11th May 2016 Tunis, Tunisia

S. Siracusano1*, V. Baglio1, S.A. Grigoriev2, L. Merlo3, V.N. Fateev4, A. S. Arico1

Performance of a PEM water electrolyser based on metallic

iridium electrocatalyst and an Aquivion membrane

1 CNR-Institute of Advanced Energy Technologies (ITAE) - Via Salita Santa Lucia sopra Contesse, 5 - 98126 Messina

2National Research University “Moscow Power Engineering Institute”, Krasnokazarmennaya, 14, 111250 Moscow, Russia

3Solvay - Viale Lombardia, 20 - 20021 Bollate (MI) – Italy

4National Research University “Kurchatov Institute”, Kurchatov sq.,1, 123182 Moscow, Russia

PEM Electrolysers

•High current densities at low cell voltages ≈ High efficiency

(even at low temperatures); Rapid start-up/response

• High resistance to duty cycles

•Eco-friendly system with increased level of safety

(no caustic electrolyte circulating)

• Smaller mass-volume characteristics: compact system

• Electrolysis of water using renewable energy sources has significant advantages:

• Production of high purity «green» hydrogen

• High efficiency (>70 % vs. LHV)

Key features of PEM electrolysis

• High differential pressure, meaning

reduced gas compression requirements

for the produced hydrogen gas

• High degree of gases purity

• Possibility of combining fuel cell and

electrolyser (regenerative fuel cell)

•High cost (PFSA membranes, noble metal electrocatalysts,

Ti bipolar plates, expensive coatings)

CAPEX

Drawbacks of PEM electrolysis

• Long-term durability up to 100 khrs not

yet achieved

OPEX

•Several technologies are currently used for water electrolysis : alkaline systems, solid oxide electrolysers

and PEM electrolysers Very promising for grid stabilisation and coupling with renewable power sources

HPEM2GASProject & Partnership description

Horizon 2020 Programme of the FCH Joint Undertaking

Beneficiary name CountryPartner

type

CONSIGLIO NAZIONALE DELLE RICERCHE (CNR-ITAE)

Italy Research

ITM Power (Trading) Ltd (ITM) United Kingdom Industry

SOLVAY SPECIALTY POLYMERS ITALY S.P.A. (SLX)

Italy Industry

IRD FUEL CELLS A/S (INDUSTRIAL RESEARCH & DEVELOPMENT A/S) (IRD)

Denmark Industry

Stadtwerke Emden GmbH (SWE) Germany Industry

HOCHSCHULE EMDEN/LEER (HS EL) Germany Research

UNIRESEARCH BV (UNR) Netherlands SME

High Performance PEM Electrolyzer for Cost-effective Grid Balancing Applications

Next generation water electrolysers must achieve a good dynamic behaviour (rapid start-up, fast

response, wider load and temperature ranges) to provide proper grid-balancing services and thus

address the increase of intermittent renewables interfaced to the grid.

The overall objective of the HPEM2GAS project is concerning with the development of a low cost PEM

electrolyser optimised for grid balancing service

The activities are addressed to both stack and balance of plant innovations for an advanced 180

(nominal)-300 kW (transient) PEM electrolyser.

The advanced system will be demonstrated in a six month field test at Emden in Germany

The aim is to bring the developed technology from TRL4 to TRL6, demonstrating the PEM electrolyser

system in a power-to-gas field test

Deliver a techno-economic analysis and an exploitation plan to bring the innovations to market

HPEM2GAS objectives

PEM Electrolysers

• Slow oxygen evolution reaction rate

• Improvement of membrane properties

• Cost

Anode:

2H2O 4H+ + 4e- + O2

Cathode:

4H+ + 4e- 2H2

e-

Mem

bra

ne

Anode Cathode

H2O

H2O, O2

H2O

H2O, H2H+ H+

Membrane Benchmark Nafion®

• Excellent Performance

• Appropriate electrochemical Stability

• Suitable Mechanical Properties

• Rapid Start-up/ Rapid response

• Dynamic behaviour

Drawbacks to overcome / Aspects to improve

Oxygen evolution reaction catalysts:

• Ru ; RuO2 a highest activity; lower stability

• Ir ; IrO2 a high activity; a better long-term stability;

less efficiency losses due to corrosion.

