Preparation And Photocatalytic Performance Of Carbon Nitride Based Composites

The excessive use of fossil energy has caused great damages to environment in the past decades,such as the emergence of ozone holes,greenhouse effect and so on.In addition,it is urgent to develop renewable and clean energies.Meanwhile,the excess of dyes,antibiotics in water have attracted people’s attention.Photocatalysis has the characteristics of mild reaction conditions,high efficiency and easy operation,which can be used in energy storage,degradation,medical treatment,and so forth.Carbon nitride is an organic semiconductor material,which is composed of C and N elements,and it is easy to obtain the material which makes carbon nitride.The suitable Eg of carbon nitride makes it be widely used in photocatalytic hydrogen production and photocatalytic degradation.Studies have found that carbon nitride materials have the problem of easy recombination of photogenerated electrons and holes,which makes carbon nitride be useful in photocatalysis.The application of carbon nitride is restricted.The ordered mesoporous carbon nitride synthesized in our laboratory has the advantages of high surface area,adjustable pore size and diverse chemical composition,which makes up for the shortcomings of bulk carbon nitride.And because of the morphological characteristics of ordered mesoporous carbon nitride,the migration path of photo-generated carriers is greatly reduced,which is more conducive to the occurrence of photocatalytic reactions.In this paper,the photocatalytic performance of graphite phase carbon nitride was improved by different methods including element doping and co-catalyst loading.The influence of different improvement methods on the photocatalysis propertieas ordered mesoporous carbon nitride was investigated.1.A series of S-doped ordered mesoporous carbon nitride were synthesized by solvent volatilization method using KIT-6-40 as hard template by changing the dopping amount of the precursor.The S-doped ordered mesoporous carbon nitride prepared by the hard template method has a larger surface area(274-300 m2·g-1)than ordered mesoporous carbon nitride with 60 m2·g-1,it has more advantages than bulk carbon nitride in surface area.In the experiment of photocatalytic degradation of Rhodamine B,as the amount of S doping gradually increased,the dark adsorption rate of S-doped ordered mesoporous carbon nitride increased from 4.5%to 22%.The degradation rate of S-doped ordered mesoporous carbon nitride was maintained at more than 90%when photodegraded for 1 h;the dark adsorption rate of S-doped ordered mesoporous carbon nitride increased from 1.6%to 22%,when compared with bulk carbon nitride.The degradation rate increased from about 25%to 97%.2.The ordered mesoporous carbon nitride was synthesized by using similar method,and the nickel sulfide was deposited onto the ordered mesoporous carbon nitride by in situ chemical deposition.The hydrogen production performance of ordered mesoporous carbon nitride was significantly improved by controlling the deposition amount of nickel sulfide.The results show that the optimized deposition amount of nickel sulfide is 3%.And the hydrogen production of the sample is 250 times that of the pure ordered mesoporous carbon nitride,reaching 700μmol·g-1·h-1.3.Select the method of electrostatic deposition and chemical reduction to synthesize Pt/g-C3N4(x wt%),and regulate the structure of the material and its performance on photocatalytic hydrogen production by changing the amount of Pt nanoparticle deposition.Loading Pt nanoparticle makes the photocurrent response of the material was significantly improved.In the electrochemical impedance test,the Rt value was reduced from 3872 Ω·cm2 to 105.7Ω·cm2,and effectively promote the transfer of photo-generated electrons,the change of struture improves the separation efficiency of photo-generated carriers in the photocatalytic reaction of the material.After a series of experiments,it can be found that when the Pt loading is 2.4%,the surface area of the material reaches 285 m2·g-1,and the rate of hydrogen evolution is 3011 μmol·g-1·h-1,it was 1075 times bigger than the material before loading.