Elemental Doping Of G-C₃N₄ With Enhanced Photocatalytic Activity

As the environmental pollution becomes more and more serious,photocatalytic technology has become a hot topic in chemical and material sciences as a new way to treat water pollution.As a special kind of organic semiconductor conjugated polymer,graphite phase carbon nitride has attracted people’s attention due to its advantages of visible light response,excellent thermal and chemical stability,non-toxicity,and low cost.However,g-C₃N₄ inherent small specific surface area,low quantum yield,high carrier recombination efficiency and narrow visible light response range（less than 460 nm for light absorption edges）limit its development in the field of photocatalysis and industrial applications.Therefore,the modification of g-C₃N₄ makes it a reliable and stable photocatalyst with excellent photocatalytic performance is of far-reaching significance.In this paper,we mpodified the graphite phase carbon nitride（in this article,we use C₃N₄to refers the graphite phase carbon nitride）,by Cl,O element doping and C₆₀compositing,which improve the photocatalytic properties of the material significantly.Cl-C₃N₄ visible light catalyst was successfully prepared by a simple water bath（oil bath）method.Photocatalytic degradation of methyl orange（MO）experiments show that the introduction of Cl element significantly improves the photocatalytic performance of the material.After 90 minutes of deuterium lamp illumination,the degradation efficiency of the 30 mg/L MO solution is as high as 85.4%,compared to the C₃N₄’s degradation rate of 5.34%,performance increased by 16 times.The photocatalytic stability test showed that the stability of Cl-C₃N₄ is poor,the degradation efficiency was reduced to half of the original by four times,which may be related to the instability of chemical bonding when Cl element was doped into C₃N₄.The O-C₃N₄/C₆₀photocatalyst can be obtained in one step by microwave reaction,this method is simple and convenient.XRD,XPS and FTIR analysis confirmed that C₆₀was generated in situ during microwave treatment,the doped O atoms replaced some of the N atoms in the material and there is a tightly bonded bond formed between C₆₀and O-C₃N₄.The specific surface area and pore size analysis showed that during the microwave reaction,a large number of mesopores were formed,and the specific surface area significantly increased from 53.366m²g^-1to 104.46m²g^-1.DRS analysis shows that O-C₃N₄/C₆₀composites have higher absorption intensity in the visible range than the C₃N₄,and the light response range is wider.Among them,O-C₃N₄/C₆₀with the reaction mixture ratio of 45 mg/4 ml,reaction temperature of 170℃.and reaction time of 10 min has the strongest light response capability.And the experimental results show that O-C₃N₄/C₆₀prepared under this condition has the best photocatalytic performance.The photodegradation rate of 10 mg/L methylene blue solution reaches 89.67%under the condition of 90 min irradiation,which is 2.4 times of the C₃N₄ degradation and 2 times of P25.At the same time,the sample also has good cycle stability.After once degradation,the photocatalytic degradation capability of the catalyst has been stabled,and the efficiency of photodegradation of methylene blue solution by light for 90 minutes is 70%,which is about 2 times of the first time photodegradation rate of C₃N₄ and P25.The photocatalytic degradation mechanism analysis shows,compared with C₃N₄ and O-C₃N₄,the photocatalytic performance of O-C₃N₄/C₆₀increased by 52.72%and 17.38%,respectively,demonstrating that the doping of O element and the introduction of C₆₀have obvious promoting effects on improve the photocatalysis performances of the material.Compared with the mechanically-mixed C₆₀and O-C₃N₄,the photocatalytic performance is improved by 16.42%.It is proved that the close connection between C₆₀and O-C₃N₄plays an important role in improving the photocatalytic performance.Therefore,the doping of O element,in-situ generation of C₆₀and the composite of C₆₀are three key factor of the improvement of photocatalytic performance of O-C₃N₄/C₆₀materials.