Generalizable Trends in Electrochemical Protonation Barriers

Abstract

Predicting activation energies for reaction steps is essential for modeling catalytic processes, but accurate barrier simulations often require considerable computational expense, especially for electrochemical reactions. Given the challenges of barrier computations and the growing promise of electrochemical routes for various processes, generalizable energetic trends in electrochemistry can significantly aid in analyzing reaction networks and building microkinetic models. Herein, we employ density functional theory and machine learning nudged elastic band models to simulate electrochemical protonation of *C, *N, and *O monatomic adsorbates from hydronium on a series of transition metal surfaces. We observe a consistent trend of decreasing protonation reaction energies yet increasing activation barriers from *O to *N to *C. Analysis of bond orders and reaction pathways provides insight into the origin of the observed trends in protonation energetics. We hypothesize that these results are relevant for polyatomic adsorbates, which can simplify analysis of reaction mechanisms and inform catalyst design.

Electrocatalysis Beyond 2020: How to Tune the Preexponential Frequency Factor

“…It remains unclear for decades how exactly to tune the symmetry factor and what material and/or interfacial property controls value of the symmetry factor. Nevertheless, present widely held assumption that the symmetry factor always has a value of 0.5 has no real foundation, which nowadays can be supported by computational models [33–35] . Therefore, the intrinsic link between exchange current and Tafel's slope is unknown.…”

“…Nevertheless, present widely held assumption that the symmetry factor always has a value of 0.5 has no real foundation, which nowadays can be supported by computational models. [33][34][35] Therefore, the intrinsic link between exchange current and Tafel's slope is unknown. Therefore, if one intends to establish any relevant structure-activity relations, all parameters that are comprised in the exchange current (Eq.…”

Multicapacitor Approach to Interfacial Proton-Coupled Electron Transfer Thermodynamics at Constant Potential

“…For the systems studied herein, q ads is always an integer value based on these analyses, reflecting the similarities between different GCC organic acid surface sites and their respective molecular analogues . However, noninteger values of q ads may be present in other systems, ,,− and our approach does not require that q ads be an integer. Note that this assumption of constant q ads is not valid when there is significant hybridization between the electrode surface and the adsorbate near the Fermi level, wherein q ads will depend on the applied potential.…”

Force-based method to determine the potential dependence in electrochemical barriers

“…Given its ability to determine potential dependence of electrochemical reactions at modest computational expense, we envision its use in developing micro-kinetic models to understand electrochemical mechanisms. 33,40…”

“…This behaviour is likely a failure of charge partitioning as a consequence of increasing hybridisation between the reacting species. 33 Furthermore, rotation of water along a reaction path leads to abrupt changes in the workfunction. Grand-canonical methods require an accurate capacitance in order to avoid cell-size dependence of reaction energetics.…”