
ime. A e each 24 h, he H2O2 solu ion was eplaced by a esh H2O2 solu ion.
To emo e he ca aly ic i on a e he Fen on eac ion, he samples we e pos - ea ed wice
in 0.5 M H2SO4 solu ion o 1 h a 80 °C. Fo he second epe i ion, 7 mg Na-EDTA was
added pe 50 mg memb ane ma e ial o addi ional e ec i eness o i on emo al A e wa ds,
he samples we e washed wo imes in esh DI wa e a 80 °C o 1 h. A e each washing
s ep, he samples we e insed wi h DI wa e .
19F MAS NMR
The 19F magic angle spinning (MAS) NMR spec a we e eco ded on a B uke A ance III
HD spec ome e using a B uke Ascend 400WB (9.6 T, 400 MHz o 1H) magne and a dual
channel 1.3 mm MAS p obe (PH MASDVT 400W1 BL1.3 N-P/H NO-I/E). The expe imen
empe a u e was main ained a 25 °C, and he MAS spinning equency was se o 30 kHz.
The 19F cen e equency was adjus ed o ma ch he (CF2)n signal a -121 ppm, using a
spec al wid h o 199.2 ppm. The ecycle delay was se be ween 1 and 10 s, depending on
he T1 elaxa ion ime o he espec i e sample. The 90° pulse leng h was se o 1.1 – 1.2 µs
a 45 W adio equency powe .
The aw da a we e p ocessed using a cus om Py hon sc ip (Py hon e sion 3.9). Spec al
i ing was pe o med using Lm i ( e sion 1.3.3.). Pseudo-Voig unc ions we e u ilized o
he i ing o he indi idual peak componen s. The de ia ion o he i om he da a poin s
was kep below 1.5% o he ampli ude o he mos in ense signal.
The ela i e in ensi ies o he SCF2/CCF2 and OCF2 signal wi h espec o he (CF2)n signal
we e calcula ed om he i ed esul s and no malized o he in eg al o he (CF2)n. E o s o
he ela i e signal in ensi ies we e calcula ed ia Gaussian e o p opaga ion. Fo his
pu pose, he oo mean squa e (RMS) o he noise pe ppm, 𝑛ppm, was de e mined be ween
he ange o -100 ppm and -90 ppm. Using
𝑛signal =4 𝜎 𝑛ppm
(6)
he e o 𝑛signal o each signal in he second con idence in e al was calcula ed whe e 𝜎 is
i s hal wid h a hal maximum in uni s o ppm.
ATR-FTIR spec oscopy
A enua ed o al e lec ion Fou ie ans o m in a ed spec oscopy (ATR-FTIR) spec a we e
collec ed a ambien empe a u e on a FT-IR spec ome e (Spec um 3, FT-IR/FIR
Spec ome e , Pe kin Elme , UK) equipped wi h he p op ie a y Uni e sal ATR Sampling
accesso y. Each spec um was eco ded om 650 o 4000 cm⁻¹ a 4 cm⁻¹ esolu ion and
was an a e age o 32 scans. Fo each memb ane (p is ine and Fen on- ea ed), i e di e en
su ace loca ions we e measu ed. The aw da a we e p ocessed using a cus om Py hon
sc ip ( 3.11.5).
Raw ansmi ance (%) da a we e con e ed o abso bance ia:
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Abso bance= −log10(T ansmission
100 )
(8)
hen baseline-co ec ed using an asymme ic leas -squa es algo i hm. Each baseline-
co ec ed spec um was no malized o he CF₂ symme ic s e ching band, νs(CF₂), a 1143
cm⁻¹ o he PTFE backbone. The i e no malized spec a pe sample we e a e aged o yield
a ep esen a i e spec um, om which mean no malized peak in ensi ies we e ex ac ed
and plo ed e sus Fen on- ea men ime o e alua e side-chain al e a ions.
Scanning Elec on Mic oscopy (SEM) and C oss-Sec ion P epa a ion
All imaging and c oss‐sec ioning we e pe o med on a Plasma Focused Ion Beam (FIB)-
SEM (TESCAN AMBER X, TESCAN). Memb anes we e moun ed on aluminium s ubs and
d ied a ambien condi ions o 24 h, hen degassed in he mic oscope chambe o 30 min.
