Adsorption and electrooxidation of carbon monoxide on polycrystalline platinum at pH 0.3–13

Couto, Andréa Boldarini; Rincón, A.; Pérez, M.C.; Gutiérrez, C.

doi:10.1016/s0013-4686(00)00714-3

Cited by 64 publications

(55 citation statements)

References 26 publications

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“…2b), agreeing again with previous observations in alkaline media for the same polycrystalline substrate 37 and Pt single crystals. 39,40 Considering the role of OH ad in the CO oxidation reaction (cf.…”

Section: Resultssupporting

confidence: 92%

“…37 for a Pt PC electrode voltammetrically-cleaned and tested in 0.5 M HClO 4 , but differs slightly from those observed for flame-annealed 38 or sputteredcleaned 27 Pt PC in H 2 SO 4 media, whereby a pre-wave some tens of millivolts negative of the main oxidation feature was observed. While these differences in the CO-stripping profiles are beyond the scope of this study, they are likely related to the different electrode preparation procedures and/or to the nature of the acids used in each study [i.e, the weakly-adsorbing ClO 4 − used herein and in Ref.…”

Section: Resultscontrasting

confidence: 54%

“…While these differences in the CO-stripping profiles are beyond the scope of this study, they are likely related to the different electrode preparation procedures and/or to the nature of the acids used in each study [i.e, the weakly-adsorbing ClO 4 − used herein and in Ref. 37, vs. the strongly adsorbed (bi)sulfate in Refs. 27 and 38].…”

Section: Resultsmentioning

confidence: 99%

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Kinetics of the Hydrogen Oxidation/Evolution Reaction on Polycrystalline Platinum in Alkaline Electrolyte Reaction Order with Respect to Hydrogen Pressure

Rheinländer

Herranz

Durst

et al. 2014

J. Electrochem. Soc.

222

236

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The hydrogen oxidation and evolution reactions (HOR, HER) are of key importance to the development of novel alkaline membrane fuel cells and electrolyzers, which feature a potential cost advantage over their acid-operating counterparts. However, their mechanism remains poorly understood even on the most catalytically-active platinum surfaces, for which such a fundamental parameter as the reactions' order with respect to the hydrogen concentration is still unknown. With this motivation, we have performed rotating disc electrode measurements on polycrystalline Pt in 0.1 M NaOH with different hydrogen partial pressures (between 10 and 100 kPa H 2 ), from which we have derived a reaction order of 1/2. The latter value has important implications in the procedure to follow in order to derive kinetic currents free of diffusion contributions. More precisely, the HOR currents must be corrected for the diffusion overpotential and converted into a mass-transport free kinetic current using a modified version of the Koutecky-Levich equation that takes into consideration this non-unit reaction order, while the HER side only needs to be ohmically compensated due to the impossibility to supersaturate the electrolye with H 2 . Most importantly, our results point at a mechanism consisting of a dissociative adsorption (Tafel) reaction combined with a one-electron transfer (Volmer) rate-determining step, in terms consistent with the well-established view of the hydrogen-bonding strength as the main HOR/HER activity descriptor. The electrochemical oxidation and evolution of molecular hydrogen are the key reactions at play in the anodes and cathodes of fuel cells and electrolyzers, respectively, which are likely energy conversion and storage devices for renewable energy concepts based on the use of H 2 as energy carrier. Beyond this practical interest, the hydrogen oxidation and evolution reactions (HOR and HER, respectively) have also played a pivotal role in the historical development of fundamental electrocatalysis theories. Indeed, the exponential relation between current and overpotential that describes the kinetics of many electrochemical reactions, viz., the Butler-Volmer equation, was originally validated for the HER, 1 which also became the first electrochemical process for which the rate-determining role of the bond strength of adsorbed intermediates (following Sabatier's principle) was verified.2 Thus, the HOR/HER has become one of the most extensively studied electrochemical reactions, particularly at low pH values and on the catalytically most active platinum-based materials relevant to proton exchange membrane fuel cells (PEMFCs) and electrolyzers. In acid electrolytes, the HOR/HER kinetics on platinum electrodes are extremely fast, so that experimental methods which afford very high mass-transport rates are required in order to unambiguously differentiate kinetic-and diffusion-overpotentials (e.g., hydrogen pump experiments in PEMFC 3 or the recently developed floating porous gas diffusion electrode method 4 ). Using t...

