The Electrolytic Formation and Dissolution of Oxide Films on Platinum

Laitinen, Herbert A.; Enke, Christie G.

doi:10.1149/1.2427886

Cited by 167 publications

(112 citation statements)

References 16 publications

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“…62 The reduction of oxide to hydrogen peroxide, which is also suggested in the literature, 63 has not been confirmed 62 but cannot be completely excluded. In this view, the smaller reduction peak in the presence of [2-Sea + ][TfO − ] could either be due to the formation of a thinner oxide layer or only a partial reduction of PtO involving the formation of H 2 O 2 .…”

Section: Resultsmentioning

confidence: 94%

2-Sulfoethylammonium Trifluoromethanesulfonate as an Ionic Liquid for High Temperature PEM Fuel Cells

Wippermann

Wackerl

Lehnert

et al. 2015

J. Electrochem. Soc.

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Tafel Oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFC).-High temperature polymer electrolyte fuel cells (HT-PEFCs) are currently based on phosphoric acid-doped polybenzimidazole-type membranes (PBI) and are operated in a temperature range of 120-180• C. HT-PEFCs have several advantages over low temperature PEFCs, such as: easier water and heat management, the possibility of recovering high-grade waste heat, a more compact cooling system and a higher CO tolerance by the anode catalyst.However, a major drawback of HT-PEFCs is the sluggish oxygen reduction reaction (ORR) kinetics in the presence of phosphoric acid. This is primarily caused by three effects: (i) The inhibition effect of phosphoric acid on the ORR because of the poisoning of the Pt catalyst due to the adsorption of the H 3 PO 4 species onto active catalyst sites. (ii) The low solubility of oxygen in phosphoric acid. (iii) The slow diffusion of oxygen through the film of phosphoric acid which covers the platinum catalyst.The adsorption of phosphate by platinum has been studied for more than 30 years 1-15 by means of cyclic voltammetry (CV), [2][3][4][5]9,[11][12][13][14][16][17][18][19][20][21] rotating disc electrode measurements (RDE), [2][3][4][5]8,9,11,13,14 electrochemical impedance spectroscopy (EIS), 13,16,22 transient measurements, 9,23,24 Fourier transform infrared spectroscopy (FTIR), 20,25-27 electrochemical quartz crystal microbalance (QCM), 18 radio tracer experiments, 28 X-ray photoelectron spectroscopy (XPS) 17 and X-ray absorption spectroscopy (XAS). 14,15 The in-operando XAS measurements recently published by Kaserer et al. show the adsorption behavior of H 3 PO 4 species on Pt/C fuel cell cathode catalysts in the temperature range of 50-170• C under the operating conditions of an HT-PEFC. 15In diluted aqueous solutions and at moderate temperatures, sulphuric acid and sulfonic acids like methanesulfonic acid (MSA) or trifluoromethanesulfonic acid (triflic acid, TFMSA) have been found to be less poisonous than phosphoric acid because sulfonate groups are less strongly adsorbed on Pt. 3,29,30 For example, Zelenay et al.,29 in a comparative study of phosphoric acid and TFMSA, showed that * Electrochemical Society Active Member. z E-mail: k.wippermann@fz-juelich.de 0.02 M TFMSA is indeed less strongly adsorbed by comparison to 0.02 M phosphoric acid at room temperature. However, the free space available for oxygen reduction is found to be similar at elevated temperatures and for concentrated solutions. 29 Under these conditions, the advantage of TFMSA lies in its higher oxygen solubility and diffusivity rather than its poisoning effect. 29 Although this result cannot be generalized, it still indicates the importance of oxygen solubility and the diffusion coefficient of oxygen in the electrolyte being used. Proton conducting ionic liquids (PIL).-With respect to alternative electrolytes for HT-PEFCs, proton-conducting ionic liquids (PILs) appear to be suitable, as they do not rely on solvents like water. Moreover...

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Section: Resultsmentioning

confidence: 94%

2-Sulfoethylammonium Trifluoromethanesulfonate as an Ionic Liquid for High Temperature PEM Fuel Cells

Wippermann

Wackerl

Lehnert

et al. 2015

J. Electrochem. Soc.

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“…This peak has been assigned to the oxidation of Pt to PtO. Based on the previous literature data 4,5,6,7,8,9 the three oxidation peaks of EtOH in Figure 11 were assigned as follows: 3 CHO to CH 3 COOH will also take place. The poisoning of the electrode occurs by the formation of PtO when the reaction A is faster than reaction B.…”

Section: Summary and Scopementioning

confidence: 84%

Scholarly Research Program. Delivery Order 0007: Characterization of Ionic Liquids as Fuel Cell Electrolytes

Keitz¹,

Katović²,

Davidson³

2004

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“…Measurements were not extended above 1. 8 v to avoid permanent damage to the electrode (1) resulting in part, perhaps, from extensive oxidation at the grain boundaries (11). A series of runs in which the time of anodization was varied showed that the charge obtained after 5 min.…”

Section: Reduction Curvesmentioning

confidence: 99%

Electrochemistry of Fuel Cell Electrodes. Surface Oxidation of Gold Electrodes

Brummer¹,

Makrides²

1963

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The surface oxides formed on electropolished gold by potentiostatic anodization in the range 1.2-1. 8 v vs. Fr/H^in the same solution, hnve bacn studied by galvanostatic reduction at current densities between 10 and 100C^ta-/errir Molar perchlorate solutions of pH 0. 04 to 2. 1 were employed. The extent of oxide formation is determined by the potential of anodization, the charge increasing linearly with the potential of formation in the range of 1.4 to 1.8 v. Cathodic chronopotentiograins show that reduction of the oxide occurs at a definite potential which depends on the cathodic current density. Current-potential curves, constructed from the chronopotentiograms, TMlow a Tafel relation with a slope of 41 mV. The exchange current for okide reduction decreases with pH and with increasing potential of formation of the oxide. The electrochemical order of the reduction reaction\is -1. 65 with respect to pH. A mechanism for reduction is suggested in wtfiich it is assumed that the reduction of an intermediate (Au ) is the slo in the overall process.

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The Electrolytic Formation and Dissolution of Oxide Films on Platinum

Cited by 167 publications

References 16 publications

2-Sulfoethylammonium Trifluoromethanesulfonate as an Ionic Liquid for High Temperature PEM Fuel Cells

2-Sulfoethylammonium Trifluoromethanesulfonate as an Ionic Liquid for High Temperature PEM Fuel Cells

Scholarly Research Program. Delivery Order 0007: Characterization of Ionic Liquids as Fuel Cell Electrolytes

Electrochemistry of Fuel Cell Electrodes. Surface Oxidation of Gold Electrodes

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