Cation- and Potential-Dependent Modulation of Hydrophobic Hydration at Electrocatalytic Interfaces
Xiaoling Yang, Guangsheng Liu, Xiao Ma, Xiangyun Xiao, Abdulrahman Allangawi, Huabin Zhang, Wan‐Lu Li
Abstract
Electrochemical reactions at solid–liquid interfaces are shaped not only by reactant–electrode interactions but also by solvent behavior within the electric double layer. Using ab initio molecular dynamics and Lum–Chandler–Weeks theory, we show how applied potential and electrolyte cations (Li +, K +, Cs + ) coregulate hydrophobic hydration at Cu(100)–water interfaces. At the potential of zero charge, a structured water bilayer suppresses cavity formation, while negative potentials induce cation-specific hydration and desolvation that reshape interfacial hydrogen bonding and water density. These effects alter cavitation free energies by 0.1–0.5 eV, directly impacting adsorption thermodynamics and favoring outer-sphere coupling pathways─such as hydrofuroin formation in furfural electroreduction. By mapping cavitation energetics, we establish how water structure and ion identity govern reaction pathways. This work introduces hydrophobic hydration as a tunable parameter in electrocatalysis, offering new opportunities to control activity and selectivity via electric double-layer engineering.