Synthesis of Pt/BiFeO3 heterostructured photocatalysts for highly efficient visible-light photocatalytic performances

Abstract

To use visible light more effectively in photocatalytic reactions, for the first time Pt cocatalyst-modified BiFeO3 (BFO) particles were successfully prepared through a hydrothermal-synthesis process followed by an impregnation process and a thermal reduction. The as-prepared photocatalysts were characterized by a number of techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) measurements. It was found that Pt nanoparticles with an average size of ca. 10nm were well dispersed on the surface of BFO particles in a metal state, and an intimate heterojunction interface between Pt and BFO was constructed. The photocatalytic activities of as-prepared pure BFO and Pt/BFO photocatalysts were evaluated by the photocatalytic degradation of methyl orange (MO) in aqueous solutions under visible light irradiation. Compared to pure BFO, the Pt/BFO photocatalysts showed significant enhancement in photocatalytic activity. Among all the Pt/BFO samples, the 1.0wt% Pt/BFO photocatalyst exhibited the optimal photocatalytic activity, which was five times that of the pure BFO. The improvement in photocatalytic activity of the BFO particles by loading Pt cocatalyst could be ascribed to the enhanced separation efficiency of visible light-generated electron–hole pairs due to the presence of heterojunction structure at the interface between Pt and BFO. The possible photocatalytic mechanism with superoxide radical species as the main active species in photocatalysis was proposed on the basis of electron spin resonance (ESR) spectroscopy and the trapping photocatalytic experiments. Moreover, the as-prepared Pt/BFO heterostructured photocatalyst also depicted high stability and durability during five successive cycles, which could favor the long-term use in the photocatalytic degradation of organic pollutants.