Advances in dual-functional photocatalysis for simultaneous reduction of hexavalent chromium and oxidation of organics in wastewater

The solar-driven photocatalytic process has been evolved as a promising technology for both hexavalent chromium reduction and organic pollutants oxidation. Although both reactions are based on the same principle of photoinduced interfacial charge transfer, different catalysts and reaction conditions are required in two processes. This review revealed the scientific advances in dual-functional photocatalytic processes that enable simultaneous hexavalent chromium reduction and organics oxidation. Firstly, the basic principles of dual-functional photocatalysis are briefly discussed whereby the key concept of the system is the simultaneous oxidation of organic pollutants via photogenerated holes and reduction of hexavalent chromium via photogenerated electrons. Then, advances in dual-functional photocatalysis for the simultaneous removal of hexavalent chromium and organics are presented and discussed in terms of catalysts classification, including TiO2-based, bismuth-based and g-C3N4-based catalysts. Finally, the prospects, challenges and new perspectives of feasible solutions for dual-functional photocatalytic catalysts design are presented. Overall, this paper provides new insights on the modulation strategies and conformational relationships of dual-functional materials for researchers in the field of photocatalysis, which is beneficial for the practical applications of dual-functional materials in environmental remediation.