© Fraunhofer ISE

Review Lecture – Session HP.3d

PEM Water Electrolysis - Present Status of Research and Development

Tom SmolinkaFraunhofer-Institut für Solare Energiesysteme ISE

18th World Hydrogen Energy Conference 2010Essen, May 18, 2010

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Agenda

Background of PEM water electrolysis activities at Fraunhofer ISE

Fundamental of PEM water electrolysis

Electrodes and Membrane Electrode Assembly

Cell design and stack construction

System layout and efficiencies

Comparison to alkaline water electrolyser(Conclusion and summary)

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The Self-sufficient Solar House in Freiburg …

… begin of R&D activities in PEM electrolysis at Fraunhofer ISE

First developments in the eighties

Field test: 1992-1995

Complete hydrogen storage system consisting of:

PEM electrolyser

(30 bar / 2 kWel)

H2 and O2 pressure tanks

PEM fuel cell

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Regenerative fuel cell:

PEM electrolysis unit

(30 bar / 2 kWel)

H2/O2 storage tanks

PEM fuel cell

No mech. compressor!

The Self-sufficient Solar House in Freiburg …

ElectricityGasHeat

Warmwater

PV panel

Electrolyser Battery FuelCell

DC Load

Storagetanks

Inverter AC load

Cooking

Heating

Ther

mal

usa

ge

Elec

tric

alu

sag

e

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For more than 20 years experience in PEM electrolysis

Material characterisation

Cell and stack design

Balance of plant

Control strategies

Power electronics

Integration with RES

System evaluation

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Schematic of a PEM electrolysis cell

cathode anode

membrane

currentdistributor

electrode(electrocatalysts)

flow fieldplate

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cathode anode

H2 0.5 O2

H2O

H+

Schematic of a PEM electrolysis cell

Anode reaction:

H2O → 0.5 O2 + 2H+ +2e-

Cathode reaction:

2H+ + 2e- → H2

Total reaction:

H2O → H2 + 0.5 O2

Vrev = 1.23 V @ STP

endothermal reaction

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Decomposition of water

100

125

150

175

200

225

250

275

300

200 400 600 800 1000 1200

Temperature [K]

Enth

alpy

of R

eact

ion

[kJ

mol

-1]

Free

Ene

rgy

of R

eact

ion

[kJ

mol

-1]

0.52

0.65

0.78

0.91

1.04

1.17

1.30

1.43

1.56

Theo

retic

al C

ell V

olta

ge [V

]ΔHR ~ Vth

H2O(l) H2O(g)

ΔGR ~ Vrev

1.0

1.2

1.4

1.6

1.8

2.0

0 200 400 600 800 1000Current Density [mA cm-2]

Cel

l Vol

tage

[V]

iR A

η An

η Cath

V rev

Thermodynamics:

Reversible losses

HHV: 3.54 kWh/Nm³ H2

Reaction kinetics:

Irreversible losses

Overpotentials and internal resistance

Cell voltage affected by temperature and pressure

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The core component: Membrane Electrode Assembly

Cross Section of a MEA (Fraunhofer ISE) and reinforecd DMS membrane (Giner)

Membrane

Thickness: 100 - 300 μm (e.g. Nafion 117)

Coated on both sides with catalysts

Reinforcement possible

Cathode

Loading: 1.0 – 2.0 mg/cm²

Pt black or Pt/C based

Anode

Loading: 1.0 – 4.0 mg/cm²

Mostly Ir, Ru, Pt, (oxide) based

~180 μm

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Performance of a PEM electrolysis cell

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.01.3

1.4

1.5

1.6

1.7

1.8

1.9

2.0

2.1

2.2

2.3

2.4

2.5

Vol

tage

[V]

Current density [A/cm²]

80°C 60°C 40°C 20°C

Influence of cell temperature

V/I characteristics of a standard Nafion based MEA from SolviCoremeasured in a 25 cm² laboratory electrolysis cell (Fraunhofer ISE)

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.01.4

1.5

1.6

1.7

1.8

1.9

2.0

2.1

2.2

2.3

2.4

2.5

50 bar 40 bar 30 bar 20 bar 10 bar

Vol

tage

[V]

Current density [A/cm²]

Influence of cell pressure

@ 1 atm @ 80°C

pressure

tempe-rature

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1.40

1.45

1.50

1.55

1.60

1.65

1.70

1.75

1.80

1.85

1.90

0.0 0.2 0.4 0.6 0.8 1.0Current density [A/cm²]

Cel

l vol

tage

[V]

Pt / SPE / (Ir5Ru1)Ox

Pt / SPE / Ir

Optimised MEAs Metal(M)

Ir1Ru2OxM0.1 Fe

Ir1Ru2OxM0.1 Ni

Ir1Ru2OxM0.1 Co

Ir1Ru2OxM0.1 Sn

Alternative catalysts for the anode

V/i characteristic @ 80°C / 1 atm, cathode: Pt black (Fraunhofer ISE)

