In Situ Electrochemistry of Formate on Cu Thin Films Using ATR-FTIR Spectroscopy and X-ray Photoelectron Spectroscopy

Area of Science:

• Electrochemistry
• Surface Science
• Catalysis

Background:

• Formate is a dominant intermediate in CO2 electrochemical reduction (CO2ER).
• Copper-based catalysts show promise for CO2ER but suffer from low selectivity and undesirable products.
• Understanding intermediate binding and surface changes under applied potential is crucial for catalyst improvement.

Purpose of the Study:

• To investigate the in situ redox surface chemistry of formate on copper thin films during CO2ER.
• To elucidate the binding mechanisms of intermediates and products on copper surfaces.
• To correlate surface changes with applied potential during electrochemical reduction.

Main Methods:

• In situ spectroelectrochemical (SEC) experiments using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR).
• Cyclic voltammetry (CV) to study electrochemical reactions and surface species.
• Ion chromatography (IC) for identifying aqueous phase products and X-ray photoelectron spectroscopy (XPS) for analyzing copper oxidation states.

Main Results:

• ATR-FTIR successfully monitored surface species in real time during CV experiments on Cu/Si wafers.
• Formate oxidation to bicarbonate was observed at 0.27 V via ATR-FTIR.
• Ion chromatography detected glycolate, glyoxylate, and trace oxalate, indicating C-C coupling reactions. XPS revealed surface oxidation of copper.

Conclusions:

• The study demonstrates the utility of in situ SEC-ATR-FTIR for real-time analysis of CO2ER intermediates on copper.
• Evidence of formate oxidation and C-C coupling reactions leading to glycolate and glyoxylate formation was established.
• Surface oxidation of copper occurs during the electrochemical reduction process, impacting catalytic performance.