Electrochemical studies of capacitance in cerium oxide thin films and its relationship to anionic and electronic defect densities

Chueh, William C.; Haile, Sossina M.

doi:10.1039/b910903j

Cited by 100 publications

(151 citation statements)

References 37 publications

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“…2b). Deposition under lower oxygen pressures (a few mTorr) led to dense films, 3,11 whereas higher pressures ($200 mTorr) led to random, disordered microstructures (not shown). The vertical alignment of both the pores and the oxide features indicates that diffusion of electronic, ionic, and gas phase species will be largely confined to one dimension, providing the desired simplification of the complex electrochemical reaction pathways.…”

Section: Resultsmentioning

confidence: 99%

High electrode activity of nanostructured, columnar ceria films for solid oxide fuel cells

Jung

Dereux

Chueh

et al. 2012

Energy Environ. Sci.

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Highly porous oxide structures are of significant importance for a wide variety of applications in fuel cells, chemical sensors, and catalysis, due to their high surface-to-volume ratio, gas permeability, and possible unique chemical or catalytic properties. Here we fabricated and characterized Sm 0.2 Ce 0.8 O 1.9Àd films with highly porous and vertically oriented morphology as a high performance solid oxide fuel cell anode as well as a model system for exploring the impact of electrode architecture on the electrochemical reaction impedance for hydrogen oxidation.

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Section: Resultsmentioning

confidence: 99%

High electrode activity of nanostructured, columnar ceria films for solid oxide fuel cells

Jung

Dereux

Chueh

et al. 2012

Energy Environ. Sci.

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“…3a). Based on previously measured oxygen vacancy concentration in the bulk and similarly deposited thin-film ceria 49 , the intrinsic bulk oxygen vacancy concentration (relative to the total oxygen content) under our experimental conditions ranges from 0.6% (at À 0.18 V) to 2 Â 10 À 4 % (at 0.35 V). These values are significantly lower than the extrinsic oxygen vacancy concentration because of Sm doping (5%).…”

Section: Resultsmentioning

confidence: 99%

Fast vacancy-mediated oxygen ion incorporation across the ceria–gas electrochemical interface

et al. 2014

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Electrochemical incorporation reactions are ubiquitous in energy storage and conversion devices based on mixed ionic and electronic conductors, such as lithium-ion batteries, solidoxide fuel cells and water-splitting membranes. The two-way traffic of ions and electrons across the electrochemical interface, coupled with the bulk transport of mass and charge, has been challenging to understand. Here we report an investigation of the oxygen-ion incorporation pathway in CeO 2-d (ceria), one of the most recognized oxygen-deficient compounds, during hydrogen oxidation and water splitting. We probe the response of surface oxygen vacancies, electrons and adsorbates to the electrochemical polarization at the ceria-gas interface. We show that surface oxygen-ion transfer, mediated by oxygen vacancies, is fast. Furthermore, we infer that the electron transfer between cerium cations and hydroxyl ions is the rate-determining step. Our in operando observations reveal the precise roles of surface oxygen vacancy and electron defects in determining the rate of surface incorporation reactions.

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“…By varying the geometric parameters of the electrode, most conveniently deposited as a patterned, dense thin film, one can examine how the ratelimiting process varies with the number density of candidate active sites, e.g., triple-phase boundary (TPB) and two-phase boundary sites, and ultimately deduce reaction pathways and rate-limiting steps. [5][6][7][8][9][10][11][12][13][14][15][16] Such an approach is pursued in this work for the study of hydrogen electro-oxidation in CsH 2 PO 4 -based fuel cells, in which Pt loadings remain prohibitively high. 4 The geometry of interest consists of circular, thin film electrodes which allow access to a wide range of geometric parameters through variation of film diameter and thickness.…”

Section: Introductionmentioning

confidence: 99%

Platinum thin film anodes for solid acid fuel cells

Haile

2011

Energy Environ. Sci.

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Hydrogen electro-oxidation kinetics at the Pt | CsH 2 PO 4 interface have been evaluated. Thin films of nanocrystalline platinum 7.5-375 nm thick and 1-19 mm in diameter were sputtered atop polycrystalline discs of the proton-conducting electrolyte, CsH 2 PO 4 , by shadow-masking. The resulting Pt | CsH 2 PO 4 | Pt symmetric cells were studied under uniform H 2 -H 2 O-Ar atmospheres at temperatures of 225-250 C using AC impedance spectroscopy. For thick platinum films (>50 nm), electro-oxidation of hydrogen was found to be limited by diffusion of hydrogen through the film, whereas for thinner films, diffusion limitations are relaxed and interfacial effects become increasingly dominant. Extrapolation to vanishing film thickness implies an ultimate interfacial resistivity of 2.2 U cm 2 , likely reflecting a process at the Pt | H 2(g) interface. Films 7.5 nm in thickness displayed a total electrooxidation resistivity,R, of 3.1 U cm 2 , approaching that of Pt-based composite anodes for solid acid fuel cells (1-2 U cm 2 ). In contrast, the Pt utilization (R À1 /Pt loading), 19 S mg À1 , significantly exceeds that of composite electrodes, indicating that the thin film approach is a promising route for achieving high performance in combination with low platinum loadings.

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Electrochemical studies of capacitance in cerium oxide thin films and its relationship to anionic and electronic defect densities

Cited by 100 publications

References 37 publications

High electrode activity of nanostructured, columnar ceria films for solid oxide fuel cells

High electrode activity of nanostructured, columnar ceria films for solid oxide fuel cells

Fast vacancy-mediated oxygen ion incorporation across the ceria–gas electrochemical interface

Platinum thin film anodes for solid acid fuel cells

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