Investigation of 30-cell solid oxide electrolyzer stack modules for hydrogen production

The 30-cell nickel-yttria stabilized zirconia (Ni-YSZ) hydrogen electrode-supported planar solid oxide electrolyzer (SOE) stack modules were manufactured and tested at 800 °C in steam electrolysis mode for hydrogen production. The electrolysis efficiency of the stack modules was higher than 100% at a total steam and hydrogen flow of 2.1 sccm cm−2, a H2O/H2 ratio of 80/20, and a current density of <0.2 A cm−2. The electrolysis efficiency, current efficiency, and actual hydrogen production rate of the stack modules increased with increasing H2O/H2 ratio at a constant current density. However, the electrolysis and current efficiencies decreased steadily at high current densities. During hydrogen production, the stack modules were operated at 800 °C and a constant current density of 0.15 A cm−2 for up to 1100 h. A steam conversion rate of 62% and current efficiency of 87.4% were obtained; the actual hydrogen production rate reached as high as 103.6 N L h−1. Post-mortem analysis showed that delamination of the LSM–YSZ oxygen electrode mainly occurred in the steam and air inlet area of the 10×10 cm2 cells.