Bridging Microscopic Interfacial Water and Macroscopic Wettability for Enhanced Hydrogen Evolution Reaction.

Area of Science:

• Electrochemistry
• Materials Science
• Surface Chemistry

Background:

• The hydrogen evolution reaction (HER) is crucial for clean energy technologies but faces challenges in electrocatalyst design.
• Optimizing HER requires managing both macroscopic surface wettability for bubble release and microscopic interfacial water structure for proton transfer.
• Highly hydrophilic surfaces, while aiding bubble release, can impede proton transfer due to strongly hydrogen-bonded water networks.

Purpose of the Study:

• To investigate the synergistic effects of macroscopic wettability and microscopic interfacial water structure on platinum electrode HER performance.
• To explore the use of polymeric modifiers to tune surface electronic structure and interfacial properties.
• To identify optimal surface conditions for enhanced proton transfer and bubble dynamics.

Main Methods:

• Modification of platinum electrodes with polymeric modifiers, specifically polyethylenimine (PEI).
• Characterization of surface wettability using contact angle measurements.
• Evaluation of HER performance by measuring overpotential at a specific current density (10 mA cm⁻²).
• In situ Raman spectroscopy to analyze interfacial water structure and hydrogen bonding.

Main Results:

• Peak HER performance was achieved on PEI-modified Pt electrodes with moderate hydrophilicity (contact angle ~15°).
• The PEI-modified surface exhibited a disordered, weakly hydrogen-bonded interfacial water network.
• This dual optimization reduced the overpotential by 229 mV at 10 mA cm⁻² compared to pristine Pt.
• In situ Raman spectroscopy confirmed an increase in weakly hydrogen-bonded water species on the PEI-modified surface.

Conclusions:

• A balance between moderate hydrophilicity and a disordered interfacial water network is key for high HER performance.
• Polymeric modification offers a viable strategy to tune both wettability and interfacial water structure.
• This research provides insights into designing advanced electrocatalytic interfaces by bridging interfacial water dynamics and electrode wettability.