Su ace mic og aphs we e acqui ed a 2 kV accele a ing ol age and 0.3 nA beam cu en
using an E e ha –Tho nley (E-T) seconda y‐elec on de ec o . C oss‐sec ions we e
p epa ed by ench milling wi h a 30 keV, 25 nA Xe⁺ beam, ollowed by polishing a 30 kV/5
nA, and imaged unde he same 2 kV/0.3 nA condi ions.
Quan i a i e bubble analysis was pe o med in ImageJ ( 1.54p) by coun ing all isible
bubbles wi hin a 3 mm ield o iew. When densi ies exceeded ~120 bubbles, coun s we e
limi ed o a ep esen a i e subse o 50–120 o main ain accu acy. The esul ing adius da a
we e p ocessed in Py hon and plo ed as a illed ke nel-densi y o e lay (no ex apola ion)
using seabo n, wi h each eac ion ime ende ed in a dis inc colo .
3. Resul s
The ela i e in ensi ies o he indi idual Na ion and Aqui ion g oups as a unc ion o Fen on
ea men du a ion can be di ec ly acked ia 19F MAS NMR ( igs. 2a and 2b, espec i ely).
No e ha he ela i e in ensi ies a e no malized o he in eg al o he (CF2)n backbone signal
and, he e o e, only p e e en ial adical a acks can be obse ed. Based on hese esul s,
wo conclusions can be d awn. Fi s , Na ion is signi ican ly mo e p one o p e e en ial adical
a acks o he side chain in Fen on deg ada ion compa ed o Aqui ion, which is indica ed by
he dec ease o Na ion SCF2/CCF2 signal as a unc ion o Fen on ea men ime. Fo he
same expe imen du a ion, only a mino dec ease can be obse ed o Aqui ion. Mo eo e ,
as he loss o he o he side chain and b anching poin signals is signi ican ly less
p onounced o e en non-exis en , i can be concluded ha he dec ease o he SCF2/CCF2
p edominan ly s ems speci ically om he scisso ing o he sul onic acid g oup. Thus, Fen on
adical a acks p e e en ially occu om he end o he side chain a he unc ional moie y o
he ma e ial.
Fo he second conclusion, he ela i e dec ease o unc ional g oups is mino , in pa icula
o Aqui ion. This is unexpec ed as o he s udies epo signi ican deg ada ion o PEMs
e en a e 24 h due o he ele a ed adical concen a ions du ing Fen on ea men . We
p opose ha hese obse a ions o igina e om he absen s ep o i on emo al a e Fen on
ea men , as i on signi ican ly a ec s line wid hs and shapes in NMR. The i ing o hese
al e ed signals can lead o subs an ially al e ed esul s, as could be con i med in ou own
es ing. The e o e, o ensu e ha he i ing esul s in his s udy a e no a ec ed by esidue
i on e en a e washing, he e ec i eness o he i on emo al wi h H2SO4 and EDTA we e
con i med wi h EPR spec oscopy, whe e no signa u e o i on was obse ed.
The NMR esul s we e con i med by ATR-IR spec oscopy expe imen s o Fen on- ea ed
Na ion and Aqui ion ( igs. 2c and 2d, espec i ely), whe e no signi ican dec ease o he
pola side chain signals could be obse ed wi hin ma gins o e o s. A a close look,
howe e , he e we e disc epancies o Na ion be ween he cons an ATR-IR -SO3H band
and he sligh ly diminishing NMR SCF2/CCF2 signal. These wo obse a ions can be b ough
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in line by conside ing ATR-IR as a highly su ace sensi i e me hod, while NMR is bulk
sensi i e. The di e ences in signal e olu ion he e o e indica e ha he exchange Fen on
me hod, whe e he ca aly ic i on cen e s a e in oduced in o he memb ane i sel , has a
signi ican ly highe impac on he inne bulk olume compa ed o he su ace o he PEM.
Figu e 2: Rela i e signal in ensi ies o SCF2/CCF2 ( ed), he OCF2 (g ey), he CFb (o ange)
and CFs ( eal, Na ion speci ic) g oups ob ained om 19F MAS (30 kHz spinning equency)
measu emen s o Na ion (a) and Aqui ion (b) as a unc ion o Fen on exposu e ime,
no malized o he (CF2)n backbone signal. No malized ATR-IR peak in ensi ies o he 969
cm⁻¹ (C–O–C symme ic s e ch mode), 982 cm⁻¹ (addi ional Na ion-speci ic C–O–C
symme ic s e ch mode), and 1056 cm⁻¹ (SO₃⁻ symme ic s e ch) bands plo ed as a
unc ion o Fen on exposu e ime o Na ion (c) and Aqui ion (d).
