In Situ Polycondensation Synthesis of NiS-g-C 3 N 4 Nanocomposites for Catalytic Hydrogen Generation from NaBH 4 .

The nanocomposites of S@g-C 3 N 4 and NiS-g-C 3 N 4 were synthesized for catalytic hydrogen production from the methanolysis of sodium borohydride (NaBH 4 ). Several experimental methods were applied to characterize these nanocomposites such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and environmental scanning electron microscopy (ESEM). The calculation of NiS crystallites revealed an average size of 8.0 nm. The ESEM and TEM images of S@g-C 3 N 4 showed a 2D sheet structure and NiS-g-C 3 N 4 nanocomposites showed the sheet materials that were broken up during the growth process, revealing more edge sites. The surface areas were 40, 50, 62, and 90 m 2 /g for S@g-C 3 N 4 , 0.5 wt.% NiS, 1.0 wt.% NiS, and 1.5 wt.% NiS, respectively. The pore volume of S@g-C 3 N 4 was 0.18 cm 3 , which was reduced to 0.11 cm 3 in 1.5 wt.% NiS owing to the incorporation of NiS particles into the nanosheet. We found that the in situ polycondensation preparation of S@g-C 3 N 4 and NiS-g-C 3 N 4 nanocomposites increased the porosity of the composites. The average values of the optical energy gap for S@g-C 3 N 4 were 2.60 eV and decreased to 2.50, 2.40, and 2.30 eV as the NiS concentration increased from 0.5 to 1.5 wt.%. All NiS-g-C 3 N 4 nanocomposite catalysts had an emission band that was visible in the 410-540 nm range and the intensity of this peak decreased as the NiS concentration increased from 0.5 to 1.5 wt.%. The hydrogen generation rates increased with increasing content of NiS nanosheet. Moreover, the sample 1.5 wt.% NiS showed the highest production rate of 8654 mL/g·min due to the homogeneous surface organization.