Preparation And Performance Of Photocatalyst Composites Based On TiO₂/g-C₃N₄

As the development of human civilization,energy and environmental issues become the two major problems.Besides,they are also the major issues and need to be seriously considered for the implement sustainable development strategies.Therefore,looking for reasonable means to solve the above problems is getting more and more attention.Solar energy,as the largest source of energy,has been widely studied by human beings and is considered as the most promising energy.However,the solar energy received by the earth surface has the disadvantages of low energy density,poor dispersion,discontinuity and instability.Therefore,how to making advantage of the solar energy more efficiently has always been a difficult point of research.Photocatalytic technology based on semiconductor materials can convert solar energy into chemical energy through a series of chemical reactions,so as to improving the utilization rate of solar energy.As a result,it can be widely applied in the fields of new energy development and improve of environmental problems.The focus of photocatalytic research is to develop semiconductor photocatalytic materials with excellent performance.However,the single-component semiconductor photocatalytic has a wide band gap,leading to a high recombination of photogenerated electronics electron-hole pairs and poor degradation stability.Meanwhile,the photoreaction ability is insufficient,thereby leading to a low the photocatalytic efficiency,which limit its application.In order to solve the above problems,the construction of heterojunction structure is an effective method.The heterojunction structure photocatalyst contains two or more semiconductors,which can form the tight surface contact or crystal phase interfacial cross-linking inside the semiconductor.In that way,a built-in electric field was formed,the separation and transmission rate of the photogenerated carriers can be increased,and the stability of the system can be improved.At the same time,the absorption spectrum of the catalyst can also be broadened to some extent,and the catalytic performance of the material will be obviously improved.In this work,the traditional photocatalyst titanium dioxide（TiO₂）and the typical non-metallic semiconductor graphite carbon nitride（g-C₃N₄）which have been studied in recent years,were used as the main materials to construct the TiO₂/g-C₃N₄ heterojunction.The photocatalytic performance was improved through two mainly aspects.The main research contents are as follows:（1）Titanium dioxide with regular spherical structure was prepared by hydrothermal method,and then combined with g-C₃N₄ to construct a binary heterostructure.In that way,the band gap of the photocatalyst can be adjusted and the generation and transmission of photogenerated electrons and holes will be accelerated.At the same time,by means of photodeposition process,noble metal Ag nanoparticles were added on the surface of the composite photocatalyst.Because of the localized surface plasmon resonance（LSPR）effect,Ag nanoparticles could further optimizes the use of solar energy and increases transfer efficiency of photogenerated carriers.In addition,Ag particles act as an electron conduction bridge in the photocatalyst and promote transmission of photogenerated carriers at the interface of g-C₃N₄ and TiO₂heterojunction.As a result,a synergistic effect is produced between these ternary components to enhance the photocatalytic performance of the sample significantly.（2）The black TiO₂ was prepared by the formation of oxygen vacancies.Meanwhile,nitrogen and sulfur elements were introduced by element doping.Through these two methods,the band gap of TiO₂ was adjusted,and the photo absorption range of TiO₂ was extended to the visible range.The photo absorption capacity and photocatalytic activity of TiO₂ under visible light was significantly enhanced.At the same time,the modified black TiO₂ is combined with g-C₃N₄,and the photocatalytic performance of the material is further strengthened by the construction of the heterojunction structure between the two components,and the excellent photocatalytic performance under visible light can be maintained to a large extent.