Engineering Oxidative Active Species Selectivity via Multi-Atom Doping: A 100% Singlet Oxygen Pathway in Peroxymonosulfate Activation

1O2 has significant advantages over free radicals in Fenton-like reactions, but the induction of a single 1O2 reaction pathway is challenging and is often accompanied by free radical reactions and direct electron transfer pathways. In this study, Zn-O-C/N and Zn-S/O-C/N catalysts were synthesized by controlling the doping of the S element, and the single 1O2 reaction pathway was successfully induced. Furthermore, Zn-O-C/N performed better than the Zn-S/O-C/N system, with higher phenanthrene (PHE) degradation rates of 76.14% compared to 62.86%. And Zn-O-C/N can achieve a maximum degradation rate of 85.62% under the developed optimization condition. The characterization results revealed that the ZnO active sites are located on the surface of the Zn-O-C/N catalyst and participate in electron mediation together with C-N. ZnS was generated with the doping of S, speculating that a large amount of ZnS with low catalytic activity is generated and occupies the active sites, thereby inhibiting the catalytic activity. Additionally, only 1O2 was generated in the two systems, without the formation of free radicals and the occurrence of direct electron transfer reaction. However, the Zn-O-C/N catalyst has been proven to have strong stability and a low amount of dissolution, demonstrating environmental safety. This study confirmed the inhibitory effect of S on the activity of the Zn-O-C/N system and provided a synthesis strategy for the catalyst design, which can only induce the 1O2 reaction pathway.