Nafion ®

Long side-chain ionomers

Aquivion ®

Short side-chain ionomer1

The Solvay Aquivion ionomer is characterized by both larger crystallinity and higher glass

transition temperature than Nafion

Pt/C cathodecatalyst

1100 g/eq870-1000 g/eq

Advanced Membrane and Electro-catalysts

Aim of this work*

1Developed by Solvay Specialty Polymers

*S. Siracusano, V.Baglio, A.Stassi, L.Merlo, E.Moukheiber, A.S.Aricò. Performance analysis of short-side-chain Aquivions perfluorosulfonic acidpolymer for proton exchange membrane water electrolysis. Journal of Membrane Science 466(2014) 1–7*S. Siracusano, V. Baglio, E. Moukheiber, L. Merlo, A.S. Aricò. Performance of a PEM water electrolyser combining an IrRu-oxide anode electrocatalystand a short-side chain Aquivion membrane. International Journal of Hydrogen Energy 40 (2015) 14430-14435

Ir anodecatalyst

30 %Pt/C Cathode Electro-Catalyst

The Pt-sulfite complex/Vulcan slurry was decomposed by adding H2O2

Sulfite-complex route*

H2PtCl6 + Na2S2O5/NaHSO3

Na6Pt(SO3)4

PtOx/Vulcan

Carbothermal reduction in inert (Ar) atmosphere at 600 °C

Pt/Vulcan

Vulcan+

2.7 nm

XRD: Pt cubic and C support

hexagonal crystallographic structures

TEM: Proper metal particle

dispersion and good homogeneity

*Aricò AS, Stassi A, Modica E, Ornelas R, Gatto I, Passalacqua E, et al. Performance and degradation of high temperature polymer electrolyte fuel cell catalysts.J Power Sources 2008;178:525-536.

(H2IrCl6 + H2O + KOH(0.5M) → Solution (pH 13 – 13.5)

Metallic Ir Anode Electro-Catalyst

Chemical Reducer Synthesis*

Then the remaining deposits (Ir black powder) were thoroughly washed off (several times) using bi-distilled water in order to bring the pH of the downtake solution within the 6–6.5 range.

NaBH4 in NaOH 1M

Dry in air at 60 - 70 °C

Stirred at room T

The solution was constantly stirred until the end of gas evolution

*S.A. Grigoriev, P. Millet, K.A. Dzhus, H. Middleton, T.O. Saetre, V.N. Fateev “Design and characterization of bi-functional electrocatalytic layers forapplication in PEM unitized regenerative fuel cells” // International Journal of Hydrogen Energy, Vol. 35, Issue 10, May 2010, pp. 5070-5076.

0

1000

2000

3000

4000

20 40 60 80 100

Cou

nts

°2 Theta

Metallic Ir Anode Electro-Catalyst

XRD

2.7 nmXRD: Cubic crystallographic

structure (JCPDS card no. 060598)

(111

)

(200

)

(220

)

(311

)(2

22)

SEM-EDX: Iridium (no impurities)

Agglomerates of fine particles

TEM: Agglomerates of fine

particles

Formulation: 30 wt. % Pt/C

Loading: ~ 0.1 mg/cm2

Deposition method: doctor blade

Composition: 67% (Pt/C) + 33 wt. % ionomer

Backing layer carbon cloth (HT ELAT)

Formulation: Ir metallic

Loading: ~ 0.4 mg/cm2

Deposition method: Spray at 80 ºC on membrane

Composition: Ir + 20 wt.% ionomer

Backing layer Ti-grid

Single Cell Configuration

Membrane: Aquivion E100-09S

Low noble metal loadings configuration

T /°C

A⋅cm-2

@ 1.6 V

A⋅cm-2

@ 1.8 V

30 °C 0.15 0.55

40 °C 0.17 0.65

50 °C 0.25 0.75

60 °C 0.3 0.85

70 °C 0.35 0.95

80 °C 0.4 1.1

90 °C 0.5 1.2

The electro-catalytic

activity increased as a

function of temperature

Electrochemical Characterization

Cathode: 30% Pt/C

Membrane: E100-09S

Anode: Ir metallic

1.3

1.4

1.5

1.6

1.7

1.8

1.9

2

2.1

0 0.5 1 1.5 2 2.5

Pot

entia

l / V

Current Density / A·cm -2

30 °C40 °C50 °C60 °C70 °C80 °C90 °C

Low noble metal loadings configuration (0.5 mg cm-2MEA)

0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.2 3.6

-Z"

/ ohm

·cm

2

Z' / ohm·cm 2

25 °C

40 °C

60 °C

80 °C

90 °C

Series and polarization

resistances decreased as the

temperature increased

T /°C

Rs / mΩ⋅cm

2Rp /

mΩ⋅cm2

30 °C 164 2830

40 °C 137 1690

60 °C 113 860

80 °C 96 475

90 °C 90 356

1.5 V

Electrochemical Characterization

0

0.1

0.2

0.3

0 0.1 0.2 0.3 0.4

-Z"

