H 2 O 2 production on a carbon cathode loaded with a nickel carbonate catalyst and on an oxide photoanode without an external bias.

Efficient H 2 O 2 production both on a carbon cathode modified with various metal salts and on an oxide photoanode was investigated. The cathodic current density and faradaic efficiency for H 2 O 2 production (FE(H 2 O 2 )) on a carbon cathode in KHCO 3 aqueous solution were significantly improved by the loading of an insoluble nickel carbonate basic hydrate catalyst. This electrode was prepared by a precipitation method of nickel nitrate and KHCO 3 aqueous solution at ambient temperature. The nickel carbonate basic hydrate electrode was very stable, and the accumulated concentration of H 2 O 2 was reached at 1.0 wt% at a passed charge of 2500C (the average FE(H 2 O 2 ) was 80%). A simple photoelectrochemical system for H 2 O 2 production from both the cathode and a BiVO 4 /WO 3 photoanode was demonstrated without an external bias or an ion-exchange membrane in a one-compartment reactor under simulated solar light. The apparent FE(H 2 O 2 ) from both electrodes was calculated to be 168% in total, and the production rate of H 2 O 2 was approximately 0.92 μmol min -1 cm -2 . The solar-to-chemical energy conversion efficiency for H 2 O 2 production (STC H 2 O 2 ) without an external bias was approximately 1.75%.