A direct-methane fuel cell with a ceria-based anode

Fuel cells constitute an attractive power-generation technology that converts chemical energy directly and with high efficiency into electricity while causing little pollution. Most fuel cells require hydrogen as the fuel, but viable near-term applications will need to use the more readily available hydrocarbons, such as methane. Present-day demonstration power plants and planned fuel-cell electric vehicles therefore include a reformer that converts hydrocarbon fuel into hydrogen. Operating fuel cells directly on hydrocarbons would obviously eliminate the need for such a reformer and improve efficiency. In the case of polymer-electrolyte fuel cells, which have been studied for vehicle applications, the direct use of methanol fuel has been reported, but resulted in fuel permeating the electrolyte. Solid oxide fuel cells - promising candidates for stationary power generation - can also use hydrocarbon fuel directly to generate energy, but this mode of operation resulted in either carbon deposition at high temperatures or poor power output at low operating temperatures. Here we report the direct electrochemical oxidation of methane in solid oxide fuel cells that generate power densities up to 0.37 Wcm^-2 at 650°C. This performance is comparable to that of fuel cells using hydrogen and is achieved by using ceria- containing anodes and low operating temperatures to avoid carbon deposition. We expect that the incorporation of more advanced cathodes would further improve the performance of our cells, making this solid oxide fuel cell a promising candidate for practical and efficient fuel-cell applications.