Active Site Evolution in Cobalt-Based Catalysts for Intensifying Water Purification: From Single-Atom to Diatomic...

Single-atom cobalt catalysts (SAC-Co) are promising for peroxymonosulfate (PMS) activation in water purification but suffer from intrinsic limitations in activity and stability due to their monometallic nature. To address these challenges, an active site evolution strategy is proposed that transforms isolated Co sites into bimetallic M/Co₁ (M═Cu, Fe, Ni, Mn) dual-atom sites (M/Co₁-CN) via ionizing radiation, significantly enhancing catalytic performance and durability. Among these, Cu/Co₁-CN exhibited sulfamethoxazole (SMX) degradation rate constants 11.7 and 31.7 times higher than those of SAC-Co and SAC-Cu, respectively. Mechanistic investigations reveal that the introduction of Cu active site modulates the electronic structure of Co active sites. The d-band center of Co (-1.455 eV) is higher than that of Cu (-3.242 eV), creating an electronic gradient that drives electron transfer from Co to Cu. Overlapping d-band peaks near the Fermi level indicate strong electronic coupling, reducing Co d-band filling and promoting Co(II) to Co(IV) oxidation while regenerating Cu sites to sustain radical generation. By enabling such tailored active sites, the Cu/Co₁-CN/PMS system demonstrated broad-spectrum micropollutant degradation, strong resistance to inorganic anion interference, and excellent stability during a continuous 96-h column experiment. This work underscores active site evolution as a powerful design principle for developing advanced water treatment catalysts.