CAREER: Electrochemically Mediated Carbon Dioxide Separation via Non-Aqueous Proton-Coupled Electron Transfer

The efficient capture of carbon dioxide (CO2) from stationary emitters and ambient air is vital in meeting climate targets. However, the conventional thermochemical methods for CO2 capture are energy-intensive, cost-prohibitive, and fossil fuel-dependent. On the other hand, emerging carbon capture approaches driven by electrochemical reactions promise mild operating conditions, flexibility for coupling to intermittent renewable energy resources, and could accommodate the multi-scale nature of carbon capture needs due to their modularity. Nevertheless, the practical deployment of existing electrochemical carbon capture processes remains hindered by issues such as oxygen sensitivity and evaporative loss. Correspondingly, this project explores a new concept for carbon capture modulated by electrochemical stimuli. The concept involves the generation of low-volatility, air-stable CO2 sorbents at an electrode surface, followed by CO2 capture in an absorber unit and the subsequent CO2 release upon switching the polarity of the electrode. The goal is to understand and ultimately harness control over the thermodynamics, reaction kinetics, and transport properties of the model electrochemical system, utilizing a multi-modal toolkit of materials synthesis, characterization, and electroanalysis. The broader impacts involve education and mentoring activities from high school through graduate levels to prepare a young generation of engineers with an interdisciplinary skillset essential to solving humanity’s sustainability challenges, which include developing high school laboratory modules on carbon capture and integrating advances in separation methods and interfacial sciences into the university’s chemical engineering curriculum. The project aims to research an electrochemical interface composed of redox-tunable Brønsted base moieties that can undergo proton-coupled electron transfer (PCET) in non-aqueous electrolytes for the reversible (re)generation of air-stable CO2 sorbents. At the molecular level, the relationship between molecular structure, Brønsted basicity, and PCET energetics will be delineated to inform the rational design of carbon capture chemistry. At the material level, microporous electrodes will be synthesized to examine the interplay between electrode microstructure and the corresponding mass and charge transport behaviors. The impact of the electrolyte environment on the PCET and CO2 chemisorption kinetics will also be systematically investigated via (electro)analytical techniques. Finally, the CO2 separation concept will be evaluated in a bench-scale prototype, and a combined experimental and modeling effort will shed light on possible degradation mechanisms and bottlenecks to promote rationally motivated improvement strategies. 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.