Interfacial Hydrogen-Bond Chain Engineering via Surface-Immobilized Ammonium Cations for Accelerated Alkaline Hydrogen Evolution

Abstract

Engineering the electrode–electrolyte interface has emerged as a critical strategy to overcome sluggish kinetics of alkaline hydrogen evolution reaction (HER). However, the dynamic and complex nature of the double electric layer makes mechanistic understanding at the molecular level and rational interfacial regulation highly challenging. Herein, we demonstrate that molecular modification of Ni-doped MoS2 catalyst with a zwitterionic molecule (z-Ni-MoS2) markedly enhances alkaline HER kinetics. In-situ Raman spectroscopy combined with ab initio molecular dynamics (AIMD) simulations reveals that the quaternary ammonium cation reconstructs interfacial water into linear hydrogen-bond chains via electrostatic repulsion of potassium ions from the z-Ni-MoS2 surface. This distinctive interfacial microenvironment enables water molecules within hydrogen-bond chains to directly relay protons to sulfur sites via a Grotthuss-associated mechanism. In contrast to the conventional diffusion-dominated, non-Grotthuss-associated mechanism, this mechanism lowers the water-dissociation barrier and promotes interfacial proton transport, thereby accelerating alkaline HER kinetics. To evaluate device-level applicability, z-Ni-MoS2 was incorporated into an anion exchange membrane water electrolyzer (AEM-WE). The system delivers outstanding performance of 5.21 A cm–2 at 1.8 V and 9.57 A cm–2 at 2 V, 80 °C, surpassing the United States Department of Energy (DOE) 2026 target (3 A cm–2 at 1.8 V). This work provides molecular-level insight for interfacial water restructuring as a design principle for high-performance alkaline HER catalysts.