Unveiling Key Interface Characteristics of Ni/Yttria-Stabilized Zirconia Solid Oxide Cell Electrodes in H 2 O Electroreduction Using Operando X-ray Photoelectron Spectroscopy.
Jinming ZhangMathias BarreauThierry DintzerMichael HaeveckerDetre TeschnerAnna EfimenkoWen LuoSpyridon ZafeiratosPublished in: ACS applied materials & interfaces (2024)
Nickel/yttria-stabilized zirconia (YSZ) composites are the most commonly used fuel electrodes for solid oxide cells. While microstructural changes of Ni/YSZ during operational conditions have been thoroughly investigated, there is limited knowledge regarding Ni/YSZ surface chemistry under working conditions. In this study, we examine the interaction between Ni/YSZ electrodes and water vapor under open circuit and polarization conditions, utilizing near ambient pressure soft and hard X-ray photoelectron spectroscopies. Miniature cells with conventional porous Ni/YSZ composite cermet cathodes were modified to facilitate the direct spectroscopic observation of the functional electrode's areas close to the interface with the YSZ electrolyte. The results highlight dynamic changes in the oxidation state and composition of Ni/YSZ under H 2 and H 2 O atmospheres. We also quantify the accumulation of impurities on the electrode surface. Through adjustments in the pretreatment of the cell, the correlation between the nickel surface oxidation state and the cell's electrochemical performance during H 2 O electroreduction is established. It is unequivocally shown that nickel surface oxidation in H 2 O electrolysis favors NiO over Ni(OH) x , providing critical insights into the mechanism of Ni-phase redistribution within the electrode during long-term operation. Depth-dependent photoemission measurements, combined with theoretical quantitative simulations, reveal that NiO and Ni phases are uniformly mixed on the surface during H 2 O electrolysis. This differs from the conventional expectation of a NiO-shell/Ni-core configuration in gas phase oxidation. These findings provide crucial insights into the surface chemistry of Ni/YSZ electrodes under conditions relevant to H 2 O electrolysis, elucidating their impact on the electrochemical performance of the cell.
Keyphrases
- metal organic framework
- carbon nanotubes
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- reduced graphene oxide
- transition metal
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- cell therapy
- gold nanoparticles
- high resolution
- hydrogen peroxide
- induced apoptosis
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- magnetic resonance imaging
- nitric oxide
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- cell death
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- molecular dynamics
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- particulate matter
- mass spectrometry
- optical coherence tomography
- monte carlo