Bismuth-based semiconductor, with superior photocatalytic activity and especially with good absorbance in visible light, have become the research hotspot in photocatalytic field recently. The valence band of bismuth-based semiconductor photocatalyst consist of Bi6s and O2p orbitals and the levels are more negative than that consisting of only O2p, which results in the decrease in the band gap. The visible-light-induced photocatalytic activity of bismuth-based semiconductor photocatalysts is higher than that of traditional TiO₂. However, the low quantum efficiency, the easy recombination of electrons and holes, and the low visible light absorption making the bismuth-based semiconductor photocatalysts far away from practical use. Therefore, we must take some measures to improve the efficiency of photocatalytic carriers, suppress the combination of photo electrons and holes, and increase the visible light absorption. This article reviews the recent development of methods for improving the photoactivity of bismuth-based semiconductor photocatalysts, mainly including morphology control, special crystal face exposing, noble metal deposition, metal ion doping, nonmetal doping, semiconductor combination and so on. The relationship between these methods and photocatalytic activity is analyzed, and it may be useful for designing highly efficient bismuth-based semiconductor photocatalysts. Besides, the main problems of the bismuth-based semiconductor photocatalysts are discussed, and the direction of development of the bismuth-based semiconductor photocatalysts is pointed out.

Contents
1 Introduction
2 Morphology and structure control
2.1 Synthesis of photocatalysts with special morphology
2.2 Porous structure
2.3 Highly active crystal face exposing
3 Noble metal depositing
4 Metal ion doping
5 Nonmetal doping
5.1 Carbon doping
5.2 Nitrogen doping
5.3 Graphene composite
5.4 Anion doping
5.5 Polymer modification
6 Semiconductor composite
7 Conclusion and outlook