Electrode kinetics of oxygen reduction on platinum in trifluoromethanesulphonic acid

Hsueh, Kan‐Lin; Chang, Howard H.; Chin, D.‐T.; Srinivasan, S.

doi:10.1016/0013-4686(95)80004-2

Cited by 20 publications

(18 citation statements)

References 7 publications

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“…Figure 2 shows typical cyclic voltammograms ͑CVs͒ for the cathode at 80°C in N 2 after the injection of pure H 2 O, TFMSA, and SA for 1 h. The shape of the CV for 5 mM TFMSA was almost identical with that for pure H 2 O, due to the weak adsorption of the TFMSA anion. 9 In contrast, for 5 mM SA, additional hydrogen adsorption/ desorption peaks appeared at ca. 0.2 V, and the onset of the surface oxide formation shifted to a more positive potential.…”

Section: Resultsmentioning

confidence: 90%

Influence of Decomposition Products from Perfluorosulfonic Acid Membrane on Fuel Cell Performance

Kabasawa

Uchida²,

Watanabe

2008

Electrochem. Solid-State Lett.

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The influence of decomposition products from perfluorosulfonic acid ͑PFSA͒ membrane on fuel cell performance was investigated by a proposed method. Aqueous solutions of various model compounds, acting as possible decomposition products from the PFSA membrane, were injected directly into a pristine cell, and changes in the cell performance were measured. The injection of sulfuric acid ͑SA͒ and perfluorocarboxylic acids ͑PFCAs͒ decreased the cell voltage, which was attributed to a decrease in the mass activity for the oxidation reduction reaction ͑ORR͒. It was found that specifically adsorbed SA and PFCAs blocked the ORR at practical cathode potentials ͑Ͼ0.6 V͒.The polymer electrolyte fuel cell ͑PEFC͒ is a promising energy source for residential cogeneration systems and electric vehicles. Perfluorosulfonic acid ͑PFSA͒ membrane materials, such as Nafion, are commonly used as the electrolyte for PEFCs due to their high conductivity and chemical stability. However, the durability of the PFSA membrane is still insufficient for the commercialization of the PEFC. 1 The mechanism of the degradation of PFSA membranes has been investigated. 1-7 Hydrogen peroxide ͑H 2 O 2 ͒ is generated at both the anode and cathode, resulting from the Pt-catalyzed reaction between the cross-over of reactant gases ͑H 2 and O 2 ͒, 1-3 or simply at the cathode, accompanying the oxygen reduction reaction ͑ORR͒. 1,4 It has been clarified that radical species, such as the hydroxyl radical ͑·OH͒, which is produced from H 2 O 2 , can decompose PFSA membranes. 1-3 During practical fuel-cell operation, various decomposition products were detected by nuclear magnetic resonance, 5 mass spectrometry, 5,6 and ion chromatography 7 ͑e.g., fluoride ions, 5,7 sulfate ions, 7 low-molecular-weight perfluorosulfonic acids, 5 and related compounds͒. 6 Such decomposition of PFSA resulted in measurable decreases in the membrane thickness. 5 It has not been clarified, however, how the individual decomposition products themselves affect the cell performance, because both the electrolyte ͑in the membrane itself, as well as within the catalyst layer͒ and the Pt/C catalyst degrade simultaneously during durability testing.In the present paper, we propose a direct and simple method to evaluate the influence of the decomposition products on the cell performance. Aqueous solutions of various model compounds, acting as the decomposition products from PFSA, were injected directly into the pristine cell ͑without degradation͒, and changes in the cell performance were measured. It was found that sulfuric acid and perfluorocarboxlic acids suppress the ORR activity at Pt/C, probably due to their specific adsorption and blockage of the electrocatalytically active Pt sites. ExperimentalPreparation of membrane-electrode assemblies.-Gas diffusion electrodes with a three-layer structure ͑carbon paper/gas diffusion layer/catalyst layer͒ were prepared in the same manner as in our previous work. 8 The geometric electrode area was 25 cm 2 , and the Pt loading amount in the electrodes was ...

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Section: Resultsmentioning

confidence: 90%

Influence of Decomposition Products from Perfluorosulfonic Acid Membrane on Fuel Cell Performance

Kabasawa

Uchida²,

Watanabe

2008

Electrochem. Solid-State Lett.

