Modelling a detailed kinetic mechanism for electrocatalytic reduction of CO2

For the first time a fully-elementary reversible kinetic model for electrocatalytic CO2 reduction towards a multitude of different products has been established and verified with experimental data. The detailed reaction mechanism was generated by compiling hypothesized reaction paths and intermediates from many different sources. Thereby a focus was put on distinguishing different embodiments of similar elementary steps: For proton-coupled electron transfer three hydrogenation mechanisms were considered and for intermediates with unclear molecular structure separate paths were modelled. The micro-kinetic model was fed with tabulated energy parameters and results of DFT calculations to simulate CO2 reduction on a Cu(100) surface for constant applied potentials. The operating conditions were chosen according to published experimental results in order to compare Faradaic Efficiencies. With these, the model parameters were successfully calibrated across a wide potential range while keeping all values within a tight interval of theoretical bounds derived from ab initio calculations and other theoretical considerations. The calibrated model was found to be in good qualitative agreement with the measurement data and also captures trends of surface coverages reported for in-situ measurements. Most interestingly, it finds the widely accepted hypothesis of dimerization via *CO intermediates to be inaccurate. Instead, coupling reactions of *CHO and *CH2 intermediates are observed. The shifting of dimerization routes with varying applied potential especially towards ethylene is supported by other experimental studies. Furthermore, this work establishes a methodology of creating and calibrating complex electrochemical micro-kinetic models. (c) 2022 The Authors. Published by Elsevier Inc. on behalf of The Combustion Institute. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

Automated summary

A fully-elementary reversible kinetic model for electrocatalytic CO2 reduction has been established and verified, including hypothesized reaction paths and intermediates. The model successfully captures trends observed in experimental data and challenges the widely accepted hypothesis of dimerization via *CO intermediates.