Fabrication of novel p-Ag2O/n-PbBiO2Br heterojunction photocatalysts with enhanced photocatalytic performance under visible-light irradiation

Abstract

The p-Ag2O/n-PbBiO2Br heterojunctions were prepared by the polyacrylamide gel synthesis and chemical deposition method. The as-synthesized Ag2O/PbBiO2Br photocatalysts were characterized in details by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscope (TEM), electron spin resonance (ESR), ultraviolet-visible diffuse reflectance spectroscopy (UV–Vis DRS) and electrochemical workstation. Compared with the pure PbBiO2Br and Ag2O, the Ag2O/PbBiO2Br photocatalysts exhibit enhanced photocatalytic activities for the degradation of methylene blue (MB) under visible-light irradiation. In particular, the Ag2O/PbBiO2Br(1:1) composite shows the optimal photocatalytic performance. The degradation efficiency of MB reaches 99.2% in 50 min, and the best reaction rate constant reaches 5.982 × 10−2 min−1, which is 7.6 and 10.2 times higher than that of pure Ag2O and PbBiO2Br, respectively. The significantly enhanced photocatalytic performance of Ag2O/PbBiO2Br photocatalysts could be attributed to the broadened light absorption and the formation of the p–n heterojunctions between Ag2O and PbBiO2Br. Consequently the photo-generated electron–hole pairs can be separated effectively. Through the ESR technique and the radical trapping experiments, the superoxide ($$\cdot {\text{O}}_{2}^{-}$$) radicals and holes are demonstrated to play the major role in the MB degradation. Finally, based on the experimental results and analyses, the photocatalytic mechanism of the Ag2O/PbBiO2Br composites was proposed.