Influence of different bismuth oxyhalides on the photocatalytic activity of graphitic carbon nitride: a comparative study under natural sunlight

The light harvesting properties and charge separation in the trending graphitic carbon nitride (g-C3N4) material have been widely explored to enhance its photocatalytic performance employing doping, morphology control and composite formation. Herein, the effect of coupling of different bismuth oxyhalides, BiOX (X = F, Cl, Br and I), on the photocatalytic performance of g-C3N4 has been studied by synthesizing BiOX/g-C3N4 composites by a facile hydrothermal method. It was found that the BiOX/g-C3N4 composites showed enhanced photocatalytic degradation of a model pollutant, Congo red dye, under natural sunlight irradiation, as compared to the bare g-C3N4 and respective BiOX. The enhanced photocatalytic performance of the composites was attributed to the appropriate band edge potential and better interfacial contact between g-C3N4 and BiOX, which suppresses charge recombination and allows their better utilization at catalytic sites than in the case of bare g-C3N4 and respective BiOX. In comparison to all the BiOX/g-C3N4 composites, BiOBr/g-C3N4 showed the degradation of Congo red at a higher rate and was also found to be effective for the degradation of a colorless fungicide, carbendazim. Further, to look into the role of the active species responsible for this activity, trapping experiments have been carried out, which revealed that OH* was the main reactive species in the degradation process and, based on these results, a suitable mechanism for the enhanced photocatalytic activity has been proposed and discussed. Hence, the BiOX/g-C3N4 composite formation has proven beneficial for achieving high photocatalytic performance and provides new insight on bismuth oxyhalides and g-C3N4 based photocatalysts for environmental remediation application.