/ ohm

·cm

2

Z' / ohm·cm 2

25 °C

40 °C

60 °C

80 °C

90 °C

Cathode: 30% Pt/C

Membrane: E100-09S

Anode: Ir

Durability Test

1.3

1.4

1.5

1.6

1.7

1.8

1.9

2

2.1

2.2

0 100 200 300 400 500 600 700 800 900 1000 1100

Cel

l Pot

entia

l / V

Time / h

1 A∙cm -2 80 °C

Interestingly: after the first hours of conditioning the cell potential progressively decreses ( efficiency increases) using the low noble metal loading configuration

Low noble metal loadings configuration (0.5 mg cm-2MEA)

-10 µV/h

• The enhanced performance for the cell after time test may be related to chemical and

diffusional aspects

• A modification of the catalyst-electrolyte interface with time may also influence the observed

behaviour

80 °C

@ 1.9 V

Before 1.55 A⋅cm-2

After 2.25 A⋅cm-2

Similar characteristics in the

activation region

Decrease of potential at high current

after the durability test

Comparison: before and after time test

After time test

Before time test

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 0.1 0.2 0.3 0.4 0.5 0.6

-Z"

/ ohm

·cm

2

Z' / ohm·cm 2

0 h1000 h

Slightly lower series and polarization resistance

after the time test in the activation region

Rs(Ω⋅cm2)

Rp(Ω⋅cm2)

Before 96 475

After 82 460

80 °C

1.5 VActivation controlled

region

Comparison: before and after time test

After time test

Before time test

Comparison: before and after time test

However, CV analysis shows a significant enhancement of coulombic charge with the time-test;

Two phenomena can be responsible of this behaviour:

An increase of surface roughness and particle dispersion (lower agglomeration) during the electrochemical operation. This phenomenon may be promoted by the insertion of ionomer micelles among particles

An oxidation of the metallic Ir to IrOx causing an increase of the double layer capacitance

After

Before

Room TAnode: H2OCathode: H2 50 cc

Investigation of MEA used in long term test

0

500

1000

1500

2000

2500

20 40 60 80 100

Cou

nts

/ a.u

.

2 Theta / degree

Anode side

MEA Used - Anode

2.7 nm MEA Fresh - Anode

3.1 nm

Anode side: No significant change in

crystallite size and in the bulk

composition before and after test

Cathode side

Cathode side: Presence of

PTFE due to GDL used as

backing layer

Investigation of MEA used in long term test

Anode side MEA UsedMEA Fresh

SEM

Ti grid Ti grid

Investigation of MEA used in long term test

Anode side MEA UsedMEA Fresh

Elem Wt% At%

CK 21.68 52.24

OK 4.46 8.08

FK 20.48 31.20

IrM 52.80 7.95

SK 0.59 0.53

Elem Wt% At%

CK 19.49 52.11

OK 6.87 13.78

FK 14.23 24.06

IrM 59.26 9.90

SK 0.14 0.14

An increase of O signal in the used sample

No Evidence impurities in the used sample

Evidence of surface oxidation?

SEM-EDX

Investigation of MEA used in long term test

TEM Anode side MEA UsedMEA Fresh

Ionomer

Ionomer

Evidence of an enhanced dispersionafter the durability test

Investigation of MEA used in long term test

XPS

0200400600800100012000

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Binding Energy (eV)

c/s

-C1s-O

KLL

-O1s

-F K

LL

-F2s

-F1s

-Ir4

p3

-Ir4

p1

-Ir4

f7-I

r4f5

-Ir4

d5-I

r4d3

-S2s -S2p

High resolution XPS spectra for Ir and O signals in the fresh and used anode

Survey

Shift of the signal of Ir4f from 60.9 eV to 62.5 eV (Ir → IrO2)

An increase of O signal in the used sample

Decrease of F content in the used sample

Fresh

Used

Ir4f

55606570750

1

2

3

4

5

6

7

8

Binding Energy (eV)

c/s

5265285305325345365385405423

4

5

6

7

8

9

Binding Energy (eV)

c/s

O1s

Fresh

Used

Fresh

Used

IrO2

Ir

F/Ir → 5.32O/Ir → 3.61

Fresh

Used

F/Ir → 9.80O/Ir → 1.44

Conclusions

Advanced membrane and electro-catalysts were developed for water electrolysis;

The electrochemical activity was investigated in a single cell PEM electrolyser consisting of a Pt/C

cathode, Ir metallic anode and an Aquivion membrane;

An excellent performance, of 1.2 A·cm-2 at 1.8 V at 90 °C, was achieved with low loading

configuration (0.5 mg cm-2MEA);

An increase in performance was observed with time;

The Physico – Chemical investigation of the MEA after the long term test indicated an oxidation of

Iridium on the surface.

The authors acknowledge the financial support of the EU through the FCH JUHPEM2GAS Project. ‘‘Work performed was supported by the Fuel Cells and HydrogenJoint Undertaking in the context of project HPEM2GAS, contract No. 700008’’

ACKNOWLEDGEMENTS