The electrochemical reduction of CO₂ has the potential to store energy from intermittent renewable sources and to produce carbon-neutral fuels and chemicals[1]. In recent years, theoretical studies of CO₂ reduction have usually applied the computational hydrogen electrode model, which allows for the determination of the energies of reaction intermediates without explicitly treating the potential and the ions in solution[2]. This thermochemical approach has been shown to correlate well with experimental onset potentials [3, 4] and applied to computational screening of new catalysts [5, 6]. However, an understanding of charge transfer barriers, kinetics, selectivity, and pH effects all require explicit consideration of solvent and charge. In this talk, I will discuss new developments in the explicit treatment of the electrochemical interface, which is based on a simple capacitor model that uses the interfacial charge to obtain barriers at constant potential [7, 8]. I will then discuss the application of such a scheme to CO₂reduction: the determination of reaction pathways on transition metals field and solvation effects[9, 10], the resultant kinetics, and the implications for catalyst design.

1. Whipple, D.T. and P.J.A. Kenis, Prospects of CO2 Utilization via Direct Heterogeneous Electrochemical Reduction. The Journal of Physical Chemistry Letters, 2010. 1(24): p. 3451-3458.

2. Nørskov, J.K., et al., Origin of the Overpotential for Oxygen Reduction at a Fuel-Cell Cathode. J. Phys. Chem. B, 2004. 108(46): p. 17886--17892.

3. Shi, C., et al., Chan, K., Yoo, J., Nørskov, J.K. Trends in electrochemical CO2 reduction activity for open and close-packed metal surfaces. Physical Chemistry Chemical Physics, 2014. 16(10): p. 4720-4727.

4. Kuhl, K.P., et al., Electrocatalytic Conversion of Carbon Dioxide to Methane and Methanol on Transition Metal Surfaces.Journal of the American Chemical Society, 2014.

5. Chan, K., et al., Molybdenum Sulfides and Selenides as Possible Electrocatalysts for CO2 Reduction. ChemCatChem, 2014. 6(7): p. 1899-1905.

6. Asadi, M., et al., Robust carbon dioxide reduction on molybdenum disulphide edges. Nature communications, 2014. 5.

7. Chan, K. and J.K. Nørskov, Electrochemical Barriers Made Simple.J. Phys. Chem. Lett., 2015: p. 2663--2668.

8. Chan, K. and J.K. Nørskov, Potential Dependence of Electrochemical Barriers from ab Initio Calculations.The Journal of Physical Chemistry Letters, 2016: p. 1686-1690.

9. Montoya, J.H., et al., Theoretical Insights into a CO Dimerization Mechanism in CO2 Electroreduction. The journal of physical chemistry letters, 2015. 6(11): p. 2032--2037.

10. Chen, L.D., Urushihara, M., Chan, K., Nørskov, J.K. Electric Field Effects in Electrochemical CO2 Reduction.ACS Catalysis, 2016.

11. Liu, X., Xiao, J., Peng, H., Hong, X., Chan, K., Nørskov, J.K. Understanding trends in CO2 reduction on transition metals. Nature Communications, 2017.