Pt current collectors artificially boosting praseodymium doped ceria oxygen surface exchange coefficients

Ma, Yuxi; Burye, Theodore E.; Nicholas, Jason D.

doi:10.1039/d1ta06237a

Cited by 5 publications

(5 citation statements)

References 141 publications

(146 reference statements)

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“…The change of P O during the high-temperature growth and cooling process does not cause any significant variation in the lattice constant, from which we can infer that the pressure in the given range does not impact on the V O concentration in the grown films, and that the deviation from V O concentration is small. It is well-documented that oxygen-deficient ceria and ceria-based materials have a propensity to readily react and store oxygen [23,24]. Consequently, the ability to manipulate the content of oxygen vacancies in the doped films is restricted under the prevailing high-temperature film growth conditions that encourage oxidation activities.…”

Section: Resultsmentioning

confidence: 99%

Tailoring dielectric permittivity of epitaxial Gd-doped CeO_2−x films by ionic defects

Palliotto,

Wu,

Rata

et al. 2024

J. Phys. Energy

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Engineering materials with highly tunable physical properties in response to external stimuli is a cornerstone strategy for advancing energy technology. Among various approaches, engineering ionic defects and understanding their roles are essential in tailoring emergent material properties and functionalities. Here, we demonstrate an effective approach for creating and controlling ionic defects (oxygen vacancies) in epitaxial Gd-doped CeO2-x (CGO) (001) films grown on Nb: SrTiO3(001) single crystal. Our results exhibit a significant limitation in the formation of excess oxygen vacancies in the films during high-temperature film growth. However, we have discovered that managing the oxygen vacancies in the epitaxial CGO (001) films is feasible using a twostep film growth process. Subsequently, our findings show that manipulating excess oxygen vacancies is a key to the emergence of giant apparent dielectric permittivity (e.g., ε′ ≈106) in the epitaxial films under electrical field control. Overall, the strategy of tuning functional ionic defects in CGO and similar oxides is beneficial for various applications such as electromechanical, sensing, and energy storage applications.

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Section: Resultsmentioning

confidence: 99%

Tailoring dielectric permittivity of epitaxial Gd-doped CeO_2−x films by ionic defects

Palliotto,

Wu,

Rata

et al. 2024

J. Phys. Energy

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“…While the impact of surface Si on the oxygen exchange kinetics of perovskite STF35 specifically is unknown, in another composition, fluorite (Ce,Pr)O 2−δ , severe degradation of k chem values has been attributed to Si poisoning, which could be alleviated by subsequent coating with La-oxide leading to recovery of the original, native k chem values . More recent work has suggested that Pt coatings may also interact beneficially with Si poisoning on films of that same composition …”

Section: Discussionmentioning

confidence: 99%

“…67 More recent work has suggested that Pt coatings may also interact beneficially with Si poisoning on films of that same composition. 19 Analysis of the temperature dependence of the oxygen surface exchange coefficient from experimental data and COMSOL simulations reveals further differences between the two samples. For Au-STF35, the approximate activation energy of k chem exhibits a spatial dependence: it is notably higher at the MIEC-film interface vs on the native film surface (∼1.5∼0.5 eV).…”

Section: Spectroscopic Findingsmentioning

confidence: 98%

“…This particular type of interface has been leveraged to boost device performance, particularly the catalytic activity toward key surface reactions. For example, the interactions between metals and ionic or mixed conductors have been applied in (metal) catalyst(oxide) support coupling in heterogeneous catalysis and highly efficient nanocomposite metal–MIEC electrodes in high-temperature fuel cells. − In these cases, the metals may be deposited onto the oxide, , ex-solved from the oxide, − or produced during complete reduction of an oxide phase within a composite, and the result is a complex, stochastic microstructure where individual interfaces and their contributions are difficult to isolate and assess in situ. Characterization is often performed on a macroscopic level, with scarce local observations of the fundamental interface behavior itself.…”

Section: Introductionmentioning

confidence: 99%

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High-Temperature 2D Optical Relaxation Visualizes Enhanced Oxygen Exchange Kinetics at Metal-Mixed Conducting Oxide Interfaces

