Fabrication of Novel n-SrTiO3/p-BiOI Heterojunction for Degradation of Crystal Violet Under Simulated Solar Light Irradiation

Novel n-SrTiO3/p-BiOI heterojunction composites were successfully fabricated by loading SrTiO3 particles onto the surface of BiOI nanoflakes via a two-step method. The as-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), energy-disperse X-ray spectroscopy (EDS), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), diffuse reflectance spectroscopy (DRS) and electrochemical measurements. The results show that the n-SrTiO3/p-BiOI heterojunction composites are composed of perovskite structure SrTiO3 and tetragonal phase BiOI. The composites exhibit excellent photocatalytic performance for the degradation of crystal violet (CV) solution under simulated solar light irradiation, which is superior to that of pristine BiOI and SrTiO3. The 30 wt.%SrTiO3/BiOI composite is found to be the optimal composite, over which the dye degradation reaches 92.5% for 30 min of photocatalysis. The photocatalytic activity of the 30 wt.%SrTiO3/BiOI composite is found to be 3.94 times and 28.2 times higher than that of bare BiOI and SrTiO3, respectively. The reactive species trapping experiments suggest that center dot O-2(-) and holes are the main active species responsible for the CV degradation. In addition, the electrochemical measurements elucidate the effective separation of photoinduced electron-hole pairs. Moreover, on the basis of experimental and theoretical results, a possible mechanism for the enhanced photocatalytic performance of the SrTiO3/BiOI heterojunction composites is also proposed.