Single layer of the passive film on Fe

Satô, Norio; Kudô, Kiyokatsu; Noda, Tetsuji

doi:10.1016/s0010-938x(70)80002-6

Cited by 94 publications

(43 citation statements)

References 4 publications

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“…It is possible to choose reactions for the two stages of cathodic reduction. The reactions must not only be consistent with the observed efficiencies, but must also take into account the observation that Fe e~ is produced in solution during Qj but not during Q2 (5,6). In addition, it is important that the choices provide an explanation for the abrupt drop in potential and change in reduction mechanism between Qt and Q2, Comparison of the present experimental results with the calculated values in Table I indicates that reaction (f) is most likely the reaction occurring during QI.…”

Section: Resultsmentioning

confidence: 93%

“…properties of oxides are better in samples oxidized at a high temperature than those oxidized at a low temperature (6,7). Micropore structures were reported (8) in dry-oxide samples, but were absent in wet-oxide samples, fabricated by H~O-N2 oxidation, which showed improved dielectric properties (9).…”

Section: Department Of Electrical and Electronic Engineering Universmentioning

confidence: 99%

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Use of 18O/SIMS and Electrochemical Techniques to Study the Reduction and Breakdown of Passive Oxide Films on Iron

Bardwell

MacDougall

Graham

1988

J. Electrochem. Soc.

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Secondary ion mass spectrometry (SIMS) has been used to study the cathodic removal and open-circuit breakdown of passive oxide films formed on Fe in ~SO-enriched borate buffer solution. For film removal by galvanostatic cathodic reduction, the initial stage of reduction resulted in a layer by layer thinning of the film. The rates of film removal with cathodic charge passed were determined to be 1.56 and 0.30 nm/mC cm -2 during the two distinct stages of reduction. These results are analyzed in terms of the various models for the passive film on Fe. Immersion of the passivated Fe electrodes in acidic sulfate solutions on open circuit resulted in a distinct potential arrest followed by a very rapid potential decrease. The length of this arrest is strongly dependent on the oxide film thickness and on the solution pH. '80 SIMS and electrochemical results are discussed in terms of mechanisms of reductive and chemical dissolution on open circuit.Despite over a century of scientific research, there is still no consensus as to the true nature of the passive oxide film on Fe. There is general agreement that the film is compact and contains Fe, O (and maybe protons), and is less than 5.5 nm thick, but there is little agreement as to its exact composition. Some confusion has certainly arisen from attempting to describe such thin layers in terms of bulk materials and some fundamental questions remain hotly contested. (i) Does the film contain H? (ii) Is the film best described as a single layer, a duplex layer, or as a single layer with concentration gradients?The technique of cathodic reduction has been used extensively to investigate the nature of the passive film and to provide support for the various proposed models. In this paper cathodic reduction is also used in conjunction with ~80 SIMS experiments to shed light on the nature, formation, and breakdown of the passive film on Fe. Passive oxide films undergo breakdown on open circuit in acidic sulfate solutions, and the mechanism of this breakdown is investigated using both '80 SIMS and cathodic reduction techniques. The results are compared with those found for galvanostatJc cathodic reduction of the film. ExperimentalFe samples were cut from a zone-refined ingot obtained from Battelle Memorial Institute. An analysis of this 99.99+% material has been published previously (1). The samples were polished with 600 grit SiC and then down to 1 ~m diamond and electropolished immediately before use. In electrochemical experiments, samples were reduced galvanostatically before stepping the potential to the required value in the passive region.Borate buffer solutions of pH 8.4, 0.15N Na2SO4 of pH 3 or 5, and pH 0.27 H2SO4 solutions were thermostated at 24~ and deaerated before use. Potentials were measured relative to a 0.15N Hg/Hg2SO4/Na2SO4 reference electrode (0.421V vs. SCE, 0.661V vs. SHE). A PAR Model 173 Potentiostat with a Model 276 interface, connected to an IBM compatible computer was used. This enabled currents to be measured as early as a few milliseconds after the p...

