Synergistic Co/Cu dual-atom catalysis on Ti3C2Tx MXene for enhanced peroxymonosulfate activation toward acetaminophen removal.

A central challenge in heterogeneous peroxymonosulfate (PMS) activation is achieving catalysts with highly active interfacial sites to enable both efficient pollutant degradation and environmentally safe water treatment. Herein, cooperative Co/Cu dual-atom sites were anchored on Ti3C2Tx MXene (Co/Cu-Ti3C2Tx). The optimized Co0.5/Cu0.5-Ti3C2Tx catalyst achieved 96.9% removal of the emerging contaminant acetaminophen (APAP) within 60 min via PMS activation, markedly outperforming its single-atom analogues by 21.0-58.6%. Response surface methodology (RSM) analysis indicated that the system operated efficiently under near-neutral pH and mild conditions. Quenching experiments and electron paramagnetic resonance (EPR) analysis suggested that APAP degradation proceeded via a coupled mechanism involving contributions from both reactive oxygen species (predominantly •OH, •O2-, and 1O2) and high-valent metal-oxo species (HVMOS). Density functional theory (DFT) calculations revealed that the synergistic interaction between Co/Cu sites enhanced PMS adsorption, improved electron transfer efficiency, and accelerated the redox cycles between Co0/Co2+ and Cu+/Cu2+, thereby cooperatively promoting the activation of PMS. Based on the identification of intermediates, the degradation pathway of APAP was proposed to involve hydroxylation of the benzene ring, ring-opening, deacetylation, and ultimately oxidative degradation. The biotoxicity of the treated effluent decreased, confirming the effectiveness and environmental safety of the process. These findings advance the mechanistic understanding of bimetallic PMS activation and present a viable approach for the remediation of water containing refractory emerging contaminants.