The electro-oxidation of chemisorbed carbon monoxide on polycrystaline rhodium in acid solution (original) (raw)
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Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1986
The ftrst stages of the electrooxtdatmn of CO prevtously adsorbed on polycrystalline Pt rn 1 M HClO, at 25°C were mvesttgated by means of the triangularly modulated triangular potenttal sweep technique. Runs were made with a Pt surface covered either partialIy or completely with adsorbed CO over a wide range of frequency and amphtude of the modulating signal Reactions between the strongly and the weakly bonded adsorbed oxygen-containing adsorbed spectes wtth the lmear and the brtdge forms of adsorbed CO were followed vta the voltammetrtc measurements. The kmetics of the vartous posstble processes are discussed in terms of previous results on the voltammetrtc electrooxtdatton of adsorbed CO and on the early stages of 0-electroadsorptton on Pt. CO adsorption on Pt produces a change m the apparent electrode capacity which is Interpreted in terms of the structure of the mner part of the electrtcal double layer.
The electrooxidation of chemisorbed co on polycrystalline platinum
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1984
The electrooxldaUon of CO on polycrystalhne Pt m 1 M HCIO 4 at 23°C under potenuodynanuc con&uons exbablts a double current peak Whether a single or a double current peak is formed depends to a great extent on the amount of CO surface coverage. The present report attempts to explain the behawour of the electrochetmcal reaction m terms of a single model revolving the participation of two CO adsorbed states on polycrystalhne Pt.
The electrooxidation of carbon monoxide on unsupported Pt agglomerates
Journal of Electroanalytical Chemistry, 2010
This work presents some insights on the CO electrooxidation on unsupported Pt nanoparticles in terms of the role played by particle size, surface crystallography, and defects, based on the results of structural and electrochemical characterization. The electrochemical properties were probed through potentiodynamic and potentiostatic CO-stripping experiments conducted in two samples of unsupported Pt nanoparticles, ''Pt (FAM)", synthesized by chemical reduction, and ''Pt (J-M)", a commercial material. Experiments were carried out in 0.1 mol L À1 HClO 4 at room temperature ($25°C). The structural, morphological, and electronic features of these materials were investigated by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and X-ray absorption Fine structure spectroscopy (XAFS), respectively. The XRD analysis indicated texture (preferential orientation) effects, in addition to a larger crystallite size for the Pt (FAM) sample. TEM images revealed a large degree of agglomeration and suggested a larger particle size for Pt (FAM) than for Pt (J-M), in addition to morphological differences between them. XAFS analysis suggested differences in the electronic structure of the materials probably caused by size effects. Cyclic voltammetry results in 0.5 mol L À1 H 2 SO 4 were obtained and discussed in terms of the surface crystallography and also on possible particle-size effects. Both potentiodynamic and potentiostatic COstripping experiments revealed different electrochemical behaviors between the unsupported Pt samples, evidencing the extremely structure-sensitive character of the CO electrochemical oxidation.
The electrooxidation of CO: a test reaction in electrocatalysis
Electrochimica Acta, 1990
This review paper aims to show how the electrochemical behaviour of CO plays a key role in the understanding of the reaction mechanism of many electrocatalytic oxidations of small organic molecules. For that purpose, the adsorption of CO on noble metal electrodes, eventually modified by foreign metal adatoms, is reviewed, taking into account both experimental (electrochemical and spectroscopic techniques) and theoretical (Extended Hiickel Model) approaches. Data from the gas phase-solid metal interface are also considered.
Journal of Solid State Electrochemistry, 2007
Polymer electrolyte fuel cells constitute one of the most important efficiency energy converters for noncentralised uses. However, the use of fuels arising from reformate processes significantly lowers the current efficiency because of anodic catalytic poison coming from adsorbed carbon monoxide (CO ad ). In this work, the influence of the addition of hydrogen peroxide in the flow current is studied, considering the adsorption and electrochemical oxidation of carbon monoxide on carbon-supported Pt (20% Pt/Vulcan) and Pt:Ru (1:1, 20% Pt:Ru/Vulcan) catalysts in 2 M sulphuric acid. The investigation was conducted applying cyclic voltammetry and on-line differential electrochemical mass spectrometry. A series of experiments has been performed to investigate the influence of the temperature as well as the time of contact and the concentration of hydrogen peroxide. Oxidation of CO ad to carbon dioxide occurs at lower potentials in the presence of hydrogen peroxide. Moreover, it is possible to remove ca. 70% of CO ad on Pt/C electrodes. On the other hand, for PtRu/C electrodes, similar charge values to those of Pt/C electrodes were obtained for the CO stripping, but the process occurs at more negative potentials. In this case, the effect of partial desorption for CO ad by interaction with hydrogen peroxide is added to the bifunctional mechanism usually considered for this alloy.
