CAREER: Promoting Selective Electrochemical CO2 Reduction by Controlling a Catalyst's Primary, Secondary, and Outer Coordination Spheres

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The conversion of carbon dioxide (CO2) into value-added products is of fundamental importance as a means of storing intermittent energy sources like solar and wind as chemical fuels. One of the challenges in CO2 conversion is that the most active catalysts for this reaction tend to simultaneously produce a number of different products such as carbon monoxide, methanol, methane, ethylene, and the side product hydrogen gas (H2). While the reduction of CO2 to any one of these chemicals is desired, the non-selective generation of multiple products is non-ideal due to problems in product separation and isolation. Using natural enzymes as inspiration, Dr. McCrory is creating synthetic systems in which catalysts are embedded within polymers that control the active site environment and reactant delivery to facilitate selective CO2 reduction to single products. The proposed research has significant broader societal impact in that it provides a framework for the development of new catalyst systems for CO2 recycling and energy storage. Concurrently, Dr. McCrory is focused on increasing energy literacy in Michigan using a 3-step education plan involving 1) graduate student training in scientific communication, 2) community outreach through interactive demonstrations at public events, and 3) the development and implementation of an exhibit at the University of Michigan Natural History Museum focused on renewable energy storage. Through this approach, Dr. McCrory is working to enable the broader community to better engage in energy policy and usage decisions. With funding from the Chemical Catalysis Program of the Chemistry Division, Dr. Charles C. L. McCrory of the University of Michigan, Ann Arbor is synthesizing new electrocatalytic materials for selective carbon dioxide reduction by controlling the primary, secondary, and outer coordination spheres surrounding the catalyst's active site. The central hypothesis for this proposal is that the reactivity and selectivity of molecular electrocatalysts for multi-electron transformations such as CO2 reduction can be modulated not only by modifying the ligand framework surrounding the metal center, but also by modifying the catalyst?s chemical environment to control H+ and substrate delivery to the metal active site. To test this hypothesis, Dr. McCrory is encapsulating planar transition metal complexes with macrocyclic ligands inside of coordinating polymers. The coordination environment, electronic structure and catalytic activity of the resulting polymer-catalyst systems are studied using a variety of spectroscopic and electroanalytical techniques. Through systematic modifications of the ligand, polymer, and reaction conditions, Dr. McCrory is independently controlling the primary, secondary, and outer coordination spheres surrounding the metal center and determining the effect of each coordination sphere on the overall catalytic activity and product selectivity. The knowledge gained from this study is crucial for the development of new catalyst-polymer composite systems for selective CO2 reduction and has significant broader societal impact in the design of new electrocatalytic systems for renewable energy storage and CO2 mitigation. In addition, Dr. McCrory is working to increase energy literacy in Michigan through the design of interactive demonstrations relevant to renewable energy storage for the general public and the development of an exhibit at the University of Michigan Natural History Museum highlighting progress and challenges in renewable energy storage. Together, the research and integrated education components of this proposal highlight a new approach to overcoming challenges in energy storage and carbon dioxide conversion and will impact the way these important issues are addressed, both at the scientific and societal level.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.