Measurement of Surface Diffusion at the Electrochemical Interface by In Situ Linear Optical Diffraction

Area of Science:

• Electrochemistry
• Surface Science
• Physical Chemistry

Background:

• Understanding adsorbate behavior on electrode surfaces is crucial for catalysis and electro-synthesis.
• Existing methods for measuring surface diffusion in electrolyte solutions are limited.
• In situ techniques are needed to study electrochemical interfaces under relevant conditions.

Purpose of the Study:

• To develop and demonstrate a new in situ optical method for measuring surface diffusion rates of adsorbates on electrode surfaces.
• To investigate the surface diffusion of adsorbed sulfur on Platinum (Pt)(111) electrodes in an electrolyte solution.

Main Methods:

• Utilizing interfering laser pulses to create a periodic spatial modulation of adsorbate coverage.
• Employing a second laser to monitor the diffusion-induced decay of this pattern via optical diffraction.
• Performing proof-of-principle measurements on sulfur adsorbed on Pt(111) in 0.1 M sulfuric acid (H2SO4).

Main Results:

• Successfully demonstrated the in situ measurement of surface diffusion rates.
• Obtained potential- and coverage-dependent diffusion constants for sulfur on Pt(111) in 0.1 M H2SO4.
• Observed significantly higher diffusion constants compared to sulfur on Pt(111) under vacuum conditions.

Conclusions:

• The developed in situ method is effective for quantifying surface diffusion in electrochemical environments.
• Surface diffusion of adsorbates in electrolyte solutions can be substantially different from that in vacuum.
• The findings highlight the importance of electrolyte effects on surface dynamics at electrode-electrolyte interfaces.