Cation-Driven Modulation of Interfacial Solvation Structures for Enhanced Alkaline Hydrogen Oxidation Kinetics

Area of Science:

• Electrochemistry
• Materials Science
• Physical Chemistry

Background:

• Alkaline hydrogen oxidation reaction (HOR) kinetics are crucial for energy technologies.
• The role of interfacial water and hydrogen-bonding in electric double layers (EDLs) is known.
• The dynamic impact of alkali metal cations (AM+) on EDL structure and HOR kinetics is poorly understood.

Purpose of the Study:

• To investigate the influence of alkali metal cations (AM+) on interfacial solvation structure.
• To elucidate the impact of AM+ dynamics on alkaline HOR kinetics.
• To reveal the mechanism by which Ni3S2/Ni catalyst modifies EDL structure and enhances HOR.

Main Methods:

• *Ab initio* molecular dynamics simulations.
• *In situ* surface-enhanced infrared absorption spectroscopy.
• Electrochemical experiments.

Main Results:

• Ni3S2/Ni catalyst lowers the potential of zero charge (PZC), leading to less crowded cation arrangements and disordered water.
• This facilitates accelerated H+/OH- shuttling via an interconnected hydrogen-bonding network.
• Unconventional cation dependence (KOH > NaOH > LiOH) observed, with K+ coordination to Ni3S2 accelerating proton transfer.

Conclusions:

• AM+ arrangement in EDL significantly controls interfacial water structure and hydrogen-bonding networks.
• Electrode PZC is a key factor in regulating AM+ arrangement and solvation environment.
• This work provides a molecular-level understanding of enhanced alkaline HOR kinetics on Ni3S2/Ni, highlighting the role of cation-water interactions.