Metal oxide nanomaterials for photocatalysis and catalysis

Abstract

Metal oxide nanomaterials are of significant research interest in areas of physics, chemistry and material science. They can exhibit metallic, semiconductor or insulator characters. A number of metal oxides are stable, biologically and chemically inert, easy to synthesize, inexpensive and environmentally benign. Metal oxides have high potential for various environmental applications including photocatalysis and catalysis. A wide range of metal oxides nanostructures can be mass produced using different simple, inexpensive and green synthesis methods which lead to different morphologies with different properties. Post-synthesis treatment can be employed to significantly modify their properties to achieve suitable materials for the utilization various applications. We have focused on the methodology of nanostructures synthesis and modification in order to have good properties for applications. Photocatalysis has been attracting much research interest for its wide applications in renewable energy and environmental remediation. Among the photocatalysts, titanium dioxide (TiO2) nanomaterial is considered as the most suitable metal oxide for practical applications. We have focused on the synthesis of visible-light active TiO2 for photocatalytic dye degradation and ambient light antibacterial application. Carbon nanotubes doping and high temperature (850oC) annealing in presence of copper were used to prepare visible-light active TiO2 for these applications. Research efforts were made to acquire understanding of the materials properties and their influence on the photocatalysis and robust antibacterial activity. Since catalytic reactions do not require photoexcitation, possible range of metal oxide materials is wider, and the topics of interest including lowering the reaction temperature as well as developing simple and inexpensive catalysts synthesis. In this thesis, different metal oxides were synthesized by a hydrothermal method and their application to CO oxidation was studied. CO oxidation is a model reaction for catalysis, in addition to being of significant practical interest for pollutants remediation for example in vehicle exhaust. Synthesized In2O3 nanocubes exhibited promising catalytic activity over CO oxidation. It also exhibited potential of being the noble metal catalysts support. Synthesized CuxO exhibited promising catalytic activity over CO oxidation and stable performance. It is found that the improved catalytic performance can likely be attributed to the presence of a small amount of Cu2O in hydrothermally synthesized samples and the presence of surface oxygen states.