Graphene oxide-encapsulated OV-Co3O4 for efficient nanoconfinement peroxymonosulfate activation: Simultaneously regulate mass transport, electron transfer and transformation behavior.

Thiamethoxam (THM), a widely detected neonicotinoid insecticide, poses potential ecological risks in aquatic environments, making its efficient oxidation and transformation product control important. Peroxymonosulfate (PMS)-based advanced oxidation processes have been widely applied for the removal of refractory contaminants, but their performance is often constrained by nonselective radical reactions, inefficient electron transfer, and sluggish mass transport. Herein, a nanoconfined graphene oxide-encapsulated oxygen-vacancy-rich Co3O4 catalyst (OV-Co3O4@GO) was rationally constructed to address these limitations. Theoretical calculations revealed that the confined interfacial microenvironment promoted PMS adsorption, reactant enrichment, and electron transfer, thereby facilitating PMS activation. Comparative reactive species experiments suggested different relative contributions of the oxidation processes in two systems. The confined system showed greater relative involvement of CoIV=O, 1O2, and electron transfer pathway, which was consistent with rapid THM and elevated TOC removal efficiency, suggesting an enhanced capacity of further oxidation for transformation products. UPLC-Q-TOF-MS analysis and ECOSAR prediction supported plausible THM transformation pathways and a tendency toward lower ecological risk for transformation products. This study highlights that regulating the local catalytic microenvironment can improve not only pollutant degradation kinetics but also PMS activation pathways and pollutant transformation behavior, providing a promising strategy for designing efficient and selective catalytic systems for water treatment.