),(),(

pTVpTV

OP

HHV=ε

Cell efficiency:

82%

89%

93%

Efficiencies > 95% at 1000 mA/cm²reported in literature

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Current collectors/distributors

Challenge:

Porous, electrically conductive and corrosion-resistant material

Solution:

Sintered Ti powder (a)

Sintered Ti felt (b)

Expanded Ti mesh (c)

Carbon-based paper (d)

a) b)

d)c)

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From cell design …

Corrosion-resistant materials

Titanium

Coated metals

Plastic-composite

Pressure-resistant cell design

Metal-cutting production

Frame construction

Die cutting

Metal-laminate

injection molded

Structured plates with applied gaskets (Hamilton Sunderstrand, Fraunhofer ISE)

30 bar 12 bar 145 bar

7 bar 14 bar

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… to stack construction for PEM water electrolyser

Giner

Fraunhofer ISE

Helion

Fraunhofer ISE

Hydrogenics

h-tec

Fraunhofer ISE

Hamilton

Kurchatov

Filter press configuration

Pressure resistance: up to 207 bar

Active area: 10 – 750 cm²

Current density: up to 2.5 A/cm²

Cell voltage: max. 2.2 V

Number of cells: < 120

H2 production rate: 2 Nl/h – 30 Nm³/h

Power input per stack: up to 160 kWel (estimated)

Proton

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1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

0 5000 10000 15000 20000 25000

Mea

n C

ell V

olta

ge (V

)

Cumulative Time (hours)

On‐going  testing

Long-term performance of PEM electrolysis stacks

Typical stack life time

5,000 - 20,000 h in a system

Stack replacement: every 5 - 9 years

In military applications up to 100,000 h reported

Hydrogenics 91E13 cells stackoperating @ 2 A/cm²

Hydrogenics 91E stack

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PEM electrolysis system = stack + balance of plant

Pressure balanced system:

O2 and H2 side operates at same pressure

Differential pressure system:

Only hydrogen side is pressurised

Cell/stack design is more sophisticated

BoP more simple and less expansive

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Commercial PEM electrolyser

Schmidlin Proton FuMA-Tech ITM Power Hydrogenics Proton Claind Proton Statoil Treadwell

Compared to alkaline systems low H2 production rates:

100 Nml/min – 15 Nm³/h today

Up to 30 Nm³/h in the near future

H2 output at 6 – 30 bar and purified up to 6.0

Applications:

Laboratory equipment (e.g. gas chromatography)

Generator cooling in power plants

Float glas manufacturing and further industrial processes (food industry)

Military (submarines) and space

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How efficent are PEM electrolysers?

Prefered measure: specific power consump-tion in kWh/Nm³ H2

High efficiencies on stack level

Moderate efficiencies on system level(low H2 production rates)

2

4

6

8

10

0.1 1.0 10.0 100.0

Hydrogen Production Rate [Nm3 h-1]

Pow

er C

onsu

mpt

ion

[kW

h N

m-3

H2]

systems

stacks

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Comparison of alkaline and PEM electrolysers

Comparable young technology, still high potential for further improvement

Principle advantages:

Simple system configuration

Very high current and power densities

High efficiencies on cell level

Very fast response time, suitable for coupling with RES

Usage of expensive materials (membrane, electrodes, bipolar plates)

Attractive competitive position for small electrolysis units << 100 Nm³/h

How large will PEM electrolysers become in the next 10 years??

Small footprint

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Comparison of alkaline and PEM electrolysers

AEL PEMELCurrent density

Power density

Efficiency (system)

System complexity

Durability / Life cycle

Investment costs

- +

-- +

+ o

- o

++ o

o -

today

AEL PEMELo ++

- ++

+ +

- o

++ +

o o

in the future

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Manufacturer of water electrolyser

Alcaline Electrolysis PEM-Electrolysis

R&D

Com-mer-

cial

This figure does not claim to be exhaustive!

Manufacturer of water electrolysers - Who is on the road?

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NEXPEL main objective: Develop and demonstrate a PEM water electrolyser integrated with RES:

75% Efficiency (LHV), H2 production cost ~ €5,000 / Nm3h‐1, target lifetime of 40,000 h

New membrane materials

New catalysts Improved MEAs

Novel stack design and new construction materials

Improved DC‐DC converter

Jan 2010 ‐ Dec 2012Co‐ordination: SINTEF

Funding: Fuel Cells and Hydrogen JUTotal Budget:  € 3,353,549

www.nexpel.eu 

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Thank you for your kind attention!

Tom Smolinka

Fraunhofer ISE

Heidenhofstr. 2 / 79110 Freiburg / Germany

Ph: +49 761 4588 5212

tom.smolinka@ise.fraunhofer.de

www.ise.fraunhofer.de

Questions?