Development of Tubular Proton Conducting Electrolysers

Einar Vøllestad2, M.L. Fontaine1, C. Denonville1, R. Strandbakke2, J.M. Serra3, D.R. Beeaff4, C. Vigen4 and T. Norby2

1 SINTEF Materials and Chemistry, 2 University of Oslo, 3 CSIC, 4 CoorsTek Membrane Sciences AS

Development of Tubular Proton Conducting Electrolysers

Einar Vøllestad2, M.L. Fontaine1, C. Denonville1, R. Strandbakke2, J.M. Serra3, D.R. Beeaff4, C. Vigen4 and T. Norby2

1 SINTEF Materials and Chemistry, 2 University of Oslo, 3 CSIC, 4 CoorsTek Membrane Sciences AS

Why high temperature proton ceramic electrolysers?

Processing and performance of early-stage single cells

Up-scaling strategies for tubular proton ceramic electrolysers

High temperature electrolysis enables utilization of waste heat resources

PCE SOE

2H2OΔH

2H2 + O2

Key differences between SOE and PCE- advantages and challenges

Solid Oxide Electrolysers Well proven technology

Scalable production High current densities at thermo-neutral voltage

Long term stability challenges Delamination of O2-electrode Oxidation and degradation of Ni-electrode with high

steam contents High temperatures

Proton Ceramic Electrolysers Less mature technology

Fabrication and processing challenges Produces dry H2 directly Potentially intermediate temperatures

Slow O2-electrode kinetics

U

2O2-

2H2O

2H2

O2

SOEC

600-800°C

4e-

U

4H+2H2

O2

2H2OPCEC

400-700°C

4e-

Development of tubular cathode supported

electrolyte cell

Development and optimization of anodes and current collection

Single tube module development and

testing

Multi-tube module testingAim: 1kW demo

H+

H+

H+

O2H2O

e-

e-

BZY

O2e-

O2

H+

H+

H+

H2O

e-

e-

BZY

O2

e-

H+

H+

H+

O2H2O

e-

e-

BZY

O2e-

O2-

Protonic conductor e- Conductor nanoparticlesMixed Oxygen ion-electronic conductor

a b c

Process integration and evaluation

High temperature electrolyser with novel proton ceramic tubular modules (2014-2017)

Tubular half-cell production

Dip-coatingsuspensions

NiO based paste

Wet milling of precursors

Solid State Reactive Sintering

Extrusion of BZCY-NiOsupport

Spray- or dip-coating

BZCY72 // BZCY72-NiO BZY10 // BZY10-NiO BZY10 // BZCY72-NiO

Dense electrolyte @ 1550°C – 24h1610°C – 6h

Porous electrolyte @ 1550°C – 24h1610°C – 6h1650°C – 6h1670°C – 6h

Dense electrolyte @ 1550°C – 24 h1610°C – 6 h

100 microns 100 microns 100 microns

40 microns 40 microns 40 microns

Development of new anode materials

1.0 1.1 1.2 1.3 1.4 1.5 1.6

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

GBCF / BZCY BSCF / BCY Pr2NiO4 / BCY LSCF / BCY BGCF / BCY BGLC (x=0) / BZCY BCZF

log

((Rp (Ω

cm2 )

1000/T (K-1)

750 700 650 600 550 500 450 400 350T (°C)

Ba1-xGd0.8La0.2+xCo2O6-δ displays best PCE O2-H2O-electrode performance(symmetrical disk samples)

0.8 1.0 1.2 1.4 1.6 1.8

-2

-1

0

1

2

X = 0.1 X = 0.5 X = 0* X = 0.3

Log(

Rp,

app(Ω

cm2 ))

1000 / T (K-1)

800 600 400

0.01

0.1

1

10

100

Rp,

app(Ω

cm2 )

T (°C)

0.04 Ωcm2

Anode processing on tubular cells

Electrolysis tests using gold as the current collector

Fired in dual atmosphere with applied bias:- 2% O2 outside, 5% H2 inside- Ecell = 1.4 V during firing (above 500°C)

Steam electrode (BGLC785) drip-coated and brush-painted

Capped and sealed using custom-made glass ceramic (CoorsTek Membrane Sciencies)

