Xiaojie Ji, Wenhui Dai, Xiaolong Zhang, Xun Xu, Luliang Liao, Ping Li, Hao Zhang, Shuwang Duo
Cobalt-based TiO2 composite catalysts exhibit promising potential for generating high-valent cobalt-oxo species (Co(IV)=O) in peroxymonosulfate-based advanced oxidation processes (PMS-AOPs). In this study, Co nanoparticles were anchored on TiO2 nanosheet arrays to fabricate a Co@TiO2 composite with a rational structural design, which served as a high-efficiency electrocatalyst for PMS activation and levofloxacin (LEV) degradation. The constructed Co@TiO2 electrochemical activation of peroxymonosulfate (EA-PMS) system achieved a LEV degradation efficiency of 99.8% within 15 min toward 20 mg/L LEV solution, with a reaction rate constant of 0.287 min-1, which exhibited superior performance compared to previously reported cobalt-based catalysts. Such enhanced catalytic performance was mainly enabled by the formation of a built-in electric field (BIEF) through Schottky contact between Co and TiO2. Directional interfacial charge migration driven by BIEF supplied electrons for Co(IV)=O generation, while the structural modulation promotes metastable Co(IV)=O to forming during oxidation reactions and sustained continuous active species production, thereby improving the overall catalytic efficiency. Both Co(IV)=O and singlet oxygen (1O2) were verified as the dominant active species responsible for pollutant degradation, and an interfacial conversion pathway from Co(IV)=O to 1O2 was confirmed in the reaction system. All intermediate byproducts produced during LEV degradation were identified as environmentally friendly. Furthermore, a continuous-flow electrochemical reactor was employed to simulate practical water treatment conditions. A stable degradation efficiency above 86% was retained after 24 h of continuous operation with extremely low cobalt leaching, demonstrates the excellent feasibility and practical application potential for the Co@TiO2 composite catalyst.