A MnFe2O4/BiVO4 film photoanode with heterojunction, co-catalytic and photothermal effects for effective solar water oxidation†
Abstract
To modify the solar water splitting performance of BiVO4 photoanodes, the search for effective co-catalysts with photothermal conversion and p-type semiconductor properties is significant. Herein, spinel MnFe2O4 nanoparticles were selected as co-catalysts and coupled on BiVO4 film to form a MnFe2O4/BiVO4 film photoanode for solar water oxidation. Relative to a BiVO4 film photoanode, the MnFe2O4/BiVO4 film photoanode achieved higher activity, faster kinetics and better stability for solar water oxidation. At 1.23 V vs. RHE, the water oxidation photocurrent on the MnFe2O4/BiVO4 film photoanode was 2.58 mA cm−2, which was more than twice that on the BiVO4 film photoanode (1.06 mA cm−2). In addition, the MnFe2O4/BiVO4 film photoanode showed stable activity in solar water oxidation for 2 h of reaction. The higher solar water oxidation performance of the MnFe2O4/BiVO4 film photoanode mainly stemmed from the synergism of its p–n heterojunction, co-catalytic and photothermal effects. Specifically, MnFe2O4 nanoparticles coupling on BiVO4 film can form p–n heterojunctions, which could promote the separation and transfer of carriers, and more holes could drive water oxidation. Meanwhile, spinel MnFe2O4 nanoparticles can capture some solar light to produce heat due to their photothermal properties, which is beneficial to the achievement of endothermic water oxidation. Furthermore, the co-catalytic properties of spinel MnFe2O4 could boost the water oxidation activity and kinetics. As a synergism result, higher solar water oxidation performance was achieved for the MnFe2O4/BiVO4 film photoanode.