Synthesis of S-doped g-C3N4 nanostructures by reflux method and study of photocatalytic and photoelectrochemical performances

Abstract

For the first time, the S-doped g-C3N4 nanostructures (SCN(x)) were prepared by the reflux method as an aqueous-based method with different weight ratios of Na2S (x) and then characterized. The results of S-doped g-C3N4 nanostructures confirmed the presence of sulfur doping in the g-C3N4 structure. Moreover, these nanostructures showed superior photocatalytic efficiency compared to the bulk g-C3N4. Among different SCN(x) nanostructures, SCN(0.2) showed the most remarkable photocatalytic performance. This outcome is attributed to a decrease in the band gap of this sample. The FESEM analysis indicated that the nanoparticles tended to adhere together in SCN(0.2) nanostructure. This phenomenon has led to the reduction of surface roughness, and improving the surface texture quality of this nanostructure. On the other hand, the lowest FWHM and PL peak intensity show an increase in crystallinity and a decrease in the amount of recombination in this nanostructure. Moreover, the evaluation of electrochemical impedance and optical current showed a decrease in the semi-circular pattern and an increase in photocurrent for the optimal sample of SCN (0.2) compared to the bulk g-C3N4. Therefore, the results of investigating the photocatalytic performance of the synthesized nanostructures show that the SCN(x) nanostructures have higher efficiency compared to the bulk g-C3N4. In addition, the SCN(0.2)) sample showed the highest photocatalytic efficiency. Compared to the other conventional deposition methods based on electrostatic or van der Waals forces, this study suggests that using the reflux technique to substitute sulfur in the g-C3N4 can be a successful approach due to the chemical bonding on to host framework. Moreover, this method may provide a facile aqueous-based route for doping in the g-C3N4 layered structure and can offer advantages compared to other common method such as simple, low cost, excellent distribution uniformity, fast reaction kinetics, high levels of purity, and environmentally friendly process.