Enhanced degradation of sulfamethoxazole by non-radical-dominated peroxymonosulfate activation with Co/Zn co-doped carbonaceous catalyst: Synergy between Co and Zn.

Bimetallic catalysts are often used for peroxymonosulfate (PMS) activation in recent years due to the synergistic effects between two different metal species. However, the synergy between Zn and other transition metal in PMS activation are rarely studied because of the ease of evaporation of Zn species at high temperature. In this work, a Co/Zn co-doped carbonaceous catalyst derived from ZIF-67@ZIF-8 (Z67@8D) was prepared successfully by the core-shell replacement strategy, and used to activate PMS for sulfamethoxazole (SMX) degradation. Due to the co-existence of Co/Zn species (e.g., Co/Zn-N site), Z67@8D showed a much higher catalytic activity than that of Z8D, Z67D, and several commercial oxides. Importantly, the CoZn synergy was deeply revealed by combining experiments and density functional theory (DFT) calculations, in which Zn could adjust the electron distribution of Co, reducing the PMS adsorption energy and thus enhancing PMS decomposition and singlet oxygen (1O2) formation. Moreover, formed ZnO and graphitic structure of Z67@8D could also promote the catalytic activity. In addition, the good stability and reusability, universal applicability, and high environmental robustness of Z67@8D were demonstrated. Our findings may provide a new insight into the Zn-based bimetallic catalysts for PMS activation and pollutant degradation.