Efficient degradation of tetracycline by PMS activation using N, P-doped hollow carbon spheres with spatial confinement effect

The advancement of cost-effective, non-metal-doped catalysts is essential for the effective degradation of aquatic contaminants. In this study, hollow carbon spheres (HCS) were synthesized from glucose using the soft stencil method. These HCS were subsequently co-doped with nitrogen and phosphorus using ammonium dihydrogen phosphate ((NH 4 ) 2 HPO 4 ) as the doping source, resulting in N, P co-doped hollow carbon spheres (NPHCS). These NPHCS served as a mediator for peroxymonosulfate (PMS) activation, applied in the degradation of tetracycline hydrochloride (TC). The unique architecture of NPHCS, characterized by hollow 3D cavities and mesoporous channels, established a spatially confined environment that markedly increased total surface exposure and number of reactive centers. This structure facilitated rapid adsorption and activation of PMS on the catalyst surface, generating reactive oxygen species more efficiently compared to unrestricted nitrogen and phosphorus-doped carbon nanosheets (NPCN) and carbon black (NPCB). The confined nano-environment of the hollow cavities shortened mass transfer pathways, substantially improving the contact and catalytic efficiency between active oxygen species and pollutants. Consequently, over 90% of TC was degraded within 20 min. This research offers a novel insight into the design of low-cost, N, P co-doped catalytic nanoreactors for improving the catalytic efficiency in non-metal-based systems.