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“…The ORR is much more complicated. And there is already a longstanding controversy on the order of the ORR on Pt. − On Au, the adsorption energy of O decreases with increasing coverage according to the theoretical calculations, and this energy is the main barrier for the ORR on Au; thus, the order of ORR on Au could be higher than 1.…”

Section: Resultsmentioning

confidence: 99%

Determination of the Electron Transfer Number for the Oxygen Reduction Reaction: From Theory to Experiment

et al. 2016

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The forced convection methods on the rotating disk and ring-disk electrodes are carefully analyzed toward their use for calculation of the electron transfer number (n) for the oxygen reduction reaction (ORR) on various catalysts. It is shown that the widely used Koutechy–Levich (KL) method is not suitable to determine n for the ORR either theoretically or experimentally. From a theoretical viewpoint, the ORR is neither a single-step nor a one-way reaction and , therefore does not fulfill the assumptions of the KL method. From an experimental viewpoint, n is significantly dependent on the angular velocity of the rotating disk electrode, contradicting the assumption of constant n in the KL theory. An improved model is used to establish the aforementioned relationship between n and angular velocity. The recommended way to determine n for the ORR in alkaline electrolytes is to use the rotating ring-disk electrode with a properly biased Au ring, supplemented by the calibration of the collection efficiency.

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“…In CH~COOK solution, 02 is predominantly reduced through a four-electron reaction 02 + 2H20 + 4e-= 4 OH- [6] and a two electron process also occurs in K2SO4 and KC1 solutions 02+H20+2e =HO2_+OH- [7] The current ratios, x, of the four-electron and two-electron reactions for 02 reduction, calculated from the intercept in various solutions, are shown in Table I K2SO4, the H202 produced is about 8.8%. In 1M CH3COOK solution, the two-electron process is only about 1.7%, with formation of about 3.3% H202, indicating that O2 is principally reduced through a four-electron reaction.…”

Section: -mentioning

confidence: 99%

Reactive Deposition of Cobalt Electrodes: V . Mechanistic Studies of Oxygen Reduction in Unbuffered Neutral Solutions Saturated with Oxygen

Jiang

Cui

Tseung

1991

J. Electrochem. Soc.

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The mechanism and kinetics of oxygen reduction were studied with a rotating Pt ring-Ni disk electrode in unbuffered neutral solutions saturated with oxygen. It was found that oxygen reduction is a first-order reaction with respect to the oxygen concentration in unbuffered neutral solutions. The current ratio of the two-electron reaction is about 18.2% in KC1 solution, as compared to 4.6% in K2SO4 solution and only 1.7% in CH3COOK. The presence of C1-ions in the solution greatly promotes the two electron process, with the production of about 30.8% hydrogen peroxide. A mechanism involving a determining step of the first charge transfer under Langmuir adsorption conditions has been proposed for 02 reduction in chloride solutions. However, in CH3COOK, O2 is primarily reduced through a four-electron reaction, since little hydrogen peroxide has been detected. In cobalt solutions, Co(OH)2 is formed at the electrode surface as the result of the preceding 02 reduction. It has been confirmed that the formation of the Co(OH)2 as well as its stability are directly related to the mechansim and kinetics of 02 reduction. ABSTRACTExperiments to study anomalous codeposition of iron and nickel were conducted from 0.5M NiSO4 and 0.5M FeSO4 solutions with pH adjusted to 3 with H2SO4, using a rotating disk electrode. The effect of adding 0.01M B(OH)3 to the plating bath was also investigated. Anomalous codeposition occurred for all electrode rotational speeds and applied potentials considered. Boric acid was found neither to affect alloy deposition current efficiency, nor to eliminate anomalous codeposition for the experimental conditions investigated. Cyclic voltammetry indicates that a borate complex formed at -1.0 V

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Electrode kinetics of oxygen reduction on platinum in trifluoromethanesulphonic acid

Cited by 20 publications

References 7 publications

Influence of Decomposition Products from Perfluorosulfonic Acid Membrane on Fuel Cell Performance

Influence of Decomposition Products from Perfluorosulfonic Acid Membrane on Fuel Cell Performance

Determination of the Electron Transfer Number for the Oxygen Reduction Reaction: From Theory to Experiment

Reactive Deposition of Cobalt Electrodes: V . Mechanistic Studies of Oxygen Reduction in Unbuffered Neutral Solutions Saturated with Oxygen

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