Atomically dispersed Co-N4 to activate peroxymonosulfate for efficient atrazine degradation: Synergistic radical and non-radical ways

Cobalt based nanomaterials are widely employed as effective catalysts for peroxymonosulfate (PMS) activation in advanced oxidation processes (AOPs). Single atom catalysts (SACs) are state-of-the-art materials that endow active metal sites with maximal exposure to the reactants. In this study, molybdenum disulfide nanospheres with a crumpled surface (cnMoS2) were designed and synthesized to decorate atomically dispersed Co-N4 sites by immobilizing Co in its unique surface fold structure with a nitrogen/carbon coating. The resulting Co-N-C-cnMoS2 catalysts were used to activate PMS for rapid degradation of atrazine (ATZ). The Co-N4 sites were considered to be the main active sites, enabling the optimal 4.8Co-N-C-cnMoS2 catalyst to remove 100 % of ATZ within 20 min. In addition, 4.8Co-N-C-cnMoS2 catalyst also showed good durability, tolerance to inorganic anions and cations, and high activity in a wide pH range. The cnMoS2 provided a platform to hold atomically Co-N4 sites, played the degradation roles though it was secondary, and moreover accelerated Co2+/Co3+ cycles. In the 4.8Co-N-C-cnMoS2/PMS system, sulfate radical (SO4• ‾), hydroxyl radicals (•OH), superoxide radical (O2• ‾) and singlet oxygen (1O2) were generated, among which SO4• ‾ and 1O2 were the predominant active substances triggering the ATZ degradation.