Rational Design, Synthesis, And Characterization Of BiVO₄-based Heterojunction Photocatalysts

Bismuth vanadate (BiVO4) has recently received a considerable attention due toits good chemical stability，high photocatalytic activity as well as excellent visiblelight response, which makes it one of the most promising visible light photocatalysts.However, its practical usage is largely suppressed by the fast recombination oflight-induced electron-hole pairs. This drawback can be effectively alleviated byconstructing BiVO4-based heterojunction photocatalysts to enhance the separation ofelectron-hole pairs. Therefore, it is significantly important to explore the ways toconstruct highly efficient BiVO4-based heterojunction photocatalysts. In this paper,we focus on the rational design, synthesis and characterization of highly efficientBiVO4-based heterojunction photocatalysts.Firstly, we studied the effects of semiconductor facet-selective deposition on thephotocatalytic activity of heterostructured photocatalysts. Specifically, we constructeda highly efficient Ag3PO4/BiVO4heterojunction photocatalyst with Ag3PO4nanoparticles selectively deposited on BiVO（4040）facets. The characterization resultsindicate that, by forming high quality Ag3PO4/BiVO4heterojunction on BiVO4（040）facets, the local structure of BiVO4is changed. Also, the energy band structures aredifferent in each facets of BiVO4. Both of them can enlarge the potential differencesbetween Ag3PO4and BiVO4to increase the charge separation efficiency. Thephotocatalytic activity of the Ag3PO4/BiVO4composite is thus greatly enhanced.These results indicate that the semiconductor facet-selective deposition can overcomethe low potential difference in heterostructured photocatalysts, which provides apromising way to construct highly efficient heterojunction photocatalysts.Then, we studied the effects of discrete decoration of nano-heterojunctions on thephotocatalytic activity of heterostructured photocatalysts. Specifically, we obtained aseries of g-C3N4/BiVO4photocatalysts with different heterojunction morphologies bya template-thermal etching route. The results show that the g-C3N4/BiVO4compositewith g-C3N4nano-islands discretely attaching on monoclinic porous BiVO4showssuperior photocatalytic activities compared to those with continuous g-C3N4filmscoating on BiVO4surfaces. The superior photocatalytic activity of the g-C3N4/BiVO4composite with g-C3N4nano-islands discrete decoration can be ascribed to theincreased charge separation efficiency, fully exposed high-reactive phase interfaces and the separated redox reaction sites, which may induce a steady state photocurrentwithin the regions near the g-C3N4-BiVO4islands-core interfaces, driven by theinternal built-up electric field at the interface. The continuous g-C3N4film coveringBiVO4surfaces can hinder the transfer of light-induced charges to the surfaces,causing a less efficient charge separation efficiency thus lower photocatalytic activity.The results indicate that the discrete decoration of nano-heterojunctions is an effectiveway to form highly efficient heterojunction photocatalysts.