Improved Surface Charge Transfer in MoO3/BiVO4 Heterojunction Film for Photoelectrochemical Water Oxidation

A MoO3/BiVO4 heterojunction film consisting of dispersed nano-MoO3 on the surface of BiVO4 nanoflake was constructed for photoelectrochemical water oxidation. In comparison with bare BiVO4 and MoO3 film, the MoO3/BiVO4 heterojunction film shows enhanced water oxidation activity. At 0.8 V vs. SCE, the photocurrent on the optimal MoO3/BiVO4 heterojunction film increases by up to about 6 times compared to that on the bare BiVO4 film. The conduction and valence band potential of MoO3 are found to be more positive than those of BiVO4, and the electric conductivity for MoO3 and BiVO4 is on the order of 10−6 S cm−1 and 10−9 S cm−1, respectively. Thus, the origin of enhanced water oxidation activity on the MoO3/BiVO4 heterojunction film can be primarily ascribed to the band potential and conductivity differences between MoO3 and BiVO4, which are advantageous for separating and transferring the surface charge of BiVO4.