Synthesis and Characterization of Transition Metal Oxide Catalysts for Environmental and Energy Storage Applications

Nowadays, environmental concerns and the global energy crisis have become two of our greatest challenges. The main purpose of this dissertation research is to design highly active mesoporous materials that can efficiently catalyze environmental and energy related reactions. Surface properties can be easily tuned by thermal treatment and cation doping, resulting in improved catalytic activities. Synthesis and characterization of the materials, catalytic activities for carbon monoxide oxidation, oxygen reduction and oxygen evolution reactions, and mechanistic studies are covered in this thesis. The first part describes the synthesis of mesoporous cobalt oxides through an inverse micelle route for low temperature carbon monoxide oxidation applications. The prepared material showed much better activity and stability compared with commercial cobalt oxide due to its nanoparticle nature and porous structure. The catalytic performance under both dry and moisture rich conditions were tested. Detailed characterization of the materials suggested that high surface areas and the presence of surface oxygen vacancies were critical for enhanced activities. In real systems, structured catalysts such as monolithic substrates coated with a layer of active material are used instead of powder form catalysts. To evaluate the potential of our catalysts to be used in practical catalytic devices, mesoporous metal oxides (MnOx, Co3O4, CeO2) were coated on cordierite substrate by dip coating and in-situ growth and were used as low temperature diesel oxidation catalysts. The resulting materials showed promising catalytic performance. The effect of particle size, loading amount and Cu doping on the catalytic performance are discussed in detail. In the last part, mesoporous cobalt oxides were used as bifunctional catalysts for oxygen reduction and oxygen evolution reactions. If a catalyst can catalyze both reactions, it will have great potential in the application of rechargeable metal air batteries. Ni and Mn doping were introduced into the cobalt oxide material to increase the conductivity and active site population. The Ni incorporated cobalt oxide exhibited the best activity, which can be considered as a potential substituent for precious metal catalysts (Pt, Ir, Ru). Furthermore, the intrinsic structure-property relationships of the materials were established