ast protocols for pem water electrolyis ...ast-1: 48h ast signal @ 90 c repetaed at least 4 times...

2nd international workshop on durabiltiy and degradation issues in PEM electrolysis cells and its components| Fouda-Onana Frédéric

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

| 2

Fuel Cells&

ElectrolyzersBattery Solar Biomass

| 3

EXPERIMENTAL RESOURCES AT DIFFERENT SCALES

| 42nd international workshop on durabiltiy and degradation issues in PEM electrolysis cells and its components| Fouda-Onana Frédéric

• High performing and durable PEM WE are need.

A linear voltage degradation of 1µV/hr translates into an additional electrical energy input of ~2 kWh/kgH2after 60,000 hours of continuous operation.

CONTEXT

* FCH JU Report « Development of Water Electrolysis in the European Unio n » L. Bertuccioli, Feb 2014

European KPI objectives*


• Most of PEM WE show a degradation voltage between 0,5 and 15 µV/h

CONTEXT

4 µV/h after 60 kh

Highly time consumming to investigate system durabilit y

Need Accelereted stress test (AST)


• PEM WE suffer from less intensive researches on durability and degradation than PEM FC

CONTEXT

Web of science:Citation report on 01/27/2016

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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)


OUTLINE

Short introduction on main degrading components in PEM WE

Analytical Methods and main outcomes

Summary


Short introduction on main degrading components in PEM WE

H+

H2O

O2H2

Porous

Ti

Pt IrO2

Membrane

H2

H+

H2O

O2H2

Porous

Ti

Pt IrO2

Membrane

H2

Anode catalystdegradation

BP degradation

Membrane degradation

Cathode catalystdegradation

Center Edge

Most of the cellcomponents may age



Pol.Curve

ECSA

G-EIS

FRR

Contact Resistance

SEM

AST Protocol

AfterIn situ analyses

In situ analyses Ex situ analyses



AST-1: 48h AST signal @ 90°C repetaed at least 4 times

AST-2: 48 h AST@ 90°C repeated at leat 4 times

AST-3: : 48 h AST@ 90°C repeated at leat 4 timeswith ∆P (PO2 = 4 bar vs. PH2 = 1 bar )

AST- 4: 48 h AST@ 90°C repeated at leat 4 times with 5ppm Fe ions

• 3 A/cm2 (E > 2V) : speed up BP corrosion• 0,3 A/cm2 : speed up membrane attack

• Longer step time at low current density to amplify the membrane chemical attack

• Suppose to amplify the oxygen permeationand accelerate the membrane attack

• Adding metal ion impurities may catalyse the Fenton reaction.



Pol.Curve

ECSA

G-EIS

FRR

Contact Resistance

SEM

AST-1AST-2AST-3AST-4





AST-1

Higher efficiency losses at high current density.

No clear impact in the « activation zone » of the Pol.Curv.

y = 1,25E-04x + 1,472E+00

y = 6,25E-04x + 1,68E+00

y = 1,02E-03x + 1,90E+00

1,3

1,5

1,7

1,9

2,1

2,3

0 50 100 150 200 250

E /

V

Time / h

j = 200 mA/cm2 j = 1000 mA/cm2 j = 2000 mA/cm2

Efficiency loss

12,1 %

7,1 %

1,6 %

1,3

1,5

1,7

1,9

2,1

2,3

0 500 1000 1500 2000 2500

E /

V

j / mA.cm-2

BoL-AST-1

After 48 h of AST-1

After 96 h of AST-1

After 144 h of AST-1

After 192 h of AST-1

1,4

1,45

1,5

1,55

1,6

10 100 1000

E /

V

j / mA.cm-2


Efficiency losses every 100h

Efficiency losses

18,3 %

10,5 %

3,4 %

AST-2

Again higher efficiency losses at high current density

1,3

1,5

1,7

1,9

2,1

2,3

0 1000 2000

E /

V

J / mA.cm-2

BoL AST-2

After 47.5h AST-2

After 95h AST-2

After 142.5h AST-2

After 190h AST-2

After 237.5h AST-2

After 285h AST-2



Efficiency losses every 100h (close to AST-2)

Efficiency losses

17 %

7,5 %

2,3 %

AST-3

Again higher efficiency losses at high current density

1,3

1,5

1,7

1,9

2,1

2,3

0 500 1000 1500 2000 2500

E /

V

j mA/cm2

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

y = 1,46E-04x + 1,47E+00

R² = 6,87E-01

y = 5,36E-04x + 1,69E+00

R² = 7,02E-01

y = 1,38E-03x + 1,92E+00

R² = 7,57E-01

1,3

1,5

1,7

1,9

2,1

2,3

0 100 200 300

E /

V

Time / h

@ 0.2 A/cm2 @ 1 A/cm2 @ 2 A/cm2


∆P (PO2 = 4 bar vs. PH2 = 1 bar )


AST-4H2O + 5 ppm Fe

AST-4 : was stopped earlier

5 ppm Fe 3+ is a too high concentration

200 mV in 48h

Few tens of ppb might be enough




Conclusion from Pol.Curve

Deg

rada

tion

slop

eµV

/h

Ageing more important at high current(caused by the resistance ).

