Integrated hierarchical Z-scheme BiOCl/NiTiO3 heterostructured photoanode and its photoelectrocatalytic application in ciprofloxacin degradation

Abstract

In this work, we explore the application of a BiOCl/NiTiO₃ heterostructured photoanode with a remarkable synergistic advantage and unique band alignment for the photoelectrocatalytic (PEC) degradation of ciprofloxacin. Combining the excellent charge transport of BiOCl and the visible-light absorption of NiTiO₃, the BiOCl/NiTiO₃ photoanode facilitated electro-hole charge separation and extended light absorption owing to its distinctive band gap energy and visible-light sensitivity. These attributes were confirmed by the impressive charge-transfer advantage (R_ct = 157 Ω) and band gap energy (E_g) of 2.08 eV obtained from the Nyquist and Tauc plots of the photoanode. Moreover, the BiOCl/NiTiO₃ heterostructured photoanode exhibited a Z-type behaviour, evident by the flow of electrons from the conduction band of BiOCl (with a higher Fermi level) to the valence band of NiTiO₃ (with a lower Fermi level). This occurrence made uncombined holes and electrons in the respective valence band of BiOCl and the conduction band of NiTiO₃ readily available for the generation of reactive oxygen species in the system. The BiOCl/NiTiO₃ heterostructure architecture significantly aided the photoelectrocatalytic degradation of ciprofloxacin in water, achieving a remarkable 94% degradation efficiency. In addition, the heterostructured photoanode displayed outstanding stability and reusability, making it a distinct advanced material for real-time operations. Furthermore, the findings from this work demonstrate a reliable strategy for high-performance PEC design while contributing to a sustainable approach for wastewater remediation applications.