Field-Driven Reactivity and Adsorbate Reorientation on Electrode Surfaces

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Electric fields affect interfacial structure and reactivity during electrochemical reactions. First-principles modeling can be used to elucidate the electrostatic potential profiles at the electrode–electrolyte interface, where these potentials can be highly inhomogeneous due to the presence of electrolyte ions and molecular adsorbates. In this presentation, periodic density functional theory (DFT) calculations are used to understand field-driven proton-coupled electron transfer reactivity and adsorbate reorientation at heterogeneous electrochemical interfaces. These calculations show that field-driven protonation of graphite-conjugated organic acids is enabled by continuous electronic conjugation between solid carbon electrodes and molecular surface sites. The redox potentials for proton-coupled electron transfer in these systems are predicted computationally, showing close agreement with experimental voltammetry measurements. Constant-potential DFT calculations are also used to understand the adsorption structure of L-cysteine on Au(111) electrode surfaces. Using a classical electrolyte model, these calculations elucidate the interactions between the cysteine adsorbate, the electrode surface, and the electrolyte ions at different applied potentials. These studies shed light on the effects of interfacial electric fields on electrochemical reactivity and adsorption geometries at solid–liquid electrochemical interfaces.