AST PROTOCOLS FOR PEM WATER ELECTROLYIS : INSIGHT ON PERFORMANCES AND COMPONENTS DEGRADATION

AST PROTOCOLS FOR PEM WATER ELECTROLYIS : INSIGHT ON PERFORMANCES AND COMPONENTS DEGRADATION

Fuel Cells & Electrolyzers Battery Solar Biomass 2

EXPERIMENTAL RESOURCES AT DIFFERENT SCALES 3

CONTEXT High performing and durable PEM WE are need. European KPI objectives * A linear voltage degradation of 1µV/hr translates into an additional electrical energy input of ~2 kwh/kgh 2 after 60,000 hours of continuous operation. * FCH JU Report «Development of Water Electrolysis in the European Union» L. Bertuccioli, Feb 2014 4

CONTEXT Most of PEM WE show a degradation voltage between 0,5 and 15 µv/h 4 µv/h after 60 kh Highly time consumming to investigate system durability Need Accelereted stress test (AST) 5

CONTEXT PEM WE suffer from less intensive researches on durability and degradation than PEM FC 150 PEM WE vs. PEM FC on Research activities on Degradation 100 50 0 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 PEM WE (40 citation report) PEM FC (1051 citation report) Keywords: degradation (PEM WE or PEM FC) Web of science: Citation report on 01/27/2016 6

OUTLINE Short introduction on main degrading components in PEM WE Analytical Methods and main outcomes Summary 7

Short introduction on main degrading components in PEM WE Cathode catalyst degradation BP degradation H 2 Pt IrO 2 H 2 O 2 Anode catalyst degradation H + Porous Ti Center Edge H 2 O Membrane Membrane degradation Most of the cell components may age 8

In situ analyses Ex situ analyses Pol.Curve Contact Resistance AST Protocol FRR ECSA After In situ analyses G-EIS SEM 9

AST-1: 48h AST signal @ 90 C repetaed at least 4 times 3 A/cm 2 (E > 2V) : speed up BP corrosion 0,3 A/cm 2 : speed up membrane attack AST-2: 48 h AST@ 90 C repeated at leat 4 times Longer step time at low current density to amplify the membrane chemical attack AST-3: : 48 h AST@ 90 C repeated at leat 4 times with P (P O2 = 4 bar vs. P H2 = 1 bar ) Suppose to amplify the oxygen permeation and accelerate the membrane attack AST- 4: 48 h AST@ 90 C repeated at leat 4 times with 5ppm Fe ions Adding metal ion impurities may catalyse the Fenton reaction. 10

In situ analyses Ex situ analyses Pol.Curve Contact Resistance After In situ analyses AST-1 AST-2 AST-3 AST-4 FRR G-EIS ECSA SEM 11

E / V AST-1 2,3 BoL-AST-1 2,1 After 48 h of AST-1 1,9 After 96 h of AST-1 1,7 After 144 h of AST-1 1,5 After 192 h of AST-1 1,3 0 500 1000 1500 2000 2500 j / ma.cm -2 E / V 2,3 2,1 1,9 1,7 1,5 1,3 y = 1,02E-03x + 1,90E+00 y = 6,25E-04x + 1,68E+00 y = 1,25E-04x + 1,472E+00 Efficiency loss 12,1 % 7,1 % 1,6 % 0 50 100 150 200 250 Time / h j = 200 ma/cm2 j = 1000 ma/cm2 j = 2000 ma/cm2 E / V 1,6 1,55 1,5 1,45 1,4 10 100 1000 j / ma.cm -2 Higher efficiency losses at high current density. No clear impact in the «activation zone» of the Pol.Curv. 12

AST-2 E / V 2,3 2,1 1,9 1,7 BoL AST-2 After 47.5h AST-2 After 95h AST-2 After 142.5h AST-2 After 190h AST-2 Efficiency losses 18,3 % 10,5 % 3,4 % 1,5 After 237.5h AST-2 After 285h AST-2 1,3 0 1000 2000 J / ma.cm -2 Efficiency losses every 100h Again higher efficiency losses at high current density 13

