Experimental and thermodynamic study on the performance of water electrolysis by solid oxide electrolyzer cells with Nb-doped Co-based perovskite anode

•BCFN was applied on traditional YSZ electrolyte with GDC interlayer.•Dense YSZ-GDC bilayer electrolyte was obtained by co-sintering at 1300 °C.•Area specific resistance of full cell is 0.195 Ω cm2 at 800 °C with 60% water vapor.•Cell voltage is 1.13 V at 1 A cm−2 at 800 °C with feedstock of 60% H2O-40% H2.•The electricity to hydrogen efficiency is 73% with generation rate of 4180 L h−1 m−2.

In this work, Solid Oxide Electrolyzer Cell (SOEC) based on Ba0.9Co0.7Fe0.2Nb0.1O3-δ (BCFN) air electrode and YSZ-GDC bilayer electrolyte was systematically investigated and the efficiency of high-temperature water electrolysis by such a cell was analyzed. Firstly, chemical compatibility test between BCFN and YSZ showed that BaZrO3 formed after heat treatment at 1000 °C for 5 h, which adversely influenced the performance of BCFN dramatically. A fully dense GDC interlayer was thus developed by co-sintering GDC layer, with addition of 0.5 at.% Fe2O3, with YSZ electrolyte at only 1300 °C. The as-prepared fuel electrode-supported eletrolyzer cell consisting of Ni-YSZ fuel electrode, YSZ-GDC bilayer electrolyte and BCFN air electrode was evaluated for water electrolysis. Specifically, at 800 °C using a feedstock of 60% H2O-40% H2, the cell showed total area specific resistance of 0.195 Ω cm2 and the cell voltage was 1.13 V with an electrolysis current of 1 A cm−2. After short-term stability test for 120 h with 1 A cm−2 electrolysis current at 800 °C, the cell showed no microstructural changes as observed by scanning electron microscopy. At last, a high-temperature water electrolysis system based on the cell studied was proposed and the system analysis shows that the overall electricity to hydrogen efficiency can reach 73% based on lower heating value of hydrogen, with a hydrogen generation rate of 4180 L h−1 m−2.