The utilization of as the fuel in a solid‐oxide fuel cell was demonstrated, with the achievement of 42 mA/cm2, the highest current density achieved with to date. Two different ionic conductor electrolyte systems have been studied, oxide ion conductors and protonic conductors; the electrolyte membranes had the common component of ceria, . The cells studied had the configurations , , air (where ) or , , air. Initial results at operating temperatures of 650 to 750°C are reported with yttria‐doped ceria, at 690°C with samaria‐doped ceria, and at 700°C with ytterbia‐doped strontium cerate.