Construction And Photocatalytic Properties Of V Or Fe-modified G-C₃N₄ 1D Tube-based Materials

The rapid development of the global economy and the lack of human environmental awareness and behaviour have brought about increasingly serious problems of energy shortage and environmental pollution.Nowadays,the value of photocatalysis technology in the fields of clean energy preparation from solar energy and pollutant degradation is widely recognized,and the preparation of efficient and stable photocatalytic materials is the key to the development of photocatalysis technology.Graphite-like carbon nitride（g-C₃N₄）is a very promising organic semiconductor material,but its practical applications are constrained by factors such as low optical quantum efficiency and lack of active sites,so how to enhance its photocatalytic performance has become a key concern for researchers.In this study,g-C₃N₄ was modified and modified through strategies such as material structure design,transition metal doping and heterostructure construction,and its performance was investigated through photocatalytic degradation of tetracycline and hydrogen production from photodegraded water.The specific work is as follows:（1）Vanadium-doped tubular carbon nitride photocatalysts were prepared and their photocatalytic degradation performance was investigated.The synthetic tubular shaped g-C₃N₄ was prepared by electrostatic spinning technique and vapour phase deposition and nitric acid etching,and then the vanadium-doped tubular g-C₃N₄ photocatalyst was synthesised by impregnation and calcination.The vanadium doping resulted in a change in the energy band structure of g-C₃N₄ and an increase in the carrier migration rate.Characterisation results demonstrate that the composite catalysts have enhanced absorption in both the UV-visible region compared to pure g-C₃N₄.In the photodegradation（λ≥420nm）reaction of tetracycline（TC）,the prepared 7V-g-C₃N₄ catalyst achieved 81.9%degradation of TC,which was four times higher than that of pure g-C₃N₄.In addition,7V-g-C₃N₄ showed good generalizability for the degradation of tetracycline antibiotics.The results of the capture experiments demonstrated that the most dominant active species in the photocatalytic reaction system was·O₂^-.The degradation intermediates of TC were analysed by HPLC-MS and the photocatalytic degradation pathway of TC was analysed.（2）Core-shell structured g-C₃N₄@Fe₂O₃ heterojunction composite photocatalysts were constructed and successfully prepared by electrostatic spinning,high temperature calcination and vapour phase deposition processes（x FCN）.The uniform growth of g-C₃N₄ on the surface of Fe₂O₃ core layer can be observed by TEM characterization.The spectroscopic and optoelectronic characterisation results show that this one-dimensional core-shell heterojunction structure can effectively promote the separation of photogenerated electrons and holes and enhance the optical quantum efficiency.The preferred photocatalytic material（4FCN）exhibited 82.6%degradation rate of TC within 90 min of light exposure,which was3.3 times higher than that of g-C₃N₄.In addition,its application to photodegradation of aquatic H₂ also showed excellent performance,with an average hydrogen production rate of212.97μmol?g^-1?h^-1,which was three times higher than that of g-C₃N₄.The composite catalysts showed good cyclability in both photodegradation of aquatic hydrogen and antibiotic degradation reactions.The effect of p H was explored during the photodegradation TC reaction,and the results showed that the 4FCN composite catalyst was well tolerated to environmental p H changes.The enhanced photocatalytic activity of the 4FCN composite catalyst can be attributed to two aspects:firstly,the composite photocatalyst has a nanotubular morphology,and the increased specific surface area can provide more active sites for the reaction;secondly,combining the experimental results with the semiconductor energy band theory Secondly,combining the experimental results with the semiconductor energy band theory,Fe₂O₃ matches the energy band structure of g-C₃N₄ to form a Z-type heterojunction,which increases the photogenerated carrier migration rate and enhances the redox ability of the composite catalyst.