Study On Preparation And Photocatalytic Activities Of Graphitic Carbon Nitride Based Composites

The conversion of solar energy to chemical energy or degradation of organic pollutants by semiconductor photocatalysis is an effective method to solve the problems of energy shortage and environmental pollution.The light quantum efficiency of traditional semiconductor photocatalysts?such as TiO₂,ZnO?are low.Semiconductor photocatalytic technology is difficult to meet the practical application because of the poor stability and insufficient utilization of solar energy.^[1,2]Therefore,The development of novel and efficient semiconductor photocatalysts has become a hot spot in the field of photocatalysis.Graphitic carbon nitride?g-C3N4?is a novel polymer semiconductor photocatalyst,which has the advantage of visible light response,two-dimensional layered structure,strong reductivity and low cost.In addition,its chemical composition and energy band structure can be controlled flexibly.^[3,4]in order to further study the application of carbon nitride composite photocatalytic materials,the structure nanocrystalline has been studied in this paper.Photocatalytic properties of nonmetallic atom doped g-C₃N₄ and g-C₃N₄ matrix composites.1.Bulk CN-pure and nanosheets CNS were prepared by conventional high-temperature thermal polymerization method and NH₄Cl gas template method,respectively.The hydrogen production rates of CN-pure and CNS samples irradiated under visible light??>420 nm?were 0.85 and 2.8 mmol/g/h,respectively.A series of CNS-ZIS composite photocatalysts with different ratios were prepared by hydrothermal method.Compared with CNS,binary composite photocatalysts broaden the range of visible light absorption and improve the photocatalytic performance of CNS-ZIS in different degrees compared with CNS and ZIS?9.4 mmol/g/h?.Among them,CNS-ZIS-0.3 has the best hydrogen production performance?14.9 mmol/g/h?.2.CNO-x photocatalysts with different oxygen doping amounts were prepared by hydrothermal method using dicyanodiamine diamine?DCNA?and dicyanodium chloride?CC?as raw materials.Oxygen doped CNO-x can flexibly adjust the range of light absorption.The band gap was reduced from 2.7 eV to 2.1 eV.It was found by a series of characterization that the borderline N atom of g-C3N4 molecular structure was replaced by O atom,and the C-O-C bond was formed with the adjacent C atom.The photocatalytic activity of CNO-x materials with different O doping amounts is better than that of bulk CN-pure sample,the results show that the photocatalytic activity of different O doped CNO-x materials is better than that of bulk CN-pure sample,and the photocatalytic activity of different O doped CNO-x materials is better than that of bulk CN-pure sample.When the molar ratio of dicyanodiamine to cyanuric chloride is 1:2,the oxygen doped CNO-2 has the best performance of 3.2 mmol/g/h,and has good catalytic stability.3.Using CNO-x sample and tetrabutyl titanate as raw materials,CNO-x-TiO₂composite catalyst was successfully prepared by hydrothermal method,and the effect of different composite ratio on hydrogen production performance of binary composite catalyst was investigated.With the increase of TiO₂ component,the hydrogen production of binary composite catalyst was studied.The light absorption edge of the composite was characterized by blue shift.It was found that the TiO₂ in the binary component was composed of anatase and rutile mixed crystal phase.CNO-1-TiO₂-40has the best photocatalytic performance?4.8 mmol/g/h?and CNO-1-TiO₂-50 has the best photocatalytic activity?31.7 mmol/g/h?under visible light irradiation.