Fundamentals and application of single-atom photocatalyst in sustainable energy and environmental applications

Photocatalysis has gained considerable interest due to changing dynamics and problems pertaining to the environment and energy crisis. Nonetheless, owing to low visible-light absorption, the higher recombination rate of electron-hole photogenerated pairs, and slow charge transportations, the performances of photocatalytic systems are significantly compromised. To improve these above-mentioned photocatalytic properties, many strategies are being considered. In this regard, single-atom photocatalyst has shown its unique capabilities in boosting photocatalytic activity and enhancing the stability. However, to obtain the mechanistic insights, advanced in-situ/operando methods of characterization and DFT measurements may collectively offer a comprehensive understanding of the nature of active sites and the photocatalyst mechanism at an atomic scale. This review summarizes the role of single atom photocatalyst in energy and environment applications. The paper starts with the introduction and fundamentals and discusses the unique characteristic of single-atom photocatalysts in terms of key properties that determine the photocatalytic yields. In the next segment, advancements in the characterization techniques in union with theoretical calculation are briefly discussed. Further, there is a side-by-side short discussion on metal-support interaction and various catalyst synthesizing strategies. Towards the end of the review, the challenges in achieving higher photocatalytic performance and the future potential of single atom photocatalysts in various applications are discussed.