Electrochemical reaction kinetics

To date the reaction kinetics at electrified interfaces has been described largely using simplified models of the interface structure and composition as well as of the interface energetics. In particular, the most prevalent approach is based on the description of the adsorbate energetics derived from charge-neutral, vacuum or vacuum-like (e.g. with water adlayers) calculations. In addition, very often, electrochemical reaction barriers are left aside and/or determined based on reaction mechanisms inspired by gas-phase catalysis. In addition the correct description of the effect of the electrode potential on the kinetics, e.g. via the variation of electrochemical reaction barriers, is still an (unsolved) challenge. 

Within our group we are trying to improve upon these methods, by developing strategies to include explicitly the effect of the potential and the water environment in reaction barriers in a consistent and computationally efficient way, namely using implicit/expicit hybrid models.

In close collaboration with previous group members (Prof. Dr. Craig Plaisance (Louisiana State University, https://www.lsu.edu/eng/che/people/faculty/plaisance.php)) we continue the development of a framework to model the electrocatalytic activity of transition metal oxide (TMO) surfaces for the Oxygen Evolution Reaction (OER). The OER is a particularly important electrochemical reaction in the field of electrochemical energy storage, since it plays a major role in the electrolysis of water or the electrochemical reduction of carbon dioxide. Finding more active and more abundant materials to catalyze the OER will allow to make these process energetically more efficient and economically more viable.

Prevalent activity models, which are based on thermodynamics only, do not consider the comparably large kinetic barriers of certain reaction steps, which dominate the catalytic activity of the OER. Hence, in order to offer a precise and more complete approach to model catalytic activity, we are developing a framework that incorporates kinetic barriers by adapting Brønstead-Evans-Polanyi (BEP) relationships. Combining the BEP relations with a simplified microkinetic model allows us to derive generalized expressions for the catalytic activity based on easily computable microscopic properties of the catalytically active sites. This model was successfully applied to the OER on various doped cobalt(II,III) oxides surfaces and we expect it to be transferable to other TMOs and similar electro-catalytic reactions.