Constructing BiOI/CeO2 p-n heterojunction with enhanced NOx photo-oxidative removal under visible light irradiation

Abstract

BiOI-loaded flower-like CeO2 (BiOI/CeO2) p-n heterojunction was synthesized via a simple two-step chemical route. The phase structure and chemical states of the heterojunction were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The transmission electron microscopic (TEM) and the scanning electron microscope (SEM) reveal the close contact between BiOI and CeO2. The formation of the p-n heterojunction is verified by the Mott-Schottky curves. The p-type BiOI with a narrow band-gap when loaded on CeO2 can not only improve the separation of photogenerated electron-hole pairs but also facilitate the absorption of visible light. The photo-oxidative removal efficiency of 9%BiOI/CeO2 among other heterojunctions for NO reaches 45.49% and remains highly stable with an efficiency of 40.40% after the five cycles. Trapping experiments and ESR measurements were conducted to explore the contribution of charge carriers and the reactive oxygen species during the photocatalytic NO removal. This work highlights that constructing such p-n heterojunction by loading BiOI on CeO2 microstructures can significantly enhance photocatalytic NO removal.