Cannot conclude without further analyses



Cyclic voltammetry

IrO2(OH)y ↔ IrO2+δ(OH)y-δ + δ (H+ + e-)



Cyclic voltammetry

Qto t= Qinner + Qouter Ardizzone et al. Electrochimica acta vol 35 n° 1- 263-267 (1990)



Cyclic voltammetry

10 mV/h scan rate

The different shapes of CV do not affect the Pol.Curv e (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)



-40

-30

-20

-10

0

10

20

30

40

50

0 0,5 1 1,5j /

mA

/cm

2

E /V

BoL

t0 + 47.5 h _ AST-2

t0 + 95h _ AST-2

t0 + 142.5 h _ AST-2

AST – 2

-100

-50

0

50

100

150

0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6

Cu

rre

nt

de

nsi

ty m

A/c

m2

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

AST – 3

AST – 1

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



RΩ independant of the current density (ohmic behaviour)

RHFLoop decrease with polarization (charge transfert behaviour )

RLFLoop decreases with polarization (charge transfert behaviou r)



With ageing R Ω decrease at high current density

RHFLoop and RLFLoop do not change with ageing (consistent with activation part Pol.curves)

The increase of R pol is due to R Ω



fc = 1 / (2π RC)

Effect of the polarization reduces the charge transfer resistance (LF loop ) that increases Cutt-off Frequency

Analyses from Bode representation

Effect of the ageing reduces the Cdlthat increases Cutt-off frequency(consistent with the outer capacitance diminution wit h the ageing)

-15

-10

-5

0

0 1 10 100 1 000

Ph

ase

/ °

Freq / Hz

[email protected]/cm2


BoL@1A/cm2

BoL@2A/cm2

-15

-10

-5

0

0,10 1,00 10,00 100,00 1 000,00

Ph

sae

°

Freq /Hz

BoL AST-1 @ 0.1A/cm2

After 48h AST-1 @ 0.1 A/cm2






Analyses from Bode representation-16

-14

-12

-10

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-6

-4

-2

0

0 1 10 100 1 000

Ph

sae

°

Freq /Hz

BoL @ 0.1A/cm2

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

-1,8

-1,6

-1,4

-1,2

-1,0

-0,8

-0,6

-0,4

-0,2

0,0

1 10 100 1 000

Ph

ase

/ °

Freq / Hz

BoL AST-1 @ 2 A/cm2

After 48 h AST-1 @ 2 A/cm2


After 144h AST-1 @ 2 A/cm2


-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

1 10 100 1 000

Ph

ase

/ °

Freq / Hz

BoL@ AST-2 @ 2 A/cm2

After 47.5h AST-2 @ 2A/cm2


After 142,5 h AST-2 @ 2 A/cm2


After 237.5h AST-2 @ 2 A/cm2


-16

-14

-12

-10

-8

-6

-4

-2

0

0 1 10 100 1 000

Ph

ase

/ °

Freq / Hz


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



Cut-off frequency shitf might be linked to the electrodedegradation

AST-1

AST-2



Fluoride is found mainly on thecathode side

Temperature and Setting currenteffect 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

Flu

orid

epp

m

water cathode side

water anode side

Current density / mA/cm 2



30 µm lost 1500 h (20 nm/h)



AST-2 and AST-3 more degrading than AST-1

AST-3 do not age more the membrane than AST-2 (contr ary to expectations)

Erratic points



Pol.Curve

ECSA

G-EIS

FRR

Contact Resistance

SEM

AST-1AST-2AST-3AST-4





Contact resistance BPP/Curr.Coll Résistance de contact « soft material » // Curr.Coll

Bulk measurement Interfacial Contact Resistance

Aged CC 20 µΩ.cm2

Fresh CC 20 µΩ.cm2

Aged (CC/IrO2) // BP 13,9 mΩ.cm2

Aged (IrO2/CC) // BP 22,6 mΩ.cm2

Fresh CC // BP 1 m Ω .cm2

GDL // aged (IrO2/CC) // BP 68 mΩ.cm2

GDL // aged (CC/IrO2) // BP 426 mΩ.cm2

GDL // fresh CC) // BP 79 m Ω .cm2

// Interface

CC/IrO2 // BP: IrO2 facing CC in contact with the BP

No bulk resistance difference

IrO2 remaining particles improve interface resistance BP/Curr Coll.

Higher contact resitance witha «soft material ».

Contact Resistance


Increase of R Ω is mainly caused by the interface « soft material »// Curr.Coll .

Results from G-EIS

Results from contact resistance



SEM qualitative analyses

BoL (After conditioning)

H2O H2O + O2

H2O + H2



BoL

EoL AST-1



BoL

EoL AST – 2



BoL

EoL AST-3



BoL

EoL AST-4



Summary

Conclusion

AST are more agressive than steady state ageing (40 ti mes faster in comparison with 5 cells – 300 cm 2 for 4000h)

AST-2 able to thin the membrane and oxidized CCMost complete ageing protocols from those tested

2nd international workshop on durabiltiy and degradation issues in PEM electrolysis cells and its components| Fouda-Onana Frédéric

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

Acknowledgements

CEA :S. ChelghoumD. Thoby

Fraunhofer :

A. Georg

Under grant agreement n° [303484]

for the Novel project

European funding:

JM :E. PriceE. Wright

Thank you for the attention

ast protocols for pem water electrolyis ...ast-1: 48h ast signal @ 90 c repetaed at least 4 times...

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