The role of electron affinity in electrochemical anion adsorption on metals.

This article investigates the factors controlling anion adsorption energies on a Pt(111) metal surface, focusing on structurally diverse anions including thiolates, carboxylates, alkoxides, and small sulfur- and oxygen-containing species. Using density functional theory (DFT), the study finds that the electron affinity of the corresponding neutral radicals is a general and dominant descriptor of anion adsorption strength, surpassing variations in radical adsorption energies across different anion classes. While prior correlations between radical adsorption energy and X–H bond dissociation energy (where X is the binding atom) hold for oxygen- and carbon-bound radicals, this relationship does not extend to sulfur-bound radicals. A combined empirical model incorporating both electron affinity and X–H bond dissociation energy improves prediction accuracy of anion adsorption energies. These findings enhance the understanding of electrostatic and covalent contributions to adsorption, with implications for surface chemistry, heterogeneous catalysis, and electrochemistry.