A comprehensive evaluation of a Ni-Al2O3 catalyst as a functional layer of solid-oxide fuel cell anode

An inexpensive 7 wt.% Ni-Al₂O₃ composite is synthesized by a glycine-nitrate process and systematically investigated as anode catalyst layer of solid-oxide fuel cells operating on methane fuel by examining its catalytic activity towards methane partial oxidation, steam and CO₂ reforming at 600-850 °C, cell performance, mechanical performance, and carbon deposition properties. Ni-Al₂O₃ shows comparable catalytic activities to Ru-CeO₂ for the above three reactions. The cell with a Ni-Al₂O₃ catalyst layer delivers maximum peak power densities of 494 and 532 mW cm⁻² at 850 °C, operating on methane-H₂O and methane-CO₂ mixture gases, respectively, which are comparable to those operating on hydrogen. Ni-Al₂O₃ is found to have better mechanical performance than Ru-CeO₂. O₂-TPO demonstrates that Ni-Al₂O₃ does not inhibit the carbon formation under pure methane atmosphere, while the introduction of steam or CO₂ can effectively suppress coke formation. However, due to the low nickel content in the catalyst layer, the coke formation over the catalyst layer is actually not serious under real cell operation conditions. More importantly, Ni-Al₂O₃ effectively protects the anode layer by greatly suppressing carbon formation over the anode layer, especially near the anode-electrolyte interface. Ni-Al₂O₃ is highly promising as an anode functional layer for solid-oxide fuel cells.