CAREER: Manipulating energy conversion chemistry with metal overlayer structures

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Intellectual MeritThe development of improved electrocatalysts for renewable fuel production from carbon dioxide (CO2) and water has the potential to enable the long term, sustainable production of storable, transportable fuels. The source of CO2 could be fossil fuel power plant emissions or the atmosphere itself. Although the most cost-effective technological scheme to accomplish this goal remains to be determined, fundamental approaches to accelerate electrochemical reactions could create a path to large-scale processes for sustainable chemical fuels while mitigating CO2 emissions. The goal of the proposed research is to understand factors that govern electrochemical energy conversion processes on transition metal surfaces. Specifically, the proposed research seeks to understand the factors that direct reaction mechanisms, activity, and selectivity for: 1) the electro-reduction of CO2 to produce fuels such as hydrocarbons and alcohols, 2) the electrocatalytic production of H2 from water, and 3) the reverse reactions for the electro-oxidation of fuels such as H2 and alcohols to produce electricity.The fundamental knowledge gained in this work will also enable improvements in efficiency for fuel cells as well as for energy storage devices in which renewable electricity is used to synthesize chemical fuels.In order to understand the factors that govern electrocatalytic energy conversion processes for renewable fuels production, the electronic and geometric structure of metal catalysts will be tailored in order to manipulate surface-adsorbate bond strengths. By this approach, the conversion of key reaction intermediates can be manipulated, leading to significant changes in mechanistic pathways, activity, and selectivity for electrochemical conversion reactions. The reaction chemistry on metals will be tuned by synthesizing a particular metal as a single, pseudomorphic overlayer on a different metal substrate. The electronic structure and lattice constant of the substrate metal will impact key catalyst properties of the metal monolayer resting on top of it. Electrochemical measurements, combined with in-situ atomic-scale imaging (scanning probe microscopy) and in-situ vibrational spectroscopy (tip-enhanced Raman spectroscopy) will gain molecular-level insights regarding surface reaction intermediates, mechanistic pathways, and metal-adsorbate bond strengths. Real-time product analysis coupled an electrochemical cell will also be used to conduct kinetic studies involving isotopes. Broader ImpactsThe proposed education activities will be integrated with the proposed research. Ph.D. students will gain hands-on expertise in catalysis and electrochemical processes for renewable fuels production, which is an emerging area. A team of undergraduate researchers will also be involved in these activities. The educational plan is designed to work with ongoing programs at Stanford University to recruit graduate and undergraduate students from under-represented groups in engineering and host K-12 science teachers to conduct summer research. In addition, Latino high school students in the San Francisco Bay Area and Puerto Rico will be mentored and encouraged to engage in STEM activities. Finally, elements of the research will be incorporated into a graduate-level spectroscopy course and an undergraduate-level chemical process separations course.