Hannes Jonsson1
University of Iceland1
Theoretical calculations of electrocatalytic reactions such as the hydrogen evolution reaction (HER), oxygen reduction reaction (ORR) and CO2 reduction reaction (CO2RR) in order to determine the mechanism and estimate the rate of the various elementary steps can be carried out various levels of theory. At the simplest level, only the free energy of intermediates is estimated from calculations in the absence of applied voltage and dielectric solution and corrections later made to account for the electrochemical environment, the so-called thermochemical model. More detailed and reliable calculations involve estimates of the activation energy barrier as well as chemical interaction with solvent molecules, and going beyond the usual generalised gradient approximation for the functional. Such calculations can give significantly different results as has been shown for HER [1], ORR [2] and CO2RR [3,4]. Still, the effect of the dielectric solution and the role of dissolved ions remains elusive [5] and calls for methodology that can be used for larger systems and longer time scale, such as hybrid simulations where the central part of the system is described using electronic structure theory while the rest is described with a potential energy function that includes polarisation [6]. Several results of ORR and CO2RR calculations will be presented and the various levels of theory compared in order to identify what is required to obtain reliable results of electrocatalysis by electronic structure calculations and rate theory.<br/><br/>[1] 'Is Doped MoS2 Basal Plane an Efficient Hydrogen Evolution Catayst? Calculations of Voltage-Dependent Activation Energy', H. Sander, H. Jónsson and J. Akola, Physical Chemistry Chemical Physics 25, 15162 (2023).<br/><br/>[2] 'Assessment of the Accuracy of Density Functionals for Calculating Oxygen Reduction Reaction on Nitrogen Doped Graphene' B. Kirchhoff, A. Ivanov, E. Skúlason, D. Fantauzzi, T. Jacob and H. Jónsson, J. Chem. Theory Comput. 17, 6405 (2021).<br/><br/>[3] 'Calculations of Product Selectivity in Electrochemical CO2 Reduction', J. Husssain, H. Jónsson and E. Skúlason, ACS Catalysis 8, 5240 (2018).<br/><br/>[4] 'Competing HCOOH and CO Pathways in CO2 Electroreduction at Copper Electrodes: Calculations of Voltage Dependent Activation Energy', M. Van den Bossche, C. Rose-Petruck, and H. Jónsson, J. Phys. Chem. C 125, 13802 (2021).<br/><br/>[5] 'On the Challenge of Obtaining an Accurate Solvation Energy Estimate in Simulations of Electrocatalysis', B. Kirchhoff, E. Ö. Jónsson, T. Jacob and H. Jónsson, Topics in Catalysis, https://doi.org/10.1007/s11244-023-01829-0 (2023).<br/><br/>[6] 'Transferable Potential Function for Flexible H2O Molecules Based on the Single Center Multipole Expansion', E. Ö. Jónsson, S. Rasti, M. Galynska, J. Meyer and H. Jónsson, J. Chem. Theory Comput. 18, 7528 (2022).