Synergistic effects of Ni1−xCox-YSZ and Ni1−xCux-YSZ alloyed cermet SOFC anodes for oxidation of hydrogen and methane fuels containing H2S

Preparation and performance of bimetallic Ni_(1−x)Co_x-YSZ and Ni_(1−x)Cu_x-YSZ anodes were tested to overcome common deficiencies of carbon and sulfur poisoning in SOFCs. Ni_1−xCo_xO-YSZ and Ni_(1−x)Cu_xO-YSZ precursors were synthesized via co-precipitation of their respective chlorides. Single cell solid oxide fuel cells of these bimetallic anodes were tested in H₂, CH₄, and H₂S/CH₄ fuel mixtures. Addition of Cu²⁺ into the NiO lattice resulted in large metal particle sizes and decreased SOFC performance. Addition of Co²⁺ into the NiO lattice to form Ni_0.92Co_0.08O-YSZ anode precursor produced a cermet with a large BET surface area and active metal surface area, thus increasing the rate of hydrogen oxidation for this sample. The performance of both bimetallics was found to quickly degrade in dry CH₄ due to carbon deposition and lifting of the anode from the electrolyte. However, Ni_0.69Co_0.31-YSZ showed superior activity in a 10% (v/v) H₂S/CH₄ fuel mixture, surpassing performance with H₂ fuel, thereby demonstrating the exciting prospect of using sulfidated Ni_(1−x)Co_x-YSZ as SOFC anodes in sulfur containing methane streams. The active anode becomes a sulfidated alloy (Ni-Co-S) under operating conditions. This anode showed enhanced performance, which surpassed those of sulfidated Ni and Co anodes, thereby suggesting a synergistic behaviour in the Ni-Co-S anode.