Recent progress on single-atom catalysts in advanced oxidation processes for water treatment

Single-atom catalysts (SACs), consisting of metal single atoms and supporting materials, have shown remarkable potential due to their ultrahigh catalytic performances, maximum atomic utilization and environmental friendliness. More recently, SACs have become ideal catalyst materials and have been extensively applied in water treatment. This review summarizes the classification of advanced oxidation processes (AOPs, e.g., photocatalysis, electrocatalysis, Fenton-like reactions, persulfate oxidation and multi-technology coupling reaction) for the degradation of organic pollutants in water on SACs. The corresponding mechanisms for the removal of organic pollutants over SACs in the above technologies are also discussed. Distinguished from traditional nanoparticles and nanoclusters, the unique electronic properties of single metal atoms and the formation of covalent bands between metallic and nonmetallic atom promote the rapid generation of reactive oxygen species (SO₄^•-, O₂^•-, •OH and ¹O₂), which endow SACs with excellent removal efficiency of organic pollutants. Finally, the opportunities and challenges of SACs applied in practical water treatment are proposed.