Photocatalytic Performance Of Modified Carbon Nitride

Recent years,carbon nitride(g-C3N4),as a visible light photocatalyst,has been attracted much attention.g-C3N4 is a flexible polymer semiconductor with a band gap of 2.4-2.8eV,which can be prepared by many precusors,such as:cyanamide,dicyandiamide,melamine,hiourea and urea.As a photocatalyst,g-C3N4 has many advantages,such as:facile,flexibility,thermal stability,chemical stability,biostability and nontoxicity.g-C3N4 exhibits application prospects in treatment of industrial waste water and water pollution.But g-C3N4 still has disadvantages which limit it’s application,such as:low quantum effetiency,low utilization of sun light,reconbination of photoelectron-hole pairs.g-C3N4 was modified including doping and conbining to enhance photocatalytic activity.In this work,a very facile one-step pyrolytic,low-cost environmental friendly method is presented for preparing the Zn-doped g-C3N4 with different Zn content by directly heating urea and zinc acetate to 550℃.During the heating process,urea and zinc acetate dissolve mutually and generate a lot of gas which promote the dispersion.Thus the Zn-doped g-C3N4 was prepared by only one step.The results show that Zn(Ⅱ)was connected with g-C3N4 by Zn-N bonds.The dope of Zn changes the structure and morphology of g-C3N4.With the Zn content increase,the tri-s-triazine structure and graphitic structure of g-C3N4 tend to aggregate and irregular.The band gap is decrease and the absorbtion range of light is increase because of the dope of Zn,and the recobination of photoelectron-hole pairs are suppressed at the same time.The results of the experiments of photodegrading methyl orange and rhodamine B with Zn doped g-C3N4 show that,the Zn doped g-C3N4 prepared by the addition of 0.1%wt of zinc acetate has the best photocatalytic performance,which is two times higher than g-C3N4.With the increase of Zn content,the photocatalytic performance tend to decrease.Zn doped g-C3N4 has considerable photocatalytic stability.Then,FePO4·2H2O was prepared by fast precipitation method,and g-C3N4/FePO4 composites with different content of FePO4 was prepared by heating urea and amorphous FePO4 to 550℃.Results show that,during the preparing process,part of Fe ion in FePO4 suspension liquid is doped into g-C3N4.The conbination of g-C3N4 and FePO4 can decrease the band gap and increase the absorbtion of visible light,also supresses the photoelectron-hole pairs.The results of the experiments of photodegrading rhodamine B with g-C3N4/FePO4 show that,the g-C3N4/FePO4 composite prepared by the addition of 1.5 mL FePO4 suspension liquid(0.1 mol/L)into 10g urea has the best photocatalytic performance,which is two times higher than g-C3N4.