Interfacial Water Structure as a Descriptor for Its Electro-Reduction on Ni(OH)₂-Modified Cu(111)

Area of Science:

• Electrocatalysis
• Surface Chemistry
• Physical Chemistry

Background:

• The hydrogen evolution reaction (HER) is vital for electrocatalysis and electrochemistry.
• Understanding pH-dependent structure-activity relationships in alkaline media remains challenging.
• Nickel hydroxide (Ni(OH)2) enhances HER on platinum, but its effect on copper is unexplored.

Purpose of the Study:

• To investigate the impact of low Ni(OH)2 coverages on the HER activity of Cu(111) surfaces.
• To elucidate the structure-activity relationships and underlying mechanisms in alkaline media.
• To explore the role of interfacial water and surface morphology.

Main Methods:

• Electrochemical scanning tunneling microscopy (EC-STM) for in situ structural analysis.
• Laser-induced temperature jump (LJ-T) experiments to study interfacial water dynamics.
• Controlled deposition of Ni(OH)2 on Cu(111) at low coverages (0.1 and 0.2 ML).

Main Results:

• Cu(111) modified with Ni(OH)2 showed a non-linear HER activity trend with increasing coverage.
• A correlation was found between surface roughness, water network ordering, and HER activity.
• 0.2 ML Ni(OH)2 led to a disordered water ad-layer, facilitating charge transfer and enhancing the HER rate.

Conclusions:

• Interfacial water reorganization is a key factor in enhancing HER on modified copper surfaces.
• Surface roughness and water network disorder act as crucial descriptors for HER activity in alkaline media.
• These findings offer new insights into designing efficient electrocatalysts for HER.