Photocatalysts of quaternary composite, bismuth oxyfluoride/bismuth oxyiodide/ graphitic carbon nitride: Synthesis, characterization, and photocatalytic activity

In this study, a novel heterojunction composite comprising oxyfluoride/bismuth oxyiodide/graphitic carbon nitride (BiOxFy/BiOpIq/g-C3N4) was prepared hydrothermally. Ternary bismuth oxyhalide photocatalyst samples were prepared using various material ratios, pH values, and hydrothermal synthesis temperatures; subsequently, the catalyst with the most favorable photocatalytic degradation rate was selected for further compounding. In this study, quaternary composite photocatalysts were produced through with different weights of g-C3N4 to identify the material with the optimal photocatalytic degradation rate. In a photocatalytic degradation rate experiment, crystal violet dye was used as to represent the pollution source. Among the ternary bismuth oxyhalide catalyst samples, those with the highest (0.2133 h−1) and second highest (0.2074 h−1) degradation rates were selected for the preparation of quaternary photocatalysts. The ternary bismuth oxyhalide with the second-best degradation rate not only successfully formed g-C3N4 quaternary composites but surpassed the degradation rate of the compound with the initially highest rate. Its degradation rate reached 0.2563 h−1, 1.24 times that before recombination, indicating the positive effect of recombination between BiOxFy/BiOpIq and g-C3N4. At 1 atm and 25 °C, the rates of photocatalytic CO2–CH4 conversion by the optimal BiOxFy/BiOpIq and BiOxFy/BiOpIq/g-C3N4 photocatalysts were 0.032 and 0.107 μmol g−1 h−1, respectively. The present results indicate the viability of the synthesizing BiOxFy/BiOpIq/g-C3N4; moreover, because of its photocatalytic activity in the presence of crystal violet and ability to reduce CO2, this material has potential for use in environmental pollution mitigation.