Modeling electrocatalysts in operating conditions: Surface restructuring and catalytic activity

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Electrochemistry is slated to play a large role in clean energy, chemical manufacturing, and environmental processes in coming years, as renewable electricity becomes increasingly available from sources such as wind and solar energy. The project focuses on two electrochemical reactions, the hydrogen evolution reaction (HER) to produce hydrogen from water, and the carbon dioxide reduction reaction (CO2RR) to convert CO2 to higher-value products. Both reactions are facilitated by catalysts. Copper-based catalysts are amongst the most active identified to date, but as with many electrocatalysts, their chemical structure changes under reaction conditions. The project focuses on understanding the reconstruction process with the goal of designing more active, selective, and stable catalysts. Specifically, the project develops and employs computational techniques to predict structural changes in response to key electrochemical process variables. Beyond the technical aspects, the project incorporates a training program for high-school teachers that brings the topics of sustainability and energy to their classrooms, while introducing students to the rapidly emerging area of molecular modeling. The project will determine, by unique first-principles, multi-scale stochastic theoretical simulations, how the surface of copper-based electrocatalysts used for the hydrogen evolution and CO2 electroreduction reactions restructures in realistic conditions of potential, solvent, and electrolyte. The influence of the potential-induced reconstruction on the electrocatalytic mechanism, activity, and selectivity of these reactions will be studied, in link with experiments. There is evidence from in-situ characterization that the surface structure of electrocatalysts is strongly modified in operational conditions. However, it is not yet possible to determine the atomic structure of the active surface, and thus, the implications of these reconstructions on the mechanisms are unknown. The proposed multiscale first-principle simulations appear to be the most adequate approach to elucidate the interface structure. Principally, new reaction mechanisms may emerge. The selectivity of CO2 electroreduction versus hydrogen evolution (the latter being a major hurdle in applications) will be studied. Several theoretical methods unique to the laboratories of the PIs, including the incorporation of electrochemical potential, solvent effects, global optimization algorithms, and STM image simulations, will be advanced, adapted, and merged to make this research possible. Close connection to the experiment is proposed, both for structural aspects, with operando scanning tunneling microscopy (STM), and to validate the predicted kinetics and selectivity. This project will educate young researchers in techniques of modern surface chemistry and catalysis, including realistic modeling, method development, quantum mechanics, and statistical mechanics. In addition, students will learn how to connect modeling efforts to experimental data and capabilities. The training will promote a highly-skilled workforce to address global challenges in the manufacture of sustainable fuels and chemicals.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.