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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A0806=A1811
Dynamic Ope a ion o an AEM Elec olysis Sys em
Augus Gladik* (1,3), Ma c Riedel (1), Rüdige -A. Eichel (2,3)
(1) Robe Bosch GmbH, Renningen/Ge many;
(2) Fundamen al Elec ochemis y (IET-1), Ins i u e o Ene gy Technology,
Fo schungszen um Jülich GmbH, Jülich/Ge many;
(3) Chai o Ma e ials and P ocesses o Elec ochemical Ene gy S o age and Con e sion,
RWTH Aachen Uni e si y, Aachen/Ge many;
*Con ac co esponding au ho s: www.EFCF.com/Con ac Reques
Abs ac
Today, alkaline elec olysis (AEL) and p o on exchange memb ane (PEM) elec olysis
ep esen he mos ele an low empe a u e elec olysis echnologies. Howe e , anion
exchange memb ane (AEM) elec olysis is eme ging as a p omising echnology ha
combines he ad an ages o he alkaline en i onmen wi h he ad an ages o using an ac i e
memb ane ins ead o a diaph agm. Fo ins ance, bo h he use o a e i idium in he anode
and luo ine-con aining memb anes can be a oided wi h his echnology.
As he sha e o enewable ene gy in he elec ici y g id is inc easing, he luc ua ion o he
elec ici y supply is ge ing mo e p ominen . Consequen ly, he abili y o an elec olyze o
adap and mee hese equi emen s o ansien ope a ion while main aining a low
deg ada ion is o g ea impo ance o he iable success o hyd ogen p oduc ion in u u e
ene gy sys ems.
This s udy examines he expe imen al s a -s op ope a ion o an AEM elec olysis s ack
ope a ed in a sys em en i onmen . The measu emen s in ol e pa ame e a ia ion and he
op imiza ion o he cold s a p ocedu e o dec ease s a -up du a ion while main aining low
deg ada ion. Analyses wi h 150 cold s a s pe pa ame e se e eal ha he deg ada ion o
he AEM elec olysis s ack co ela es wi h he s eepness o he cu en slope du ing he
ol age amp-up. By applying a gen le s a p ocedu e, a deg ada ion o 10 µV s a -1 could
be obse ed, while applying a subs an ially as e cu en inc ease esul s in deg ada ion
a es o 26 µV s a -1 leading o a signi ican ly dec eased li e ime o he elec olyze . The
p ima y objec i e is o de elop an in-dep h unde s anding o he capabili ies and limi a ions
o an AEM elec olysis sys em ega ding he en i e ansien ope a ion including s a and
s op p ocedu es.
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
The global ansi ion owa ds sus ainable ene gy sou ces in ensi ies he ocus on e icien
hyd ogen p oduc ion echnologies. G een hyd ogen, p oduced ia wa e elec olysis, is a
i al componen in deca bonizing a ious sec o s, including indus y, ene gy s o age and
anspo applica ions. Among he di e en elec olysis echnologies, anion exchange
memb ane wa e elec olysis (AEMWE) eme ges as a p omising me hod due o i s
ad an ages, such as ope a ing in alkaline condi ions and elimina ing he need o a e and
cos ly i idium. AEMWE employs a hyd oxide ion-conduc ing memb ane, allowing o
di e en ial p essu e ope a ion and enhancing esilience o p essu e luc ua ions. This
capabili y is pa icula ly ad an ageous in applica ions wi h enewable ene gy sou ces, such
as wind and sola . The in e mi en na u e o hese ene gy sou ces necessi a es
elec olyze s ha can ope a e in ansien condi ions, esponding o luc ua ing powe inpu s
[1]. Cold s a beha io , de ined as he pe o mance o an elec olyze s a ing om ambien
empe a u e and ze o ol age, is an impo an aspec o ansien ope a ion. I is hus c i ical
o he e ec i e in eg a ion o AEMWE sys ems in o enewable ene gy g ids. Unde s anding
he impac o a ious s a ing pa ame e s - such as ol age amp-up a es, a ge ol ages,
and hea ing s a egies - on he cold s a p ocess and subsequen deg ada ion is essen ial
o op imizing sys em pe o mance and longe i y. This s udy in es iga es hese ac o s
h ough a se ies o expe imen s designed o quan i y hei e ec s on he cold s a beha io
and deg ada ion o an AEMWE s ack.
