Structure of the (Bi)carbonate Adlayer on Cu(100) Electrodes

Area of Science:

• Surface Science
• Electrochemistry
• Computational Chemistry

Background:

• Understanding surface interactions is crucial for catalysis and materials science.
• The behavior of adsorbed species on metal surfaces influences electrochemical processes.
• Copper surfaces are relevant in various electrochemical applications.

Purpose of the Study:

• To investigate the adsorption of bicarbonate on a Copper(100) surface.
• To characterize the ordered adlayer phases formed under electrochemical conditions.
• To elucidate the role of water in stabilizing the adsorbed layer.

Main Methods:

• In situ scanning tunneling microscopy (STM) was employed to visualize adlayer structures.
• Electrochemical measurements were performed in a 0.1 M KHCO3 electrolyte.
• Density functional theory (DFT) calculations were used to model the adlayer composition and stability.

Main Results:

• Coexistence of distinct ordered adlayer phases with ( x6 )R45° and (4x4) unit cells was observed.
• The adlayer exhibited dynamic behavior and a reversible order-disorder phase transition at 0 V vs. RHE.
• DFT calculations confirmed the presence of coadsorbed carbonate and water molecules.
• Liquid water in the electrolyte was identified as a key stabilizing factor for the adlayer.

Conclusions:

• The adsorption of bicarbonate on Cu(100) leads to complex, dynamic ordered structures.
• Water molecules play a significant role in stabilizing the coadsorbed carbonate-water layer.
• The observed phase transition highlights the sensitivity of the adlayer to electrochemical potential.