Review of various strategies to boost the photocatalytic activity of the cuprous oxide-based photocatalyst

Cuprous oxide (Cu2O) is a semiconductor with some interesting features, such as abundance in nature, low cost, low toxicity, and facile synthesis. It crystallizes in cubic structure and has a bandgap of 2.0–2.2 eV. Such a narrow bandgap renders it suitable as a visible-light photocatalyst. Nonetheless, the issues with photocorrosion, stability, and fast recombination of charge carriers restrict its application in photocatalysis. Although Cu2O is thermodynamically stable in air, it eventually degrades into copper(II) oxide in the presence of moisture and light. One viable strategy to enhance its stability against photocorrosion and to delay charge carrier recombination is to incorporate other materials to form composite photocatalytic materials. This review discusses the various methods used in improving the properties of Cu2O and the future outlook of this photocatalyst. The review begins with the basic structure, electronic and optical properties of Cu2O followed by the synthesis methods for preparing pristine and composite Cu2O photocatalysts as well as the strategies used in enhancing the photocatalytic performance of Cu2O. The promising applications in a wide range of photocatalytic reactions are summarized to illustrate its potential use. Finally, the challenges on the use of Cu2O photocatalysts are addressed as a concluding remark.