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Section: Resultsmentioning

confidence: 93%

Section: Department Of Electrical and Electronic Engineering Universmentioning

confidence: 99%

Use of 18O/SIMS and Electrochemical Techniques to Study the Reduction and Breakdown of Passive Oxide Films on Iron

Bardwell

MacDougall

Graham

1988

J. Electrochem. Soc.

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“…Sato et al (9) have suggested that the Fe203 or FeOOH might reduce to Fe304. The solubility of Fe (OH)e in these solutions is sufficient to allow all the ferrous ion to go into solution.…”

Section: Discussionmentioning

confidence: 99%

The Cathodic Reduction of Gamma-FeOOH, Gamma-Fe[sub 2]O[sub 3], and Oxide Films on Iron

Cohen¹,

Hashimoto

1974

J. Electrochem. Soc.

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A comparison has been made of the galvanostatic reduction of iron oxide films formed by deposition on platinum and by anodic or air oxidation of iron. The major reduction process is that of Fe + + + ion to Fe + + ion in solution. Some ferrous ion is adsorbed on the unreduced oxide. There is no evidence for reduction to an intermediate solid phase. The results indicate that the two waves observed in the cathodic reduction of anodically formed (or air-formed) films are due to the presence of the two "phases" Fe304 and 7-Fe~O3 in the as-formed films.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.218.248.209 Downloaded on 2015-03-22 to IP Vol. 121, No. I

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“…For example, the reduction process of iron oxides in alkaline aqueous electrolytes is still ambiguous even though it has been studied for several decades: Sato proposed that Fe 2 O 3 was reduced to lower valence oxide in 1970. 22 Patrik verified that Fe 2 O 3 was reduced to Fe 3 O 4 then to Fe(OH) 2 with in situ X-ray absorption near-edge spectroscopy. 23 However, some scientists still believe that Fe 2 O 3 is directly reduced to Fe(OH) 2 at the first stage.…”

Section: ■ Introductionmentioning

confidence: 90%

Rate-Limiting Step in Batteries with Metal Oxides as the Energy Materials

Wang

Shang

Zhang

et al. 2018

ACS Appl. Mater. Interfaces

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Metal oxides are used as the energy materials in some aqueous and nonaqueous batteries. However, a large overpotential and poor rate-performance limit their wide application. Low electrical conductivity of the oxide is commonly considered to be the reason for these limitations. The present study specifically reveals the electrochemical reduction process of α-FeO particles by using a cyclic voltammetry technique combined with an electron spectroscopy technique. SEM and TEM observe the phase and crystal structure transformation process during α-FeO reduction at the nanoscale, and EDS analyzes the composition change of particles at various periods. The surface of α-FeO particles is reduced to an amorphous compound first, and then O ions diffuse from the crystal matrix toward the outside simultaneously causing defects inside the particles. Experiments prove that γ-FeO, FeO, CuO, and BiO have the same rate-limiting step as α-FeO; that is, O ions diffuse inside the oxide particles toward the outside. The diffusion coefficients of O in these metal oxides are also estimated. This study demonstrates that the ionic conductivity of metal oxides is the critical factor which affects the overpotential and rate-performance of the batteries with these oxides as active material, and the O ion diffusion coefficient must be considered when selecting or designing metal oxides as energy material. The conclusion that O diffusion in oxides is the rate-limiting step of their reduction may be applicable to a group of oxides whose reduction reaction is not involved in ion diffusion from an electrolyte into their crystal matrix.

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Single layer of the passive film on Fe

Cited by 94 publications

References 4 publications

Use of 18O/SIMS and Electrochemical Techniques to Study the Reduction and Breakdown of Passive Oxide Films on Iron

Use of 18O/SIMS and Electrochemical Techniques to Study the Reduction and Breakdown of Passive Oxide Films on Iron

The Cathodic Reduction of Gamma-FeOOH, Gamma-Fe[sub 2]O[sub 3], and Oxide Films on Iron

Rate-Limiting Step in Batteries with Metal Oxides as the Energy Materials

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