Proton Accumulation Modulated Surface Potential in Proton Conducting Ceramics Revealed by Near-Ambient Pressure X-ray...

Area of Science:

• Materials Science
• Electrochemistry
• Surface Science

Background:

• Proton conducting electrochemical cells (PCECs) are promising for energy conversion.
• Nonuniform proton concentration in PCECs hinders performance and understanding.
• Characterizing local proton distribution under operating conditions is crucial but challenging.

Purpose of the Study:

• To investigate the distribution of proton concentration in PCECs under operating conditions.
• To demonstrate the utility of in situ near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) for this purpose.
• To correlate proton distribution with defect chemistry and local electrical potential.

Main Methods:

• Utilized in situ near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS).
• Employed a symmetric Au/BaZr_0.9Y_0.1O_3-δ/Au cell with a 1 V DC bias.
• Analyzed O 1s XPS spectra to deconvolute hydroxyl groups and determine proton concentration distribution.
• Combined XPS with impedance analysis.

Main Results:

• In situ NAP-XPS successfully mapped proton concentration distribution across the PCEC electrolyte.
• An applied electric field induced proton accumulation at the counter electrode.
• Proton accumulation layers were thicker at 500 K than at 670 K due to higher hydroxyl group concentration.
• Proton distribution significantly affected the chemical environment of metal elements and local electrical potential.

Conclusions:

• In situ NAP-XPS is a powerful tool for probing local proton concentration in PCECs.
• Understanding proton distribution is key to optimizing defect chemistry and enhancing PCEC performance.
• The study advances the fundamental understanding of proton defect chemistry in energy conversion devices.