Copper Doping and Sulfur Vacancy Engineering Synergistically Facilitate the Generation of High‐Valent Co Species in Cobalt Sulfide for Peroxymonosulfate Activation

ABSTRACT

A series of copper‐doped cobalt sulfides (Cu _x Co _3‐x S ₄ ) were synthesized via a hydrothermal method for peroxymonosulfate (PMS) activation. Copper doping successfully induced the formation of sulfur vacancies within the cobalt sulfide lattice. The combined effect of Cu dopants and the generated sulfur vacancies effectively modulated the electronic configuration of cobalt centers, thereby enhancing its redox cycling efficiency. The optimized Cu _0.4 Co _2.6 S ₄ catalyst demonstrated remarkable catalytic performance in the degradation of sulfamethoxazole (SMX), achieving an apparent degradation rate constant of 0.952 min ⁻¹ , which is approximately 6.6 times higher than that of undoped Co ₃ S ₄ (0.145 min ⁻¹ ). Radical quenching experiments and electron paramagnetic resonance (EPR) spectroscopy identified high‐valent cobalt‐oxo species (Co ^IV ═O) and superoxide radicals (O ₂ · ⁻ ) as the dominant reactive oxygen species. Density functional theory (DFT) calculations further revealed that copper doping optimizes the electronic configuration of cobalt sites, facilitating electron transfer with PMS and promoting the formation of high‐valent cobalt intermediates. Moreover, the catalyst maintained 87% SMX removal efficiency after four consecutive cycles and showed broad applicability for degrading various refractory organic pollutants. This work elucidates the enhancement mechanism of cobalt sulfide catalytic activity through electronic structure reconstruction and defect engineering via copper doping.