Simulations of the electrochemical reduction of CO2 to hydrocarbons and alcohols show the importance of explicitly including water molecules and hydronium ions in the double layer. The intemediates in the reaction path for the reduction turn out to be different from the ones deduced from calculations without water being present and without taking the proton transfer from the bilayer into account. The activation energy of the various elementary steps, both Heyrovsky mechanism for proton transfer from the water phase and Tafel mechanism for adsorbed hydrogen reacting with the C-species, is estimated from minimum energy path calculations. A range of close packed metal surfaces (including Cu, Ag, Au, Ni, Fe, Rh, Ir and Pt) are compared and the rate of both CO2 reduction and hydrogen formation evaluated using harmonic transition state theory. The reason for the unique properties of Cu electrodes for hydrocarbon and alcohol formation, as well as the reason why methane is formed rather than methanol, can be deduced from the calculations. The calculated relative rates are in remarkably good agreement with experimental results from several research groups. A two parameter descriptor is established that can help identify improved catalysts for these important reactions.

Calculations of electrochemical reduction of CO2 to hydrocarbons and alcohols

256th National Meeting (2018)

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