Efficient Photoelectrocatalytic Degradation of Tetracycline on the Ov-TiO2 Anode Coupled with Cathodic Oxygen Reduction to Produce H2O2

Abstract

Electrochemical O₂ reduction through a two-electron process (2e^– ORR) to produce H₂O₂ on-site has attracted more attention, but how to make full use of the anodic reaction and investigate its synergistic effect on the 2e^–ORR remains to be further studied. Herein, a coupled electrochemical system was constructed in an H-type cell using TiO₂ nanotubes with oxygen vacancy (Ov-TiO₂) and P-doped porous carbon (P-MC) as the anode and cathode, respectively, on which the degradation of tetracycline (TC) and on-site H₂O₂ production occurred simultaneously. The results show that Ov-TiO₂ exhibits excellent photoelectrocatalytic (PEC) activity for TC degradationin an electrolyte containing chloride ions (Cl^–), and more than 95% of TC can be efficiently degraded within 8 min. Interestingly, an enhanced 2e^– ORR performance is achieved on the cathode with a higher H₂O₂ yield of 5.23 mol h^–1 g_cat^–1 (Faraday efficiency of >90%), which is 5.13 times higher than that using TiO₂ as the anode (1.02 mol h^–1 g_cat^–1), indicating that Ov and illumination on TiO₂ can not only promote the degradation of TC but also accelerate the 2e^– ORR on the cathode. The mechanism of this coupled system was also investigated. Based on these findings, the anodic cell has been successfully used for the efficient treatment of other wastes (dye and antibiotics) and as an effective bactericide. In a word, this work opens an avenue to develop highly efficient electrochemical system both for organic pollutant treatment on the anode and on-site H₂O₂ production on the cathode.