Single metal atom oxides as photocatalysts: synthesis, characterization, and their role in degradation and hydrogen evolution – a mini-review

Abstract This review emphasizes single-metal-atom oxides as effective photocatalysts for the degradation of organic pollutants and photocatalytic hydrogen production, particularly in enhancing systems based on single-metal-atom oxides for the degradation of organic dyes and hydrogen evolution. Single metal oxides, alone or in combination with semiconductors, increase efficiency. Single-metal-atom oxides facilitate charge separation in situations involving tight bandgaps, whereas, in broader bandgaps, they promote visible/NIR activity via up-conversion luminescence. Incorporated into Z-scheme heterostructures, single-metal-atom oxides diminish recombination by promoting electron transport. In this review, oxide-supported single-atom catalysts are discussed about their synthetic procedures, characterizations, and reaction mechanism in photocatalysis, such as photocatalytic hydrogen generation, degradation, and electron transfer. The single-metal-atom oxides are anchored on the oxide materials such as TiO2, Fe3O4, Bi2MoO6, rGO, and CoO. Moreover, altering single-metal-atom oxides via doping and incorporating functional groups on their surfaces modifies their properties, indicating the potential for more efficient photocatalysts modified with single-metal-atom oxides in forthcoming studies.