The hydrogen sulfated fullerenol C-60 (OSO3H)(n) (OH)(n) shows proton conductivity under ambient conditions. Electrolysis of water vapor in air was examined using a membrane electrode assembly (MEA) of the fullerene-based proton conductor. Electrochemical measurements showed that hydrogen is generated without additional humidification of the MEA. The hydrogen generation rate has a strong dependence on temperature that is related to proton conductivity, and on water partial pressure that is related to the activation energy attributed to the changing of proton transport mechanisms from proton hopping to vehicular type. (C) 2002 The Electrochemical Society.