Photoelectrochemical reduction of aqueous protons with a CuO|CuBi2O4 heterojunction under visible light irradiation.

A p-type heterojunction photoelectrode consisting of platinized CuBi2O4 layered on a CuO film was prepared. The CuO|CuBi2O4|Pt electrode photo-generates H2 in pH neutral aqueous solution during visible light irradiation and exhibits a substantially enhanced photocurrent compared to CuO|Pt and CuBi2O4|Pt electrodes. Reduced electron-hole recombination by the band offsets in the heterostructure is responsible for the improved photoelectrochemical performance of CuO|CuBi2O4 with a small band-gap of approximately 1.5 eV.