Theoretical Investigation of CO2 Activation and Chemical Conversion on Catalytic NanoparticlesAustin, Natalie (2018) Theoretical Investigation of CO2 Activation and Chemical Conversion on Catalytic Nanoparticles. Doctoral Dissertation, University of Pittsburgh. (Unpublished)
AbstractGrowing fossil fuel consumption to meet energy demands has led to elevated levels of CO2 (a greenhouse gas) in the atmosphere, which could have a significant impact on the environment. Novel methods for CO2 utilization by catalytic conversion to useful chemicals and fuels are of marked interest for the mitigation of the greenhouse gas footprint. We used electronic structure calculations to assess the conversion of CO2 by metal nanocatalysts. Our work was focused on Cu based, M-doped (M= Ni and Zr) heterogenous nanoparticles and their adsorption and activation of CO2. The strong adsorption and activation of CO2 we observed was attributed to nanoparticle charge transfer to CO2. Due to the oxophilic nature of Zr, the interaction of CO2 with oxidized Cu-Zr was also assessed. We determined that oxidized Zr sites on Cu-Zr can still adsorb and activate CO2 which indicated that Cu-Zr nanoparticles are promising materials for CO2 conversion to industrially relevant products. As an alternative to traditional heterogeneous catalysts, we used computational methods to investigate ligand-protected Au nanoclusters as electrocatalysts for the conversion of CO2 to CO. We found that CO2 electroreduction over fully ligand-protected nanoclusters was not feasible because of unfavorable energies required to stabilize CO2 reduction intermediates. However, we determined that it is thermodynamically feasible to remove ligands from the nanoclusters at experimentally applied potentials. The generated surface sites on the partially ligand-removed nanoclusters were shown to be active for CO2 reduction as they significantly stabilized reduction intermediates. The generated sites were also active for H2 evolution, which agrees with experimental observations that these two processes compete. Interestingly, we found that a specific mode of ligand removal results in a catalyst that was both active and selective for CO2 reduction. In this work, we used computational tools to provide insights into the effects of nanoparticle morphology and composition on the electronic properties of the nanoparticle. Using these insights, we developed active and selective catalysts for CO2 conversion. Our investigations into nanoparticle properties and metal-adsorbate interactions, rationalized experimental observations and could serve as design guidelines for developing catalysts for valuable fuels and chemicals production from CO2. Share
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