A photocatalytic reactor, capable of generating an electric current by consumption of a fuel containing organic material, comprises a direct oxidation fuel cell including an anode and a cathode. The anode is a photocatalysis-assisted anode which comprises a photocatalyst on a surface of an electrically-conductive substrate so arranged as to be receptive to light. A light-transmissive proton-conductive membrane is arranged between the anode and the cathode, such that light passes through said membrane as a final stage in the optical path to the photocatalyst. The photocatalyst promotes oxidation of organic material and generates electron-hole pairs. The reactor, configured to support multiple cells in a stacked array, is provided with inlet(s) for introducing said fuel and connector(s) for connection to an external electrical circuit.