Construction of heterojunctions by coupling two semiconductors together is one of the most efficient ways to realize the electron-hole pair separation. In this short paper, I systematically discuss the properties of heterojunction photocatalysts in all cases. The formation of space charge regions, built-in electric field and potential barriers at the interface regions of thermally equilibrated heterojunctions are analyzed in details. When the heterojunctions are used for photocatalysis, the transfer behavior and mechanism of photo-excited non-equilibrium carriers between the constituent semiconductors are discussed. It is demonstrated that the heterojunction properties, carrier transfer behavior and photocatalytic mechanism depend highly on the semiconductivity (N-type or P-type), work function (or Fermi level), and CB/VB potentials of the constituent semiconductors. All types of the heterojunction photocatalysts are expected to exhibit enhanced photocatalytic performances. This paper provides an important insight into the understanding of heterojunction photocatalytic mechanism and design of excellent heterojunction composite photocatalysts.

通过将两个半导体耦合在一起来构造异质结是实现电子-空穴对分离的最有效方法之一。在本文中，我系统地讨论了所有情况下异质结光催化剂的性能。详细分析了热平衡异质结的界面区域的空间电荷区域，内置电场和势垒的形成。当异质结用于光催化时，讨论了组成半导体之间光激发的非平衡载流子的转移行为和机理。结果表明，异质结性质，载流子迁移行为和光催化机理高度依赖于半导电性（N型或P型），功函（或费米能级），以及组成半导体的CB / VB电位。期望所有类型的异质结光催化剂都表现出增强的光催化性能。本文对异质结光催化机理的理解和优良的异质结复合光催化剂的设计提供了重要的见解。