As ea men o PEMs in Fen on’s eagen s only p oduces limi ed deg ada ion on a chemical
scale o his s udy, SEM was u ilized o e alua e he impac on memb ane mo phology.
He e, he changes we e signi ican ly mo e p onounced and could e en be obse ed by eye,
as he once anspa en memb anes u n opaque. Zooming in wi h SEM, he smoo h and
ea u eless su ace o p is ine Na ion is co e ed wi h su ace bubbles e en a e 30 minu es
( ig. 3a), which change in adius and densi y as a unc ion o eac ion ime ( ig. 3c).
Speci ically, a e 30 minu es o Fen on exposu e, su ace bubbles wi h adii o ~0.06–0.18
mm eme ged. A 90 minu es, bubble densi y inc eased clea ly while he size dis ibu ions
na owed and shi ed owa ds smalle bubbles. Smoo h egions pe sis ed be ween isola ed
bubbles. A e 1 day, smoo h a eas anished as bubbles g ew and coalesced in o i egula ,
me ged ea u es lacking disc e e bo de s. This end con inued o 3 days o eac ion ime.
In bo h cases, he co esponding his og ams in Figu e 3c b oaden subs an ially, wi h
measu ed adii exceeding ~0.20 mm. Howe e , because bubbles coalesced, mo phologies
lacked well-de ined edges, hence ue bubble sizes a longe exposu es a e likely
unde es ima ed.
Aqui ion showed a simila end ( ig. 3b). Howe e , su ace bubbles exhibi ed smalle adii
a signi ican ly na owe size dis ibu ion. In addi ion, he bubbles esis ed me ging in o la ge
s uc u es, e en unde p olonged exposu e ime.
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Figu e 3: Fen on‐induced blis e ing in PFSA memb anes. (a, b) Rep esen a i e SEM
mic og aphs o (a) Na ion and (b) Aqui ion a e independen Fen on ea men o 0 min
(p is ine), 30 min, 90 min, 1 day and 3 days. In bo h polyme s, blis e densi y isibly ises
wi h exposu e ime. (c, d) Ke nel‐densi y es ima ion o blis e adii measu ed om he
co esponding SEM images o (c) Na ion and (d) Aqui ion a eac ion imes o 30 min
(pu ple), 60 min (ligh pu ple), 90 min (magen a), 1 day ( ed) and 3 days (o ange).
A close inspec ion o he su ace p o usions e eals ou cha ac e is ic mo phologies: in ac
ounded bubbles, bu s -cap bubbles, sli -like ea s, and collapsed “ olcano” s uc u es.
C oss-sec ional cu s expose unde lying oids o hese ea u es. O e all, his sugges s an
inside‐ou , gas‐e olu ion–d i en o igin o bo h Na ion and Aqui ion, whe ein in e nal gas
gene a ion pushes h ough he polyme o c ea e hese su ace p o usions du ing Fen on -
ea men .
The esul s a e suppo ed by 19F T1 elaxa ion NMR s udies, which indica e signi ican
changes in local s uc u e due o a non- i ial e olu ion o T1 as a unc ion o eac ion ime.
He e, i can be highligh ed ha o Na ion, T1 is a ec ed mainly a p olonged exposu e imes,
while o Aqui ion, a s ong dec ease o T1 is al eady obse ed a e 24 hou s.
In conclusion, hese obse a ions we e channeled in o a e isi ed model o ex si u Fen on
deg ada ion expe imen s ha is depic ed in ig. 4. Fi s , Fe2+ is in oduced in o he memb ane,
which binds o he SO3H g oups o he PEM ( ig. 4a). As H2O2 is added o he sys em, HO•
a e o med a he Fe2+ cen e s by con e ing i o Fe3+ in a as eac ion ( ig. 4b). P e ious
s udies assumed a subsequen a ack o he adicals p edominan ly a he SO3H side chains,
leading o a loss o unc ionali y ( ig. 4c). While hese eac ions occu , he indings in his
s udy indica e ha his p ocess is slow. Howe e , long pola side chains such as he ones
p esen in Na ion seem o a o adical a acks compa ed o sho side chain PEMs.
