Construction of FeWO4/BiVO4 Z-Scheme heterojunctions with an internal electric field for efficient photo-Fenton degradation of organic pollutants

Inefficient electron transfer and the Fe^2 + /Fe³⁺ cycling remained significant obstacles in the photo-Fenton reaction. In this paper, FeWO₄ particles were distributed on the surface of BiVO₄ using a two-step hydrothermal method to form a heterojunction structure, aiming to improve interfacial electron transfer efficiency and promote Fe²⁺/Fe³⁺ cycling. Through band structure analysis and density functional theory (DFT) calculations, the FeWO₄/BiVO₄ (FWBV) composite was found to exhibit an internal electric field (IEF) at the interface. This IEF facilitates the directional migration of photogenerated electrons, thereby enabling efficient charge transfer. Moreover, transient photovoltage (TPV) measurements showed that introducing FeWO₄ effectively extended the lifetime of photogenerated electrons, promoting Fe²⁺/Fe³⁺ cycling and consequently generating more reactive species. Therefore, the FWBV composite exhibited excellent photo-Fenton performance. The optimal FWBV composite achieved a degradation efficiency of 93.6 % for 10 mg/L of Tetracycline hydrochloride (TCH) within 15 min, surpassing the performance of pure FeWO₄ (56.63 %) and BiVO₄ (58.92 %). Furthermore, a possible mechanism for TCH degradation was proposed based on reactive species capture experiments and electron paramagnetic resonance (EPR) analysis. This work provided important insights for designing and constructing heterojunction structures with high electron transfer performance.