Impact of CO and H 2 S on single cell and stack performance

Transcription

1 Impact of CO and H 2 S on single cell and stack performance S. Escribano, A. Finkler (CEA-stack tests) PA. Jacques, I. Profatilova, S. Jeune (CEA-Single cell) WORKSHOP 6-7 JUNE 2017 HYDROGEN FUEL QUALITY ASSURANCE FOR PEM FUEL CELLS 3 rd HYCORA Workshop

2 Contamination tests on 25 cm² Single cells and 10 cells PC stack Effect of CO on PEMFC performance with low loaded anodes at fixed I and under Dynamic Load Cycles Impact of H 2 S on performance under pure or CO polluted Hydrogen Analyses of CO and H 2 S adsorption by Cyclic Voltametry 2

3 CEA tests - PowerCell 10 (195cm²) cells stack cathode side CV Anode side CV Low loaded anodes 3

4 Full test of PC stack: Impact of steady state curent, FC-DLC, concentration of CO 2-4 hours per stage : typically one max trip of driving between stop 1 stage : 1 day, at least 1 night between 2 stages After 140 Hrs : CV up to 1 V to clean anode 1ppm CO 2 ppm CO Pure H2 CV after each stage Operating time only (no stop time) 4

5 Comparison of different pollution with 2ppm CO: History + [CO] Coverage Pt/CO (anode tech.) 5

6 FC-DLC reference under pure H2 (Imax: 0,8 A/cm 2 ) 6

7 FC-DLC under 1 ppm CO (Imax: 0,8 A/cm 2 ) 7

8 FC-DLC under 2 ppm CO (Imax: 0,8 A/cm 2 ) 8

9 Coverage of Pt by CO AL degradation FC-DLC: both bridge and linear CO? 9

10 Coverage of Pt by CO FC-DLC (2 ppm) linear CO only, self cleaning? AL degradation FC-DLC: both bridge and linear CO? 10

11 Coverage of Pt by CO When plateau reach: linear CO bonding? AL degradation FC-DLC: both bridge and linear CO? 11

12 FC-DLC under 1 ppm CO (Imax: 0,8 A/cm 2 ) DLC n 4 DLC n 10 Increasing impact mainly at higher loads 12

13 CO cleaning by Air permeation Additional test on aged stack Test of de-contamination by Air flow cathode side & Air permeation Aim: to check efficiency towards CO removal compared to CV up to 1V as performed previously Reminder of the complete test history of PC stack n 1 13

14 CO cleaning by Air permeation Additional test on aged stack Test of de-contamination by Air flow cathode side & Air permeation Aim: to check efficiency towards CO removal compared to CV up to 1V as performed previously Conducted with 1 ppm CO contamination at fixed current 2 cases after contamination: 1. N2 short period anode side + 1h40 Air anode closed + CV 2. N2 short period anode side + 1h40 Air anode closed + 2 days + CV Cleaning almost Ok but CO not fully removed 14

15 H2S impact studies 15

16 H2S impact study Tests on PC 10 cells stack Objective: impact of H2S on the stack behaviour vs. CO contamination Method planned: contamination by 1 ppm CO at fixed i (0,5 A/cm²) + De-contamination Stack disconnected of the test bench Stack submitted to H2S / N2 flow resp. A/C sides (without operation) Contamination by 1 ppm CO at fixed i (0,5 A/cm²) De-contamination (avoiding removal of H2S) Cleaning of S by CV Effect of CO after sulfur full removal thanks to CV up to higher voltage Comparison before / after experiments with H2S 16

17 H2S impact study Tests on PC 10 cells stack Tests with H2S and CO on a new stack H2S 100 ppm 3 days H2S 1% - 4 h H2S 1% - 1 h H2S 1% - 1 h 50 H2S 1% - 1 h BoT CO & i-v curves 17

18 H2S impact study Tests on PC 10 cells stack After H2S: 0,70 V First test with lower H2S content 1st CV 2nd CV CO ox S ox + 1ppm CO (97A) 0,65 V Small impact on performance CV anode side 0,8V (CO) 1,4 V (S) Impact on anode and on perf. of S species adsorbed? 18

19 H2S impact study Tests on PC 10 cells stack After 4h 0,62 V Test with higher H2S content to evaluate clear impact on stack performance and anodes More impact on performance Comp. Of the two H2S cases S ox Effect of S species adsorbed ok! 19

20 H2S impact study Tests on PC 10 cells stack Test with higher H2S content to evaluate clear impact No CO peak After H2S: 0,63 V S ox + 1ppm CO (97A) 0,58 V Small impact of CO on performance CV anode side 0,8V (CO) 1,4 V (S) 20

21 H2S impact study Tests on PC 10 cells stack Test with higher H2S content to evaluate clear impact After H2S: 0,63 V No CO peak S ox + 1ppm CO (97A) 0,58 V Small impact of CO on performance CV anode side 0,8V (CO) 1,4 V (S) 21

22 H2S impact study Tests on PC 10 cells stack Test with higher H2S content to evaluate clear impact Cleaning of S by CV (1,4V) 22

23 H2S impact study Tests on PC 10 cells stack Test with higher H2S content to evaluate clear impact Cleaning of S by CV (1,4V) 23

24 H2S impact study Tests on PC 10 cells stack Test with higher H2S content to evaluate clear impact Cleaning of S by CV (1,4V) Hdes/Pt Pt ox Hads/Pt 24

25 H2S impact study Tests on PC 10 cells stack Test with higher H2S content to evaluate clear impact Cleaning of S by CV (1,4V) Hdes/Pt Pt ox Hads/Pt 25

26 H2S impact study Tests on PC 10 cells stack Test with higher H2S content to evaluate clear impact Cleaning of S by CV (1,4V) Hdes/Pt Pt ox Hads/Pt 26

27 H2S impact study Tests on PC 10 cells stack Test with higher H2S content to evaluate clear impact Cleaning of S by CV (1,4V) Hdes/Pt Pt ox Hads/Pt 27

28 Effect of FC-DLC CV (1st scan) before / after CO 1ppm & CO + DLC Pt ox Beneficial effect against S coverage of FC-DLC and/or OCV steps included? Some perf recovery under pure H2 Anode cleaning but also cathode effect possible? 28

29 0,8 Effect of H2S coverage & CO on performance 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0 BoL 1st H2S contamination 100ppm 3 days 1st H2S contamination 100ppm 3 days + 1ppmCO + cleaning/cv 4th H2S contamination 1% 1h 5th H2S contamination 1% 1.8h 5th H2S contamination 1% 1.8h + 1ppmCO + 11DLC 5th H2S contamination 1% 1.8h + 1ppmCO + 11DLC + cleaning/cv + H2pur + CV U mean H2 pur (V) Umean 1ppmCO (V) 29

30 H2S impact study Tests on PC 10 cells stack Effect of H2S and CO tests 30

31 H2S impact study Tests on PC 10 cells stack Full reversibility by CV? Effect of H2S and CO tests CV End of Test recovery of Pt but still S species adsorbed Only small trend (shift of Ptox peak) 31

32 Conclusions With low loaded MEA, impact of 1 and 2 ppm CO is significant, (it was not with high loaded MEA) History of the MEA is important and impact is not constant all along the test residual CO absorbed on catalyst? maturation of the anode catalyst? acceleration of the degradation of the other parts of the MEA (cathode, membrane)? H2S tests effect on performance depending on coverage CO mitigation BUT if strong coverage Very low contents to be studied on the stacks 32

33 Thank you