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Section: Resultssupporting

confidence: 92%

Section: Resultscontrasting

confidence: 54%

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Kinetics of the Hydrogen Oxidation/Evolution Reaction on Polycrystalline Platinum in Alkaline Electrolyte Reaction Order with Respect to Hydrogen Pressure

Rheinländer

Herranz

Durst

et al. 2014

J. Electrochem. Soc.

222

236

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“…The relative surface coverage values are thus perturbed, and if mass transport of CO is relatively low then an extended steady-state oxidation process is observed on the reverse scan before CO ads species again dominate. [37] Two CO oxidation features have previously been noted in the literature, [34,38] namely a stripping peak corresponding to the oxidation of bridge-and linear-chemisorbed CO on the Pt, and in quiescent solution a prior, more cathodic peak, corresponding to the oxidation of solution phase CO at CO-free Pt islands. [38] These islands are believed to extend up to 3 mm in diameter, and are lost when the solution is agitated due to increased mass-transport of CO. [38] Therefore such islands are not expected at a microelectrode where mass-transport to the electrode surface is already relatively high, and only one single (chemisorbed CO) stripping peak was observed.…”

Section: Electrochemistry Of Hydrazine In Co-saturated Solutionsmentioning

confidence: 91%

Towards Mixed Fuels: The Electrochemistry of Hydrazine in the Presence of Methanol and Formic Acid

Aldous

Compton

2011

ChemPhysChem

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The electrochemistry of formic acid, carbon monoxide and methanol have been investigated and evaluated in combination with hydrazine. Hydrazine was observed to display the anticipated steady-state oxidation waves at platinum (Pt) microelectrodes by cyclic voltammetry, and upon introduction of carbon monoxide (CO) gas, the Pt surface was fully passivated (prior to CO oxidation). However, the two individual responses of hydrazine and formic acid (HCOOH) are to be additive when combined in solution. No detrimental effects were observed upon the hydrazine voltammetry, even in the presence of excess formic acid, despite formic acid clearly displaying characteristic self-poisoning tendencies (primarily due to the formation of CO) in its own voltammetry. Effects intermediate to those of CO and formic acid were observed when methanol was present. Currents were essentially additive at low methanol content, but hydrazine oxidation current decreased by about 40% when an 100-fold excess of methanol was present, corresponding to poisoning by methanol dehydrogenation intermediates. These results are discussed with relevance to mixed fuels for more flexible or powerful fuel cells, and the possible formation of a random microelectrode array (templated by strongly adsorbed poison) on the microelectrode surface.

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“…Such conclusion comes from different studies using basal planes and stepped Pt electrodes [6]. In addition, it is also well-known that the CO electro-oxidation reaction on platinum electrodes strongly depends on the surface composition and the electrolyte solution (acidic or alkaline) [7][8][9], as well as the nature of both cations [10] and anions [11]. For Pt(s)-[(n-1)(111)×(110)] electrodes in acid medium, potentiostatic CO stripping experiments at full coverage are characterized by the presence of a single CO oxidation peak [2,6,12].…”

Section: Introductionmentioning

confidence: 99%

On the behavior of CO oxidation on shape-controlled Pt nanoparticles in alkaline medium

Farias

Vidal‐Iglesias

Solla-Gullón

et al. 2014

Journal of Electroanalytical Chemistry

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In this work, the behavior of the CO electro-oxidation reaction on shape-controlled Pt nanoparticles in alkaline medium was examined in order to understand the effect of the surface structure on this reaction. A series of experiments using Pt nanoparticles of different surface structures/shapes was used and the results obtained were compared with the previous knowledge gained from stepped platinum single crystal electrodes. Independently of the preferential orientation of the nanoparticles, the CO oxidation voltammetry exhibits two main peaks: one at ca. 0.56-059 V and the second one at 0.66 -0.67 V, being the intensity of the peaks dependent on the shape of the nanoparticle. These two peaks have been assigned to the oxidation of CO on the (111) terraces and on the rest of the sites, respectively. The appearance of two differentiated peaks reveals that these (111) terraces and the rest of the sites on the nanoparticle surface behave independently of the presence of the other type of sites, that is, they are not connected. The results are discussed considering the effects of the surface mobility of CO and of the OH adsorption properties on the different sites in the oxidation peaks.

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Adsorption and electrooxidation of carbon monoxide on polycrystalline platinum at pH 0.3–13

Cited by 64 publications

References 26 publications

Kinetics of the Hydrogen Oxidation/Evolution Reaction on Polycrystalline Platinum in Alkaline Electrolyte Reaction Order with Respect to Hydrogen Pressure

Kinetics of the Hydrogen Oxidation/Evolution Reaction on Polycrystalline Platinum in Alkaline Electrolyte Reaction Order with Respect to Hydrogen Pressure

Towards Mixed Fuels: The Electrochemistry of Hydrazine in the Presence of Methanol and Formic Acid

On the behavior of CO oxidation on shape-controlled Pt nanoparticles in alkaline medium

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