Improved photoelectrochemical activity of CaFe2O4/BiVO4 heterojunction photoanode by reduced surface recombination in solar water oxidation.

A bismuth vanadate photoanode was first fabricated by the metal-organic decomposition method and particles of calcium ferrite were electrophoretically deposited to construct a heterojunction photoanode. The characteristics of the photoanodes were investigated in photoelectrochemical water oxidation under simulated 1 sun (100 mW cm(-2)) irradiation. Relative to the pristine BiVO4 anode, the formation of the heterojunction structure of CaFe2O4/BiVO4 increased the photocurrent density by about 60%. The effect of heterojunction formation on the transfer of charge carriers was investigated using hydrogen peroxide as a hole scavenger. It was demonstrated that the heterojunction formation reduced the charge recombination on the electrode surface with little effect on bulk recombination. The modification with an oxygen evolving catalyst, cobalt phosphate (Co-Pi), was also beneficial for improving the efficiency of CaFe2O4/BiVO4 heterojunction photoanode mainly by increasing the stability.