Preparation Of PTCDA And Fluorinated Aminobenzonitrile Modificated Carbon Nitride Materials And Their Photocatalytic Hydrogen Evolution From Water

With the development of the technology and the improvement of the life quality of human beings, the demand quantity of natural resources has become larger and larger, thus the prombles of energy crisis and environmental pollution have become serious day by day. Photocatalysis has great applied potential in solar energy conversion and environmental pollution control. In recent years, due to its special electronic band structure and good chemical stability, graphitic carbon nitride(g-C3N4), a stable, metal free and low-cost visible light catalyst, has been widely used in multiple photocatalysis field such as photocatalyzed hydrogen evolution from water. However, the photocatalytic activity of bulk g-C3N4 is limited by its low light absorption ability and poor electrical conductivity. To extend the light absorption of g-C3N4, several methods have been developed such as the surface modification and the nonmetal doping have been developed. To improve the electrical conductivity of g-C3N4, the method of chemical copolymerization is discovered to be efficient in recent years.In this paper, two kinds of bulk g-C3N4 was firstly prepared by thermal polymerization under Ar/air atmosphere, which were denoted as g-C3N4 and og-C3N4 respectively. Then they were modified by some methods to enhance its photocatalytic performance without destroying the basic chemical structures. Ordered mesoporous carbon nitride pg-C3N4 and carbon nitride nanosheet sg-C3N4 were prepared by method of nano-casting and thermal etching exfoliation respectively. The photocatalytic activity of g-C3N4, pg-C3N4, sg-C3N4 for hydrogen evolution from water containing 10 vol% TEOA as sacrifice agent under visible light(≥400 nm) by 4.0 wt% Pt loding were 13.1 μmol·h-1, 30.1 μmol·h-1 and 40.2 μmol·h-1 repectively, showing that morphology optimization can enhance the photocatalytic activity of the material.Hybrid materials x%-PT-pg-CN(x=0.5, 1, 3, 5) and x%-PT-sg-CN(x=0.2, 0.5, 1, 3, 5) with different contents of PTCDA(3, 4, 9, 10-Perylenetetracarboxylic acid anhydride) were prepared via amidation reaction, here x is the weight ratio of PTCDA to pg-C3N4 or sg-C3N4. The results showed that the photocatalytic activity of the hybird materials for hydrogen evolution from water.was declined with the increase of PTCDA content. Although the modification of g-C3N4 by PTCDA could extend the light absorption of carbon nitride, and improved the separation efficiency of the electron and hole, the addition of PTCDA might reduce the LUMO of hybird materials, thus its reduction ability was reduced. Therefore, the photocatalytic activity of the hybird materials for hydrogen evolution from water was declined with the increase of PTCDA content.Different posotion fluorinated aminobenzonitrile modificated carbon nitride materials were prepared by copolymerization, denoted as og-C3N4, ATFBN-CN0.05, ABN-CN0.05, AFN-6-CN0.05 and AFN-5-CN0.05 respectively. The band gap of the above materials calculated from Classical Tauc Approach formula are: 2.69 e V, 2.69 e V, 2.63 e V, 2.57 e V and 2.61 e V respectively. The photocatalytic activity of the above materials for hydrogen evolution from water containing 10 vol% TEOA as sacrifice agent under visible light(≥400 nm) were(Sorted in order of size): AFN-5-CN0.05(54.2 μmol·h-1) >AFN-6-CN0.05(37.3 μmol·h-1) >ABN-CN0.05(33.4 μmol·h-1)>ATFBN-CN0.05(30.1 μmol·h-1)>og-C3N4(13.0 μmol·h-1). The photocalytic activity of AFN-5-CN0.05 is the highest one, and it is about 4.17 times higher than that of og-C3N4. This enhanced photocatalytic activity can be explained as that the location of F atom in the 5th position of AFBN-5 promotes the copolymerization reaction and lead to F doping at the same time, and as a result, the photocatalytic activity of the materials for hydrogen evolution from water was improved.