Intrinsic Mechanism Analyses of Significantly Enhanced Photoelectrochemical Performance of the Bi₂MoO₆/BiVO₄ System

In this paper, the electrodeposition and hydrothermal methods were used to prepare the Bi₂MoO₆/BiVO₄ photoelectrode, and the intrinsic mechanism of significantly enhanced photoelectrochemical performance of the prepared Bi₂MoO₆/BiVO₄ heterojunction system was studied. Work functions of Bi₂MoO₆ and BiVO₄ were analyzed using a scanning Kelvin probe, and the direction of the heterojunction electric field and the transfer direction of photogenerated carriers were finally determined by the relative positions of the energy bands and the Fermi levels of Bi₂MoO₆ and BiVO₄. A type II Bi₂MoO₆/BiVO₄ heterojunction system was finally confirmed to be formed. Formation of the type II Bi₂MoO₆/BiVO₄ heterojunction system reduces the recombination efficiency of photogenerated electrons and holes and thus improves the photoelectrochemical performance. The photogenerated current density of the Bi₂MoO₆/BiVO₄ photoelectrode reaches 1.47 mA·cm^-2, which is 4.9 times that of pure BiVO₄ and thousands of times that of Bi₂MoO₆. The successful application of a scanning Kelvin probe in the verification of the heterojunction type provides theoretical and technical bases for the design and construction of efficient heterojunctions.