ABSTRACT

Public Abstract:

Title: CAREER: Novel redox-active electrolyte additives to enhance efficiency and direct product selectivity in electroreduction reactions
Proposal 1653430: McCloskey, Bryan

This project will generate fundamental knowledge in the field of electrochemical engineering that is critical to a number of energy conversion and storage technologies. The project will advance knowledge in electrochemical reduction reactions for two targeted applications. The first is a Lithium-O2 battery (commonly called a lithium-air) for transportation applications. This battery chemistry promises high energy and power density that would be required for propulsion in an automobile. The second application is for CO2 electrochemical reduction, a method to sequester or reuse CO2 and convert it into a higher valued fuel or chemical. Both of these applications share the need for more fundamental knowledge on how the underlying electrochemical reduction reactions work within the device, whether a battery or CO2 conversion device. This project looks at how the electrolyte phase in the device interacts with the electrode where the key reduction chemistry occurs on the surface of the electrode. The project looks at electrolyte components that could act as charge carriers to facilitate the key electrochemical reactions that take place at the interface of the electrode surface and the electrolyte medium. This fundamental research may provide a route to energy sustainability and reduced vehicle emissions. The educational plan will leverage research and outreach activities to benefit the electrochemical engineering research community and graduate and undergraduate and pre-college students in the East Bay Area of San Francisco, California. The PI is expanding undergraduate student research experiences with a symposium and mentoring program. To fill a gap in available electrochemical engineering educational resources, a series of online video modules will be constructed to teach fundamental concepts to scientists and students interested in electrochemistry. Outreach activities will also continue to teach simple electrochemical concepts to underrepresented elementary students in East Bay communities.

The overall objective of this proposed research is to improve efficiency and selectivity of important electrochemical reduction reactions, specifically O2 and CO2 reduction, by incorporation of appropriately selected redox-active molecules (redox mediators) into the electrolyte. Redox mediators are molecules that undergo a reversible charge transfer reaction where the forward reaction describes the reduction reaction and the reverse reaction describes the oxidation reaction. The PI has shown in preliminary work that the nonaqueous oxygen reduction reaction mechanism can be beneficially manipulated through the inclusion of redox-active molecules into the electrolyte. Improved selectivity and energy efficiency has been indicated using this approach although the underlying mechanisms are unclear and could be related to interactions between O2, reduced oxygen intermediates, electrons, the redox mediator, and ions in solution. The project will also look at CO2 electrochemical reduction reactions, particularly to form multi-carbon products for fuels or chemicals. The use of redox mediators could open an entirely new avenue of research on the CO2 reduction reaction. The project will look at both electron/ion transfer to O2/CO2 and employ selected redox molecules that will impact the mechanism of the O2 and CO2 reduction reactions thereby providing a route to improved product selectivity and efficiency. The project's tasks will leverage unique quantitative experimental capabilities, including quantification of product distributions using, differential electrochemical mass spectrometry, online electrochemical gas chromatography, and nuclear magnetic resonance spectroscopy. The PI will identify useful classes of redox-active molecules that can alter the mechanism of charge transfer to O2 and CO2, thereby providing a route to improving desirable product formation selectivity and energy efficiency in each system.

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