Preparation Of Carbon Nitride/Oxide Semiconductor Hierarchy Structure And Its Photocatalytic Performance

In recent years,the large consumption of fossil energy and the accompanying environmental problems has the seriously affected human life and development.Thus,it is urgent to find out a way to tackle energy crisis and environmental thesis.As a green strategy to convert low-density solar energy into high-density chemical fuels,semiconductor photocatalytic technology has shown great prospects in mitigating energy crisis and solving environmental pollution.Carbon nitride?C₃N₄?with suitable band structure,good thermal stability,low cost of raw materials and facile preparation method,which has been widely used in the fields of photocatalytic water splitting,degradation of pollutants,chemical synthesis.However,the bulk C₃N₄ suffers from the disadvantages of rapid recombination of electron-hole pairs,confined specific surface area,and poor conductivity,which hindered its practical applications.Therefore,it is necessary to improve the performance of C₃N₄ with proper modification.To date,many methods including element doping,construction of special morphology,establishment of heterostructures with other semiconductors,and exfoliation has been developed.Among various strategies,coupling C₃N₄ with other semiconductor photocatalyst to construct hiberarchy heterojunction structure is considered as a reliable and effective method to improve its performance.Based on the above analysis,the main contents include:1.Preparation of C₃N₄-based hiberarchy heterojunction photocatalysta).Combination of C₃N₄ nanosheets with metal oxide semiconductor photocatalystWe developed a simple and low-cost bottom-up method for production of porous few-layer C₃N₄,obtained by a sequential molecule self-assembly,alcohol molecules intercalation,thermal-induced exfoliation and polycondensation process.On the basis of the C₃N₄ exfoliation,we synthesized a series of C₃N₄/metal oxide heterojunction photocatalysts by utilizing layered-microrod precursor and metal salt as starting material and subsequent vacuum-assisted intercalation,solvothermal and thermal polycondensation process.The detailed procedure is as follows:the tetrabutyl titanate?TBOT?and cerium nitrate?Ce?NO₃?₃?were dispersed in the mixture of ethanol and glycerol,then with the help of vacuum-assisted intercalation,finally reticular C₃N₄nested with TiO₂ nanoparticles?RCN/TiO₂?and C₃N₄/CeO₂ were obtained after thermal polycondensation process.b).Combination of tubular C₃N₄ with metal oxide semiconductor photocatalystHierarchical nitrogen-doped TiO₂/C₃N₄ tubular heterostructure consisting of C₃N₄microtube trunks and TiO₂ nanothorns on the outer surface of C₃N₄ microtube?N-TiO₂/C₃N₄-O?was fabricated using hexagonal rod-like layered supramolecule as precursor by solvothermal and subsequent calcination process.2.Photocatalytic performanceThe obtained C₃N₄-based hiberarchy heterostructure photocatalysts were applied in the fields of photocatalytic hydrogen evolution,pollutants degradation,and organic synthesis.The results showed that the few-layer C₃N₄ nanosheets,RCN/TiO₂ and N-TiO₂/C₃N₄-O are beneficial for photocatalytic hydrogen production.The CeO₂/C₃N₄heterojunction photocatalyst exhibited excellent performance in photocatalytic oxygen production and degradation of pollutants,it also has good stability.The remarkable improvement of the activity for C₃N₄-based heterojunction photocatalyst is mainly attributed to following reason:the construction of heterostructure can improve the absorption of visible light and promote the separation of photogenerated carriers;the special morphology can increase the specific surface area to provide more active site and shorten the diffusion distance of photogenerated electrons and the reactants.