Microwave-assisted fabrication of g-CN nanosheets sustained BiS heterojunction composites for the catalytic reduction of 4-nitrophenol.

In this work, we report a stable g-CN, BiS, and g-CN/BiS composite catalysts were prepared via a facile one-pot microwave-assisted method and characterized. The orthorhombic phase and nearly spherical shape of the particles with an average diameter of 5-25 nm of g-CN/BiS composite were obtained from XRD and TEM. The composite also exhibits a high surface area (32.15 m/g), which may provide convenient transportation and diffusion for substrate molecule. The optical studies were displayed the g-CN/BiS composite has a sharp absorption band in the visible region, higher charge separation, and reduced recombination rate. These results show that the BiS NPs have good crystallinity and are uniformly deposited on the surface of the g-CN sheet. The catalytic performance of the g-CN/BiS composite for the reduction of 4-NP to 4-AP was exhibited approximately 100%, which is 1.48 and 2.34 times higher than the BiS and g-CN catalysts, respectively. The pseudo-first-order rate constant was estimated as 1.648 × 10  min for the reduction of 4-NP using g-CN/BiS composite in 1 h reaction time. The effect of catalyst dosage (0-30 mg) was also investigated for the reduction of 4-NP using g-CN/BiS composite catalyst. Moreover, the reusability of the g-CN/BiS composite was exhibited a better reduction of the 4-NP even after 5 cycles and it was found that 8% reduction in the initial reduction rate. The obtained results from this study show that g-CN/BiS composite has the potential efficiency and stability to make it an ideal catalyst for the reduction of toxic effluents and wastewater treatment.