Polydopamine functionalized TiO2 with N doping, oxygen vacancies, and carbon layers for enhanced photoelectrocatalytic performance

The development of a photoelectrode featuring both excellent reusability and a simple preparation process remains exceptionally challenging for TiO₂-based photoelectrocatalytic technology. Herein, a three-dimensional photoelectrode with N doping, oxygen vacancies (O_vs), and carbon layers (NTC) was prepared via the "carbothermal reduction-pressing-calcination" method. The photoelectrode degraded 97.94% of tetracycline (TC) within 60 min. The first-order kinetic constant for this degradation was 27.3 times higher than that of TiO_2-x, and the photoelectric synergy factor reached as high as 13.9. The photoelectrode also demonstrated outstanding anti-interference capability for pH, electrolyte concentration, anions, etc., and was suitable for different water matrixes and various antibiotics removal. In particular, the degradation efficiency of TC decreased by only 1.33% after 20 cycles, demonstrating the excellent reusability of NTC. Furthermore, photoexcited holes (h⁺) were the dominant active species, and singlet oxygen (¹O₂) and superoxide radicals (•O₂⁻) played an auxiliary role in removing TC. Finally, possible degradation pathways for TC were proposed and demonstrated to be effective in reducing the toxicity of the pollutant by the Toxicity Evaluation Software Tool (T.E.S.T) and phytotoxicity experiments. This progress might bring new insights into the design and construction of TiO₂-based photoelectrodes.