The Effection Of The Way Of Exfoliction G-C₃N₄ Nanosheets For Its Photocatalytic Evolution Hydrogen Under Visible Light

Photocatalytic redox technology has been recognized as a potential answer to the global energy crisis and environmental pollution.Graphene-like C₃N₄,especially the g-C₃N₄ nanosheets with unique band structure and chemical thermal stability,exhabits excellent performancein the degradation of pollutants,CO2 reduction,photocatalytic production hydrogen.Therefore,in this article,g-C₃N₄ nanosheets and NiS/g-C₃N₄ were prepared byexfoliatingbulk g-C₃N₄.The effect of different exfoliating methods and NiS loading on the physical and chemical properties and catalytic activity of gC₃N₄ nanosheets was studied and the photocatalytic mechanism of hydrogen production on as-prepared g-C₃N₄/NiS was discussed.The bulk g-C₃N₄ was simply prepared by the thermal condensation of melamine.g-C₃N₄ nanosheets were prepared by the post-thermal oxidation etching process,ultrasonic assisted-liquid exfoliation method and chemical exfoliation method.X-ray powder diffraction?XRD?,transmission electron microscopy?TEM?,UV-Vis diffuse reflectance spectroscopy?DRS?,Fourier transform infrared?IR?and photoelectrochemical performance test were used to characterizethe samples.Photocatalytic activities of the samples were investigated by photocatalytic production hydrogen of visible light??420 nm?.Results show that the hydrogen production rate of g-C₃N₄ nanosheets prepared by thermal oxidation is the best,592 ?mol.g-1.h-1?2.0wt%Pt/CNNS-1?,which was 4.5 times of bulk g-C₃N₄.The high catalytic activity is mainly due to the large specific surface area?175.9 m2/g?,the small energy gap?2.82 eV?,the intensive separation efficiency of photogenerated electron-hole.In addition,the effects of preparation conditions,sacrificial agent concentration and Pt loading were systematically studied.The optimum hydrogen production rate of g-C₃N₄ nanosheets was 711 ?mol.g-1.h-1,when triethanolamine is 10v% and the deposition amount of Pt is 2.5wt%??420 nm?.NiS/g-C₃N₄ was prepared by electrostatic adsorption-hydrothermal method.XRD,TEM,XPS,DRS and photoelectrochemical performance test were used to characterize the samples.Results show that NiS was uniformly deposited on the surface of g-C₃N₄,and the light absorption capacity of the sample was enhanced after NiS deposition.The photocatalytic activities of the sampleswere investigated by photocatalytic production hydrogen of visible light??420 nm?.Results show that the hydrogen production rate of g-C₃N₄/1.75wt% NiS is the best?413 ?mol.g-1.h-1?,which was 1.2 times of 1.0wt% Pt/g-C₃N₄.