| The rapid development of modern society is accompanied by the problems of environmental pollution and energy shortage.The treatment of organic pollutants in water environment and the research of clean energy have attracted much attention from researchers for solving above problems.Among many solutions,photocatalytic technology shows broad application prospects and important research significance in environmental governance and clean energy production.And its core lies in the design and synthesis of photocatalysts with excellent performance.In this paper,graphitic carbon nitride（g-C3N4）is used as research material,The prepared composite material has excellent visible light activity.The brief contents of this paper are as follows:（1）The anatase-rutile mixed crystal TiO2/g-C3N4with hierarchical structure are successfully prepared by impregnation-calcination method using g-C3N4and Ti Cl4as raw materials.The g-C3N4in the composites effectively prevent the agglomeration of the in-situ grown TiO2,and its content could be adjusted by changing the calcination temperature.The reaction kinetic constant of the composite prepared under suitable condition for degrading tetracycline hydrochloride is 4.3 time than that of pure g-C3N4at optical light condition,and the highest hydrogen production activity is 1031μmol/g/h,which are 6.2 and 12.7 times of g-C3N4and TiO2,respectively.Combined with the characterization of the phase composition,microstructure and optoelectronic properties of the photocatalyst,the excellent photocatalytic performance of low temperature mixed crystal TiO2/g-C3N4should be attributed to the hierarchical porous structure of the material and the tight heterostructure constructed between mixed crystal TiO2and g-C3N4.The above factors can provide abundant active sites for photocatalytic reaction,facilitating the transfer of reactants and products,and significantly improving the separation efficiency of photogenerated carriers.（2）The TiO2/g-C3N4composites with adjustable mixed crystal ratio and microstructure are synthesized by one-pot impregnation-calcination method using melamine and Ti Cl4as raw materials.The dosage of melamine has a significant effect on the morphology of the material and the crystal ratio of TiO2,the decomposition of g-C3N4in the synthesis process deepens the color of composite and enhances the visible light absorption capacity,thereby affecting the catalytic performance of the composite for TCH degradation.About 92%TCH can be degraded by the prepared composite within 1 h under optical light condition,and the reaction kinetic constant is 4.4 times than that of pure g-C3N4.The excellent performance of the composites put down to its porous structure,high specific surface area,and higher photogenerated carrier separation efficiency of the heterojunction formed by mixed crystal TiO2with g-C3N4.（3）The NiO/Ag/g-C3N4composites are successfully prepared by localization-induced effect of Ag nanoparticles anchored on g-C3N4nanosheets,which using urea,Ag NO3and Ni（CH3COO）2·4H2O as raw materials by step-by-step photochemical deposition-calcination method.Ag nanoparticles not only acted as the positioning agent for Ni O loading,but also as a bridge for eˉmigration between g-C3N4and Ni O during the photocatalytic reaction.The best average H2evolution rate of Ni O/Ag/g-C3N4composite under optical light condition is 586μmol/g/h,which are 3.5and 2.5 times than those of Ag/g-C3N4and Ni O/g-C3N4under the same experimental conditions,respectively.The enhanced hydrogen production activity of the composites is attributed to the synergistic effect of Ni O and Ag nanoparticles.In other words,Ag nanoparticles effectively capture photogenerated eˉand act as a channel to migrate eˉto Ni O,which acts as an active center for the hydrogen evolution reaction.There are 47figures,7tables and 154 references in this paper. |
