Laser induced oxidation Raman spectroscopy as an analysis tool for iridium-based oxygen evolution catalysts

Area of Science:

• Materials Science
• Electrochemistry
• Spectroscopy

Background:

• Industrial analysis of electrocatalyst degradation requires efficient methods.
• Raman spectroscopy is suitable, but metallic iridium is Raman inactive.
• Iridium's high oxidation sensitivity can be exploited for analysis.

Purpose of the Study:

• To establish Laser Induced Oxidation Raman Spectroscopy (LIORS) for analyzing iridium catalysts.
• To investigate the influence of particle size on iridium oxidation sensitivity.
• To assess electrocatalyst deterioration during proton exchange membrane electrolysis (PEMEL).

Main Methods:

• Development and application of Laser Induced Oxidation Raman Spectroscopy (LIORS).
• Controlled laser-induced oxidation of iridium powders of varying particle sizes.
• Analysis of spectral changes to determine oxidation thresholds and transformation temperatures.
• Comparison of pristine and operated electrocatalysts.

Main Results:

• LIORS successfully analyzed iridium catalysts, correlating oxidation sensitivity with particle size.
• Smaller iridium particles exhibited significantly higher oxidation sensitivity.
• Operated electrocatalysts showed increased oxidation sensitivity, indicating smaller particle sizes due to dissolution.
• Pre-oxidation of iridium during electrolysis lowered the energy barrier for IrO2 formation.

Conclusions:

• LIORS is a novel, effective method for qualitative, chemical, and structural analysis of iridium catalysts.
• Catalyst particle size is a critical factor influencing oxidation sensitivity.
• LIORS can detect catalyst degradation in PEMEL by assessing changes in oxidation sensitivity and transformation temperatures.
• The method provides a straightforward screening approach for industrial PEMEL applications.