Building the bimetallic site of Co2Mo3O8/Co9S8 heterojunction via interface electronic reconfiguration to enhance peroxymonosulfate activation for singlet oxygen formation

Abstract

A novel bimetallic heterojunction catalyst (Co₂Mo₃O₈/Co₉S₈) with hydrangea-like structure was prepared by a straightforward one-pot hydrothermal and pyrolysis method, which was then applied for the efficient activation of peroxymonosulfate (PMS) in wastewater purification. Density functional theory (DFT) simulations revealed that the formation of the Co₂Mo₃O₈/Co₉S₈ heterojunction increased the adsorption energy of PMS and elongated the O–O bond within PMS. Moreover, an internal electric field generated within the heterojunction further activated PMS through electron-deficient centers, establishing a degradation mechanism primarily dominated by non-radical pathways. Meanwhile, the exist Co(II) and Mo(IV) involved as active sites for enhanced catalytic performance through the redox cycling of metal valence states. In the optimized Co₂Mo₃O₈/Co₉S₈-PMS system, the target pollutant doxycycline (DOX) was rapidly and efficiently degraded, with a relatively low activation energy (3.93 kJ·mol⁻¹). Furthermore, the system demonstrated strong adaptability to interference from inorganic anions, humic acid, and pH variations, while effectively removing various pollutants. It consistently maintained a relatively high DOX removal efficiency in cyclic experiments and continuous flow reaction experiments. The present study provided new insights for improving the rational design of bimetallic heterojunction catalysts, and contributed to a more effective and sustainable solution for environmental remediation.