Persulfate activation by single-atom catalysts for the removal of organic pollutants: A review

Single-atom catalysts (SACs) have received enormous attention in the field of catalysis due to their inherent merits, such as nearly 100% atomic efficiency, environmental friendliness, and unique physicochemical properties. The emerging SACs have facilitated the development and advancement of catalysis. The rapidly increasing applications of SACs in various fields, including oxygen evolution reaction, organic synthesis, hydrogen evolution reaction, and CO₂ reduction, reflect their enormous potential. Recently, SACs have been extensively used in persulfate (PS) activation for refractory organic pollutants degradation in the aqueous environment. SACs exhibit distinct advantages of both homogeneous and heterogeneous catalysis, demonstrating a prospective application in PS activation. This review first introduces the synthesis and characterization schemes of SACs in PS activation. Second, the factors influencing PS activation by SACs, including coordination numbers, type of coordination atoms, the spin state of metal sites, type of carriers, and the loading amount of metal atoms, are described. Third, the applications and activation mechanisms of SACs are summarized. Finally, the opportunities and challenges confronted by SACs and their future development prospects in advanced oxidation processes (AOPs) are put forward.