In-situ synthesis and enhanced photocatalytic nitrogen fixation property of novel NiS/g-C3N4 heterostructure photocatalysts with nitrogen vacancy

Abstract

Rapid recombination of the photo-generated charge carriers leads to the poor photocatalytic nitrogen fixation property of pristine graphite-like carbon nitride (g-C3N4). To enhance the photocatalytic performance of g-C3N4, nickel sulfide (NiS) nanoparticles were anchored onto the surface of g-C3N4 by using the in-situ decomposition-thermal polymerization method in this work. The incorporation of NiS cocatalyst expanded the absorption range, enhanced the efficiency of separating photo-generated charge carriers, reduced the band gap from 2.78 eV to 2.47 eV, increased the specific surface area 7.1 m2·g−1 to 19.5 m2·g−1, and enlarged the photo-current density, which can inhibit the recombination of photo-generated charge carriers. Furthermore, the emergence of the nitrogen vacancy occurred during the in-situ synthetic process as a result of the thermal decomposition of thioacetamide hydrolysate, thereby leading to an enhancement in the photocatalytic nitrogen fixation efficiency. The results of the nitrogen fixation experiment demonstrated that 13 % NiS/g-C3N4 exhibited the highest activity, with a photocatalytic nitrogen fixation rate of 8.15 mg/L. This rate is 7.6 times greater than that of pure g-C3N4, which can be attributed to several factors, including a higher separation rate of photogenerated electrons, a larger specific surface area, a wider range of responsiveness to visible light, and the presence of the nitrogen vacancy.