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Rapid recombination of the photo-generated charge carriers leads to the poor photocatalytic nitrogen fixation property of pristine graphite-like carbon nitride (g-C 3 N 4). To enhance the photocatalytic performance of g-C 3 N 4 , nickel sulfide (NiS) nanoparticles were anchored onto the surface of g-C 3 N 4 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-C 3 N 4 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-C 3 N 4 , 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. [Display omitted] • NiS modified g-C 3 N 4 is prepared by an in-situ decomposition-thermal polymerization. • NiS/CN shows nitrogen vacancy, wide absorption range and efficient charge transfer. • NiS/CN exhibits enhanced photocatalytic nitrogen fixation performance. [ABSTRACT FROM AUTHOR]

• AgI modified g-C 3 N 4 is prepared by an in-situ decomposition-thermal polymerization. • AgI modified g-C 3 N 4 shows nitrogen vacancy, reduced band gap, and efficient charge transfer. • AgI modified g-C 3 N 4 exhibits enhanced photocatalytic nitrogen fixation performance. It is of great significance to develop N 2 photo-fixation under mild conditions with solar energy as the only energy input. Herein, we report a convenient in-situ decomposition-thermal polymerization method to obtain AgI modified g-C 3 N 4 heterogeneous catalyst with nitrogen vacancy for enhanced photocatalytic nitrogen fixation. The 2.5% AgI loaded g-C 3 N 4 composite exhibited the best performance for N 2 photo-fixation (150 mg/L/h/g Cat) due to the existence of nitrogen defects, reduced band gap, enhanced separation efficiency of the photo-generated charge carriers and the strong reduction power of more negative conduction band. Furthermore, a feasible reaction mechanism was proposed for the photocatalytic nitrogen fixation process. [ABSTRACT FROM AUTHOR]

• Ag/B-doped g-C 3 N 4 was prepared by an in-situ decomposition-thermal polymerization. • Ag/B-doped g-C 3 N 4 showed reduced band gap and efficient charge separation. • Ag/B-doped g-C 3 N 4 exhibited enhanced photocatalytic nitrogen fixation performance. Photocatalytic nitrogen fixation is considered as a promising strategy for ammonia production. In this study, non-metallic boron and noble metal silver modified graphitic carbon nitride were prepared by a direct in-situ decomposition-thermal polymerization method with dicyandiamide, boric acid and silver nitrate as the precursors. It was shown that Ag/B-doped g-C 3 N 4 composites with optimal mass ratio exhibited improved photocatalytic ammonia production under simulated sunlight illumination by a factor of 5.5 and 1.5 times compared with the pristine g-C 3 N 4 and B-doped g-C 3 N 4 , respectively. The superior photocatalytic property was attributed to the decreased band gap and formation of mesopores after boron doping, which enlarged the specific surface area and created abundant reactive sites on the g-C 3 N 4 nanosheets. In addition, the loaded silver nanoparticles greatly inhibited the recombination of photogenerated charge carriers through heterojunction interface. This work provided new deep insights into the reasonable structure of g-C 3 N 4 composite system for photocatalytic nitrogen fixation reactions. [ABSTRACT FROM AUTHOR]

• I-doped g-C 3 N 4 were synthesized by an in-situ decomposition-thermal polymerization. • I-doped g-C 3 N 4 showed reduced band gap and extended PL lifetime. • I-doped g-C 3 N 4 exhibited enhanced photocatalytic nitrogen fixation performance. Photocatalytic nitrogen fixation has attracted great attention recently due to the mild condition with solar energy as the only energy input. In this work, the iodine-doped g-C 3 N 4 with carbon vacancies has been successfully synthesized via a one-step thermal-decomposition method. The results showed that the band gap of g-C 3 N 4 decreased and the average PL lifetime of g-C 3 N 4 increased after iodine doping. This demonstrated the expansion of light responsive range and the high separation efficiency of the photo-generated charge carriers in iodine-doped g-C 3 N 4. The g-C 3 N 4 with 10 wt% iodine doping exhibited excellent performance and well stability for the photocatalytic nitrogen fixation under simulated sunlight irradiation within 3 h (200.8 mg/L/g cat), which is 2.8 times as high as that of bulk g-C 3 N 4 , owing to the reduced band gap, existence of carbon vacancies and enhanced separation efficiency of the photo-generated charge carriers. A feasible mechanism was proposed for photoinduced charge separation and nitrogen photofixation over iodine-doped g-C 3 N 4. [ABSTRACT FROM AUTHOR]