Simultaneous time-resolved ATR-SEIRAS and CO-charge displacement experiments: The dynamics of CO adsorption on polycrystalline Pt

Silva, Camila D.; Cabello, Gema; Christinelli, Wania A.; Pereira, Ernesto C.; Cuesta, Ángel

doi:10.1016/j.jelechem.2016.10.034

Cited by 18 publications

(26 citation statements)

References 48 publications

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“…For the process of COads layer formation on a polycrystalline Pt surface in an acid media, experiments employing slow mass transport (CO extremely diluted or titrating Pt surface with CO molecules 18 ), with monitoring of the CO stretching frequencies of COads by in situ attenuated total reflectance-surface enhanced IR absorption spectroscopy, showed that CO preferentially occupies sites consisting of low coordinated atoms (defects) 18 . A similar conclusion was reached previously by Cuesta et al 19 , employing similar spectroscopic techniques. In a previous paper 20 , apparent non-preferential CO site occupation on Pt electrodes in an acid media at very early stages in the formation of the COads layer was possibly wrongly identified, because the CO gas did not meet the condition of being extremely diluted in the solution.…”

Section: Introductionsupporting

confidence: 91%

“…In a previous paper, apparent nonpreferential CO site occupation on Pt electrodes in an acid medium at very early stages in the formation of the CO ads layer was possibly wrongly identified because the CO gas did not meet the condition of being extremely diluted in the solution. In fact, under this last condition, it seems that there is no preferential CO site occupation (as can be seen in the spectra reported elsewhere). Employing stepped Pt surfaces, it was concluded that the set of sites at the bottom side of steps, which are (111) terrace sites, are the hardest sites to be occupied by CO .…”

Section: Introductionsupporting

confidence: 68%

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Surface Defects as Ingredients That Can Improve or Inhibit the Pathways for CO Oxidation at Low Overpotentials Using Pt(111)-Type Catalysts

et al. 2020

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All scientific reports regarding the electro-oxidation of CO on Pt, without exception, show that this reaction is favored on Pt surfaces rich in defects. In fact, "ordinary" or simple CO pre-oxidation is a typical process of surface defected catalysts, obeying the conditions of a full COads layer formed at suitably low potentials, such as those of the hydrogen under-potential deposition (HUPD) region. Among the Pt(111)-type surfaces, non-defected Pt(111) has the lowest catalytic activity for CO electro-oxidation. As a novelty, this paper reports that an unusual CO pre-oxidation appears on a non-defected Pt(111) surface, depending on the COads layer preparation, that is, for a COads layer prepared by cooling the flame annealed Pt(111) electrode in a CO atmosphere. The magnitude of this unusual CO pre-oxidation decreases as the Pt surface becomes rich in steps/defects, and using stepped surfaces, this unusual stage of CO electro-oxidation at low overpotentials is revealed to be connected with long-range order on the (111) plane. Interestingly, both "ordinary" and unusual CO pre-oxidations take place on the (111) terrace domains, but only "ordinary" CO pre-oxidation is favored on surfaces rich in defects. We propose a mechanism of indirect participation of the steps/defects in catalysis, according to which, at low overpotentials, steps/defects on the surface act as ingredients that can improve or inhibit the pathways for the CO electro-oxidation reaction, but do not serve as the most active sites themselves. Therefore, at least on extended platinum

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Section: Introductionsupporting

confidence: 91%

Section: Introductionsupporting

confidence: 68%

Surface Defects as Ingredients That Can Improve or Inhibit the Pathways for CO Oxidation at Low Overpotentials Using Pt(111)-Type Catalysts

et al. 2020

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“…Interestingly, while at potentials below 0.1–0.16 V, both in sulfuric and perchloric acid CO L and CO B /CO M appear simultaneously within our time resolution (although the ratio between the intensities of the CO L and CO B /CO M bands is much smaller than at a high coverage, a well-known fact ,− ), once this potential is reached, CO B /CO M is clearly preferred over CO L which, when a concentration of methanol 0.01 M in perchloric acid is used, takes as much as 30 s longer to appear on the electrode surface than CO B /CO M . A recent time-resolved ATR-SEIRAS study of the adsorption of CO on Pt electrodes in the same potential range on which this study has focused found that CO L sites are occupied first, with CO B /CO M appearing slightly later . Therefore, the behavior observed here has to be connected with the activity and availability of specific sites for the dehydrogenation reaction and how that availability is determined by the applied potential.…”

