Visible-light-driven g-C3N4/AgBiS2 S-scheme photocatalyst for N2 fixation and rhodamine B degradation

The design of photocatalysts, which uses free and available sunlight as a driving force to generate ammonia from nitrogen (N2) and remove organic pollutants from wastewater, is helpful to develop a sustainable chemical industry. The novel g-C3N4 nanosheet/AgBiS2 nanocomposite with visible-light response was successfully fabricated for the first time using a simple heating process. The purity, microstructure, morphology, photoelectrochemical, and electronic features of the obtained photocatalysts were studied using X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), high-resolution TEM, X-ray photoelectron spectroscopy, diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, photoluminescence, Brunauer–Emmer–Teller surface area, photocurrent responses, and electrochemical impedance spectroscopy. The g-C3N4 nanosheet/AgBiS2 nanocomposite possessed excellent photocatalytic activity for rhodamine B (RhB) degradation and N2 fixation upon visible illumination. The photocatalytic ammonium production reached 3780 μmol L−1 g−1 over g-C3N4 nanosheet/AgBiS2 nanocomposite, increases of 3.15- and 2.85-fold compared to that of g-C3N4 nanosheet and AgBiS2, respectively, as well as 99% improvement in degradation efficiency for RhB removal. The improved activity of g-C3N4 nanosheet/AgBiS2 nanocomposite can be ascribed to the formation of suitable heterojunction, suppressing the recombination of photogenerated charges, while facilitating their transfer. A plausible photocatalytic mechanism was proposed based on the experimental outcomes and photoelectrochemical properties. The g-C3N4 nanosheet/AgBiS2 nanocomposite proved to be significantly reusable and stable after five and four runs of N2 fixation and RhB degradation, respectively.