Multi-spectroscopic study of electrochemically-formed oxide-derived gold electrodes

Area of Science:

• Materials Science
• Electrochemistry
• Surface Chemistry

Background:

• Oxide-derived metals exhibit enhanced catalytic properties compared to their native counterparts.
• The specific mechanisms behind the improved performance of oxide-derived gold (OD-Au) remain unclear.
• Understanding the structural and chemical states of OD-Au is crucial for optimizing its catalytic applications.

Purpose of the Study:

• To investigate the structural and chemical nature of electrochemically formed oxide-derived gold (OD-Au).
• To elucidate the presence and role of subsurface gold oxide remnants in OD-Au.
• To correlate the findings with the enhanced catalytic performance of OD-Au.

Main Methods:

• Employing *operando* non-resonant sum frequency generation (SFG) spectroscopy to probe surface dynamics.
• Utilizing *ex situ* high-pressure X-ray photoelectron spectroscopy (HP-XPS) for detailed surface composition analysis.
• Generating OD-Au from polycrystalline gold in an acidic aqueous medium (H3PO4, pH = 1) under various oxidizing conditions.

Main Results:

• Electrochemical data indicated a metallic gold surface, but SFG signals suggested the presence of subsurface gold oxide remnants.
• HP-XPS results proposed these remnants to be in the form of Au2O3 or Au(OH)3.
• SFG measurements demonstrated that reducing electrochemical treatments could restore the metallic gold state by releasing the subsurface oxide.

Conclusions:

• Remnants of gold oxide persist beneath the topmost metallic gold layer in electrochemically prepared OD-Au.
• These subsurface oxide species are likely responsible for the enhanced catalytic properties observed in OD-Au.
• The study provides a potential explanation for the improved catalytic activity of OD-Au, paving the way for further research and development.