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1991
The chemisorption of CO on a Rh electrode in 0.5 M HCIO, and 1 M NaOH was studied by cyclic voltammetry and UV-Visible Potential-Modulated Reflectance Spectroscopy (PMRS). Electrooxidation of dissolved CO on Rh is negligible in acid. On the contrary, the stationary current in base reaches = l/5 of the diffusion-limited value. We report a voltammetric peak due to the oxidation of dissolved CO in base, which can be observed only for CO admission potentials < 0.1 V vs. RHE, and which precedes the sharp peak for oxidation of (chemisorbed and dissolved) CO. The potential of this sharp peak in base is independent of the admission potential up to Eadm = 0.47 V, but for higher values the peak potential increases linearly with J&,,,, probably due to the formation of a rhodium oxide prior to CO admission. The amount of CO chemisorbed on Rh in base is independent of the presence on the electrode surface of a thick layer of electrochromic oxide previously grown by potential cycling, which we attribute to CO chemisorption continuing to take place on the unoxidized Rh surface. The PMR spectrum of Rh on which CO is chemisorbed shows a well-defined maximum, which appears at 265 and 295 nm in acid and base, respectively. This PMRS maximum is due to an electric field effect, since its height is independent of the modulation frequency, and grows linearly with the modulation amplitude. Reflectograms recorded at the wavelength of the PMRS maximum during a slow potential sweep prove conclusively that it originates in the chemisorbed CO. The PMRS maximum at 265 nm is attributed to linearly chemisorbed CO, and that at 295 nm to bridged CO.
Electrochemical Behaviour Of Carbon Dioxide On Platinum And Rhodium
Anales des la Asociacion Quimica Argentina
The electroadsorption and electroreduction of carbon dioxide, and the subsequent electrooxidation of reduced carbon dioxide was studied on polycrystalline and electrofaceted Pt and on polycrystalline Rh electrodes. The influence of the adsorption potential and the adsorption time was established. Combining voltammetric charge measurements and differential electrochemical mass spectrometry (DEMS) analysis, three adsorbates were tentatively identified, namely COOH and CO in bridge and linear configurations on Pt, and COH in triple and single adsorption configurations on Rh. By applying medium frequency potential routines on the Pt-adsorbate/sulphuric acid interface, the existence of equilibrium between adsorbates was demonstrated. Resumen Se estudia la electroadsorción y la electrorreducción de dióxido de carbono como así también la electrooxidación del dióxido de carbono reducido sobre Pt policristalino y electrofacetado y sobre Rh policristalino. Se determina la influencia del potencial y del tiempo de adsorción. Mediante el empleo de técnicas combinadas voltamperométricas y de espectrometría de masa diferencial (DEMS), se identificaron tres adsorbatos posibles sobre Pt, COOH y CO en configuración lineal y puente, y dos sobre Rh, COH en configuraciones de adsorción simple y triple. Mediante la aplicación de perturbaciones de potencial a la interfase Pt-adsorbato/ácido sulfúrico acuoso, se demuestra la existencia de un equilibrio entre los adsorbatos.
Electrooxidation of CO and H 2 /CO Mixtures on Pt(111) in Acid Solutions
The Journal of Physical Chemistry B, 1999
Electrocatalysis of CO oxidation and the interfacial structure of the CO adlayer (CO ad ) on the Pt(111) surface in 0.5 M H 2 SO 4 were examined by using the rotating disk electrode method in combination with in situ surface X-ray diffraction measurements. The results presented here elucidate the roles played by two different forms of CO ad : one which is oxidized at lower overpotentials, in the so-called preoxidation region, we characterize as a weakly adsorbed state (CO ad.w ), and a strongly adsorbed state (CO ad,s ) which is oxidized at higher overpotentials. The CO ad,w state forms at saturation coverage by adsorption at E < 0.15 V and assumes a compressed p(2 × 2) structure containing 3 CO molecules in the unit cell (0.75 CO/Pt). We propose that oxidative removal of CO ad,w is accompanied by simultaneous relaxation of the CO adlayer, and that the remaining CO ad (≈0.6 CO/Pt) assumes a new bonding state which we identify as CO ad,s . The CO ad,s state is present in a structure lacking long-range order. Despite the reduced coverage by CO ad , H 2 electrooxidation is still completely poisoned at potentials below 0.6 V. The electrooxidation of CO in solution is proposed to occur via the CO ad,w state at 0.6-0.8 V, and via the CO ad,s at higher potentials.
Adsorption and electrooxidation of carbon monoxide on polycrystalline platinum at pH 0.3–13
Electrochimica Acta, 2001
Over the whole pH range 0.3-13 electrooxidation of dissolved CO on polycrystalline Pt was found to depend dramatically on the CO dosing potential, occurring at about 0.6 or 0.9 V for CO dosing potentials lower or higher, respectively, than about 0.4 V versus the reversible hydrogen electrode. Only in the former case a small anodic peak at about 0.5 V appeared in stripping voltammograms of chemisorbed CO, suggesting that dissolved CO electrooxidation at 0.6 V takes place on a small fraction of Pt sites that are free from CO. These findings are in agreement with literature reports for pH 0.3 and 14.