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

Transcription

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

2 Fuel Cells & Electrolyzers Battery Solar Biomass 2

3 EXPERIMENTAL RESOURCES AT DIFFERENT SCALES 3

4 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

5 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

6 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 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

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

8 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

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

10 AST-1: 48h AST 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

11 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

12 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, 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 % 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, j / ma.cm -2 Higher efficiency losses at high current density. No clear impact in the «activation zone» of the Pol.Curv. 12

13 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, J / ma.cm -2 Efficiency losses every 100h Again higher efficiency losses at high current density 13

14 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 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 Time / A/cm2 1, j ma/cm 2 Efficiency losses every 100h (close to AST-2) Again higher efficiency losses at high current density 14

15 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

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

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

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

19 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

20 AST 1 AST 2 50 j / ma/cm ,5 1 1,5 BoL t h _ AST-2 t0 + 95h _ AST-2 t h _ AST-2 AST E /V 100 Current density ma/cm ,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 t ,5h AST-3 t h AST-3 t ,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 21

22 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

23 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

24 Analyses from Bode representation f c = 1 / (2π RC) Phase / BoL@0.1A/cm2 BoL@0.5A/cm2 BoL@1A/cm2 BoL@2A/cm2 Phsae BoL 0.1A/cm2 After 48h 0.1 A/cm2 After 96h 0.1 A/cm2 After 144h 0.1 A/cm2 After 192h 0.1 A/cm Freq / Hz 0 0,10 1,00 10,00 100, ,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

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

26 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)

27 30 µm lost 1500 h (20 nm/h) 27

28 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

29 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

30 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

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

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

33 BoL EoL AST-1 33

34 BoL 34

35 BoL EoL AST-3 35

36 BoL EoL AST-4 36

37 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

38 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