Dorchies Florian, Serva Alessandra, Sidos Astrid, Michot Laurent, Deschamps Michaël, Salanne Mathieu, Grimaud Alexis
Chimie du Solide et de l'Energie, UMR 8260, Collège de France, 75231 Paris Cedex 05, France.
Réseau sur le Stockage Electrochimique de l'Energie (RS2E), CNRS FR3459, 80039 Amiens Cedex, France.
J Am Chem Soc. 2024 Jun 26;146(25):17495-17507. doi: 10.1021/jacs.4c05538. Epub 2024 Jun 11.
Optimizing electrosynthetic reactions requires fine tuning of a vast chemical space, including charge transfer at electrocatalyst/electrode surfaces, engineering of mass transport limitations, and complex interactions of reactants and products with their environment. Hybrid electrolytes, in which supporting salt ions and substrates are dissolved in a binary mixture of organic solvent and water, represent a new piece of this complex puzzle as they offer a unique opportunity to harness water as the oxygen or proton source in electrosynthesis. In this work, we demonstrate that modulating water-organic solvent interactions drastically impacts the solvation properties of hybrid electrolytes. Combining various spectroscopies with synchrotron small-angle X-ray scattering (SAXS) and force field-based molecular dynamics (MD) simulations, we show that the size and composition of aqueous domains forming in hybrid electrolytes can be controlled. We demonstrate that water is more reactive for the hydrogen evolution reaction (HER) in aqueous domains than when strongly interacting with solvent molecules, which originates from a change in reaction kinetics rather than a thermodynamic effect. We exemplify novel opportunities arising from this new knowledge for optimizing electrosynthetic reactions in hybrid electrolytes. For reactions proceeding first via the activation of water, fine tuning of aqueous domains impacts the kinetics and potentially the selectivity of the reaction. Instead, for organic substrates reacting prior to water, aqueous domains have no impact on the reaction kinetics, while selectivity may be affected. We believe that such a fine comprehension of solvation properties of hybrid electrolytes can be transposed to numerous electrosynthetic reactions.
优化电合成反应需要对广阔的化学空间进行微调，包括电催化剂/电极表面的电荷转移、传质限制的工程设计以及反应物和产物与其环境的复杂相互作用。混合电解质是将支持盐离子和底物溶解在有机溶剂和水的二元混合物中，它为这一复杂难题增添了新的内容，因为它们提供了一个独特的机会，可在电合成中利用水作为氧或质子源。在这项工作中，我们证明调节水 - 有机溶剂相互作用会极大地影响混合电解质的溶剂化性质。结合各种光谱学方法与同步加速器小角X射线散射（SAXS）以及基于力场的分子动力学（MD）模拟，我们表明可以控制混合电解质中形成的水相区域的大小和组成。我们证明，在水相区域中，水对于析氢反应（HER）的反应活性比与溶剂分子强烈相互作用时更高，这源于反应动力学的变化而非热力学效应。我们举例说明了基于这一新知识为优化混合电解质中的电合成反应带来的新机遇。对于首先通过水的活化进行的反应，微调水相区域会影响反应动力学，并可能影响反应的选择性。相反，对于在水之前发生反应的有机底物，水相区域对反应动力学没有影响，但选择性可能会受到影响。我们相信，对混合电解质溶剂化性质的这种深入理解可以应用于众多电合成反应。
