Oxygen vacancies-enriched Cu/Co bimetallic oxides catalysts for high-efficiency peroxymonosulfate activation to degrade TC: Insight into the increase of Cu+ triggered by Co doping

Abstract

Bimetallic CuCo-doped graphene-like carbon nanosheets (CuCo@GCNs) were synthesized via a facile and efficient process using agarose as carbon templates to activate peroxymonosulfate (PMS) for tetracycline (TC) degradation. In this study, CuCo@GCNs/PMS system exhibited excellent TC removal efficiency (0.182 min−1), which was unaffected by various water matrices and applicable to a wide pH range (3.44–8.44). Radicals (SO4•−, •OH, and O2•−) and non-radical (1O2) pathways collectively contributed to catalytic TC oxidation based on quenching experiments and electron paramagnetic resonance (EPR) analysis. Density functional theory (DFT) calculations revealed that the mechanism of PMS molecules activated on the surface of CuCo@GCNs, in which CoO provided more catalytic sites while Cu2O further enhanced electron transfer. Moreover, the synergistic effect of CuCo bimetal could accelerate redox cycles of Cu+/Cu2+ and Co2+/Co3+, inducing the generation of abundant oxygen vacancies (OVs), thus enhancing PMS activation performance. Three potential TC degradation pathways were proposed according to fifteen possible intermediates detected by liquid chromatography-mass spectrometry (LC-MS). In brief, this work provides an efficient CuCo@GCNs heterogeneous catalyst and a new insight into PMS activation, which extends the application of bimetallic materials for environmental remediation.