Enhanced photocatalytic activities of NiS decorated reduced graphene oxide for hydrogen production and toxic dye degradation under visible light irradiation

Semiconductor nanoparticles have extensively studied for a decade on photocatalytic hydrogen production and remediation of toxic pollutants due to their better activities at nano regime and quantum efficiency. The present study reports on the preparation of NiS nanoparticles decorated reduced-graphene oxide nanocomposite (RGO) as an effective visible photo-catalyst for H2 production and a toxic organic dye degradation. NiS and RGO were synthesized by hydrothermal and modified Hummer's method, respectively. The synthesized nanocomposite was thoroughly investigated for its structural and optical properties by various techniques such as XRD, UV-Vis-DRS, FT-IR, Raman, FE-SEM, HR TEM, EDAX, XPS, AFM, BET and XPS. The morphology indicates sphere like particles of NiS dispersed on the surface of the RGO layers. Raman spectral analysis of the nanocomposite materials showed the ID/IG intensity ratios in RGO-NiS (1.00) and GO (1.08) which confirmed that the prepared nanocomposite material has lesser defects. The specific surface area of the prepared nanocomposite was found to be 142.68 m2 g-1. Different experimental parameters such as effect of pH, loading of catalyst and kinetics of dye photodegradation and H2 production were optimized to maximize the photocatalytic activities of the nanocomposite materials. It was observed that maximum % of dye degradation occurred at neutral pH with catalyst loading of 10 mg/10 mL of 10 ppm dye and exhibited 99% degradation under visible light irradiation for 6 h. The prepared nanocomposite material was also employed for H2 production from water through photo-splitting method and it resulted in a maximum hydrogen production as 1368 and 2946 mmol g1h-1 for RGO-NiS and RGO-NiS/Pt respectively with loading of 100 mg catalyst. It was observed that 4.6 and 2.19 fold increase in hydrogen production with pristine NiS and RGO-NiS nano composite respectively with good reusability. Hence, the prepared visible active RGO-NiS nanocomposite could be a suitable catalyst for the oxidation of organic impurities and hydrogen generation from water. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.