Ion solvation kinetics in bipolar membranes and at electrolyte–metal interfaces

• Published in: Nature energy 2024-05, Vol.9 (5), p.548-558
• Main Authors: Rodellar, Carlos G., Gisbert-Gonzalez, José M., Sarabia, Francisco, Roldan Cuenya, Beatriz, Oener, Sebastian Z.
• Format: Article
• Language: English
• Subjects: 639/4077/909/4086; 639/638/161/886; 639/638/77/885; Activation energy; Bias; Capacitance; Catalysis; Catalysts; Economics and Management; Electric fields; Electrocatalysts; Electrolytes; Energy; Energy conversion; Energy Policy; Energy Storage; Energy Systems; Enthalpy; Entropy; Entropy of activation; Hydrogen evolution reactions; Interfaces; Kinetics; Membranes; Renewable and Green Energy; Solvation; Water demand; Water splitting
• ISSN: 2058-7546; 2058-7546
• DOI: 10.1038/s41560-024-01484-z

Ion (de)solvation at solid–electrolyte interfaces is pivotal for energy and chemical conversion technology, such as (electro)catalysis, batteries and bipolar membranes. For example, during the electrocatalytic hydrogen evolution reaction in alkaline media, water needs to be dissociated and hydroxide ions solvated—a process that is not well understood. Here we study water dissociation and ion solvation kinetics in isolation at polymeric bipolar membrane and electrolyte–metal interfaces. We discover bias-dependent relationships between the activation entropy and enthalpy, which we link to a bias-dependent dispersion of interfacial capacitance. Furthermore, our results indicate that OH − solvation is kinetically slower than H + solvation and that the solvation kinetics display characteristics that are independent of the catalyst structure. We attribute this to a universal amount of excess charge needed to induce electric fields that alter the interfacial entropy of water. Of fundamental interest, these results are critical to enable knowledge-driven bipolar membrane and electrocatalyst design. Ion solvation at solid–electrolyte interfaces is crucial in various components of energy conversion technologies, including water splitting electrocatalysts and bipolar membranes, but is poorly understood. Here the authors study ion solvation kinetics in these systems, highlighting the key role of interfacial capacitance in determining behaviour.