AST-3 P (P O2 = 4 bar vs. P H2 = 1 bar ) E / V 2,3 2,1 1,9 1,7 1,5 BoL AST-3 After 47.5h AST-3 After 95h AST-3 After 142.5h AST-3 After 190h AST-3 After 237.5 h AST-3 E / V 2,3 2,1 1,9 1,7 1,5 1,3 y = 1,38E-03x + 1,92E+00 R² = 7,57E-01 y = 5,36E-04x + 1,69E+00 R² = 7,02E-01 Efficiency losses 17 % 7,5 % 2,3 % y = 1,46E-04x + 1,47E+00 R² = 6,87E-01 0 100 200 300 Time / h @ 0.2 A/cm2 @ 1 A/cm2 @ 2 A/cm2 1,3 0 500 1000 1500 2000 2500 j ma/cm 2 Efficiency losses every 100h (close to AST-2) Again higher efficiency losses at high current density 14

AST-4 H 2 O + 5 ppm Fe 200 mv in 48h AST-4 : was stopped earlier 5 ppm Fe 3+ is a too high concentration Few tens of ppb might be enough 15

Conclusion from Pol.Curve Degradation slope µv/h Ageing more important at high current (caused by the resistance). Cannot conclude without further analyses 16

Cyclic voltammetry IrO 2 (OH) y IrO 2+δ (OH) y-δ + δ (H + + e - ) 17

Cyclic voltammetry Q tot = Q inner + Q outer Ardizzone et al. Electrochimica acta vol 35 n 1-263-267 (199 18

Cyclic voltammetry 10 mv/h scan rate The different shapes of CV do not affect the Pol.Curve (activation part) After 196 h(eol) CV unusal shape, probably too resitive contact resistance After 144 h appearence of Hupd peak (0 < E < 0,3 V RHE ) 19

AST 1 AST 2 50 j / ma/cm2 40 30 20 10 0-10 -20-30 0 0,5 1 1,5 BoL t0 + 47.5 h _ AST-2 t0 + 95h _ AST-2 t0 + 142.5 h _ AST-2 AST 3 150-40 E /V 100 Current density ma/cm2 50 0-50 -100 0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 Cell voltage / V BoL _ AST-3 t0 + 47,5h AST-3 t0 + 95h AST-3 t0 + 142,5h AST-3 t0 + 190h AST-3 t0 + 237,5h AST-3 Same conclusion for AST2 and AST-3 than AST-1 No effect of the active surface area change on the Pol.Curves With ageing, appears H upd peak 20

21

R Ω independant of the current density (ohmic behaviour) R HFLoop decrease with polarization (charge transfert behaviour) R LFLoop decreases with polarization (charge transfert behaviour) 22

With ageing R Ω decrease at high current density R HFLoop and R LFLoop do not change with ageing (consistent with activation part Pol.curves) The increase of R pol is due to R Ω 23

Analyses from Bode representation f c = 1 / (2π RC) Phase / -15-10 -5 BoL@0.1A/cm2 BoL@0.5A/cm2 BoL@1A/cm2 BoL@2A/cm2 Phsae -15-10 -5 BoL AST-1 @ 0.1A/cm2 After 48h AST-1 @ 0.1 A/cm2 After 96h AST-1 @ 0.1 A/cm2 After 144h AST-1 @ 0.1 A/cm2 After 192h AST-1 @ 0.1 A/cm2 0 0 1 10 100 1 000 Freq / Hz 0 0,10 1,00 10,00 100,00 1 000,00 Freq /Hz Effect of the polarization reduces the charge transfer resistance (LF loop ) that increases Cuttoff Frequency Effect of the ageing reduces the Cdl that increases Cutt-off frequency (consistent with the outer capacitance diminution with the ageing) 24

