Using a proton conductor based on SrZrO3 or CaZrO3 as a solid electrolyte, three attempts have been made to react CH4 with CO2 efficiently. When the mixture of CN4 and CO2 was used as a fuel gas for a SOFC, the cell provided stable electric power. Furthermore, the electrochemical hydrogen pump accelerated both the reforming of CH4 with CO2 and the oxidative coupling of CH4 with CO2.