Increasing levels of greenhouse gases and dwindling fossil resources emphasize the need for sustainable chemical synthesis. Since CO2 is a readily available feedstock throughout the world, CO2 valorization, i.e., the conversion of CO2 into valuable chemicals, is a highly attractive concept. Due to its very nature as the energy depleted carbon "sink", CO2 has a very low reactivity. Electrocatalysis offers the most attractive means to activate CO2 through reduction: the electron is the "cleanest" reducing agent whose energy can be tuned to the thermodynamic optimum. In practice, a catalyst is required and the overpotentials need to be minimized. Computational investigations of the reaction mechanism of such electrocatalytic reactions are the first step towards rational (in silico) catalyst design. Despite recent progress in modelling electrocatalytic reactions, determining the actual mechanism and selectivities between competing reaction pathways is still not straight forward. In this contribution we will present prototypical results for the coupling of CO2 to alkenes[1] and its competition with carbonate formation. Investigating the carbonate formation, we reveal that the popular zeroth order approach of Norskov [3] has severe shortcomings, when coupled to an implicit solvent model. However, the explicit inclusion of the electrochemical potential into the electronic structure computations through the Filhol and Neurock[2] approach, allows to access more detailed insights, shedding light on coverage effects and the influence of counterions. Finally, we show that despite the electrochemical activation, the elementary step of the first coupling of CO2 to an alkene leads to a high energy intermediate, which explains the considerable overpotentials and slow kinetics observed experimentally[1]. [1] C.-H. Li, G.-Q. Yuan, X.-C. Ji, X.-J. Wang, J.-S. Ye, H.-F. Jiang Electrochim. Acta 2011, 56, 1529. [2] M. Mamatkulov, J. S. Filhol, Phys. Chem. Chem. Phys. 2011, 13, 7675. [3] J. K. Norskov, J. Rossmeisl, A. Logadottir, L. Lindqvist, J. R. Kitchin, T. Bligaard, H. Jonsson, J. Phys. Chem. B 2004, 108, 17886.

Modelling heterogeneous electrocatalytic CO2 valorization

249th National Meeting (2015)

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