Skip to main content
Seminar | Materials Science

Mechanistic Insights into the Interfacial Electrochemistry of Carbon-Based Electrocatalysts

MSD Seminar

Abstract: The electrification of our energy systems is widely explored as a way to roll back global greenhouse gas emissions and remediate atmospheric CO2 levels. For example, electrification can be paired with the existing renewable energy sources, e.g., wind, solar or hydroelectric, to drive processes important to energy storage, conversion, and fuel or chemical production. Electrocatalysis plays an important role in electrochemical transformations, as it can drastically improve the conversion efficiency and product selectivity.

Here, I will present two studies involving molecular electrocatalysts and their operative electrocatalytic mechanisms for reactions relevant to energy storage and conversion. The first study explores the effects of immobilization of a molecular hydrogen evolution reaction (HER) electrocatalyst on the proton reduction mechanism. The immobilization strategy involved the preparation of monolayer two-dimensional nanosheets composed of graphene nanoribbons (GNR). The edges of GNR contain N-centers for efficient coordination of molecular Rh-based HER catalysts to form a molecule-electrode hybrid material, RhGNR-2DNS. The RhGNR-2DNS was found to be active for HER over a broader range of aqueous pH conditions as compared to the molecular analogs. The improved catalysis was attributed to two factors. First, responsive” bipyrimidine-based ligands dramatically altered the reactivity of reduced Rh active sites. Second, catalyst immobilization prevented the aggregation which resulted in deactivation of the molecular analogs.

The second study explores molecular redox shuttles, a new class of triarylmethyl-based carbocations, 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. Critically, it also identified an important redox potential-related design criteria which will be instructive to future redox mediator work. Collectively, my work contributes to a deeper understanding to the field of electrochemical catalysis research and highlights the intricate interplay between homo- and heterogeneous catalyst-mediated pathways