Unveiling Key Interface Characteristics of Ni/Yttria-Stabilized Zirconia Solid Oxide Cell Electrodes in H₂O...

Area of Science:

• Materials Science
• Electrochemistry
• Surface Science

Background:

• Nickel/yttria-stabilized zirconia (Ni/YSZ) composites are standard fuel electrodes for solid oxide cells.
• Limited understanding exists regarding Ni/YSZ surface chemistry under operational conditions, particularly during water electrolysis.

Purpose of the Study:

• To investigate the surface chemistry of Ni/YSZ electrodes interacting with water vapor under various operating conditions.
• To correlate surface chemistry changes with the electrochemical performance of solid oxide cells during water electroreduction.

Main Methods:

• Utilized near ambient pressure soft and hard X-ray photoelectron spectroscopies to analyze Ni/YSZ electrodes.
• Employed miniature cells modified for direct spectroscopic observation of the electrode-electrolyte interface.
• Combined depth-dependent photoemission measurements with theoretical simulations.

Main Results:

• Observed dynamic changes in Ni/YSZ oxidation state and composition under H2 and H2O atmospheres.
• Quantified impurity accumulation on the electrode surface.
• Established that nickel surface oxidation in H2O electrolysis favors NiO over Ni(OH)2, and revealed a uniform NiO/Ni surface mixture, contrary to expected core-shell structures.

Conclusions:

• Nickel surface oxidation state is critical for Ni/YSZ electrode performance in H2O electrolysis.
• Findings provide insights into Ni-phase redistribution mechanisms and electrode stability during long-term operation.
• The study elucidates the surface chemistry governing Ni/YSZ electrode behavior in solid oxide cells for water electrolysis.