Section: Resultsmentioning

confidence: 68%

Methanol Dehydrogenation on Pt Electrodes: Active Sites and Role of Adsorbed Spectators Revealed through Time-Resolved ATR-SEIRAS

et al. 2021

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The dynamics of methanol dehydrogenation to adsorbed CO (COad) on polycrystalline Pt in the hydrogen underpotential adsorption (Hupd) region has been investigated under potentiostatic conditions using time-resolved surface-enhanced infrared absorption spectroscopy in the attenuated total reflection mode (ATR-SEIRAS) after a potential step. Our experiments reveal that the electrooxidation of methanol to COad is possible at potentials at least as negative as 0.01 V versus reversible hydrogen electrode and occurs nearly exclusively at (111)- and (100)-oriented defect sites, whereby (111)-oriented defects show higher activity unless blocked by spectator species. Under conditions in which, due to a combination of low methanol concentration and sufficiently negative potential, the formation of COad is very slow, we have been able to determine the singleton frequency of linearly bonded COad (COL) on Pt (2002 cm–1 ± 2 between 0.01 and 0.06 V). Under these conditions, the slow increase in the coverage of COad (θCO), as revealed by the increase of the integrated intensity of the bands corresponding to COL and bridge or multiple-bonded COad (COB/COM), is not accompanied by an increase in the COL stretching frequency (νCOL), which initially remains constant and then increases sharply, an effect that repeats itself several times, giving rise to a staircase-like increase of νCOL before it starts to increase monotonously in parallel with θCO. We attribute this behavior to the progressive population of terraces by COad diffusing from the defect sites where it has been formed. We also detected under these conditions a band at 1677 cm–1, which we attribute to adsorbed formyl (HCOad) and which we suggest is the last intermediate in the oxidation leading from methanol to COad. Our experiments also allow the direct spectroscopic determination of the rate of formation of COad at the limit of zero coverage (θCO → 0), from which Tafel plots revealing the potential dependence of the reaction rate when θCO → 0 can be drawn. These plots, together with the potential dependence of the time elapsed between the first observation in spectra of COB/COM and that of COL, provide evidence of the important role played by adsorbed spectators in determining the reaction rate.

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“…The thickness of the gold film and the deposition rate (fixed at 0.006 nm s -1 ) were controlled with a quartz crystal microbalance. In the case of platinum, thin film electrodes were chemically deposited following the procedure described by Silva et al [39]. Once in the spectroelectrochemical cell, the gold and platinum thin film electrodes were cleaned by applying a few voltammetric cycles up to 1.70 V in the 0.1 M HClO 4 solution.…”

Section: Methodsmentioning

confidence: 99%

Squaric acid adsorption and oxidation at gold and platinum electrodes

Cheuquepán

Martínez-Olivares

Rodes

et al. 2018

Journal of Electroanalytical Chemistry

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The adsorption and oxidation of squaric acid (3,4-dihydroxycyclobut-3-ene-1,2-dione, H 2 C 4 O 4 , SQA) at platinum and gold electrodes were studied spectroelectrochemically in perchloric acid solutions. Voltammetric experiments demonstrate that reversible adsorption takes place at gold electrodes in the double-layer region. As a difference with platinum electrodes, no dissociative adsorption processes leading to the blocking of the electrode surface are detected. ATR-SEIRAS experiments show potential-dependent adsorbate bands at potentials below 1.20 V RHE that, according to DFT calculations, can be assigned to adsorbed squarate. For platinum electrodes, the potential-dependent adsorption of squarate anions is coupled with the oxidative stripping of adsorbed carbon monoxide, which is formed upon dissociative SQA adsorption. Bonding of squarate species to the platinum and gold surfaces involves two oxygen atoms in a bidentate configuration, with the molecular plane perpendicular to the metal surface. The ATR-SEIRA spectra obtained for gold electrodes in the SQA oxidation region show bands for adsorbed bicarbonate anions formed from dissolved carbon dioxide molecules. In the case of platinum, distinct bands are observed for adsorbed oxidation products which probably are formed upon opening of the SQA ring.

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Simultaneous time-resolved ATR-SEIRAS and CO-charge displacement experiments: The dynamics of CO adsorption on polycrystalline Pt

Cited by 18 publications

References 48 publications

Surface Defects as Ingredients That Can Improve or Inhibit the Pathways for CO Oxidation at Low Overpotentials Using Pt(111)-Type Catalysts

Surface Defects as Ingredients That Can Improve or Inhibit the Pathways for CO Oxidation at Low Overpotentials Using Pt(111)-Type Catalysts

Methanol Dehydrogenation on Pt Electrodes: Active Sites and Role of Adsorbed Spectators Revealed through Time-Resolved ATR-SEIRAS

Squaric acid adsorption and oxidation at gold and platinum electrodes

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