Photocatalysis, in which solar photons are used to drive redox reactions to produce clean energy resources or to decompose environmental pollutants, has attracted considerable attention as we are facing the increasing challenges of diminishing fossil fuels and severe environmental pollution. Significant efforts have been made to develop various photocatalysts which can fundamentally dictate the overall efficiency of the solar energy conversion system. As a typical class of semiconductor photocatalysts, TiO₂ based composites have been widely investigated and well reviewed in literatures. Therefore, this review mainly gives a concise overview of several novel non-TiO₂ photocatalysts with a focus on their structural architectures and components which affect the catalytic activity. The article here includes five sections. After the first introduction section, the general working principles of semiconductor photocatalysts are presented in the second section. The main factors such as the light harvesting ability, the charge separation efficiency, the structure of the catalyst and the photoelectrochemical stability influencing the overall efficiency of photocatalytic reactions are discussed in section 3. Novel photocatalysts include Ag₃PO₄ based composites, non-TiO₂ metal oxides, sulfides, bismuth compounds and cobalt compounds are reviewed in section 4. Lastly, the fundamental challenges and perspectives of semiconductor photocatalysts are briefly brought up in section 5.

Contents
1 Introduction
2 Process and mechanism of photocatalysis
3 Factors affecting the photocatalytic efficiency
3.1 Light harvesting ability
3.2 Separation efficiency of photogenerated charges
3.3 Active specific surface area
3.4 Stability and recoverability
4 Novel photocatalysts without TiO₂ involved
4.1 Ag₃PO₄ based photocatalysts
4.2 Metal oxides
4.3 Sulfides
4.4 Bismuth compounds
4.5 Cobalt compounds
5 Conclusion and outlook