Selective Analysis of Redox Processes at the Electrode Interface with Time-Resolved Raman Spectroscopy

Area of Science:

• Electrochemistry and sustainable chemical industry
• Spectroscopic analysis of electrochemical interfaces
• Advanced analytical techniques for chemical reactions

Background:

• Electrochemical reactions are vital for sustainable chemistry, requiring precise analysis of electron transfer and solution composition near electrode surfaces.
• Traditional Raman spectroscopy lacks sensitivity for low concentrations and minor changes at electrode interfaces.
• Time-, potential-, and spatially resolved analysis is crucial for understanding electrochemical processes.

Purpose of the Study:

• To demonstrate the capability of surface-enhanced Raman scattering (SERS) and resonance Raman (rR) spectroscopy for analyzing electrochemical reactions.
• To achieve spatially and time-resolved analysis of solution composition at and near electrode surfaces with high sensitivity.
• To elucidate electro(catalytic) reactions at electrode interfaces using advanced spectroscopic methods.

Main Methods:

• Utilizing SERS and rR spectroscopy with SERS-active gold electrodes prepared by electrochemical surface roughening.
• Employing a combination of smooth and roughened gold electrodes to differentiate surface and resonance enhancement effects.
• Analyzing redox couples like ferrocene, ABTS, [Ru(bpy)3]2+, and TMA for spectral analysis and identification of transient species.

Main Results:

• SERS and rR spectroscopy enable selective, spatially resolved analysis of species at low concentrations (<1 mM) near electrode surfaces (<1-2 nm and within 5 μm).
• Demonstrated label-free, non-specific adsorption, and non-resonance-enhanced detection of concentration changes at the electrode surface.
• Successfully identified transient soluble species in real-time during the reversible oxidation of 4,N,N-trimethylaniline (TMA) using localized enhancement.

Conclusions:

• SERS and rR spectroscopy provide powerful tools for detailed, real-time analysis of electrochemical reactions at electrode interfaces.
• This approach overcomes the sensitivity limitations of nonresonant Raman scattering for studying low-concentration species.
• The dual function of electrodes in surface enhancement and electron transfer analysis opens new avenues for elucidating electrocatalytic mechanisms.