| Hydrogen is a kind of clean,renewable and storable energy,which plays an important role in solving the increasingly severe environmental and energy crisis.Hydrogen production by electrolytic water is a widely used industrial hydrogen production technology,but the energy consumption is too large,so it is urgent to develop a low-energy hydrogen production technology,which can not only meet the demand of renewable energy,but also eliminate the poison of fossil fuels.Photocatalysis technology is attracting attention because it can effectively solve energy problems by converting solar energy into chemical energy and because it is clean and free of secondary pollution.Ti O2,a traditional photocatalytic material,can only absorb UV light and cannot make full use of solar energy,Therefore,its application in photocatalysis has been greatly limited.Therefore,developing a new type of semiconductor photocatalyst to improve its absorption and photocatalytic performance in the visible region is a key problem to be solved.N-rich graphite phase g-C3N4 is a new photocatalytic material which has been widely concerned due to its strong stability.g-C3N5has a different CN skeleton structure from g-C3N4,and has higher thermodynamic stability and smaller band gap.However,High carrier migration and high recombination rate of photogenerative carriers are the two major bottlenecks that restrict their efficient photoelectric conversion efficiency.In order to improve the photocatalytic efficiency of g-C3N5,a new type of photocatalytic material was synthesized by using g-C3N5 as a carrier and by combining with other inorganic materials.The details are as follows:（1）SnS2/C3N5 composites were prepared by hydrothermal synthesis using 3-amino-1,2,4-triazole as the raw material of g-C3N5.On this basis,the structure,optical absorption band and carrier transmission characteristics are characterized by various means.Compared with g-C3N5,Sn S2/C3N5 composite photocatalytic material has a slightly narrow light absorption range,but it can effectively improve the photogenerated charge migration rate,reduce the electron-hole pair recombination rate,and improve the photocatalytic performance of g-C3N5.The photocatalytic hydrogen production experiments were carried out under simulated solar illumination.The experimental results showed that the hydrogen production performance of all Sn S2/C3N5 composites was improved.The hydrogen production capacity of 5%Sn S2/C3N5 composites was 5409μmol,which was 3.4 times that of pure g-C3N5.The photocatalytic degradation MB experiment showed that 5%Sn S2/C3N5composite can degrade 95%of contaminants within 40 minutes,showing good photocatalytic degradation performance.（2）Bi2S3 was added to g-C3N5 to prepare materials with excellent photocatalytic ability.The precursor was prepared by two-step heat treatment method,and then Bi2S3/C3N5composites were prepared by hydrothermal synthesis method.Through the characterization of the material morphology,structure and photoelectric properties,it is shown that the composite material forms a heterogeneous structure,showing better light absorption and photoelectric performance.The photocatalytic degradation and photocatalytic hydrogen production experiments show that 1%Bi2S3/C3N5 has the best photocatalytic degradation efficiency of 90%within 60 minutes,The hydrogen yield was 2938μmol,about 3.5 times that of undoped g-C3N5.It has good cyclic stability,and the performance remains unchanged after 3 cycles.The experimental results show that the role of Bi2S3 and g-C3N5 in the composite system is used to construct the Type-II heterogeneous structure with strong electric conversion ability.Under the premise of enhancing the photogenerated charge separation ability,the recombination probability of the photogenerated electron-hole is reduced,and the photocatalytic ability is further enhanced.In conclusion,in this paper,a new type of non-metallic polymer material g-C3N5 is combined with other materials in different ways to form heterojunction,so as to effectively improve the photogenerated charge migration rate and Improve the separation efficiency of photogenic charge.It was found that the photocatalytic performance of Sn S2/C3N5 and Bi2S3/C3N5composites was significantly improved compared with g-C3N5.Therefore,this work provides a new idea for the design of efficient photocatalytic degradation and hydrogen-producing activity of nitrogen-rich carbon nitride photocatalysts. |
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