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(?)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.