| Summary: | Doctor of Philosophy Department of Chemical Engineering Bin Liu Our heavy dependence on fossil fuels allows a large amount of CO₂ to be directly emitted into the atmosphere. There is strong evidence that the rise of atmospheric CO₂ level causes a cascade of severe environmental issues such as ocean acidification, sea level rises, long drought, and intense heat waves. This thesis explores relevant catalysis technologies that will transform CO₂ into a building block species for chemicals production. Catalytic CO₂ utilization faces major limitations because of the chemical stability of this molecule. Multiple technologies such as dry reforming of methane (DRM) and CO₂ hydrogenation have demonstrated their technological and economical potentials to overcome CO₂ conversion’s limitations. Yet, the catalysis science and technology for CO₂ utilization is far from mature. Effective and affordable catalysts suitable for industrial-scale applications are not readily available. Fundamentally, the catalytic reactivities of simple mono-functional catalysts are limited by the so-called Sabatier principle. Moreover, the best performing catalysts often rely on expensive noble metals. Catalyst discovery and design have shifted focus toward composite, bifunctional materials manufactured from earth-abundant elements. Breakthroughs have already been made in ammonia synthesis, CO oxidation, water-gas-shift reaction, and hydrogen production reactions. DRM converts CO₂ and CH₄ (both are potent greenhouse gases) into syngas, a versatile industrial mixture. Currently, DRM catalysts are challenged by inadequate reactivity and short lifetime. In this thesis, systematic investigations were carried out to understand the mechanistic origin of DRM on the dual-site models representative of real-life bifunctional catalysts. An unconventional material, Co₃Mo₃N (a ternary nitride), was the focus in this study. Earlier experimental studies indicated that Co₃Mo₃N is active and durable, but the source of its reactivity and stability remain ...
|
|---|