The performance optimization of isolated atomically dispersed metal active sites is critical but challenging. Here, TiO 2 @Fe species-N-C catalysts with Fe atomic clusters (ACs) and satellite Fe-N 4 active sites were fabricated to initiate peroxymonosulfate (PMS) oxidation reaction. The AC-induced charge redistribution of single atoms (SAs) was verified, thus strengthening the interaction between SAs and PMS. In detail, the incorporation of ACs optimized the HSO 5 - oxidation and SO 5 ·−  desorption steps, accelerating the reaction progress. As a result, the Vis/TiFeAS/PMS system rapidly eliminated 90.81% of 45 mg/L tetracycline (TC) in 10 min. The reaction process characterization suggested that PMS as an electron donor would transfer electron to Fe species in TiFeAS, generating 1 O 2 . Subsequently, the h VB + can induce the generation of electron-deficient Fe species, promoting the reaction circulation. This work provides a strategy to construct catalysts with multiple atom assembly–enabled composite active sites for high-efficiency PMS-based advanced oxidation processes (AOPs).

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The performance optimization of single‐atom catalysts (SACs) is important but remains challenging. Taking advantage of accompanying in situ formation of atomic clusters (ACs)/nanoparticles (NPs) during the preparation of SACs can be a promising solution. The coupled ACs/NPs and single atoms (SAs) can be highly efficient in catalyzing various reactions (e.g., oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), CO2 reduction reaction (CO2RR), N2 oxidation reaction (NOR), etc), showing superior activity, selectivity, and stability. The mechanisms can be mainly categorized as ACs/NPs intensified SAs, SAs intensified ACs/NPs, and reactions proceeding on both ACs/NPs and SAs. The proposed mechanisms may be applicable to rationalize the excellent catalysts consisting of ACs/NPs and SAs. In the end, the existing issues and further development directions are put forward. This review is expected to simultaneously contribute to the development and application of highly efficient SACs and the in‐depth understanding of the single‐atom catalysis (SAC).

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