A Review of X-ray Photoelectron Spectroscopy Technique to Analyze the Stability and Degradation Mechanism of Solid Oxide Fuel Cell Cathode Materials

Abstract

Nondestructive characterization of solid oxide fuel cell (SOFC) materials has drawn attention owing to the advances in instrumentation that enable in situ characterization during high-temperature cell operation. X-ray photoelectron spectroscopy (XPS) is widely used to investigate the surface of SOFC cathode materials because of its excellent chemical specificity and surface sensitivity. The XPS can be used to analyze the elemental composition and oxidation state of cathode layers from the surface to a depth of approximately 5–10 nm. Any change in the chemical state of the SOFC cathode at the surface affects the migration of oxygen ions to the cathode/electrolyte interface via the cathode layer and causes performance degradation. The objective of this article is to provide a comprehensive review of the adoption of XPS for the characterization of SOFC cathode materials to understand its degradation mechanism in absolute terms. The use of XPS to confirm the chemical stability at the interface and the enrichment of cations on the surface is reviewed. Finally, the strategies adopted to improve the structural stability and electrochemical performance of the LSCF cathode are also discussed.

XPS Study on Calcining Mixtures of Brucite with Titania

“…Other researchers have also studied MgO composites using the XPS technique [5]. Garcia et al studied sintered MgO with the addition of nanoparticles in different percentages by weight (iron oxide and aluminum oxide) using the XPS technique, to determine the oxidation states generated after laser irradiation with different wavelengths (532 and 1064 nm).…”

Spindle Nanorods of CeO2 and NiS Heterointerface Coated by the NC Layer: A High-Performance Bifunctional Electrocatalyst for Water Splitting

“…The Ni 2p spectrum is dominated by Ni 2p 3/2 and Ni 2p 1/2 , respectively (Figure d), accompanied by two satellite vibration peaks (879.5 and 860.8 eV) . The characteristic peaks at 852.9 and 870.9 eV belong to Ni 2+ species, and the characteristic peaks of Ni 3+ species correspond to 855.7 and 873.7 eV . Significantly, the peak of Ni 3+ in the NC/NiS-CeO 2 electrode has a positive shift of 0.5 eV compared to the NC/NiS electrode, which further confirms that the electrons are transferred from NiS to CeO 2 when the CeO 2 –NiS heterogeneous interface is formed.…”

“…31 The characteristic peaks at 852.9 and 870.9 eV belong to Ni 2+ species, and the characteristic peaks of Ni 3+ species correspond to 855.7 and 873.7 eV. 40 Significantly, the peak of Ni 3+ in the NC/NiS-CeO 2 electrode has a positive shift of 0.5 eV compared to the NC/NiS electrode, which further confirms that the electrons are transferred from NiS to CeO 2 when the CeO 2 −NiS heterogeneous interface is formed. In addition, the peak area of Ni 3+ is larger than that of Ni 2+ , which is attributed to the oxidation of Ni 2+ on the surface of air.…”

Effective Suppression of LSCF Air Electrode Degradation by Air Cleaning

“…The segregated SrO phase can also react with SO 2 and CO 2 species in the air to form SrSO 4 and SrCO 3 phases, respectively, which considerably affects the electrochemical performance of the LSCF electrode (4,6).…”