1. Expe imen al
1.1. Tes Bench
The expe imen s a e conduc ed using a cus om-buil AEMWE sys em es bench, which
includes a s ack o 19 cells, each wi h an ac i e a ea o app oxima ely 60 cm². This esul s
in a s ack powe ou pu o app oxima ely 2.2 kW. The anion exchange memb ane u ilized is
100 µm hick and inco po a es qua e na y ammonium g oups o ionic conduc i i y. The
anode is u ilizing a Co₃O₄-based ca alys , while he ca hode employs a pla inum ca alys .
The sys em is designed o ope a e unde ambien p essu e on he anode side and a 30 ba
on he ca hode side. On he anode side, po assium hyd oxide (KOH) elec oly e is ci cula ed
by a cen i ugal pump a a low a e o 2.5 mL cm⁻² min⁻¹ and a empe a u e o 50 °C. The
es bench is equipped wi h a ious senso s and con ol sys ems o moni o and adjus
ope a ional pa ame e s, including empe a u e, p essu e, and cu en densi y. The se up
also includes a da a acquisi ion sys em o eco d eal- ime measu emen s o each senso .
Elec ochemical impedance spec oscopy (EIS) o up o 17 indi idual cells is possible.
1.2. S a P ocedu e
The s a p ocedu e is di ided in o ou dis inc phases: Condi ioning, ol age amp-up,
empe a u e-d i en cu en inc ease, and empe a u e inc ease.
Condi ioning phase: Ini ially, he elec oly e pump and elec ic hea e a e ac i a ed o 90
seconds o ensu e p ope hyd a ion o he memb ane. This s ep is c ucial o c ea e cons an
condi ions p io o each s a ing p ocess o high quali y measu emen s bu can po en ially
be sho ened o omi ed o indus ial applica ions.
Vol age amp-up: Following condi ioning, he ol age is apidly inc eased o he e e sible
cell ol age o 1.23 V wi hin 0-5 seconds. A e eaching he e e sible ol age, he ol age
is g adually amped up o he a ge ol age, which a ies be ween 1.7 V and 2.1 V, o e a
speci ied amp-up du a ion ( anging om 12 o 240 seconds).
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Tempe a u e-d i en cu en inc ease: Once he a ge ol age is eached, he sys em
ope a es in a po en ios a ic mode, allowing he cu en o inc ease o he a ge ed cu en
densi y o 0.85 A cm⁻² due o he empe a u e ise in he sys em.
Tempe a u e inc ease: A e achie ing he a ge cu en densi y, he elec ic hea e is
u ned o , and he sys em con inues o ope a e in a gal anos a ic mode. The empe a u e
is allowed o ise o he nominal ope a ing empe a u e o 50 °C, a which poin he
elec olyze is conside ed o be in s eady-s a e ope a ion.
1.3. Deg ada ion Analysis
Deg ada ion analyses a e pe o med h ough epe i i e s a -s op cycles, wi h each cycle
consis ing o a s a p ocedu e (see sec ion 1.2) ollowed by 10 minu es o ull load ope a ion.
The cu en is hen educed linea ly o ze o, and he AEMWE s ack is cooled o ambien
empe a u e. The s ack ol age is in en ionally discha ged o 0 V o simula e a cold s a
a e ex ended down ime.
EIS is employed o moni o changes in cell esis ance h oughou he deg ada ion analysis.
EIS measu emen s a e conduc ed a a ious poin s du ing he s a -s op cycles o assess
he impac o ope a ional pa ame e s on he elec ochemical pe o mance o he AEMWE
s ack. The da a ob ained om EIS a e analyzed using equi alen ci cui models as desc ibed
by Gladik e al. [2] o quan i y he esis i e and capaci i e componen s o he cell, p o iding
insigh s in o he deg ada ion phenomena.
2. Resul s and Discussion
2.1. Cold S a Beha io
Cold s a s a e pe o med as desc ibed in sec ion 1.2 o de e mine he in luence o amp-up
du a ion, a ge ol age, and hea ing s a egy on he s a du a ion.
