A comparative study on recent progress in efficient ZnO based nanocomposite and heterojunction photocatalysts: A review

Highlights: • A comparative study on ZnO based binary/multiple nanocomposite and heterojunction photocatalysts. • Hydrothermally produced ZnO/CuO heterostructure shows the best photocatalytic action. • Thermal growth of γ-Fe₂O₃-ZnO-biochar multiple nanocomposite exhibited the highest photocatalytic activity. • Overall, the best photocatalytic action observed for the ZnO/CuO binary heterostructure. -- Abstract: ZnO based binary and multiple heterojunction/nanocomposite photocatalysts get profound attentions due to its solving the world crises of energy supply and utilizing sun power potential to generate H₂, coal oil materials and degradation of various pollutants. In the past decade, a number of motivating fulfillments have been done on the ZnO based heterojunction/nanocomposite photocatalysts, which are significant materials for the photocatalytic process. However, the proficiency of the photocatalysis stands low because of the swift electron-hole reincorporation and low light usage. So, to solve these issues huge efforts have been made considered. Specially, the produced high quality ZnO based heterojunction/nanocomposite photocatalysts are exhibited in order to have higher photocatalytic action due to the spatial dissociation of photo-induced electron-hole couples. The aim here is to clarify increment process of the photocatalytic activity of the ZnO based binary and multiple heterojunction/nanocomposite photocatalysts, and also methodically outlines recent efficient developments related to the sketch and production of ZnO based heterojunction/nanocomposite photocatalysts. They are very encouraging for a number of variety supplications in UV–Vis light photocatalytic area, regarding with photocatalytic hydrogen generation, CO₂ depletion, environmental restitution, and organic photosynthesis. Particularly, attentions have given to the fundamental principles of the various proficient ZnO based heterojunction/nanocomposite photocatalysts and recent efforts about the improvement of ZnO based heterojunction/nanocomposite photocatalysts for variety photo-degradation supplications. Furthermore, it is also provided that a brief summary and perspective on the improvements and as well as next directions in the field of ZnO based heterojunction/nanocomposite photo-catalysts. Finally, the recent researches about the ZnO based binary and multiple heterojunction/nanocomposite photocatalysts are compared in terms of their photocatalytic performance. and Amongst all, the hydrothermally produced ZnO/CuO p-n heterojunction has shown the highest photocatalyst performance of 92.62% in 5 min.