Heterostructure Fe₂O₃/BiVO₄ as a Photoanode for a Visible-Light-Responsive Photocatalytic Fuel Cell

Searching earth-abundant materials for photocatalytic fuel cells (PFCs) remains an important goal for energy conversion and storage, and the construction of semiconductor composite materials is an effective method to improve the photochemical properties of photoelectrodes in PFCs. Herein, a simple hydrothermal method is used to load an Fe₂O₃ layer on a BiVO₄ film for use in the photoanode of a PFC, and the electrochemical results show that the short-circuit current density (<i>J</i>_sc) and the open-circuit voltage (<i>V</i>_oc) of the PFC reach 3.05 mA/cm² and 0.84 V under simulated solar irradiation, respectively. Furthermore, a detailed analysis of the density of states, charge density difference, and work functions of the Fe₂O₃/BiVO₄ heterojunction is discussed by the density functional theory (DFT) method, showing the proper band alignment and the existence of a built-in electric field at the interface with the direction from BiVO₄ to Fe₂O₃, which greatly improves the performance of the PFC. This research provides a clear mechanism for the Fe₂O₃/BiVO₄ heterojunction in the PFC system.