Enhancing CO2 Reduction by Controlling the Ensemble of Active Sites

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Artificial carbon recycling, using waste CO2 as a starting material, is a promising solution for energy and environmental sustainability. The investigators aim to develop catalysts which more efficiently incorporate CO2 into precursors for commercial products or into liquid fuels such as ethanol, thus re-using CO2 generated as waste from burning fossil fuels. The main challenge to efficiently catalyzing these reactions is balancing the binding of the reactants with the release of the products. The investigators predict that using a core of a weakly binding first metal, with dispersed atoms of a strongly binding second metal over its surface, will result in an optimum balance of binding properties and increase the efficiency of the catalyzed reaction. The investigators will vary amount of the strongly binding metal on the catalyst's surface, then characterize its structure and test its effectiveness. The catalyst compositions and design rules resulting from this investigation are expected to encourage incorporating waste CO2 into fuels and commercial products. The investigators' educational goals are to provide hands-on laboratory training to graduate and undergraduate students and to promote learning for K-12 students with a strong focus on underrepresented groups by partnering with the Women in Science and Engineering and Family Academic Program organizations. The investigators aim to develop fundamental understanding of the CO2 reduction electrocatalysis on practical high-surface-area catalysts by synthesizing mixed-metal nanoparticle catalysts containing a weakly binding M1 core (M1 = Au, Ag, Cu) with varying amounts of strongly binding M2 atoms (M2 = Ni, Pd, Pt) dispersed over the surface. They will test the hypothesis that catalysts with discrete, atomically dispersed ensembles of M2 on the surface of M1, will exhibit the advantages of both M1 and M2 and will show to enhanced energy efficiency and reaction rate for CO2 reduction as compared to monometallic catalysts. The activity of these catalysts will be evaluated using batch electrolysis and gas-diffusion electrode cells. The surface structure and absorption properties will be probed using state-of-the-art electron microscopy and X-ray spectroscopic characterizations, surface-specific electrochemical analysis and product-resolved electrocatalytic studies. These experimental efforts will be focused using results from density functional theory and cluster expansion calculations. The methods and concepts established during this study are expected to be generally applicable to other catalytic materials and reactions, shedding new light on the development of heterogeneous catalysts using the knowledge acquired in the investigation of these bimetallic M2@M1 nanoparticles.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.