Modification And Characterization Of Graphitic Carbon Nitride And Its Application To Photocatalytic Hydrogen Evolution From Water Splitting

Hydrogen energy is a potential new-style energy with clean,non-polluting and high combustion value,so the development and utilization of hydrogen energy has attracted widespread attention.The technology of photocatalytic hydrogen evolution from water splitting is a green and effective way to obtain hydrogen,which can convert low-density solar energy into high-density hydrogen energy.The effective development and utilization of hydrogen energy can alleviate the two major global issues of environmental pollution and energy shortage.The exploitation of photocatalysts is the most important thing for the photocatalytic hydrogen evolution from water splitting.In this paper,graphitic carbon nitride?g-C₃N₄?was used as the main material modified with adjusting the morphology,loading Pt nanoparticles and compositing with SiC.Therefore,the composite photocatalyst materials of g-C₃N₄-Pt,g-C₃N₄-SiC and g-C₃N₄-SiC-Pt was prepared.The morphologies and structures of the as-prepared photocatalysts were characterized,and the performance of photocatalytic hydrogen production was investigated.First,the g-C₃N₄-SiC composite photocatalyst was successfully prepared by the combination method of sol deposition and calcination.In the condition of the mass ratio of SiC to g-C₃N₄ is 5%and calcination at 500? for 4 h prepared the g-C₃N₄-SiC photocatalyst,which was showed good photocatalytic activity in visible light.The rate of H2 evolution reached 543.6 ?mol h-1 g-1,and the quantum efficiency reached 2.52%.Then,based on this condition the photocatalysts of g-C₃N₄-Pt and g-C₃N₄-SiC-Pt were prepared by the combination of a biosynthesis method and sol deposition with simple,rapid and environmentally friendly.The photocatalysts of g-C₃N₄-Pt and g-C₃N₄-SiC-Pt were shown good photocatalytic activity in visible light.The rate of H2 evolution reached 582.4 and 595.3 ?mol·h^-1·g^-1,and the quantum efficiency reached 2.70%and 2.76%,respectively.Finally,the morphological structure of as-prepared photocatalysts were characterized by Scanning Electron Microscope?SEM?,Transmission Electron Microscope?TEM?,X-ray diffraction?XRD?and X-ray Photoelectron Spectroscopy?XPS?,the result of characterization revealed that the g-C₃N₄ is a two-dimensional material with a few layers.Furthermore g-C₃N₄,SiC and Pt nanoparticles combined tightly and Pt nanoparticles were successfully loaded and well dispersed on the surface of g-C₃N₄ and g-C₃N₄-SiC.As for the g-C₃N₄-SiC composite photocatalyst,SiC was well dispersed on the surface of g-C₃N₄,what's more,a few SiC were wrapped by g-C₃N₄ and formed core-shell structure.The analysis results of UV-vis Diffuse Reflection Spectroscopy?UV-vis DRS?showed the absorption wavelength range was widened and the absorption efficiency was increased in visible light of the g-C₃N₄-Pt,g-C₃N₄-SiC and g-C₃N₄-SiC-Pt photocatalysts.The results of Photoluminescence spectroscopy?PL?measurements showed the recombination rate of photogenerated electron-hole pairs was reduced,so the photocatalytic activity for as-prepared photocatalysts was increased.The reason of photocatalytic activity increased can attribute to the Mott-Schottky and the organic-inorganic heterojunction formed in the interface of Pt nanoparticles,SiC and g-C₃N₄,which will enhance the separation efficiency of the photogenerated electron-hole pairs.In summary,the g-C₃N₄ was modified with adjusting the morphology,loading Pt nanoparticles and compositing with SiC,which can improve the photocatalytic activity of the pure g-C₃N₄.