(544go) Enhancement of Photocatalytic Activity of Carbon Nitride By Hydrogen Peroxide Under Visible Light: A Closer Inspection on Reaction Intermediates

A major global problem in the 21st century is water pollution caused by different types of organic substances. Photocatalysis is a promising technology with applications towards several environmental issues, particularly in water purification. The most commonly used photocatalyst is titanium dioxide, but it requires ultraviolet (UV) light irradiation to be excited. Graphitic carbon nitride is a newly discovered photocatalyst with a lower bandgap energy and it can be excited by visible light irradiation thereby eliminating the need of an additional UV light source. In the current work, carbon nitride was synthesized from dicyandiamide by thermal polymerization and characterized with XPS, FTIR, SEM, EDX and TGA. As the rate of photodegradation by pure carbon nitride is low, we have incorporated only a small amount of hydrogen peroxide in the system that resulted in about two fold increase in the rate of photodegradation of the organic pollutants compared to pure carbon nitride under visible light irradiation. A dye (methylene blue) and a herbicide (paraquat) were used as the model organic pollutants to investigate such photodegradation. The dual role of hydrogen peroxide along with the presence of carbon nitride can be associated with the generation of additional highly reactive hydroxyl radicals in presence of photocatalyst and prevention of recombination of holes and electrons of carbon nitride thereby improving its photocatalytic activity. The efficiency of the dual system was also analyzed with the variation of dose of photocatalyst, initial pollutant concentration and pH of the solution. Liquid Chromatography-Mass Spectroscopy (LCMS) analysis of the reaction mixtures was used to determine the intermediate products and reaction pathways by which the photodegradation took place. The overall results suggest that the dual system of carbon nitride and hydrogen peroxide can be used as a potential photocatalyst to decompose organic pollutants under visible light.