New findings on CO electrooxidation at platinum nanoparticle surfaces

Brimaud, Sylvain; Pronier, Stéphane; Coutanceau, Christophe; Léger, Jean‐Michel

doi:10.1016/j.elecom.2008.08.045

Cited by 68 publications

(70 citation statements)

References 20 publications

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“…15 It was found that the OCP value in the 0. solution is 0.25 V (Figure 3a). The voltammetric stripping carried out from this potential in the solution free of HCOOH (Figure 3b) shows an electrooxidation peak at 0.76 V. Both, electrochemical, 28,29 and spectroscopic, 8,9,[20][21][22] evidences indicate that this peak corresponds to the CO ad species. Thus, it is likely that in these conditions the following spontaneous dissociative adsorption is produced,…”

Section: Discussionmentioning

confidence: 99%

Kinetic Study of the Formic Acid Oxidation on Steady State Using a Flow Cell

Luque

Chialvo

2017

J. Electrochem. Soc.

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The formic acid oxidation (FAO) reaction is studied on platinum in acid solutions using a specially designed flow cell and different experimental techniques, such as open circuit potential decay, chronoamperometry, voltammetric stripping, HCOOH concentration pulses and rotating disc electrode. It allows for the first time the evaluation of the surface coverage of irreversibly adsorbed reaction intermediates on steady state conditions. It is found that the unique species adsorbed irreversibly is CO (E < 0.5 V). It is demonstrated that at higher potentials the adsorption of the intermediate species involved in the FAO is highly reversible and their decomposition is the rate determining step. From the analysis of the results and taken into account available spectroscopic measurements, a new reaction mechanism is proposed, which is compatible with all the known experimental evidences and allows the interpretations of previous unexplained results. The formic acid oxidation (FAO) on metallic electrodes has been intensely studied, particularly because among several candidate fuels for low temperature fuel cells, HCOOH is considered one of the most promising.1,2 However, in spite of the attention paid to this reaction on platinum, its kinetic mechanism remains uncertain. The different authors only agree in that the reaction mechanism involves basically two parallel pathways, direct and indirect respectively.2-12 The direct path starts from the HCOOH electroadsorption step giving an active intermediate, which is then oxidized to CO 2 . Meanwhile, the adsorbed carbon monoxide intermediate is formed in the indirect pathway. In this context, it should be taken into account that at room temperature formic acid is thermodynamically unstable, as its decomposition through both dehydrogenation and dehydration processes has negative values of the reaction Gibbs free energies, although the corresponding reaction rates are negligible. [13][14][15] However, in contact with metals such as those usually employed as electrocatalysts, the spontaneous decomposition is strongly catalyzed, involving adsorbed species. [13][14][15] In electrochemistry this situation corresponds to the open circuit potential (OCP). Consequently, the kinetic studies of the formic acid electrooxidation should consider the simultaneous occurrence of both processes, catalytic (dehydrogenation and/or dehydration) and electrocatalytic (direct and/or indirect), which are coupled by reaction intermediates that are common to both.On the other hand, the revision of the literature indicates that the kinetic study of the FAO was preferably carried out on the basis of the voltammetric response in a solution of HCOOH with H 2 SO 4 or HClO 4 as supporting electrolyte. [2][3][4][5][6][7][8][9][10][11][12] There are some studies that have also used chronoamperometric measurements, 7-11,16 dynamic electrochemical impedance spectroscopy 17,18 and hydrodynamic impedance spectroscopy. 19 In the latter case, a no significant mass transfer effect was reported in the voltammetric an...

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Section: Discussionmentioning

confidence: 99%

Kinetic Study of the Formic Acid Oxidation on Steady State Using a Flow Cell

Luque

Chialvo

2017

J. Electrochem. Soc.

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“…As has been recently reported, the voltammograms obtained for stripping of a monolayer of adsorbed carbon monoxide can provide further insights regarding the crystalline surface structure of platinum electrodes [26,31,33,[36][37][38][39][40] . Figure 3 shows a CO stripping voltammogram for a polished polycrystalline platinum disc electrode recorded in 1 m H 2 SO 4 .…”

Section: Deposition Of Mesoporous Platinum Filmsmentioning

confidence: 96%

“…In addition, the onset for CO oxidation commences at approximately À0.34 V versus SMSE, which is much lower than the corresponding potential for the polished polycrystalline Pt electrode shown in Figure 3 (À0.04 V vs. SMSE), but similar to values reported for a range of single crystal platinum electrode surfaces and highly facetted Pt nanocrystals. [26,36,42] To investigate the relationship between the three peaks observed for CO stripping on the mesoporous Pt electrode, three successive cycles were recorded with progressively increasing upper potential limits as shown in Figure 5. The potential was held at À0.65 V whilst the CO monolayer was formed and the CO was displaced from the solution, see above.…”

Section: Deposition Of Mesoporous Platinum Filmsmentioning

confidence: 99%

Study of Carbon Monoxide Oxidation on Mesoporous Platinum

2010

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H(1) mesoporous platinum surfaces formed by electrodeposition from lyotropic liquid crystalline templates have high electroactive surface areas (up to 60 m(2) g(-1)) provided by the concave surface within their narrow (≈2 nm diameter) pores. In this respect, they are fundamentally different from the flat surfaces of ordinary Pt electrodes or the convex surfaces of high-surface-area Pt nanoparticles. Cyclic voltammetry of H(1) mesoporous Pt films in acid solution is identical to that for polycrystalline Pt, suggesting that the surfaces of the pores are made up of low-index Pt faces. In contrast, CO stripping voltammetry on H(1) mesoporous Pt is significantly different from the corresponding voltammetry on polycrystalline Pt and shows a clear prewave for CO oxidation and the oxidation CO at lower overpotential. These differences in CO stripping are related to the presence of trough sites where the low-index Pt faces that make up the concave surface of the pore walls meet.

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“…In acidic medium, CO oxidation reaction on these shape-controlled Pt nanoparticles showed a clear CO oxidation peak multiplicity that was attributed to CO oxidation from ordered (100) and (111) domains as well as from disordered surface domains [23][24][25][26]. As found on Pt single crystal electrodes, the sharp CO oxidation peak at high potentials was assigned to the CO oxidation on two-dimensional (100) terraces because this contribution well correlates with the amount and quality of the (100) domains present at the surface of the nanoparticles.…”

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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New findings on CO electrooxidation at platinum nanoparticle surfaces

Cited by 68 publications

References 20 publications

Kinetic Study of the Formic Acid Oxidation on Steady State Using a Flow Cell

Kinetic Study of the Formic Acid Oxidation on Steady State Using a Flow Cell

Study of Carbon Monoxide Oxidation on Mesoporous Platinum

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

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