Synthesis of Bi2O3/BiVO4 heterojunction with enhanced photocatalytic activity via single-step hydrothermal method

The single-step hydrothermal method was used to synthesize Bi 2 O 3 /BiVO 4 heterojunctions (BBVs) with various Bi 2 O 3 /BiVO 4 molar ratios.The surface characteristics of the prepared photocatalysts were analyzed by X-ray diffractometry (XRD), scanning electron microscopy, transmission electron microscopy, ultraviolet (UV)-visible-light (Vis.)spectrophotometry, surface area analysis, X-ray photoelectron spectroscopy and fluorescence spectrophotometry.C.I. Reactive Red 2 (RR2) was used as the parent compound to evaluate the photocatalytic activity of photocatalysts under UV and Vis.irradiation.The XRD peak intensity of BiVO 4 declined as the amount of Bi 2 O 3 in the BBVs increased.The surface areas of all BBVs exceeded those of Bi 2 O 3 and BiVO 4 and all of the samples exhibited strong absorption in the Vis.region.The optimal Bi 2 O 3 /BiVO 4 molar ratio was 0.25 and the corresponding photocatalyst was denoted as 0.25 BBV.The RR2 photodegradation rate constant of 0.25 BBV was 1.9 times that of BiVO 4 under UV irradiation, which was in turn 3.5 times that of BiVO 4 under Vis.irradiation.The improved photodegradation efficiency of BBVs is attributed to the effective separation of photo-generated carriers by the formed heterojunction.The results of a radical-trapping experiment revealed that the photo-generated holes and superoxide anion radicals were the primary reactive species in the BBV photocatalytic systems.