An internal reforming molten carbonate fuel cell having a membrane for intercepting carbonate vapor and hydrated vapor is disclosed. The intercepting membrane is made from nickel or nickel alloy which has a high electrical conductivity, corrosion resistant property in an anode environment, and a low affinity for the carbonate vapor. Due to the presence of the intercepting membrane, the transfer of the carbonate vapors and hydrated vapors to the internal reforming catalyst is markedly retarded to prolong the catalytic activity. As a result, a longer operating molten carbonate fuel cell can be obtained.