Support work-function dependent Fenton-like catalytic activity of Co single atoms for selective cobalt(IV)=O generation.

In Fenton-like reactions, high-valent cobalt-oxo (Co^IV=O) has attracted increasing interests due to high redox potential, long lifetime, and anti-interference properties, but its generation is hindered by the electron repulsion between the electron rich oxo- and cobalt centers. Here, we demonstrate Co^IV=O generation from peroxymonosulfate (PMS) activation over cobalt single-atom catalysts (Co-SACs) using in-situ Co K-edge X-ray absorption spectra, and discern that Co^IV=O generation is dependent on the support work-function (W_F) due to the strong electronic metal-support interaction (EMSI). Supports with a high W_F value like anatase-TiO₂ facilitate the binding of PMS-terminal oxo-ligand to Co sites by extracting Co-d electrons, thus decreasing the generation barrier for the critical intermediate (Co-OOSO₃^2-). The Co atoms anchored on anatase-TiO₂ (Co-TiO₂) exhibited enhanced Co^IV=O generation and superior activity for sulfamethoxazole (SMX) degradation during PMS activation. The normalized steady-state concentration of Co^IV=O in Co-TiO₂/PMS system was three orders of magnitude higher than that of free radicals, and 1.3- to 11-fold higher than that generated in other Co-SACs/PMS systems. Co-TiO₂/PMS sustained efficient removal of SMX with minimal Co²⁺ leaching under continuous flow operation, suggesting its attractive water purification potential. Overall, these results underscore the significance of support selection for enhanced generation of high-valent metal-oxo species and efficient PMS activation in supported metal SACs.