Preparation And Application Of Porous GC 3 N 4 Visible Light Photocatalyst

Semiconductor photocatalysts have attracted unprecedented attention in mitigate the environmental issues and energy crisis,and mainly concentrated in photocatalytic H₂ evolution and photocatalytic degradation of contaminants.Among various photocatalyst materials,titanium dioxide?TiO₂?is the most famous photocatalysts owing to its low cost,high photocatalytic activity,good stability and nontoxicity.Nevertheless,the relatively wide band gap of³.2 eV for anatase TiO₂ and the rapid recombination of photoinduced electron-holes are major drawbacks in its poor photocatalytic activity,which seriously restricts its application.The polymeric graphitic carbon nitride?g-C₃N₄?has drawn ever booming attention as a noble metal-free semiconductor photocatalyst owing to its unique physical and chemical properties.The band gap of g-C₃N₄ is².7 eV,indicating a strong absorption in visible light region.However,its photocatalytic efficiency also faces the invalidation because of the bulk g-C₃N₄ with low specific surface area(<10 m² g^-1),poor quantum efficiency,and easy recombination of the photoinduced charge carriers,which restricts the photoinduced redox reaction.Furthermore,building heterostructures combining the g-C₃N₄ with other appropriate semiconductors is the effective way to facilitate the mobility efficiency of photogenerated charge carriers,and result in enhanced photocatalytic performance.This paper developed direct template-calcination method to synthesize the Meso-g-C₃N₄/g-C₃N₄ nanosheets laminated homojunction photocatalyst using melamine andaminocyanamideasco-precursorsandSiO₂asthetemplate.(Meso-g-C₃N₄/Ti³⁺-TiO₂)had been prepared via calcination-sonication assisted method using amino cyanamide as precursors,combined with a solid-state chemical reduction method.The prepared samples were evidently investigated by X-ray diffraction,Fourier transform infrared spectroscopy,scanning electron microscopy,transmission electron microscopy,X-ray photoelectron spectroscopy,N₂ adsorption,and UV-visible diffuse reflectance spectroscopy,respectively.The methyl orange solution and phenol in wastewaters were chosen as target pollutants to evaluate the removed rate of photocatalysts.Meanwhile,the photocatalytic activity for hydrogen evolution under the simulated solar light?AM 1.5?irradiation were evaluated.The research results of this paper were as follows:?1?Meso-g-C₃N₄/g-C₃N₄ nanosheets laminated homojunction photocatalyst using melamine and amino cyanamide as co-precursors and SiO₂ as the template was synthesized by direct template-calcination method.The results of experiment showed that the photocatalyst exhibited excellent photocatalytic activity due to the synergetic effects of the g-C₃N₄ and Meso-g-C₃N₄.(Degrades 91.0%methyl orange with 90 min illumination and photocatalytic hydrogen evolution¹15.6?mol h^-11 g^-1),and result in enhanced photocatalytic performance.?2?Ti³⁺self-doped TiO₂/g-C₃N₄ mesostructured nanosheets heterojunctions(Meso-g-C₃N₄/Ti³⁺-TiO₂)had been prepared via calcination-sonication assisted method using amino cyanamide as precursors,combined with a solid-state chemical reduction method.The results showed that special laminated heterojunctions were formed between Ti³⁺-TiO₂ and Meso-g-C₃N₄ which favored the separation of photogenerated electron-hole pairs.The enhanced photocatalytic activity may be ascribed to the synergetic effect of the mesoporous structure providing sufficient surface active sites,and Ti³⁺self-doping and the formed heterojunctions promoting the spatial separation of photogenerated electron-hole pairs.The Meso-g-C₃N₄/Ti³⁺-TiO₂ heterojunctions exhibited high photocatalytic activity for degradation of phenol in wastewaters?93.1%?and hydrogen evolution(²90.2?mol h^-11 g^-1)under visible light irradiation.Compared with Meso-g-C₃N₄/g-C₃N₄,Meso-g-C₃N₄/Ti³⁺-TiO₂ showed better photocatalytic hydrogenation performance.