Operando Soft X-ray Absorption Spectroscopic Study on a Solid Oxide Fuel Cell Cathode during Electrochemical Oxygen...

Area of Science:

• Materials Science
• Electrochemistry
• Spectroscopy

Background:

• Understanding electrode material electronic structures under operating conditions is crucial for energy conversion devices.
• Traditional methods often fail to capture dynamic changes during electrochemical reactions at elevated temperatures.

Purpose of the Study:

• To establish and demonstrate an operando soft X-ray absorption spectroscopic technique for analyzing electrode materials.
• To investigate the electronic structural changes of La₂NiO₄₊δ during electrochemical oxygen reduction.

Main Methods:

• Development of an operando soft X-ray absorption spectroscopy setup capable of high-temperature (up to 773 K) and controlled atmosphere analysis.
• Electrochemical polarization and oxygen reduction reaction (ORR) studies on a La₂NiO₄₊δ dense-film electrode.
• Acquisition and analysis of O K-edge and Ni L-edge X-ray absorption spectra.

Main Results:

• Successfully obtained clear X-ray absorption spectra under various oxygen partial pressures and temperatures.
• Observed significant changes in O K-edge spectra with varying oxygen partial pressure and applied electrical potential.
• Noted minimal changes in Ni L-edge spectra, indicating localized electronic alterations primarily involving oxygen.
• A pre-edge peak in O K-edge spectra, linked to Ni 3d-O 2p hybridization, showed distinct responses to cathodic and anodic polarization.

Conclusions:

• The developed operando technique effectively probes dynamic electronic structure changes in electrode materials during electrochemical reactions.
• Electrochemical polarization significantly alters the electronic structure of the La₂NiO₄₊δ electrode, particularly affecting oxygen's electronic states.
• The findings provide insights into the mechanism of electrochemical oxygen reduction at the electrode surface.