Unusual Promoting Effect of Ni–Cu Alloy Formation on Carbon Deposition in Carbonate-Superstructured Solid Fuel Cell with Methane Fuel

Copper is usually exploited to modify nickel-based anodes for solid oxide fuel cells for inhibiting coke formation due to its low cost, higher electronic conductivity, and inert property to carbon formation. Herein, however, it was found that the formation of a Ni–Cu alloy promoted coke formation in carbonate-superstructured solid fuel cells (CSSFCs). Namely, a Ni–Cu alloy anode suffered remarkable carbon deposition that is approximately 2 orders of magnitude greater than that in either a Ni–Cu bimetallic anode or a pure Ni anode in a CSSFC with methane fuel. The Ni–Cu alloy anodes exhibit expanded lattice parameters and surface enrichment of copper, balancing the methane decomposition and carbon diffusion processes and leading to the formation of carbon filaments, thereby diminishing both the peak power densities and the overall stability of the CSSFC.