BiVO4photocatalysis design and applications to oxygen production and degradation of organic compounds: a review

Bismuth vanadate, BiVO4, is a visible-light response semiconductor for photocatalysis applications such as organic pollutants degradation, oxygen production and carbon dioxide reduction. However, as a single-phase photocatalyst, BiVO(4)efficiency is limited by the unpreferable recombination of the photoexcited electron (e(-)) and hole (h(+)). Thus, strategies have been designed to enhance the photocatalytic efficiency by promoting the separation of electrons and holes. This can be done by controling the morphology and crystallographic facets of BiVO4, and by building p-n junction photocatalytic systems with a combination of n-type semiconductors (BiVO4) and p-type semiconductors or a monoclinic-tetragonal heterostructure of BiVO4. In particular, a direct p-n junction photocatalytic system with tetragonal zircon-structured BiVO4(t-z) and monoclinic scheelite-structured BiVO4(m-s) combination has recently attracted attention. Here we review the synthesis of the monoclinic-tetragonal heterostructured BiVO(4)photocatalyst (m-t BiVO4) by calcination, hydrothermal, microwave-assisted hydrothermal and solvothermal methods. m-t BiVO(4)formation and the transmission phase between t-z and m-s are controlled by the calcining temperature, precursor pH, metal doping content, type of solvent, implementation of precursors and reaction conditions. We discuss m-t BiVO(4)crystal structure, optical characteristics and photocatalytic principles. Successful formation of BiVO(4)crystals with a m-s/t-z heterostructure is based on data from X-ray diffraction (XRD), Raman and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). In the m-t BiVO(4)heterostructure, a direct p-n junction photocatalytic system is established. When this system is exposed to visible light, the electrons in the conduction band of m-s BiVO4, a n-type semiconductor, migrate easily to the conduction band of t-z BiVO4, while the holes on valence band of t-z BiVO4, a p-type semiconductor, move to the valence band of m-s BiVO(4)through an internal electric field. As a result, the e(-)/h(+)charge carriers are spatially separated.