| With the development of traditional industrial economy,environmental pollution and energy crisis have become more and more obvious.Finding new and clean energy that can replace traditional energy has become an urgent task.Therefore,photocatalytic technology with solar energy as the core has emerged.Although this technology has been applied to photolysis of water to produce hydrogen,degradation of organic pollutants,nitrogen fixation,sterilization and disinfection,etc.,the development space still needs to be improved.The main disadvantages of traditional semiconductor materials,such as poor photoresponse,low photogenerated charge separation efficiency,and high recombination rate,severely limit the utilization efficiency of sunlight,which has not been completely resolved.Therefore,solving the above problems has become the core problem of photocatalytic technology at this stage.As one of the most common industrial raw materials,urea and melamine have the advantages of simple preparation and low cost.At the same time,they are also the most popular raw materials for preparing photocatalyst carbon nitride.Although carbon nitride has the advantages of simple preparation method,low cost,good light response,and stable chemical properties,it still has the defects of traditional semiconductors.The development of comprehensive,highly active,practical and practical,efficient and stable catalysts has become a key task in today’s research.Based on the above problems,the research content of this article is as follows:（1）Heptazine crystalline carbon nitride（HCN）was synthesized by the method of secondary calcination of molten salt.During the synthesis process,the morphology,crystallinity and surface defects of the sample were adjusted by changing the type of molten salt and the method of intervening ball milling.XRD confirmed the successful synthesis of sample HCN and a certain increase in crystallinity.The morphology and structure of the samples were analyzed by SEM and TEM.UPS,Mott-Schottky,and BET have confirmed that HCN-Li Na K has the narrowest band gap and the largest specific surface area,thereby reducing the energy required for electrons to transition from the valence band to the conduction band and increasing the contact area between the sample and the reaction solution.Finally,the photocatalytic activity evaluation system was used to test the hydrogen production performance of the samples by photolysis.The experimental results show that when three molten salts（NaCl,KCl,Li Cl）are used as the liquid polymerization medium and triethanolamine is used as the sacrificial agent,the sample HCN-Li Na K has the best hydrogen production performance,the hydrogen production at 420 nm can be as high as 2.77 mmol·g-1·h-1,and the quantum efficiency is 13.7%.Compared with the initial carbon nitride,the performance has been significantly improved.At the same time,the effects of different sacrificial agents and different Pt loadings on the performance of photocatalytic hydrogen production were also explored.（2）Based on the above system,a series of doped crystalline carbon nitrides （HCCN-x）were prepared using a combination of hydrothermal and ball milling methods.It was subsequently confirmed by XRD that the introduction of5-aminotetrazole（TA）did not destroy the original skeleton of crystalline carbon nitride,indicating the successful synthesis of the sample.The structure and morphology of the material were tested by SEM,TEM and other test methods.By changing the amount of TA doping,the effect of the amount of TA doping on the morphology,structure and performance of the material was systematically studied.The experimental results show that when the doping amount of TA is 50%,the photocatalytic effect of the sample HCCN-50 is the best.When the 420 nm filter is used as the cut-off filter,the hydrogen production rate can reach 4.5 mmol·g-1·h-1,and the quantum efficiency at 435 nm can reach 17.5%.Compared with the previous chapter,the performance has been further improved. |
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