H₂O₂ production on a carbon cathode loaded with a nickel carbonate catalyst and on an oxide photoanode without an...

Efficient H₂O₂ 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 H₂O₂ production (FE(H₂O₂)) on a carbon cathode in KHCO₃ 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 KHCO₃ aqueous solution at ambient temperature. The nickel carbonate basic hydrate electrode was very stable, and the accumulated concentration of H₂O₂ was reached at 1.0 wt% at a passed charge of 2500C (the average FE(H₂O₂) was 80%). A simple photoelectrochemical system for H₂O₂ production from both the cathode and a BiVO₄/WO₃ photoanode was demonstrated without an external bias or an ion-exchange membrane in a one-compartment reactor under simulated solar light. The apparent FE(H₂O₂) from both electrodes was calculated to be 168% in total, and the production rate of H₂O₂ was approximately 0.92 μmol min^-1 cm^-2. The solar-to-chemical energy conversion efficiency for H₂O₂ production (STC_H ) without an external bias was approximately 1.75%.