Hydrocarbon-fueled solid oxide fuel cells with surface-modified, hydroxylated Sn/Ni–Ce0.8Gd0.2O1.9 heterogeneous catalyst anode†
Ni-catalyst-based anode-supported solid oxide fuel cells (SOFCs) operating with H2 fuel are highly efficient, low-emission, electrochemical energy conversion devices. However, the economical production of hydrogen is a challenge, and there is immense interest to use hydrocarbon fuels directly with SOFC. Unfortunately, the solid-carbon generated continuously by hydrocarbon cracking accumulates on the Ni-metal surface and leads to rapid decline in performance. We show here that 1 atom% Sn (with respect to Ni) incorporated onto a surface-modified Ni–Ce0.8Gd0.2O1.9 (GDC) cermet anode with extended three-phase boundaries, where O2− ions, electrons, and fuels get together, acts as an excellent decoking agent. The hydrophilic Sn doped on the surface of Ni is hydrated and hydroxylated by reacting with the water vapour produced by the electrochemical oxidation of the fuel, and the hydroxyl groups aid the oxidation of neighbouring carbon and drive off as CO2. Moreover, the enlarged three-phase boundaries of the anode allow O2− ions to rapidly reach the deposited carbon as well as the hydrocarbon gas and electrochemically oxidize them. With this modified Sn/Ni–GDC catalyst anode, GDC electrolyte, and La0.6Sr0.4Co0.2Fe0.8O3−δ cathode, more than 200 h of operation with a methane-fueled SOFC is demonstrated here.