Chapter 5 - Polymeric graphitic-carbon nitride and its composites for the photocatalytic removal of phenolic compounds

Abstract

The detoxicification of waste water containing phenolic compounds using semiconductor photocatalyst has been researched over the years. The emergence of metal free polymeric g-C3N4 (GCN) as photocatalytic material in this prospect is mainly attributed to its narrow gap and suitable band edge positions combined with their low level of toxicity. However, GCN also suffers from the drawbacks such as limited visible light response, low degree of charge carrier separation, and inability to generate hydroxyl radicals that are vital for the degradation of phenolic compounds in the aqueous medium. In this chapter, modifications of GCN to overcome these deficits and to achieve maximum efficiency for the phenol degradation is discussed. The influence of solution pH, oxidizing agents, and applied potential clearly suggests that the optimization of reaction parameters for each modified GCN is essential to achieve high performance. The preparation methods, charge carrier mechanisms, and degradation pathways are discussed at the relevant stages. Further, reduction of 4-nitrophenol (4-NP) to respective 4-aminophenol (4-AP) 4-nitroaniline are presented and reduction mechanisms proposed using GCN based composites are emphasized. The gap analysis is amended to provide room for further research development towards the fabrication of efficient GCN material. It is concluded that GCN serve as photocatalyst for the degradation reactions and as an excellent support for various semiconductors to trigger selective transformation of simple organic molecules.