Application of the Flooded‐Agglomerate Model to Study Oxygen Reduction on Thin Porous Coating Rotating Disk Electrode

Perez, Joelma; Tanaka, Auro Atsushi; González, Ernesto Rafael; Ticianelli, Edson A.

doi:10.1149/1.2054744

Cited by 64 publications

(57 citation statements)

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“…32 One of the electrochemical methods that has allowed a close study of certain electrode reactions on supported catalysts is the thin porous coating rotating disk electrode (TPC/RDE). 33 This technique was used for the study of oxygen reduction, [34][35][36] and methanol oxidation 37 on carbon supported catalysts, allowing kinetic and mechanistic characterizations. In this work, the TPC/RDE technique was used to study the activity of several Pt-Ru/C electrocatalysts for the oxidation of CO prepared by different methods which were eventually submitted to a thermal treatment in a hydrogen atmosphere.…”

Section: Introductionmentioning

confidence: 99%

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Carbon monoxide oxidation on Pt-Ru electrocatalysts supported on high surface area carbon

Colmati¹,

Lizcano-Valbuena²,

Câmara³

et al. 2002

J. Braz. Chem. Soc.

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Este trabalho descreve a preparação e caracterização de ligas dispersas de Pt-Ru sobre carbono de alta área superficial, as quais foram avaliadas para a oxidação de CO em eletrodos de disco rotatório/camada fina porosa e para a oxidação de hidrogênio em células a combustível de eletrólito polimérico alimentadas com hidrogênio contendo 100 ppm de CO. Tratamentos térmicos (H 2 , 300 °C) aplicados aos catalisadores melhoram a tolerância a pequenas quantidades de CO e, em alguns casos, reduzem o potencial necessário para promover a oxidação de CO durante a varredura do potencial. Sob condições operacionais em uma célula a combustível na presença de CO, foi observado que os melhores resultados foram obtidos quando a liga Pt-Ru/C foi preparada por redução simultânea dos íons Pt (IV) e Ru (III), diferentemente da redução seqüencial.This work describes the preparation and characterization of Pt-Ru alloys dispersed on high surface area carbon, which were evaluated for CO oxidation on thin porous coating rotating disk electrodes and for hydrogen oxidation on polymer electrolyte fuel cells fed with hydrogen containing 100 ppm CO. A thermal treatment (H 2 , 300 o C) applied to the catalysts improves the tolerance to small quantities of CO and, in some cases, reduces the potential necessary to promote the CO oxidation during a linear potential scan. Under operational conditions in a fuel cell in the presence of CO it was observed that the best results were obtained when the Pt-Ru/C alloy was prepared by simultaneous reduction of the ions Pt (IV) and Ru (III), as opposed to a sequential reduction.Keywords: carbon monoxide, Pt-Ru alloys, supported catalysts, thermal treatment IntroductionIn recent years there has been a steadily growing concern with the degradation of the environment and the effect of pollutants on human health.1 High levels of pollutants are produced by internal combustion engines, particularly those running on diesel, in large urban centers. Today, the use of clean energy sources is considered an urgent necessity and, among the alternatives, fuel cells are attracting much interest.2 In particular, polymer electrolyte membrane fuel cells (PEMFC), are considered good candidates for transportation and portable applications because they are capable of delivering high power densities and can start operating at room temperature.In spite of the efforts to develop the direct methanol fuel cell (DMFC), which has the advantage of using a liquid fuel, the most efficient low temperature fuel cells still use hydrogen as fuel. The cheapest way of producing hydrogen is by reforming fossil fuels or low molecular weight alcohols.3 This process produces 6-7% CO, which can be reduced to 1-2% by a shift reaction and to levels smaller than 100 ppm by partial oxidation. 4 This CO adsorbs strongly on the Pt catalyst of the fuel cell electrode inhibiting the anodic reaction. The DMFC is not free of this problem, because the oxidation of methanol on Pt produces CO as an intermediate. 5 The possibility of using PEMFC in transportatio...

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Section: Introductionmentioning

confidence: 99%

“…works. [34][35][36] The TPC/RDE was constructed using a PTFE cylinder with a cavity 0.15 mm deep and 0.19 cm 2 area. The carbon supported catalyst was agglomerated with a 6% PTFE suspension (DuPont) and placed in the cavity.…”

mentioning

confidence: 99%

Carbon monoxide oxidation on Pt-Ru electrocatalysts supported on high surface area carbon

Colmati¹,

Lizcano-Valbuena²,

Câmara³

et al. 2002

J. Braz. Chem. Soc.

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“…[39][40][41] Otherwise, the EIS of ORR on Pt in a three-electrode RDE system is seldom reported in the literature. Most importantly, the EI spectra of ORR in RDE configuration are entirely different from those of the theoretical and experimental impedance spectra consisting of two or three semi-circles reported in literature on fuel cell cathode with porous gas-diffusion electrode.…”

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confidence: 99%

Electrochemical Impedance Spectroscopy of Oxygen Reduction Reaction (ORR) in a Rotating Disk Electrode Configuration: Effect of Ionomer Content and Carbon-Support

