Surface sulfur vacancies enhanced electron transfer over Co-ZnS quantum dots for efficient degradation of plasticizer micropollutants by peroxymonosulfate activation

Abstract

Peroxymonosulfate (PMS) activation in heterogeneous processes is a promising water treatment technology. Nevertheless, the high energy consumption and low efficiency during the reaction are ineluctable, due to electron cycling rate limitation. Herein, a new strategy is proposed based on a quantum dots (QDs)/PMS system. Co-ZnS QDs are synthesized by a water phase coprecipitation method. The inequivalent lattice-doping of Co for Zn leads to the generation of surface sulfur vacancies (SVs), which modulates the surface of the catalyst to form an electronic nonequilibrium surface. Astonishingly, the plasticizer micropollutants can be completely degraded within only tens of seconds in the Co-ZnS QDs/PMS system due to this type of surface modulation. The interfacial reaction mechanism is revealed that pollutants tend to be adsorbed on the cobalt metal sites as the electron donors, where the internal electrons of pollutants are captured by the metal species and transferred to the surface SVs. Meanwhile, PMS adsorbed on the SVs is reduced to radicals by capturing electrons, achieving effective electron recovery. Dissolved oxygen (DO) molecules are also easily attracted to catalyst defects and are reduced to O 2 •− , further promoting the degradation of pollutants. A new strategy is reported to generate electron-rich/poor reaction sites on the catalyst surface by constructing sulfur vacancies through Co doping into the ZnS QDs lattice. PMS and DO are captured by sulfur vacancies and reduced to reactive oxygen species, thus rapidly degrading organic pollutants.