The esul s indica e ha he pa ame e s in luence he cold s a beha io o he AEMWE
sys em in a ying deg ees. A as e amp-up du a ion (12 s) esul s in a educed s a
du a ion o app oxima ely 454 s, compa ed o 606 s o a slowe amp-up (240 s). Howe e ,
as e amp-ups also lead o inc eased ol age o e shoo s o single cells inside he s ack
and he e ec on he s a du a ion is limi ed. The a ge ol age du ing he s a p ocedu e
plays a c ucial ole. Inc easing he a ge ol age om 1.7 V o 1.9 V educes he s a
du a ion by 74 %, demons a ing ha highe ol ages acili a e quicke ansi ions o ull load
ope a ion. Howe e , highe ol ages a e gene ally associa ed wi h inc eased deg ada ion
a es [3]. Hea ing wi h an ex e nal hea e educes he s a -up du a ion. Howe e , he
empe a u e inc ease in he sys em emains he mos sluggish p ocess du ing he s a ing
p ocess and he ins alled powe o he ex e nal hea e is gene ally limi ed by economic
conside a ions. The s udy shows ha he ene gy equi emen o he hea e is always highe
han he ene gy sa ing due o he highe ope a ing empe a u e o he elec olyze . The
compa a i ely slow empe a u e inc ease o he sys em can ul ima ely only be a oided by
selec ing a highe a ge ol age.
2.2. Deg ada ion Analysis
As pa o he deg ada ion analyses, he a ge ol age is a ied be ween 1.9 V and 2.1 V
and he amp-up du a ion be ween 12 s and 120 s in o de o analyze deg ada ion e ec s
caused by as s a ing p ocesses. Fo each pa ame e se , 150 cold s a s a e pe o med
(Fig. 1). The inc ease in cell ol age is shown as deg ada ion pe s a , wi h he lowes
deg ada ion o 10 µV s a -1 occu ing a he lowe a ge ol age (1.9 V) and he longe
amp-up du a ion (120 s). A a ge ol age o 2.1 V and a amp-up du a ion o 120 s esul s
in a deg ada ion o 11 µV s a -1. A a ge ol age o 1.9 V and a amp-up du a ion o 12 s
esul s in a deg ada ion a e o 15 µV s a -1. The highes deg ada ion o 26 µV s a -1 occu s
a a highe a ge ol age (2.1 V) and sho e amp-up du a ion (12 s). I can be seen ha
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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bo h a highe a ge ol age and a sho e amp-up du a ion lead o a highe deg ada ion
a e. A mo e in-dep h analysis o he da a e eals a dependence o he deg ada ion on he
maximum inc ease in cu en du ing he s a ing p ocess [2]. These indings sugges ha
while highe a ge ol ages can accele a e he s a up p ocess, hey also con ibu e o
inc eased deg ada ion, highligh ing he need o a balanced app oach in op imizing s a
p ocedu es. As s a -s op cycles a e expec ed o inc ease deg ada ion, he low deg ada ion
alues obse ed du ing he deg ada ion analyses show a high abili y o AEMWE sys ems
o in e mi en ope a ion [4]. Deg ada ion a ge s o 2030 o AEMWE s acks a e below
15 μV h−1 du ing s a iona y ope a ion [5].
Fig. 1: Deg ada ion analyses wi h 150 s a -s op cycles o he AEMWE sys em and a
a ia ion o he a ge ol age U a ge and he amp-up du a ion amp-up du ing s a up.
Based on [2].
The EIS measu emen s p o ide u he insigh s in o he deg ada ion mechanisms occu ing
wi hin he AEMWE s ack. The analysis o he Nyquis plo s e eals dis inc changes in he
esis i e componen s o he cells o e he cou se o he deg ada ion analyses. The high-
equency esis ance (HFR), ep esen ed by R₀ in he equi alen ci cui model, exhibi s a
dec ease o app oxima ely 1.5 mΩ cm² du ing he deg ada ion analyses. This educ ion in
esis ance may indica e imp o ed ionic conduc i i y o educed con ac esis ance wi hin he
cell.
Con e sely, he esis ances associa ed wi h he elec ode p ocesses, R₁ and R₂, show an
inc ease, sugges ing ha deg ada ion is p ima ily occu ing a he elec odes. Speci ically,
R₁, which co esponds o he hyd ogen e olu ion eac ion (HER), inc eases by 2.3 mΩ cm²,
while R₂, associa ed wi h he oxygen e olu ion eac ion (OER), inc eases by 4.2 mΩ cm².
