Controlled fabrication of TiO₂/C₃N₄ core–shell nanowire arrays: a visible-light-responsive and environmental-friendly electrode for photoelectrocatalytic degradation of bisphenol A

Photoelectrocatalytic (PEC) oxidation is a promising method in water treatment due to the synergistic effect of photocatalytic (PC) oxidation and electro-oxidation. Up to now, developing visible-light-responsive, efficient and environmental-friendly electrode for PEC degradation application is still a challenge. In this work, novel and environmental-friendly TiO₂/C₃N₄ core–shell nanowire arrays as an electrode were investigated for PEC degradation of bisphenol A (BPA). TiO₂ nanowire arrays provide a direct electron pathway, g-C₃N₄ serves as a stable and environmental-friendly visible light sensitizer, and effective charge spatial separation can be achieved across the well-matched core–shell interface. Compared with TiO₂ nanowire arrays, TiO₂/C₃N₄ core–shell nanowire arrays exhibit higher PC and PEC performance. The photocurrent response of the TiO₂ nanowire arrays is enhanced about two times after C₃N₄ shell deposition. And the PEC performance of TiO₂/C₃N₄ core–shell nanowire arrays is significantly enhanced, which is one time higher than that of TiO₂ (under 1.0 V external potential). The enhancement of PEC performance of TiO₂ nanowire arrays after C₃N₄ modification can be attributed to the synergistic photoelectric effect, well-matched interface and efficient charge separation induced by the type-II TiO₂/C₃N₄ band alignment. Moreover, the intermediate products of BPA degradation by PEC oxidation were analyzed by gas chromatography–mass spectrometry and five specific products were identified, and then two possible pathways for BPA degradation by PEC process were proposed.