Stoichiometry-dependent photocatalytic performance of bismuth-based oxychlorides BixOyCl

In this work, bismuth-based oxychloride photocatalysts such as BiOCl, Bi 3 O 4 Cl, Bi 12 O 17 Cl 2 , Bi 24 O 31 Cl 10 and Bi 12 O 15 Cl 6 were prepared by a solvothermal (or hydrothermal) method with the controlled amount between Bi(NO 3 ) 3 ·5H 2 O and NH 4 Cl. 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, Bi 12 O 15 Cl 6 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, Bi 3 O 4 Cl, Bi 12 O 17 Cl 2 and Bi 24 O 31 Cl 10 , respectively. Bi 12 O 15 Cl 6 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 O 2 - 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, Bi 3 O 4 Cl, Bi 12 O 17 Cl 2 , Bi 12 O 15 Cl 6 and Bi 24 O 31 Cl 10 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.