Efficient Photon Conversion via Double Charge Dynamics CeO₂–BiFeO₃ p–n Heterojunction Photocatalyst Promising toward N₂ Fixation and Phenol–Cr(VI) Detoxification

Abstract

For better exciton separation and high catalytic activity, the most trailblazing stratagem is to construct defect engineered low-dimensional p-n heterojunction framed photocatalytic systems. In this context, we have developed a rod-sheet (1D-2D) p-n heterojunction of MCeO₂-BiFeO₃ by a simple hydrothermal method and scrutinized its photocatalytic performance toward N₂ fixation and phenol/Cr(VI) detoxification. The intimate contact between MCeO₂ and BiFeO₃ in the junction material is well established via X-ray diffraction (XRD), UV-vis diffuse reflectance spectrosopy (DRS), transmission electron microscopy (TEM), and photoelectrochemical studies. Further, scanning electron microscopy (SEM) and TEM pictures clearly support the decoration of MCeO₂ nanorods over BiFeO₃ sheets and also depict the junction boundary. Additionally, photoluminescence (PL), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and Raman measurements give solid evidence toward the presence of an oxygen vacancy. Moreover, the Mott-Schottky result indicates a feasible band edge potential favoring the p-n heterojunction with a built-in electric field between BiFeO₃ and MCeO₂ favoring a double charge dynamic. The MCeO₂-BFO p-n junction displays a notable catalytic activity, i.e., 98.2% Cr(VI) reduction and 85% phenol photo-oxidation, and produces 117.77 μmol h^-1 g^-1 of ammonia under light irradiation. Electrochemical analysis suggests a four-electron/five proton-coupled N₂ photoreduction pathway. The designed oxygen vacancy oriented p-n heterojunction suffering double charge migration shows significant catalytic performance due to effective electron-hole separation as justified via PL, electrochemical impedance spectra (EIS), and Bode phase analysis.