Flow-Cell-Compatible Operando Surface-Enhanced Raman Spectroscopy for Probing Reaction Intermediates during Carbon...

Area of Science:

• Electrocatalysis
• Surface Science
• Spectroscopy

Background:

• Elucidating reaction intermediates is crucial for understanding electrocatalysis.
• Electrochemical carbon dioxide reduction reaction (CO2RR) mechanisms vary significantly between H-cells and flow cells.
• Accurate operando characterization under realistic conditions is challenging.

Purpose of the Study:

• Develop a flow-cell-compatible operando surface-enhanced Raman spectroscopy (SERS) platform.
• Enable sensitive detection of transient intermediates in CO2RR.
• Establish a general spectroscopic strategy for mechanistic studies.

Main Methods:

• Integrated silica-coated gold nanorods (AuNRs@SiO2) optimized for 785 nm excitation.
• Utilized plasmonic resonance for signal enhancement and fluorescence suppression.
• Employed a benchmark copper catalyst in a flow cell setup.

Main Results:

• Directly detected key transient intermediates (*CO2- and *HOCCOH) previously inaccessible.
• Resolved adsorbed *CO into distinct components (bridge-bonded, low-frequency, high-frequency).
• Established a quantitative correlation between *CO speciation and C2 selectivity.

Conclusions:

• The developed AuNRs@SiO2 platform enables sensitive operando SERS measurements under practical CO2RR conditions.
• Direct detection of intermediates provides critical insights into CO2RR mechanisms in flow cells.
• Highlights the necessity of realistic mass transport considerations for accurate mechanistic studies.