Bi12SiO20/g-C3N4 heterojunctions: Synthesis, characterization, photocatalytic activity for organic pollutant degradation, and mechanism

Abstract

This work reports the synthesis of new and efficient composite photocatalysts (Bi12SiO20/g-C3N4) via the controlled hydrothermal method. The Bi12SiO20/g-C3N4 composites were characterized by XRD, SEM-EDS, HRTEM, FT-IR, XPS, DRS, BET, PL, and EPR. In comparison to pure Bi12SiO20 and g-C3N4, the Bi12SiO20/g-C3N4 materials showed significantly higher photocatalytic activity for degradation of crystal violet (CV) under visible-light irradiation (99% in 48 h). The 5 wt% Bi12SiO20/g-C3N4 composite revealed the highest rate constant of CV degradation (0.078 h−1); 15 and 2 times larger than the constants obtained with individual Bi12SiO20 and g-C3N4, respectively. Further investigation of the photocatalytic activity of the 5 wt% Bi12SiO20/g-C3N4 materials were performed on other organic pollutants. 98% degradation of 2-hydroxybenzoic acid (2-HBA) and 99.5% degradation of rhodamine-B (RhB) were achieved upon exposure to visible-light irradiation for 72 h with 5 wt% Bi12SiO20/g-C3N4. Bi12SiO20/GO (graphene oxide) composites were also synthesized to compare the photocatalytic activities of different Bi heterojunctions. It was found that Bi12SiO20/g-C3N4 photocatalysts had enhanced photocatalytic activity in degradation of CV and 2-HBA and were considerably more stable in recycling experiments in comparison to Bi12SiO20/GO photocatalysts. Lastly, the plausible photocatalytic mechanism for the Bi12SiO20/g-C3N4 composite material was proposed and the principal active species involved in the photodegradation of CV were investigated using scavenger and ESR experiments. The Bi12SiO20/g-C3N4 composite demonstrates good photocatalytic activity, stability and reusability, demonstrating its prospective use in photodegradation applications under visible-light irradiation.