Collaborative catalysis of single atoms and atomic clusters as dual sites for confined peroxymonosulfate activation to coordinate radical and singlet oxygen pathways

Single-atom catalysts have attracted tremendous research interest in advanced oxidation water treatment, while their efficiency and recyclability were restricted by speciation. Deliberate manipulation of single-atom (SAs) accumulation and distribution to tune the catalyst efficiency and route constitutes an area of great interest but a challenging pursuit. Here, we developed a series of novel spherical porous carbon materials from biomass waste with a three-dimensional distribution of Fe. Fe SAs and atomic clusters (ACs) are simultaneously formed in catalysts, and their distribution from the outer surface to the inner core varies with pyrrolic N content. The cooperation of SAs and ACs serves as a pair of redox sites linked with graphitic carbon to coordinate the electron circulation with peroxymonosulfate (PMS), generating radical and singlet oxygen for antibiotic degradation. The confined environment and the cooperation of dual sites perpendicular to the carbon plane were first reported, which enhanced the generation of reactive species. These advantages afforded efficient degradation (up to 229 % improved in kinetics and 133 % improved in degradation) with heightened recyclability (up to 150 % improved) compared to surface-doped SAs or ACs-dominated catalyst. Furthermore, this approach achieved efficient utilization of atomic metal sites compared to previously documented metal-based atomically dispersed catalysts. This study reveals the synergy of SAs and ACs in a confined environment for cyclic electron transfer and inspires a new version for designing atomically dispersed Fe within the 3D structure for advanced water decontamination.