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1. BaCo0.4Fe0.4Zr0.1Y0.1O3−σ Cathode Performance for Proton Conducting Solid Oxide Fuel Cells with BaZr0.8−xCexY0.1Yb0.1O3−δ Electrolytes

   https://doi.org/10.1149/2754-2734/ad040c  

   Li, Wenhao; Sozal, Md Shariful; Drozd, Vadym; Durygin, Andriy; Cheng, Zhe (October 2023, ECS Advances)

   BaCo0.4Fe0.4Zr0.1Y0.1O3−σ (BCFZY) is a proton, oxygen-ion, and electron-hole conducting cathode material for intermediate temperature solid oxide fuel cells. Its electrode reaction mechanism in air with moisture is not well understood. In this study, three types of symmetrical cells with the same BCFZY cathode were fabricated over three related proton conducting electrolytes: BaZr0.8−xCexY0.1Yb0.1O3−δ (x = 0.1, 0.4, and 0.7). The cathode shows similar performance over three different electrolytes in dry air but different responses to moisture introduction. The differences are hypothesized to relate to the mutual diffusion at the cathode/electrolyte interface. Such a hypothesis is supported by different techniques such as XRD Rietveld refinement of BCFZY cathode in mixtures with different electrolytes after firing, energy-dispersive X-ray spectroscopy (EDS) line scanning for element concentration distribution at the cathode/electrolyte interface, as well as electrochemical test for a related BaCoFeO-type cathode with Zr replaced by Ce. 

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2. In situ characterizations of solid–solid interfaces in solid‐state batteries using synchrotron X‐ray techniques

   https://doi.org/10.1002/cey2.131  

   Lucero, Marcos; Qiu, Shen; Feng, Zhenxing (July 2021, Carbon Energy)

   Abstract The solid–solid electrode–electrolyte interface represents an important component in solid‐state batteries (SSBs), as ionic diffusion, reaction, transformation, and restructuring could all take place. As these processes strongly influence the battery performance, studying the evolution of the solid–solid interfaces, particularly in situ during battery operation, can provide insights to establish the structure–property relationship for SSBs. Synchrotron X‐ray techniques, owing to their unique penetration power and diverse approaches, are suitable to investigate the buried interfaces and examine structural, compositional, and morphological changes. In this review, we will discuss various surface‐sensitive synchrotron‐based scattering, spectroscopy, and imaging methods for the in situ characterization of solid–solid interfaces and how this information can be correlated to the electrochemical properties of SSBs. The goal is to overview the advantages and disadvantages of each technique by highlighting representative examples, so that similar strategies can be applied by battery researchers and beyond to study similar solid‐solid interface systems. 

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3. Structure–property relationships describing the buried interface between silicon oxide overlayers and electrocatalytic platinum thin films

   https://doi.org/10.1039/c8ta06969g  

   Beatty, Marissa E.; Chen, Han; Labrador, Natalie Y.; Lee, Brice J.; Esposito, Daniel V. (November 2018, Journal of Materials Chemistry A)

   Encapsulation of an active electrocatalyst with a permeable overlayer is an attractive approach to simultaneously enhance its stability, activity, and selectivity. However, the structure–property relationships that govern the performance of encapsulated electrocatalysts are poorly understood, especially those describing the electrocatalytic behavior of the buried interface between the overlayer and active electrocatalyst. Using planar silicon oxide (SiO x )-encapsulated platinum (Pt)/titanium (Ti) bilayer thin films as model electrodes, the present study investigates the physical and electrochemical properties of the SiO x |Pt buried interface. Through a combination of X-ray photoelectron spectroscopy and electroanalytical measurements, it is revealed that a platinum oxide (PtO x ) interlayer can exist between the SiO x overlayer and Pt thin film. The thickness and properties of the PtO x interlayer can be altered by modifying (i) the thickness of the SiO x overlayer or (ii) the thickness of the Pt layer, which may expose the buried interface to oxophilic Ti. Importantly, SiO x |Pt electrodes based on ultrathin Pt/Ti bilayers possess thinner PtO x interlayers while exhibiting reduced permeabilities for Cu 2+ and H + and enhanced stability during cycling in 0.5 M H 2 SO 4 . These findings highlight the tunability of buried interfaces while providing new insights that are needed to guide the design of complex electrocatalysts that contain them. 

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4. Deal–Grove-like thermal oxidation of Si (001) buried under a thin layer of SrTiO3

   https://doi.org/10.1063/1.5097839  

   Guo, Wei; Posadas, A. B.; Demkov, A. A. (February 2020, Journal of Applied Physics)

   Dry oxidation of Si (001) beneath a thin epitaxial SrTiO3 layer has been studied using furnace annealing in flowing oxygen. A 10-nm layer of SrTiO3 is epitaxially grown on Si with no SiO2 interlayer. For such a structure, an annealing temperature of 800 °C was found to be the limiting temperature to prevent silicate formation and disruption of the interface structure. The effect of annealing time on the thickness of the SiO2 layer was investigated. In situ x-ray photoelectron spectroscopy and reflection-high-energy electron diffraction were used to ensure that the quality of SrTiO3 is unchanged after the annealing process. The experimental annealing data are compared with a theoretical oxygen diffusion model based on that of Deal, Grove, and Massoud. The model fits the experimental data well, indicating that oxygen diffusion through the SrTiO3 layer is not the limiting factor. One can therefore readily control the thickness of the SiO2 interlayer by simply controlling the annealing time in flowing oxygen. 

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5. Effect of Substrate Temperature on the Electrochemical and Supercapacitance Properties of Pulsed Laser-Deposited Titanium Oxynitride Thin Films

   https://doi.org/10.1115/1.4065535  

   Chris-Okoro, Ikenna; Som, Jacob; Cherono, Sheilah; Liu, Mengxin; Nalawade, Swapnil Shankar; Lu, Xiaochuan; Wise, Frank; Aravamudhan, Shyam; Kumar, Dhananjay (February 2025, Journal of Electrochemical Energy Conversion and Storage)

   Abstract Electrocatalytically active titanium oxynitride (TiNO) thin films were fabricated on commercially available titanium metal plates using a pulsed laser deposition method for energy storage applications. The elemental composition and nature of bonding were analyzed using X-ray photoelectron spectroscopy (XPS) to reveal the reacting species and active sites responsible for the enhanced electrochemical performance of the TiNO electrodes. Symmetric supercapacitor devices were fabricated using two TiNO working electrodes separated by an ion-transporting layer to analyze their real-time performance. The galvanostatic charge–discharge studies on the symmetric cell have indicated that TiNO films deposited on the polycrystalline titanium plates at lower temperatures are superior to TiNO films deposited at higher temperatures in terms of storage characteristics. For example, TiNO films deposited at 300 °C exhibited the highest specific capacity of 69 mF/cm2 at 0.125 mA/cm2 with an energy density of 7.5 Wh/cm2. The performance of this supercapacitor (300 °C TiNO) device is also found to be ∼22% better compared to that of a 500 °C TiNO supercapacitor with a capacitance retention ability of 90% after 1000 cycles. The difference in the electrochemical storage and capacitance properties is attributed to the reduced leaching away of oxygen from the TiNO films by the Ti plate at lower deposition temperatures, leading to higher oxygen content in the TiNO films and, consequently, a high redox activity at the electrode/electrolyte interface. 

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