EFCF 2025: Low-Temp. Fuel Cells, Elec olyse s & H2 P ocessing 1 – 4 July 2025, Luce ne Swi ze land
h ps://doi.o g/10.5281/zenodo.17244133 A1117 Page 8/9
Ad e sely, a subs an ially highe impac occu ed on he mo phology o he memb ane. This
is co ela ed o he as o ma ion o O2 gas molecules by Fe3+ ca alyzed eac ion o OH• wi h
H2O2 ( ig. 4d), ha , a su icien p oduc ion a es, c ea e gas oids in he gas-impe meable
PEMs. This causes p essu e induced comp ession inside he memb ane, which d i es
changes in sho ange o de o he memb ane, such as c ys alline and amo phous egions
( ig 4e).
Figu e 4: G aphical illus a ion o he p e e ed deg ada ion pa hway du ing he Fen on-
ea men . (a) Du ing p e- ea men wi h an acidic FeSO₄ solu ion, Fe²⁺ ions a e
coo dina ed by SO₃-g oups, inc easing cha ge ans e conduc i i y. (b) The addi ion o a
30% H₂O₂ solu ion o ms hyd oxyl (HO•) adicals while Fe²⁺ is oxidized o Fe³⁺. (c) These
highly eac i e adicals a ack he ionome , deg ading sul onic acid g oups, as sugges ed
by 19F MAS-NMR and ATR-IR da a. (d) Howe e , he Fen on- ea men appea s o impac
he mo phology o he ionome mo e han i s chemical s uc u e. Oxygen molecules a e
o med in se e al side eac ions o he Fen on mechanism, o example h ough he
spli ing o hyd ope oxyl (HOO•) adicals wi h Fe³⁺. (e) I oxygen is o med a high eac ion
a es, i canno escape he ionome ’s hyd ophilic po e s uc u e immedia ely.
Consequen ly, gas oids o m in he po es, inc easing hei size as mo e oxygen is
p oduced. The solid phase o he memb ane is comp essed by he p essu e o igina ing
om he gas oids, a ec ing he diso de and c ys allini y wi hin he ionome .
Re e ences
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and Sus ainable Ene gy Re iews (111), 2019.
[6] E. Wallnö e -Og is e al., A e iew on unde s anding and iden i ying deg ada ion
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de elopmen , and esea ch. In e na ional Jou nal o Hyd ogen Ene gy (65), 2024.
[7] S. H. F ensch e al., Impac o i on and hyd ogen pe oxide on memb ane deg ada ion
o polyme elec oly e memb ane wa e elec olysis: Compu a ional and expe imen al
in es iga ion on luo ide emission. Jou nal o Powe Sou ces (420), 2019.
[8] T. Kinumo o e al., Du abili y o pe luo ina ed ionome memb ane agains hyd ogen
pe oxide. Jou nal o Powe Sou ces (158), 2006.
[9] A. Bosnjako ic e al., Na ion Pe luo ina ed Memb anes T ea ed in Fen on Media:
Radical Species De ec ed by ESR Spec oscopy. Jou nal o Physical Chemis y B
(108), 2004.
[10] S- Shahgaldi e al., The impac o sho side chain ionome on polyme elec oly e
memb ane uel cell pe o mance and du abili y. Applied Ene gy (217), 2018.
[11] V. P abhaka an e al., In es iga ion o PEM Deg ada ion Kine ics and Deg ada ion
Mi iga ion Using In Si u Fluo escence Spec oscopy and Real-Time Moni o ing o
Fluo ide-Ion Release. ECS T ansac ions (50), 2013.
[12] L. Ghassemzadeh e al., E alua ing chemical deg ada ion o p o on conduc ing
pe luo osul onic acid ionome s in a Fen on es by solid-s a e 19F NMR spec oscopy.
Jou nal o Powe Sou ces (196), 2011.
[13] F.C. Teixei a e al., Chemical s abili y o new na ion memb anes doped wi h
bisphosphonic acids unde Fen on oxida i e condi ions. In e na ional Jou nal o
Hyd ogen Ene gy (48), 2023.
[14] S. Kundu e al., Compa ison o wo accele a ed Na ion™ deg ada ion expe imen s.
Polyme Deg ada ion and S abili y (93), 2008.
Keywo ds: EFCF2025, H2, LowTemp. Fuel Cells & Elec olyse s, PEMs, deg ada ion,
Fen on, analy ics
Rema k: This wo k is licensed unde C ea i e Commons A ibu ion 4.0 In e na ional
