Synthesis And Photocatalytic Properties Of Graphitic Carbide Nitride And Sulfide Composite Photocatalysts

As the massive burning of fossil fuels,the environmental problems are worsening year by year,and fossil fuels have been increasingly exhausted.It is urgent to find new,green,cheap and renewable energy sources to replace traditional fossil energy sources.Hydrogen energy is considered as the ideal energy in the 21st century because of its wide source,high combustion calorific value,clean and pollution-free,storage,various utilization forms and wide application.Photocatalytic water splitting hydrogen production is one of the most promising ways of hydrogen production,which is driven by endless solar energy and abundant water.Under the action of semiconductor photocatalyst,photogenerated carriers are used to decompose water for hydrogen production.The design and development of new,efficient and broad spectral response photocatalyst is the key to the practical application of photocatalytic technology.In this paper,three series of nearly twenty composite photocatalysts have been designed and prepared by selecting cheap and readily available g-C₃N₄ and metal sulfides with good visible light response as research objects.The main research contents are as follows:???Preparation and photocatalytic performance of CdS Petal array grown on g-C₃N₄nanosheets composite photocatalysts.The following eight composites were synthesized by precipitation hydrothermal method:?1?CN-CdS?0.05?,?2?CN-CdS?0.1?,?3?CN-CdS?0.2?,?4?CN-CdS?0.4?,?5?CN-CdS?0.8?,?6?CN-CdS?1.6?,?7?CN-CdS?2?,?8?CN-CdS?3??g-C₃N₄ is labeled CN?,they were characterized by IR,XRD,SEM,TEM,XPS methods,the properties of hydrogen production was studied by UV-vis,PL spectrum,photocatalytic experiment and cycle experiment,all samples were loaded 3%Pt cocatalyst in the photocatalytic experiments.Experiments show that CN-CdS composites had a unique flower petals-shaped structure,the H₂ production rate of eight composites are 638.6?mol g^-1 h^-1,678?mol g^-1 h^-1,700.8?mol g^-1 h^-1,849.2?mol g^-1 h^-1,1286.4?mol g^-1 h^-1,2633.2?mol g^-1 h^-1,817.6?mol g^-1h^-1,680?mol g^-1 h^-1,respectively,the highest hydrogen production is CN-CdS?1.6?,and the H₂ production rate of CN-CdS?1.6?is 20 times than pure C₃N₄,this is due to formate heterojunction between g-C₃N₄ and CdS,inhibited the recombination of photo-generated electrons and holes,and improved the photocatalytic activity of CN-CdS?1.6?,cycling test showed that CN-CdS loaded Pt noble metal had good photochemical stability.???Noble-metal-free ternary g-C₃N₄-Zn_0.5Cd_0.5S-NiS nanocomposites for enhanced visble light photocatalytic water splitting H₂-production.The following nine composites were synthesized by precipitation hydrothermal method:?9?CN-ZCS-1,?10?CN-ZCS-2,?11?CN-ZCS-3,?12?CN-ZCS-4,?13?CN-ZCS-5,?14?CN-ZCS-0.5%NiS,?15?CN-ZCS-1%NiS,?16?CN-ZCS-2%NiS,?17?CN-ZCS-3%NiS?C₃N₄ is labeled CN,ZnCdS is labeled ZCS?,they were characterized by IR,XRD,SEM,TEM,XPS methods,the properties of hydrogen production was studied by UV-vis,PL spectrum,photocatalytic experiment and cycle experiment.Experiments show that CN-ZCS-xNiS composites have a random particle structure,the H₂ production rate of nine composites are 18420.9?mol g^-1 h^-1,21906.9?mol g^-1 h^-1,26173?mol g^-1 h^-1,26980.84?mol g^-1 h^-1,23968.6?mol g^-1 h^-1,42785.4?mol g^-1 h^-1,53190.66?mol g^-1 h^-1,33810?mol g^-1 h^-11 and 30454.2?mol g^-1 h^-1,respectively,the highest hydrogen production is CN-ZCS-1%NiS,the H₂ production rate of CN-ZCS-1%NiS is 405 times than pure g-C₃N₄,this is due to formate heterojunction between g-C₃N₄ and ZnCdS,and the synergy of NiS,facilitate the separation of photo-generated electrons and holes,thus the photocatalytic performance of CN-ZCS-1%NiS was improved significantly,cycling test showed that g-C₃N₄,ZnCdS and NiS composite photocatalyst had good photochemical stability.???Study the hydrogen performance of g-C₃N₄-CdS composites which contain different types of Ni-based cocatalyst?NiS,Ni₂P,Ni?OH?₂?in visble light.The following there composites were synthesized by precipitation hydrothermal method:?18?g-C₃N₄-CdS-1%NiS,?19?g-C₃N₄-CdS-1%Ni₂P,?20?g-C₃N₄-CdS-1%Ni?OH?₂,were characterized by IR,XRD,SEM,TEM,XPS methods,the properties of hydrogen production was studied by UV-vis,PL spectrum,photocatalytic experiment and cycle experiment.Experiments show that the H₂ production rate of three Ni-based composites are 38139.2?mol g^-11 h^-1,31364?mol g^-11 h^-11 and 27974.4?mol g^-11 h^-1,respectively.The H₂production rate of them is 298 times,245 times and 218 times than g-C₃N₄,respectively.Apparently,g-C₃N₄-CdS-1%NiS had the best hydrogen production capability,this is due to formate heterojunction between g-C₃N₄ and CdS,and the synergy of NiS,facilitate the separation of photo-generated electrons and holes,thus the photocatalytic performance of g-C₃N₄-CdS-1%NiS was improved,cycling test showed that ternary composite photocatalyst had good photochemical stability.