In situ formation of a solid oxide fuel cell (SOFC) cermet anode by NiWO4 reduction

The presented work describes a process for producing a mixed-conducting SOFC cermet anode through the in situ reduction of a ternary oxide. A porous nickel tungstenate (NiWO4) was screen-printed and bonded onto an yttrium-stabilized zirconia (YSZ) electrolyte-supported SOFC by treatment at 1000 °C for 1 h. An (La,Sr)MnO3/Ce0.9Gd0.1O2(LSM/GDC) was utilized as the cathode with the NiWO4 acting as the anode for the SOFC. The ∼1-cm diameter fuel cell with a ∼100-μm thick YSZ electrolyte was tested in H2 fuel at 800 °C. During the insertion of the H2 fuel, the NiWO4 was reduced to form a Ni/WOx cermet composite that consisted of a fine mixture of Ni-nanoparticles dispersed over the porous WOx support structure. A maximum power density of ∼104 mW cm−2 was attained for the reduced NiWO4 anode, even with an un-optimized and dense microstructure, on an electrolyte-supported cell. The power density was increased to ∼165 mW cm−2 with the incorporation of GDC powder into the NiWO4 anode. The same NiWO4/GDC composite was tested within a fuel stream of H2 containing 10 ppm PH3. The cell's degradation rate was 0.006 V h−1 for 5 h at 750 °C, which is similar to that observed for conventional Ni/YSZ cermets.

► SOFC cermet anode in situ synthesized by reduction of NiWO4 composition. ► XPS analysis showed that anode was composed of Ni, W, WO2, and WO3 mixture. ► Electrolyte-supported SOFC showed 104 mW cm−2 (800 °C) with unoptimized microstructure. ► Gd-doped ceria additions to NiWO4 anode increased SOFC performance.