Stoichiometry-dependent photocatalytic performance of bismuth-based oxychlorides BixOyCl

Abstract

In this work, bismuth-based oxychloride photocatalysts such as BiOCl, Bi3O4Cl, Bi12O17Cl2, Bi24O31Cl10 and Bi12O15Cl6 were prepared by a solvothermal (or hydrothermal) method with the controlled amount between Bi(NO3)3·5H2O and NH4Cl. The as-prepared photocatalysts were analyzed by X-ray diffraction (XRD) patterns, field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance (UV–vis DRS) and photoluminescence (PL) spectra. The photocatalytic activity was evaluated by degrading rhodamine B (RhB) molecules under visible light irradiation. Among those bismuth-based oxychloride photocatalysts, Bi12O15Cl6 showed the highest RhB photodegradation activity of 99.85% within 30 min, and its first-order photodegradation rate constant value was 2.30, 5.51, 4.31 and 4.72 folds higher than those of BiOCl, Bi3O4Cl, Bi12O17Cl2 and Bi24O31Cl10, respectively. Bi12O15Cl6 had the larger BET specific surface area and pore volume than other samples, which could provide more reactive sites. According to the results of free radical capture experiments, h+ played a major role and O2-contributed to a lesser extent in the degradation of RhB. Thus, a possible photocatalytic mechanism was proposed. This result showed that the crystal, band structure and morphology of BiOCl, Bi3O4Cl, Bi12O17Cl2, Bi12O15Cl6 and Bi24O31Cl10 had a great influence on the photocatalytic performance. This research suggested that the various influencing factors should be studied to better understand the photochemical properties of a photocatalysts. The present work may make some contributions to the field of photocatalysis technology.