Spectroscopy vs. Electrochemistry: Catalyst Layer Thickness Effects on Operando/In Situ Measurements

Area of Science:

• Electrocatalysis
• Materials Science
• Spectroscopy

Background:

• Operando/in situ X-ray absorption spectroscopy (XAS) is vital for electrocatalysis research.
• Thick catalyst layers (CLs) are often needed for good signal-to-noise in XAS.
• These thick layers can introduce ion and mass transport limitations, affecting results.

Purpose of the Study:

• To investigate the influence of catalyst layer thickness on spectro-electrochemical findings.
• To understand how morphology and packing density affect Pd-hydride formation during XAS.
• To determine the impact of transport limitations on observed hydride formation trends.

Main Methods:

• In situ X-ray absorption spectroscopy (XAS) was performed on Pd/C nanoparticles and Pd-aerogel.
• Rotating disk electrode (RDE) measurements were used with varying catalyst loadings.
• Comparison of spectro-electrochemical data across different electrode configurations.

Main Results:

• Catalyst layer thickness was found to be a dominant factor in observed Pd-hydride formation trends.
• Different catalyst morphologies (Pd/C vs. Pd-aerogel) showed varying responses to thickness.
• Spectro-electrochemical data is significantly influenced by ion and mass transport limitations in thicker layers.

Conclusions:

• Minimizing catalyst layer thickness is essential for accurate operando/in situ XAS in electrocatalysis.
• Thin-film control measurements are recommended to validate results from thicker catalyst layers.
• Careful consideration of electrode design is needed to mitigate transport limitations in spectro-electrochemical studies.