The kinetics of the electrochemical formation and reduction of monomolecular oxide layers on platinum in 0.5 M H2SO4

Vetter, K.; Schultze, J.W.

doi:10.1016/s0022-0728(72)80510-2

Cited by 82 publications

(122 citation statements)

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“…Water desorbed from both thick and thin anodic films at temperatures on Pt occurs at the edges of islands [5]. The model assumes that an initial coverage 8 0 hasthe same geometry as would result from desorption to 8 0 from saturation.…”

Section: Discussionmentioning

confidence: 99%

“…Vetter and Schultze [5] also analyzed charging and stripping curves and concluded that the coverage of adsorbed oxygen did not exceed a few percent, with a rate-determining, field-dependent place exchange leading to a phase oxide that represented most of the anodic charge. Fleischmann et al [6] proposed the formation of four different "oxides" on Pt anodes.…”

Section: Introductionmentioning

confidence: 99%

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AES and TDS studies of electrochemically oxidized Pt(100)

Wagner

Ross

1985

Applied Surface Science

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Anodic films formed on Pt(lOO) in 0.3M HF using a quasi thin-layer electrochemical cell within a vacuum envelope were transferred to ultra-high vacuum for study by AtS and TDS. Films generated at potentials above 1.lV (RHE) survived emersion and pumpdown in a hydrated state. As the emersion potential increased, the lntegrated H 2 0 and 02 thermal desorption signals , also using stripping studies, concluded that, after surface adsorption started at D.8V, dermasorption (sorption into the first few layers of the metal) commenced at 1.DV. Dermasorption and surface adsorption continued together .up to 1.6V, where a monolayer of PtD was thought to be present. At higher potentials some of the PtD was further oxidized.Vetter and Schultze [5] also analyzed charging and stripping curves and concluded that the coverage of adsorbed oxygen did not exceed a few percent, with a rate-determining, field-dependent place exchange leading to a phase oxide that represented most of the anodic charge. Fleischmann et al. [6] proposed the formation of four different "oxides" on Pt anodes. AngersteinKozlowska et ale [7] have given the most detailed interpretation of voltammetric and ellipsometric data to date. They have proposed a series of oxidation steps which occur as a polycrystalline Pt electrode is swept to 3 progressively higher potentials in acidic electrolyte. The initial oxidation, in the potential region 0.8-0.93V(RHE), was ascribed to reversible hydroxylation of the surface. Above 0.93V place exchange between adsorbed hydroxyl species and Pt occurs, and electrochemical irreversibility sets in. The place exchange is a rather slow process, and leads to complex aging behavior. In the potential range of ca. 1.0 to 1.2V (depending upon time factors) the peak potential of the subsequent reduction wave is independent of the total oxidation charge. This invariance was ascribed to constant Pt-O geometry, and the charge passed in this region was considered due to oxidative deprotonation of the hydroxyls previously incorporated into the surface. The above conclusions were based upon analysis of details of cyclic voltammetry curves. Optical studies showed that for oxidation up to a charge of 0.6e-/Pt the same value of the ellipsometric parameter ~ was observed for a given surface charge on both the anodic-going and cathodicgoing sweeps. For more complex oxidations the ~/Q curves for the anodic and cathodic sweeps diverged, suggesting that the oxidized species first formed was also the first reduced. This species was suggested to be the reversible hydroxyl groups residing at the surface. A change in the ~/Q slope at 0.5e-/Pt (anodic direction) was ascribed to the onset of formation of the deprotonated oxide. At 1.0 e-/Pt (1.13V) a further change was seen in the ~/Q slope, which then continued unchanged out to at least 2 e-/Pt. The identification of the individual chemical species in this complex scheme was indirect and has awaited confirmation by direct spectroscopic and structural studies. and Pt (+1V). Long polarization at 3.2...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

AES and TDS studies of electrochemically oxidized Pt(100)

Wagner

Ross

1985

Applied Surface Science

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“…The kinetics of oxide formation and reduction was studied by voltammetry and potentiostatic or galvanostatic techniques. 1,[4][5][6][7][8][9][10][11][12][13][14] The results were combined with spectroscopic methods and kinetic models were proposed for oxide formation and reduction. 5,15 Mathematical models were developed by hypothesizing several surface species and their rates for formation and reduction.…”

Section: Introductionmentioning

confidence: 99%

“…5 Under such circumstances, experimental investigation that examines the rate of oxide formation and reduction will help develop strategies for optimizing the potential range in practical PEFCs. Early work by Vetter and Schultze 14 shows that the rate of oxide formation and reduction can be described as Tafel equation having two state variables, namely, potential and oxide coverage. In their formulation, the same oxide coverage was selected as the initial condition before measuring the reduction rate because they observed that the properties of the oxide layer was influenced by formation conditions.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Oxide Formation and Reduction at Pt Catalyst in Polymer Electrolyte Fuel Cells

Suzuki

Morimoto

2016

Electrochemistry

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The rates of oxide formation and reduction at platinum catalyst in polymer electrolyte fuel cells were measured potentiostatically with various potential histories to reveal the kinetics of the reactions. Reaction rates during potential holds after an anodic or a cathodic sweep were examined as a function of potential and PtOH-equivalent oxide coverage. At 500 and 600 mV vs. RHE, the oxide coverage increased or decreased with increasing time depending on the potential history; this result indicates that the surfaces with different potential histories have different surface states. Oxide reduction rates were compared by changing potential and duration for oxide formation to attain the same coverage before the reduction. Oxide formed at a higher potential for a shorter period of time was easier to reduce than oxide formed at a lower potential for a longer period of time. This indicates that the oxide-formation potential and/or oxide-formation time are factors to determine the oxide reduction rate.

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“…As Belanger and Vijh (55) have correctly pointed out, the aim of the work performed by Vetter and Schultze (63)(64)(65) was different from that of Conway's group in that Vetter and Schultze were not concerned with the mechanism of the initial oxide formation. They found that the oxide charge (Qqx) is proportional to log t for t from 2 msec to 1000 sec in potentiostatic experiments with potentials between 1.0 V and 2.0 V, and that is proportional to potential for polarization times between 2 msec and 1000 sec.…”

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confidence: 97%

Electrocatalysis of the anodic oxidation of As(III) on platinum and other noble-metal electrodes

Cabelka

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The kinetics of the electrochemical formation and reduction of monomolecular oxide layers on platinum in 0.5 M H2SO4

Cited by 82 publications

References 28 publications

AES and TDS studies of electrochemically oxidized Pt(100)

AES and TDS studies of electrochemically oxidized Pt(100)

Kinetics of Oxide Formation and Reduction at Pt Catalyst in Polymer Electrolyte Fuel Cells

Electrocatalysis of the anodic oxidation of As(III) on platinum and other noble-metal electrodes

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