Hydrophobicity Modulated Interfacial Water Distribution for Enhanced Kinetics of HER

The interfacial water structure is crucial for the hydrogen evolution reaction (HER) performance. However, the explicit relationship between the local interfacial water structure and the HER process remains elusive. Here, we engineer a hydrophilic-hydrophobic Ni-PTFE interface to modulate the interfacial water organization and enhance HER kinetics. Electrochemical measurements reveal that the Ni-PTFE composite significantly reduces the HER overpotential from 36 to 19 mV at 10 mA·cm^-2, comparable to the performance of the precious metal catalyst Pt. In situ ATR-SEIRAS indicates that the proportion of H₂O_(above-gap) at the hydrophilic-hydrophobic Ni-PTFE interface increased from 36.6% to 50.5%, facilitating proton transfer and water dissociation. Density functional theory calculations further demonstrated that the hydrophobic PTFE rearranges interfacial water on the Ni surface into a wave-like distribution centered around the PTFE segments, leading to alternating water-rich and water-deficient regions that spatially differentiate active sites for water dissociation and H₂ detachment, respectively. The study offers an insight into enhancing HER performance through strategic hydrophobic modification aimed at regulating interfacial water structure.