Carbon monoxide on platinum

H. P. Kaukonen, R. M. Nieminen. Computer simulations studies of the catalytic oxidation of carbon monoxide on platinum metals. J Chem Phys 97 4380- 386, 1989. 

On the surface of metal electrodes, one also hnds almost always some kind or other of adsorbed oxygen or phase oxide layer produced by interaction with the surrounding air (air-oxidized electrodes). The adsorption of foreign matter on an electrode surface as a rule leads to a lower catalytic activity. In some cases this effect may be very pronounced. For instance, the adsorption of mercury ions, arsenic compounds, or carbon monoxide on platinum electrodes leads to a strong decrease (and sometimes total suppression) of their catalytic activity toward many reactions. These substances then are spoken of as catalyst poisons. The reasons for retardation of a reaction by such poisons most often reside in an adsorptive displacement of the reaction components from the electrode surface by adsorption of the foreign species. 

Watanabe M, Motoo S. 1975a. Electrocatalysis by ad-atoms. Part in. Enhancement of the oxidation of carbon monoxide on platinum by mthenium ad-atoms. J Electroanal Chem 60 275-283. 

Korzeniewski C, Pons S, Schmidt PP, Severson MW. 1986. A theoretical analysis of the vibrational spectrum of carbon monoxide on platinum metal electrodes. J Chem Phys 85 4153-4160. 

Anderson AB, Neshev NM. 2002. Mechanism for the electro-oxidation of carbon monoxide on platinum, including electrode potential dependence—Theoretical determination. J Electrochem Soc 149 E383-E388. 

Love B, Lipkowski J. 1988. Effect of surface crystallography on electrocatalytic oxidation of carbon-monoxide on platinum-electrodes. ACS Symp Ser 378 484-496. 

Large platinum carbonyl clusters have been investigated as models for the adsorption of carbon monoxide on platinum surfaces and on platinum electrodes. An issue is how large the clusters must be before they adopt the properties of the bulk metal. Teo et al. have investigated the magnetic properties of the clusters [Pt6(CO)12]2+, [Pt9(CO)18]2+, [Pt y(CO)22f+, and... 

Adsorbed carbon monoxide on platinum formed at 455 mV in H2S04 presents a thermal desorption spectrum as shown in Fig. 2.4b. As in the case of CO adsorption from the gas phase, the desorption curve for m/e = 28 exhibits two peaks, one near 450 K for the weakly adsorbed CO and the other at 530 K for the strongly adsorbed CO species. The H2 signal remains at the ground level. A slight increase in C02 concentration compared to the blank is observed, which could be due to a surface reaction with ions of the electrolyte. Small amounts of S02 (m/e = 64) are also observed. 

Exchange reactions between bulk and adsorbed substances can be studied by on-line mass spectroscopy and isotope labeling. In this section the results on the interaction of methanol and carbon monoxide in solution with adsorbed methanol and carbon monoxide on platinum are reported [72], A flow cell for on-line MS measurements (Fig. 1.2) was used. 13C-labeled methanol was absorbed until the Pt surface became saturated. After solution exchange with base electrolyte a potential scan was applied. Parallel to the current-potential curve the mass intensity-potential for 13C02 was monitored. Both curves are given in Fig. 3.1a,b. A second scan was always taken to check the absence of bulk substances. 

Exepriments in the gas phase have supplied us with considerable knowledge on the state of adsorbed carbon monoxide on platinum. 

Since the early work of Langmuir (1), the chemisorption of carbon monoxide on platinum surfaces has been the subject of numerous investigations. Besides its scientific interest, an understanding of CO chemisorption on Pt is of considerable practical importance for example, the catalytic reaction of CO over noble metals (such as Pt) is an essential part of automobile emission control. 

Effect of Surface Crystallography on Electrocatalytic Oxidation of Carbon Monoxide on Platinum Electrodes... 

For the average length of life of carbon monoxide on platinum he obtained the following data ... 

The use of equation (3.2) to study the behaviour of catalysts is known as solid electrolyte potentiometry (SEP). Wagner38 was the first to put forward the idea of using SEP to study catalysts under working conditions. Vayenas and Saltsburg were the first to apply the technique to the fundamental study of a catalytic reaction for the case of the oxidation of sulfur dioxide.39 Since then the technique has been widely used, with particular success in the study of periodic and oscillatory phenomena for such reactions as the oxidation of carbon monoxide on platinum, hydrogen on nickel, ethylene on platinum and propylene oxide on silver. 

Ertl, G. (1989). The oscillatory catalytic oxidation of carbon monoxide on platinum surfaces. In Spatial inhomogeneities and transient behaviour in chemical kinetics, (ed. P. Gray, G. Nicolis, F. Baras, P. Borckmans, and S. K. Scott), ch. 37, pp. 563—76. Manchester University Press. 

Following the initial work by Langmuir (7) the catalytic oxidation of carbon monoxide on platinum has been investigated frequently with polycrystalline samples (132, 183-190) as well as with single crystal surfaces (149, 151, 191-197) by applying stationary and nonstationary methods including the molecular beam technique. The general trends observed are... 

The review paper by Razon and Schmitz [87] on bifurcation, instability and chaos for the oxidation of carbon monoxide on platinum. 

The papers of Wicke and Onken [88] and Razon et al. [89] which give different views on the almost similar dynamics observed during the oxidation of carbon monoxide on platinum. Wike and Onken [88] analyze it as statistical fluctuations while Razon et al. [89] analyze it as chaos. Later, Wicke changes his view and analyzes the phenomenon as chaos [90]. 

The pressed-salt method can be used to overcome this difficulty because it can be used to observe spectra of carbon monoxide on platinum particles which are not supported on silica or alumina (14)- It is possible to use commercial platinum black, but best results are obtained if the platinum particles are formed by reduction of chloroplatinic acid while it is dispersed on the powdered salt. After reduction in hydrogen at 300° C., the sample was treated with CO and transferred to the die. An essential feature of this technique is a final treatment with CO after the sample is in the die. The die is sealed with Apiezon Q wax to prevent exposure to the atmosphere between the time of the final treatment with CO and the application of pressure to form the salt disk. 

Elementary Steps in the Catalytic Oxidation of Carbon Monoxide on Platinum Metals T. Engel and G. Ertl The Binding and Activation of Carbon Monoxide, Carbon Dioxide, and Nitric Oxide and Their Homogeneously Catalyzed Reactions... 

Adsorption of carbon monoxide on platinum is not irreversible, since on switching carbon monoxide gas concentrations or with switching to pure hydrogen, the electrode potential rapidly relaxes and reverts to those values previously obtained for the absence of carbon monoxide. This shows that the kinetics of adsorption/desorption are rapid and reversible... 

Narayanasamy, J., Anderson, A. (2003). Mechanism for the electrooxidation of carbon monoxide on platinum by HjO. Density functional theory calculation. /. Electroanalytical Chem. 554-555,35-40. 

Spiral waves also arise in the oxidation of carbon-monoxide on platinum surfaces [10]. In 1972 they have been discovered by Winfree [79] in the photosensitive Belousov-Zhabotinsky (BZ) reaction, see for recent investigations for example [83, 84, 87]. Both reactions are studied in the SFB 555. The classical BZ reaction is a catalytic oxidation of malonic acid, using bromate in an acidic environment. Experimentally it exhibits well reproducible drift, meander and chaotic motions of the spiral wave and its tip. 

Z. Tang, D. Geng, and G. Lu, Electrocatalytic oxidation of carbon monoxide on platinum-modified polyanihne film electrode. Thin Solid Films, 497, 309-314 (2006). 

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