Solid oxide electrolysis cells (SOECs) use a combination of heat and electricity to electrocatalytically decompose water into oxygen and hydrogen

High temperatures (600-1000 °C) reduce the Gibbs free energy needed to reduce water and avoids the need for noble metals in comparison to low temperature PEM

∆𝐺 = ∆𝐻 − 𝑇 ∆𝑆

SOECs have benefited from solid oxide fuel cell (SOFC) advancements

Lifetime of SOECs is much lower than SOFCs, 9000 hours of operation compared to 40,000 [1, 2]

Transport limitations thought to cause diffusion of cations and high oxygen partial pressure at the anode-electrolyte interface, leading todelamination[3-5]

Introduction to SOECs Anodes deposited with a short spray pulse time, high air flow

rate, and low pin height were found to be most uniform Exhibiting uniform thickness, particle agglomerate size, and

pore size

A shorter spray pulse time deposited less ink onto the electrolyte, allowing complete solvent to evaporation and preventing an ink film where, particles could agglomerate

Spraying at higher flow rates and lower pin heights produced smaller ink droplets, limiting particle agglomeration

Particle agglomeration led to porenetwork limitations and a non-uniform thickness

Preparation of Uniform Anodes

Control of anode porosity will allow the systematic study of oxygen diffusion in SOEC anodes

Variation of solvent concentration provided control of anode porosity

Anode Porosity Control Pressure assisted spray deposition was to controllably prepare anodes

Solvent based inks were ball milledfor 20 hours and sonicated for 10 min

To achieve the desired morphology sprayparameters were adjusted

The important parameters were foundto be spray pulse time, the height thepin was lifted, the air flow rate, and thelevel of ink in the spray cup.

Spraying Setup

Polarization behavior of prepared anodes were tested and compared

Prior to electrolysis thin (2.4 μm) anode showed less hysteresis than thick (11.5 μm) anode

Given time for equilibration the performance of the thick anode greatly improved

No reduction in voltage over time was seen for the thin anode

Equilibration time is thought to allow oxygen diffusion rate to match oxygen evolution rate

Electrochemical Results

[1] Tietz F, Sebold D, Brisse A, Schefold J. Degradation phenomena in a solid oxide electrolysis cell after 9000 h of operation. J Power Sources. 2013 2/1;223(0):129-35.[2]Mai A, Iwanschitz B, Schuler JA, Denzler R, Nerlich V, Schuler A. Hexis’ SOFC System Galileo 1000 N – Lab and Field Test Experiences. ECS Trans. 2013 Oct 6;57(1):73–80.[3] Virkar AV. Mechanism of oxygen electrode delamination in solid oxide electrolyzer cells. International Journal of Hydrogen Energy. 201009;35(18):9527–43.[4] Kim J, Ji H-I, Dasari HP, Shin D, Song H, Lee J-H, et al. Degradation mechanism of electrolyte and air electrode in solid oxide electrolysis cells operating at high polarization. International Journal of Hydrogen Energy. 2013 6;38(3):1225–35.[5] Martin M. Materials in thermodynamic potential gradients. The Journal of Chemical Thermodynamics. 2003 Aug;35(8):1291–308.[6] Chen K, Jiang SP. Failure mechanism of (La,Sr)MnO3 oxygen electrodes of solid oxide electrolysis cells. International Journal of Hydrogen Energy. 2011 Aug;36(17):10541–9.

References

Comparison of polarization behavior of anodes with varied porosity

Electrical Impedance Spectroscopy (EIS) measurements to determine what transport processes are changing during equilibration

Conclusions & Future Work

Production and Testing of Solid Oxide Electrolysis Cell (SOEC) Anodes Graeme C. Clancy: Queen’s-RMC Fuel Cell Research Centre, Kingston, On, Canada

Ink LSM (g) [wt%] YSZ (g)

[wt %]

PVP (g) [wt%] IPA (ml) Porosity

Base

Line

(0.1652

±0.0010 g)

[0.55 %]

(0.1651

±0.0020 g)

[0.55 %]

(0.0066

±0.0019g)

[0.029 %]

(37.4ml)

[98.9%]

0.57

±0.036

Mid

Porosity

(0.1648

±0.0001g)

[0.44 %]

(0.1648

±0.0002 g)

[0.44 %]

(0.0066

±0.0003g)

[0.018 %]

(47.3 ml)

[ 99.4%]

0.64

±0.050

Prepare SOEC anodes of uniform morphology to test the effect of microstructure on transport

Prepare anodes of varied porosity to study diffusion limitations

Objectives

0.7

1

1.3

1.6

1.9

2.2

2.5

2.8

-0.3 -0.25 -0.2 -0.15 -0.1 -0.05 0

VO

LTA

GE

[V]

CURRENT DENSITY [A/CM2]

BL-30-04#2 0hrs upBL-30-04#2 0 hrs downBL-30-04#2 Post-Electrolysis UpBL-30-04#2 Post-Electrolysis downBL-30-04#3 0hrs upBL-30-04#3-0hrs down

-0.5

0.5

1.5

2.5

3.5

-0.5

0.5

1.5

2.5

3.5

105 110 115 120 125 130 135

Cu

rren

t D

ensi

ty

[A c

m-2

]

Vo

ltag

e [V

]

Time [hours]

Volt…

Ontario-China Research andInnovation Fund (OCRIF)

[6]