Facile synthesis of Pt assisted Bi-Bi2WO6−x with oxygen vacancies for the improved photocatalytic activity under visible light

Pt assisted self-modified microflower like Bi2WO6 composites (Pt/Bi-Bi2WO6−x) were prepared using a simple in-situ NaBH4 reduction method. The characterization of these samples was systematically studied and the photocatalytic activity of as-prepared samples was evaluated through the degradation of bisphenol A (BPA) under visible light illumination. The results indicated that the self-modified Bi-Bi2WO6−x presented the high separation efficiency of photo-generated carriers due to the introduction of the oxygen vacancies and metallic Bi. Furthermore, because of the presence of Pt on Bi-Bi2WO6−x, a higher concentration of generated oxygen vacancies was also obtained, resulting in the excellent photocatalytic performance. The 2%Pt/0.2Bi-Bi2WO6−x sample exhibited the highest degradation efficiency of BPA under visible light illumination, which was approximately 2.88 times and 1.52 times as high as that of Bi2WO6 and 0.2Bi-Bi2WO6−x, respectively. In addition, the degradation efficiency clearly improved at high pH value. The highest degradation efficiency was obtained at alkaline solution (pH = 9). According to the mechanism study, the enhanced photocatalytic property on 2%Pt/0.2Bi-Bi2WO6−x should be attributed to the presence of oxygen vacancies on the material surface, since oxygen vacancies states were partly overlapping of with the valence band (VB), and increased the width of VB, reducing the band gap of Bi2WO6. The possible photocatalytic mechanism was also simulated by chemical calculations, which was proposed to guide further related studies.