Analyses from Bode representation AST-1 AST-2 Phsae Phase / -16-14 -12-10 -8-6 -4-2 0-16 -14-12 -10-8 -6-4 -2 0 BoL @ 0.1A/cm2 0 1 10 100 1000 Freq /Hz 0 1 10 100 1 000 Freq / Hz BoL + 48h AST-1 @ 0.1 A/cm2 BoL + 96h AST-1 @ 0.1 A/cm2 BoL + 144h AST-1 AST-1 @ 0.1 A/cm2 BoL + 192h AST-1 @ 0.1 A/cm2 BoL@0.1A/cm2 After 1st AST-2 @0.1A/cm2 After 2nd AST-2 @0.1A/cm2 After 3rd AST-2 @ 0.1A/cm2 After 4th AST-2 @0.1A/cm2 After 5th AST-2 @0.1A/cm2 After 6th AST-2 @0.1A/cm2 Phase / -2,9-2,7-2,5-2,3-2,1-1,9-1,7-1,5-1,3-1,1-0,9-0,7-0,5 Phase / -1,8-1,6-1,4-1,2-1,0-0,8-0,6-0,4-0,2 0,0 BoL AST-1 @ 2 A/cm2 After 48 h AST-1 @ 2 A/cm2 After 96 h AST-1 @ 2 A/cm2 After 144h AST-1 @ 2 A/cm2 After 192 h AST-1 @ 2 A/cm2 1 10 100 1000 Freq / Hz 1 10 100 1 000 Freq / Hz BoL@ AST-2 @ 2 A/cm2 After 47.5h AST-2 @ 2A/cm2 After 95h AST-2 @ 2 A/cm2 After 142,5 h AST-2 @ 2 A/cm2 After 190 h AST-2 @ 2 A/cm2 After 237.5h AST-2 @ 2 A/cm2 After 285h AST-2 @ 2 A/cm2 Cut-off frequency shitf might be linked to the electrode degradation 25

Fluoride ppm water cathode side water anode side Fluoride is found mainly on the cathode side Current density / ma/cm 2 Temperature and Setting current effect on FRR* These results lead us to define AST parameters (0,3 A/cm 2 and high temeprature 90 C) * M.Chandesris et al. Int.J.Hyd. Energy, 40 (2015) 1353-1366 26

30 µm lost 1500 h (20 nm/h) 27

Erratic points AST-2 and AST-3 more degrading than AST-1 AST-3 do not age more the membrane than AST-2 (contrary to expectations) 28

In situ analyses Ex situ analyses Pol.Curve Contact Resistance After In situ analyses AST-1 AST-2 AST-3 AST-4 FRR G-EIS ECSA SEM 29

Contact Resistance Analytical Methods and main outcomes Contact resistance BPP/Curr.Coll Résistance de contact «soft material» // Curr.Coll Bulk measurement Interfacial Contact Resistance Aged CC 20 µω.cm 2 Fresh CC 20 µω.cm 2 Aged (CC/IrO 2 ) // BP 13,9 mω.cm 2 Aged (IrO 2 /CC) // BP 22,6 mω.cm 2 Fresh CC // BP 1 m Ω.cm2 GDL // aged (IrO 2 /CC) // BP 68 mω.cm 2 GDL // aged (CC/IrO 2 )// BP 426 mω.cm 2 GDL // fresh CC) // BP 79 m Ω.cm 2 // Interface CC/IrO 2 // BP: IrO 2 facing CC in contact with the BP No bulk resistance difference IrO 2 remaining particles improve interface resistance BP/Curr Coll. Higher contact resitance with a «soft material». 30

Results from contact resistance Results from G-EIS Increase of R Ω is mainly caused by the interface «soft material»// Curr.Coll. 31

SEM qualitative analyses BoL (After conditioning) H 2 O H 2 O + O 2 H 2 O + H 2 32

BoL EoL AST-1 33

BoL 34

BoL EoL AST-3 35

BoL EoL AST-4 36

Summary Conclusion AST are more agressive than steady state ageing (40 times faster in comparison with 5 cells 300 cm 2 for 4000h) AST-2 able to thin the membrane and oxidized CC Most complete ageing protocols from those tested 37

Acknowledgements CEA : S. Chelghoum D. Thoby Fraunhofer : JM : European funding: A. Georg E. Price E. Wright Under grant agreement n [303484] for the Novel project AST PROTOCOLS FOR PEM WATER ELECTROLYIS : INSIGHT ON PERFORMANCES AND COMPONENTS DEGRADATION Thank you for the attention