Graphene based catalysts for environmental and energy applications

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When a semiconductor photocatalyst which is suspended in an aqueous medium is irradiated by light, the generated charged species (electron and holes) travel to the surface to produce very active oxidizing radicals that are capable of oxidizing organic material present in the solution. The generated e-- h+ pairs can also cause the splitting of the water molecule to elemental hydrogen and oxygen. Thus photocatalysis can be applied for cleaning up recalcitrant pollutants and provide clean energy source if solar energy is used as the light source; the development of photocatalysts with high activity is one of most active research fields because of the tremendous potential of photocatalysis in waste treatment and in providing clean energy. In the past several years, an important part of our research effort was on the use, synthesis and testing of TiO2 based catalysts for the treatment of recalcitrant organic compounds that resist conventional biological and chemical treatment. In particular, we have used the commercially-available TiO2 Degussa catalyst and UV radiation for the treatment of various organic compounds found in various waste water streams from diverse industries such electronics processing and pharmaceutical industry. We have also synthesized doped TiO2 catalyst with high photocatalytic activity so that visible light can be used for the process. The present proposed research is concerned with the use of graphene/TiO2 nanocomposite catalysts synthesized in our laboratory and which can be used in a wide range of applications. Graphene is a very thin sheet of two dimensional carbon atoms arranged in a honeycomb structure that has some outstanding properties such as extremely large surface area, high transparency and excellent electron conductivity. These properties make it very attractive for its use as a support for catalysts for electronic and energy conversion devices such as fuel cells as well as for photocatalysis. In addition to the synthesis of the catalyst and its effect on its properties the research program will focus on the use of the catalyst for the destruction of several compounds found in the waste waters from the microelectronics processing and pharmaceutical industries. Three types of graphene will be used: pristine graphene (G), graphene oxide (GO) and nitrogen functionalized graphene produced by plasma synthesis (NG) in the Plasma Processing Laboratory at McGill. The experimental work will focus on the activity of the catalyst and the identification of the reaction mechanism and intermediate products. Thus in addition to the development of environmentally friendly processes and devices for two important industrial areas in Canada (microelectronics and pharmaceuticals), the proposed research is expected to increase our understanding of the properties of the catalytic materials, kinetics and mechanisms of the photocatalytic reactions thus contributing to our fundamental knowledge of catalysis. Finally it is expected that at least four Ph.D., three Masters and several undergraduate students will receive training in research during the program.