Controlled hydrothermal synthesis of BiOxCly/BiOmBrn/g-C3N4 composites exhibiting visible-light photocatalytic activity

The first systematic synthesis of bismuth oxychloride/bismuth oxybromide/graphitic carbon nitride (BiOxCly/BiOmBrn/g-C3N4) nano-composites used a controlled hydrothermal method. The structure, morphology and characteristic of BiOxCly/BiOmBrn/g-C3N4 photocatalyst were measured by XRD, UV–vis-DRS, FT-IR, FE-TEM, FE-SEM-EDS, PL, BET, HR-XPS and EPR. Under visible light irradiation, the photodegradation activity was evaluated for the decolorization of crystal violet (CV) and 2-hydroxybenzoic acid (2-HBA) in aqueous solution. The catalytic performance showed that, when using sample BB2C1-4-250-30 wt% g-C3N4 composite as a photocatalyst, the best reaction-rate-constant (k) was 0.071 h−1. It was 1.5 times higher than the k value of BB2C1-4-250 as a photocatalyst. From the scavenging effect of various scavengers, the results of EPR showed that reactive OH was the main scavenger, while O2−, h+ and 1O2 were the second scavenger in CV degradation. In this study, a possible photodegradation mechanism was proposed and discussed. In this work, our method of BiOxCly/BiOmBrn/g-C3N4 preparation could be used for future mass production and the BiOxCly/BiOmBrn/g-C3N4 composite materials could be applied to the environmental pollution control in future. Figure abstract. Schematic diagram of synthesis method and photocatalysis for as-prepared BiOxCly/BiOmBrn/g-C3N4 under different conditions. [Display omitted] •This is the first report on a series of BiOCl/BiOBr/g-C3N4 heterojunctions.•BiOCl/BiOBr/g-C3N4 can be prepared via the hydrothermal method.•The efficiency is enhanced apparently for BiOCl/BiOBr/30 wt % g-C3N4.•Photocatalytic mechanism of BiOCl/BiOBr/g-C3N4 was investigated and discussed.•OH plays the major role; O2−, 1O2 and h+ plays the minor in the CV degradation.