Harnessing the power of single-atom catalysts: a promising solution for organic pollutant remediation under light exposure

Single-atom catalysts have garnered significant attention in the field of photocatalysis due to their exceptional electronic structure, impressive selectivity, high atomic utilization efficiency, and unsaturated coordination centers. Under light conditions, the single-atom photocatalysts are excited, leading to the generation of highly active electron-hole pairs. These pairs can effectively degrade organic pollutants that are adsorbed on the surface of the single-atom photocatalyst, yielding substances such as H2O and CO2. In addition, single-atom photocatalysts exceptional metal dispersion and adjustable coordination environments. These unique characteristics can enhance the photocatalytic performance in several ways including the improvement of optical response, promotion of charge carrier transfer behavior, and manipulation of surface reaction processes. These effects contribute to the overall enhancement of the photocatalytic efficiency of single-atom catalysts. This review comprehensively summarizes the main preparation methods of single-atom photocatalysts, including wet chemical method, thermochemical method and photochemical method, and the advantages and disadvantages of various methods are outlined. At the same time, the effect of single-atom photocatalyst on the degradation of various organic pollutants in water is discussed. Most of them have a degradation rate of more than 95% for organic pollutants. Furthermore, the key factors affecting the degradation efficiency of organic pollutants are clarified, including the loading of single atoms, solution pH, initial pollutant concentration, catalyst quantity and coexisting ions and dissolved organic matter. These factors show quite different interference ability in degradation reaction. Moreover, this review also summarizes the mechanism and potential applications of single-atom photocatalysts in the degradation of organic pollutants. Finally, it describes the current limitations in research on single-atom photocatalysts and highlights future research directions. This provides a theoretical foundation for the development of cost-effective, stable and efficient single-atom photocatalysts, as well as the advancement of organic pollutant degradation.