Interfacial Electrochemistry of Carbon-Based Materials for Electrocatalysis

The so-called “electrification” of our energy systems is being widely explored as a way to help roll back global greenhouse gas emissions and remediate atmospheric CO2 levels. For example, electrification can be paired with already existing renewable energy sources, e.g., wind, solar or hydroelectric, and used to electrochemically drive processes important to energy storage, conversion, and fuel or chemical production. Past the basic integration of electrochemistry, electrochemical catalysis can be employed to drastically improve the efficiency and selectivity of these electrochemical processes. My research focuses on the development of carbon-based electrocatalysts and fundamental investigations of their electrocatalytic mechanisms for reactions relevant to energy storage and conversion. Through a combination of theoretical analysis and experimental investigation, it elucidates the intricate interplay between molecular model systems and real-world electrocatalysts. Exploring the hydrogen evolution reaction (HER) activity of molecular Rh-based electrocatalysts and analogous Rh-coordinated graphene nanoribbon films (RhGNR-2DNS) revealed the diverging behaviors of homogeneous and heterogeneous systems. While molecular species lost HER activity in basic aqueous conditions, RhGNR-2DNS maintained its activity over the full aqueous pH window. The proximity of RhGNR-2DNS to the electrode surface and the local electric fields experienced as a result are implicated in the broader HER activity, thus demonstrating the usefulness of our immobilization approach. In another study, a new class of triarylmethyl-based carbocations was reported as discharge redox mediators (ORR electrocatalysts) for the Li-O2 battery. The redox mediators were identified to operate through an outer-sphere mechanism and their performance in full Li-O2 cells showed remarkable (up to 36-fold) enhancements to battery discharge capacities. It was further demonstrated how the redox mediation process can control Li-O2 cell potentials and suppress parasitic, surface-mediated ORR.