Skiba

Perry

2022

ACS Appl. Mater. Interfaces

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Solid-state heterointerfaces are of interest for emergent local behavior that is distinct from either bulk parent compound. One technologically relevant example is the case of mixed ionic/electronic conductor (MIEC)–metal interfaces, which play an important role in electrochemistry. Metal–MIEC composite electrodes can demonstrate improved catalytic activity vs single-phase MIECs, improving fuel cell efficiency. Similarly, MIEC surface reaction kinetics are often evaluated using techniques that place metal current collectors in contact with the surface under evaluation, potentially altering the response vs the native surface. Techniques enabling direct and local in situ observation of the behavior at and around such heterointerfaces are needed. Here, we develop a spatially resolved optical transmission relaxation (2D-OTR) method providing continuous evaluation of local, high-temperature, controlled atmosphere defect kinetics across a ∼1 cm2 sample area simultaneously in a contact-free manner. We apply it to observe the spatial variance of oxygen incorporation and evolution rates at ∼525–620 °C, in response to step changes in oxygen partial pressure, on MIEC SrTi0.65Fe0.35O3–x films as a function of distance from porous Pt and Au layers. Using this model geometry, we find significant enhancements in kinetics adjacent to the metals that decay over a few millimeter distance. To extract kinetic parameters, we fit the short-term optical data (initial portion of relaxations) with an exponential decay function appropriate for surface-exchange-limited kinetics, yielding apparent surface exchange coefficients (k chem) with spatial resolution, decreasing with distance from the metal. To understand the kinetic processes governing the complete (long-term) optical relaxations, we performed COMSOL simulations, which demonstrated that a combination of laterally varying k chem and in-plane diffusion controls the observed kinetics over the full time range. Further support for spatially varying k chem comes from demonstrations of changing surface and bulk chemistry vs distance from the metal–MIEC interface, by X-ray photoelectron and optical absorption spectroscopies, respectively. Although microporous Pt and Au are not excellent electrodes in isolation, both metals exert a synergistic effect on the oxygen surface exchange rate in the presence of the mixed conducting film.

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“…On the other hand, Pt is well known as a catalyst for oxygen reactions [50,51] and the employed Pt buffer layer could-upon diffusion to the surface-lead to modifications of the observed oxygen kinetics of ceria. [52,53] However, no such effect was found during exchange and back-exchange experiments by comparing CGO thin films simultaneously deposited on Pt/Si and MgO single-crystal substrates, as shown in Figure S9 (Supporting Information).…”

Section: Iers For Surface Limited Thin Film Scenariomentioning

confidence: 99%

Isotope Exchange Raman Spectroscopy (IERS): A Novel Technique to Probe Physicochemical Processes In Situ

et al. 2023

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A novel in situ methodology for the direct study of mass‐transport properties in oxides with spatial and unprecedented time resolution, based on Raman spectroscopy coupled to isothermal isotope exchanges, is developed. Changes in the isotope concentration, resulting in a Raman frequency shift, can be followed in real time, which is not accessible by conventional methods, enabling complementary insights for the study of ion‐transport properties of electrode and electrolyte materials for advanced solid‐state electrochemical devices. The proof of concept and strengths of isotope exchange Raman spectroscopy (IERS) is demonstrated by studying the oxygen isotope back‐exchange in gadolinium‐doped ceria (CGO) thin films. Resulting oxygen self‐diffusion and surface exchange coefficients are compared to conventional time‐of‐flight secondary‐ion mass spectrometry (ToF‐SIMS) characterization and literature values, showing good agreement, while at the same time providing additional insight, challenging established assumptions. IERS captivates through its rapidity, simple setup, non‐destructive nature, cost effectiveness, and versatile fields of application and thus can readily be integrated as new standard tool for in situ and operando characterization in many laboratories worldwide. The applicability of this method is expected to consolidate the understanding of elementary physicochemical processes and impact various emerging fields including solid oxide cells, battery research, and beyond.

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Pt current collectors artificially boosting praseodymium doped ceria oxygen surface exchange coefficients

Abstract: The chemical oxygen surface exchange coefficient (kchem) values used to quantify and rank oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalyst performance for high-temperature, oxygen-exchange-enabled devices (such as...

Cited by 5 publications

References 141 publications

Tailoring dielectric permittivity of epitaxial Gd-doped CeO_2−x films by ionic defects

Tailoring dielectric permittivity of epitaxial Gd-doped CeO_2−x films by ionic defects

High-Temperature 2D Optical Relaxation Visualizes Enhanced Oxygen Exchange Kinetics at Metal-Mixed Conducting Oxide Interfaces

Isotope Exchange Raman Spectroscopy (IERS): A Novel Technique to Probe Physicochemical Processes In Situ

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Pt current collectors artificially boosting praseodymium doped ceria oxygen surface exchange coefficients

Abstract: The chemical oxygen surface exchange coefficient (kchem) values used to quantify and rank oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalyst performance for high-temperature, oxygen-exchange-enabled devices (such as...

Cited by 5 publications

References 141 publications

Tailoring dielectric permittivity of epitaxial Gd-doped CeO2−x films by ionic defects

Tailoring dielectric permittivity of epitaxial Gd-doped CeO2−x films by ionic defects

High-Temperature 2D Optical Relaxation Visualizes Enhanced Oxygen Exchange Kinetics at Metal-Mixed Conducting Oxide Interfaces

Isotope Exchange Raman Spectroscopy (IERS): A Novel Technique to Probe Physicochemical Processes In Situ

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Product

Resources

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Tailoring dielectric permittivity of epitaxial Gd-doped CeO_2−x films by ionic defects

Tailoring dielectric permittivity of epitaxial Gd-doped CeO_2−x films by ionic defects