Single segment, reduced at 1000°C for 24h in 5% H2

Electrolysis tests of single cell

0 50 100 150 200 250

1.0

1.5

2.0

600°C550°C

650°C700°C

Pot

entia

l (V

)

Current (mA cm-2)

pO2: 80 mbar pH2O: 1.5 barpH2: 300 mbar

Improved performance with increasing steam content and current load

4 5 6 7 8

3

2

1

0

-1

OCV 11 mA cm-2

21 mA cm-2

64 mA cm-2

Z// (Ωcm

2 )

Z/ (Ωcm2)

Both electrolyte and electrode performance improved with increased steam content

0.00 0.05 0.10 0.15 0.20 0.250.8

1.0

1.2

1.4

1.6

1.8

pH2O: 1.5 bar

pH2O: 0.5 bar

Vol

tage

(V)

Current density (mA cm-2)

High ohmic resistance indicates current collection limitations

Electrode resistance an order of magnitude higher than expected values from button cell testing

0 50 100

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

Rp

(Ωcm

2 )

Log(

Rp

(Ωcm

2 ))

I (mA cm-2)

550 600 600 (x =0.5) 650 700 700 (x = 0.5)

1

Target: 0.2Ωcm2

1.0 1.2 1.4 1.6-2

-1

0

1

2

1000/T (K-1)

log(

Rp(Ω

cm2 ))

RP (x = 0) RP modelled RP modelled (x = 0) RP (x = 0.3) RP (x = 0.5)

700 600 500 400

0.01

0.1

1

10

100

Rp(Ω

cm2 )

T (°C)

Tube segment 1.5 bar steam

Button cell wet air

Scaling up – segmented tubes to drive up the voltage

Scaling up – stacking individual segments

Scaling up – “Printing in series”

Segmented-in-series tubular cells

Porous support

H2 electrode (PCEC cathode)

H2O+O2 electrode (PCEC anode) with integrated and patterned external current

collection

Novel interconnectsH2O + O2 flow

H2 flow

Electrolyte

Novel external current collectors at closed/open ends of tube

1

1 BZCY (SSRS) + sintering aid + pore formers

2BZY10 (SSRS or oxide)or BZCY72 (SSRS or oxide)+ NiO

3 BZCY72 or BZY10 (SSRS or oxide)

Manufacturing process

Powder conditioning

Pastes preparation

Production of tubes by extrusion and collars

Dip-coating of tubes

Slurries preparation

Annealing of tubes (hang-firing)

• Milling of SSRS precursors and oxide powders

• Drying• Sieving• Batching

• Water based slurryfor SSRS mixtures

• Organic basedslurries for oxidemixtures

• Drying• Cutting• Masking and coating

• Drying in air (organicbased coating) or at 60°C for water basedsuspensions

Green supports with electrodes

Green support coated with cathode (green) and electrolyte (white) layers

Hang-firing of cells

Clean room activities

3 cm

20 cm

Parameters investigated

SupportsSupport +

fuel electrode

Support + fuel electrode +

electrolyte

Shrinkage; porosity• Annealing• PF content• Sintering aid

Shrinkage, porosity• Coated part • Uncoated part

Thickness of electrode• Viscosity• Powder loading

Shrinkage, porosity• Coated part• Uncoated part

Thickness of electrode• Viscosity• Powder loading

Thickness and densification of electrolyte• Oxide vs SSRS• Powder loading

NiO-BZCY

BZCY electrolyte

NiO-BZCY

BZCY electrolyte

NiO-BZCY

Support Support

100 µm

100 µm

50 µm50 µm50 µm

Broken section: several segments; non-optimized sintering

Optimized processing parameters for multi-layer sintering

23

30 µm

300 µm

Dense electrolyte

Dense NiO-BZCY (porosity will be generated by NiOreduction to Ni)

Porous BZCY support

Conclusions High temperature proton ceramic electrolysers can produce dry,

pressurized hydrogen

Processing and manufacturing of tubular half cells is now well established

State-of-the-art electrolyser anodes are developed on button cell scale Deposition and firing protocols for tubular cells currently being developed

Segmented-in-series tubular cells are needed to reduce total current of tubes in real operational conditions

Acknowledgements

The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) for the Fuel Cells and Hydrogen Joint Technology Initiative under grant agreement n° 621244.

Thank you for your

attention!