(127h) Insight into Electrolyte and Ion Effects in Carbon Dioxide Reduction Electrocatalysis

Developing a systematic understanding of electrolyte effects in electrocatalysis is a critical step toward engineering the electrolyte, and the corresponding electrochemical interface, for optimal electrocatalytic performance. Experimentally, it has been demonstrated that many properties of the electrolyte significantly affect the selectivity and activity of electrocatalytic processes [1]. Accurate theoretical study of metal-electrolyte interfaces and electrolyte effects has historically been challenging, as it requires simultaneously including detailed electronic structure and chemisorption effects from the metal and the many intermolecular interactions and long-range electrostatic interactions from the electrolyte, all of which must be sampled over a thermodynamic ensemble of configurations.

In this work, we use density functional theory (DFT) and an explicit solvent model of the metal-water interface coupled with a global optimization algorithm to study the structure of the electrolyte at the interface and its interactions with reactive intermediates [2]. We focus on a set of intermediates relevant to CO₂ and CO reduction. We first study the uncharged metal-water interface to investigate solvent-adsorbate interactions. Alkali metal cations are added to the model to directly investigate ion-adsorbate interactions. We discover systematic trends in adsorbate-electrolyte interactions among adsorbates, and relate these to the adsorbate dipole moment and hydrogen bonding affinity. We discover that the large alkali ion effects on intermediate binding energies can be largely explained by an electrostatic field dipole interaction model. Our analysis clarifies the effects of ion and solvent structures on critical quantities such as intermediate binding energies and work functions, which have important applications in kinetic models of this system and heterogeneous electrocatalytic systems in general.

[1] J. Resasco et al. J. Am. Chem. Soc. 139, 32, 11277-11287 (2017)

[2] T. Ludwig et al. J. Phys. Chem. C 123, 5999-6009 (2019)