Surface-oxide growth at platinum electrodes in aqueous H2SO4

Jerkiewicz, Gregory; Vatankhah, Gholamreza; Lessard, Jean; Soriaga, Manuel P.; Park, Yeon-Su

doi:10.1016/j.electacta.2003.11.008

Cited by 230 publications

(356 citation statements)

References 32 publications

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“…Fundamentally they argued that the 10 formation of a hydroxyl species is not implicated in oxide formation above 0.8V(RHE) † , and so the hydroxyl species cannot be present. As a result of this paper some have even claimed that this has been 'unambiguously proven' 21 and that the initial oxide growth on Pt leads directly to the formation 15 of PtO 20,21,23 . In addition all the papers upon which Alsabet et al based their supporting arguments were done at potentials above 0.8 V [18][19][20][21][22][23] and as shall be demonstrated in this paper this potential may already be near the saturation coverage of hydroxyl species 20 and the onset of irreversibility could well be closer to the onset of formation a monolayer of oxide and not hydroxyl.…”

Section: Oxide Versus Hydroxyl Formationmentioning

confidence: 91%

“…As a result of this paper some have even claimed that this has been 'unambiguously proven' 21 and that the initial oxide growth on Pt leads directly to the formation 15 of PtO 20,21,23 . In addition all the papers upon which Alsabet et al based their supporting arguments were done at potentials above 0.8 V [18][19][20][21][22][23] and as shall be demonstrated in this paper this potential may already be near the saturation coverage of hydroxyl species 20 and the onset of irreversibility could well be closer to the onset of formation a monolayer of oxide and not hydroxyl. Therefore if the formation of hydroxyl is sufficiently fast at these potentials, then the caution that Harrington et al 20 added to their paper, that their observed transfer coefficient 25 could also be consistent with a slow one-electron transfer as the rate determining step followed by a further electron transfer in a faster step, may well need to be considered.…”

Section: Oxide Versus Hydroxyl Formationmentioning

confidence: 91%

See 1 more Smart Citation

The role of adsorbed hydroxyl species in the electrocatalytic carbon monoxide oxidation reaction on platinum

Kucernak

Offer

2008

Phys. Chem. Chem. Phys.

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The assumption that "OH ads " or other oxygen containing species is formed on polycrystalline or nanoparticulate platinum through a fast and reversible process at relatively low potentials is often made. In this paper we discuss the implications of this assumption and the difficulty in reconciling it with experimental phenomena. We show how presenting chrono-amperometric transients as log-10 log plots for potentials steps in the presence and absence of an adlayer of carbon monoxide o n polycrystalline platinum is particularly useful in understanding the time evolution of the CO oxidation reaction. When using log-log plots a clear power law decay can be observed in the transients both in the presence and absence of an adlayer of carbon monoxide. We explain this as an extension of current theory, such that the rate determining step in both cases is the formation of 15 a hydrogen bonded water-OH ads network, strongly influenced by anions, and that CO ads oxidation occurs, at least in part by the diffusion of OH ads through this network. We hypothesize that, at low potentials the formation of OH ads at active sites is fast and reversible but that transport of OH ads away from those sites may be rate limiting. The assumption that overall OH ads formation on platinum is fast and reversible is therefore highly dependent upon the platinum surface and th e 20 experimental conditions and it may not be appropriate for polycrystalline surfaces in sulphuric acid. Therefore, although the formation of OH ads on platinum in the absence of strongly adsorbing anions on 'ideal' surfaces is almost certainly fast and reversible, on realistic fuel cell relevant surfaces under non-ideal conditions this assumption cannot be made, and instead the formation of an OH ads adlayer may be somewhat slow and is associated with the formation of hydrogen bonded 25 water-OH ads networks on the surface. We expect this to be a more realistic description for what occurs during CO ads oxidation on fuel cell relevant catalysts which are highly heterogeneous and which have a highly defective surface. IntroductionThe formation of oxides on platinum surfaces at high potentials is relatively well studied yet contentious. The role of the species typically called "OH ads " in the surface catalysis of platinum catalysts is crucial in understanding a large 5 number of reactions, of which the most common example is the carbon monoxide oxidation reaction (COOR). The nature of this species is somewhat controversial, although Anderson has recently shown through theoretical ab initio charge selfconsistent methods that OH ads should form on a Pt surface at a 10 potential of about 0.6 V. Several investigators claim that OH ads is the species responsible for reacting with adsorbed CO ads , and that this is a chemical Langmuir-Hinshelwood (L-H) reaction [1][2][3][4][5][6][7] . The lowest potentials at which the COOR has been reported is 150 mV for carbon supported platinum 8 , 200 15 mV for a porous platinum electrode 9 and for polycrystalline platinum 10 , and ...

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Section: Oxide Versus Hydroxyl Formationmentioning

confidence: 91%

Section: Oxide Versus Hydroxyl Formationmentioning

confidence: 91%

The role of adsorbed hydroxyl species in the electrocatalytic carbon monoxide oxidation reaction on platinum

Kucernak

Offer

2008

Phys. Chem. Chem. Phys.

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“…Similar results were reported by Vetter and Schultze through galvanostatic measurements for polycrystalline Pt in H 2 SO 4 . 15 At ª < 0.07, deviation from Tafel equation is observed in the low current density region. Particularly, the current density is above the extrapolated Tafel lines for oxide formation.…”

Section: Oxide Formation/reduction Without Preceding Potential Holdmentioning

confidence: 99%

“…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. 5,[16][17][18] The effect of parameters in the models on voltammograms was discussed, or the models were validated by appropriate selection of parameters that reproduce experimental voltammograms.…”

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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“…Thus, the CVs are represented in the limited range of 0.81.5 V. Almost all of the anodic current observed in Fig. 2(b) is attributed to the PtO formation 27) or the adsorption of oxygen species (OH ad , O ad ):…”

Section: Microelectrochemical Measurementsmentioning

confidence: 99%

Microelectrochemical Study on the Surface Oxidation of Pt: The Effects of Crystal Orientation and Grain Boundary

et al. 2014

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Microelectrochemical polarization measurements of polycrystalline Pt were performed to clarify the effect of the crystal orientation and grain boundary on the surface oxidation of Pt. Cyclic voltammograms (CV) for Pt(100)-like and Pt(110)-like grains on polycrystalline Pt after mechanical polishing showed no anodic peak below 1.35 V, which is similar to that for well-annealed Pt(111) single crystal. The anodic current of Pt(110)-like grain was significantly larger than Pt(100)-like. A small but concrete current increase appeared around 1.051.3 V in the CV of the surface including grain boundaries. This suggests the grain boundary may be the preferential site for the dissolution.

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Surface-oxide growth at platinum electrodes in aqueous H2SO4

Cited by 230 publications

References 32 publications

The role of adsorbed hydroxyl species in the electrocatalytic carbon monoxide oxidation reaction on platinum

The role of adsorbed hydroxyl species in the electrocatalytic carbon monoxide oxidation reaction on platinum

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

Microelectrochemical Study on the Surface Oxidation of Pt: The Effects of Crystal Orientation and Grain Boundary

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