This end indica es ha he deg ada ion mechanisms a e mo e p onounced a he anode,
whe e he OER is kine ically mo e demanding.
The esis ance R₃ wi h he lowes equency, which may ep esen mass anspo and
concen a ion g adien phenomena, dec eases by an a e age o 2.4 mΩ cm². This dec ease
could be a ibu ed o imp o ed mass anspo pa hways wi hin he elec ode s uc u e,
po en ially esul ing om mechanical changes du ing he deg ada ion p ocess.
The indings o his s udy highligh he complex in e play be ween ope a ional pa ame e s
and he pe o mance o AEMWE sys ems du ing ansien ope a ion. The abili y o op imize
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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he cold s a beha io while minimizing deg ada ion is c ucial o he success ul in eg a ion
o AEMWE sys ems in o enewable ene gy applica ions.
The esul s sugges ha he a ge ol age has he mos ex ensi e impac o op imize he
s a du a ion. Op imizing he s a p ocedu e in ol es a ca e ul balance be ween s a
du a ion and deg ada ion. Addi ionally, he managemen o cu en slopes du ing s a up is
c i ical. Implemen ing a con olled cu en inc ease s a egy, a he han a pu ely ol age-
con olled app oach, may help mi iga e deg ada ion.
3. Conclusion and Ou look
This s udy p o ides aluable insigh s in o he s a up beha io o an AEMWE sys em unde
a ious ope a ional pa ame e s. The indings indica e ha bo h he amp-up du a ion and
a ge ol age signi ican ly a ec he s a du a ion and deg ada ion a es. While as e amp-
ups and highe a ge ol ages can educe s a up imes, hey also lead o inc eased
deg ada ion. Howe e , i is shown ha he cu en amp has a signi ican ly mo e de imen al
in luence on li e ime han jus a high a ge ol age, which emphasizes he necessi y o a
ca e ul op imiza ion o he chosen pa ame e s. Mo eo e , he analysis unde sco es he
impo ance o managing he maximum cu en inc ease du ing s a up o mi iga e
deg ada ion while main aining sho s a du a ions. The esul s sugges ha AEMWE
sys ems exhibi obus ness agains cyclic ope a ion, wi h deg ada ion a es emaining wi hin
indus ially ele an limi s (10 µV s a -1 – 26 µV s a -1) e en a e ex ensi e s a -s op cycles.
Fu u e wo k will ocus on he shu down p ocedu es and dynamic powe luc ua ions as
complemen a y aspec s o in e mi en ope a ion. The sensi i i y owa ds ope a ing
pa ame e s du ing hese p ocesses and hei e ec on he deg ada ion o he AEMWE
sys em will be u he in es iga ed o ul ima ely be able o ep esen he holis ic dynamic
ope a ion.
Re e ences
[1] V. Ma inez Lopez, H. Zia , J. Ha e ko , M. Zeman, O. Isabella, Dynamic ope a ion o
wa e elec olyze s: A e iew o applica ions in pho o ol aic sys ems in eg a ion,
Renewable and Sus ainable Ene gy Re iews, 2023
[2] A. Gladik, M. Riedel, R.-A. Eichel, Anion exchange memb ane elec olysis a wo k –
in es iga ing impac o s a ing pa ame e s and s a -s op ope a ion on cold s a
beha io and deg ada ion, Jou nal o Powe Sou ces, 2025
[3] S.M. Alia, S. S a iha, R.L. Bo up, Elec olyze du abili y a low ca alys loading and wi h
dynamic ope a ion, Jou nal o The Elec ochemical Socie y, 2019
[4] A.K. Niaz, J.-Y. Pa k, H.-T. Lim, Ope a ional pa ame e s co ela ed wi h he long- e m
s abili y o anion exchange memb ane wa e elec olyze s, In e na ional Jou nal o
Hyd ogen Ene gy, 2021
[5] Clean Hyd ogen Join Unde aking, S a egic esea ch and inno a ion agenda 2021-
2027, 2022
Keywo ds: EFCF2025, H2, LowTemp. Fuel Cells & Elec olyse s, AEM, S a -s op,
Deg ada ion, Dynamic ope a ion
Rema k: This wo k is licensed unde C ea i e Commons A ibu ion 4.0 In e na ional