Singh

Devivaraprasad

Kar

et al. 2015

J. Electrochem. Soc.

151

112

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Oxygen reduction reaction (ORR) in acidic media is investigated at various potentials in a thin-film rotating disk electrode (TF-RDE) configuration using electrochemical impedance spectroscopy (EIS). The ionomer-free and ionomer-containing thin-film catalyst layers are composed of Pt black and carbon-supported Pt catalysts of different metal loadings (5 and 20 wt%). The simplest EI spectrum consisting of an arc or a semi-circle is obtained at high potentials with ionomer-free Pt catalyst layers. The most complex spectrum consisting of a high frequency (HF) arc and two semi-circles is observed in the mixed diffusion-controlled region of the ionomer-containing catalyst layer with high loading of carbon-supported Pt. The nature of the EI spectrum is decided by the constituents of the thin-film catalyst layer and by the operating potential. The evolution of the EI spectra with ionomer and carbon contents is underlined. The effect of rotation rate (rpm) of the electrode on the impedance spectrum is also investigated. A series of equivalent circuits is required to completely describe the EI spectra of ORR. The kinetic parameters and the electrochemical surface area of the catalysts are derived from the impedance spectrum. Oxygen reduction reaction (ORR) is one of the most important reactions at the cathode side in low-temperature fuel cells (e.g., polymer electrolyte fuel cells (PEFCs) and direct methanol fuel cells (DMFCs)) and metal-air batteries.1-14 Because of the sluggish ORR kinetics and the stability issues of the catalyst in the electrochemical environment, expensive precious metal catalysts are often used in these electrochemical devices to catalyze the ORR. 15 Conventionally, the performance of the catalyst is evaluated in an operating fuel cell mode using the DC methods. [16][17][18] The information gathered from a DC analysis usually provides the sum of various polarizations of the electrode, which is difficult to separate into individual contributions. 19 On the other hand, electrochemical impedance spectroscopy (EIS), one of the AC methods, is a sensitive tool to investigate electrode-electrolyte interface and it allows the simultaneous resolution of various charge-transfer and mass-transfer processes (kinetic, ohmic, and diffusion). It involves a small sinusoidal electrical perturbation around a steady-state value and measures the impedance along with the phase angle. However, the interpretation of the EI spectra is difficult. Often, simple fitting models based on equivalent circuit analogues and physical models are used to extract the parameters those represent the underlying cell processes. [20][21][22][23][24][25][26] Springer et al. proposed the theoretical impedance spectrum of ORR on porous gas-diffusion electrode using the flooded-agglomerate electrode model in series with a thin electrolyte film. 20,25 The model predicted by Raistrick shows three semi-circles in the spectrum attributed to the charge-transfer process (ORR); agglomerate diffusion (depletion of the oxygen concentration in the pores...

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“…The high values (theoretical value: 120 mV dec −1 [35]) are most likely due to the same effects that are described above. The shift in the Tafel slope due to the transition from the low to the high current density regime is commonly observed, and can be explained by different effects: (i) A change of the charge-transfer coefficient [37,38], (ii) different reactant adsorption mechanisms (Temkin vs. Langmuir mechanism for low and high current regimes, respectively) [35,39], (iii) a change in surface coverage with oxygen-containing species [40], and (iv) further porosity related diffusion effects [41,42]. …”

Section: Oxygen Reduction Activitymentioning

confidence: 99%

Improved stability of mesoporous carbon fuel cell catalyst support through incorporation of TiO2

Bauer

Song

Ignaszak

et al. 2010

Electrochimica Acta

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The electrochemical stability of Pt deposited on mesoporous carbon, which was either applied in its unmodified state or coated with 20 wt% TiO 2 , was investigated by cyclic voltammetry in N 2 purged 0.5 M sulfuric acid. XRD analysis revealed that TiO 2 was present in the anatase phase. The mean Pt particle diameter was ∼6 and ∼4 nm for mesoporous carbon with and without TiO 2 , respectively. Pt supported on TiO 2 modified substrates was more stable than Pt supported on conventional mesoporous carbon when subjected to 1000 cycles in the potential range from 0.05 to 1.25 V vs. RHE. This was evident from the observation that the support with TiO 2 retained ∼53% of the electrochemically active surface area relative to the state observed after 100 cycles, whereas ∼33% of the active area remained in the case without TiO 2 . The oxygen reduction mass activity was identical for both fresh samples (i.e., 18 A g −1 Pt). After 1000 cycles the mass activity decreased to 10 A g −1 Pt for the case without TiO 2 , whereas with TiO 2 the deactivation was minor; i.e., the mass activity after 1000 cycles was 17 A g .

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Application of the Flooded‐Agglomerate Model to Study Oxygen Reduction on Thin Porous Coating Rotating Disk Electrode

Cited by 64 publications

References 4 publications

Carbon monoxide oxidation on Pt-Ru electrocatalysts supported on high surface area carbon

Carbon monoxide oxidation on Pt-Ru electrocatalysts supported on high surface area carbon

Electrochemical Impedance Spectroscopy of Oxygen Reduction Reaction (ORR) in a Rotating Disk Electrode Configuration: Effect of Ionomer Content and Carbon-Support

Improved stability of mesoporous carbon fuel cell catalyst support through incorporation of TiO2

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