Interface and Defect Engineering in 3D Co3O4-Ov/TiO2 to Boost Simultaneous Removal of BPA and Cr(VI) upon Photoelectrocatalytic/Peroxymonosulfate (PEC/PMS) System

Abstract

The combination of photoelectrocatalytic (PEC) and peroxymonosulfate (PMS) is an innovative strategy for environmental treatment. And fabricating a highly efficient photoelectrode is the most pivotal factor in PEC reactions. This study designs an advanced Co₃O_4-Ov/TiO₂ photoelectrode by a dual-modification strategy encompassing interface engineering and defect engineering. The photoelectric characterization validates the synergy of oxygen vacancies and dual heterojunctions. Simulated electron density distribution and Kelvin probe force microscopy (KPFM) elucidate the charge transfer pathway between Co₃O_4-Ov and TiO₂. ¹O₂ and SO₄ ^.− are confirmed to be primarily responsible for the BPA oxidation in PEC/PMS system by radical scavenger experiments and the EPR technique. And the attack sites of BPA are precisely identified based on the Fukui index. Furthermore, density functional theory (DFT) calculations testify that Co₃O_4-Ov can improve the adsorption capacity of PMS and reduce the energy barrier of the reaction process, while XPS analysis showed Co³⁺/Co²⁺ redox couple can accelerate PMS activation. Enhanced anode oxidation can effectively promote cathode reduction and consequently Co₃O_4-Ov/TiO₂-PMS/PEC system presents a superior removal of both pollutants within only 15 min with fast kinetics (0.15 min⁻¹ for BPA, 0.29 min⁻¹ for Cr(VI)). This work provides unique insight into designing a highly efficient PMS/PEC system for simultaneous pollutant treatment.