Methanol on platinum

K. Franaszczuk, E. Herrero, P. Zelenay, A. Wieckowski, J. Wang, and R.I. Masel, A comparison of electrochemical and gas-phase decomposition of methanol on platinum surfaces, J. Phys. Chem. 96(21), 8509-8516 (1992). 

Adsorption due to the operation of chemical forces is called chemisorption. A typical example of chemisorption is also the adsorption of methanol on platinum electrodes, which is accompanied by a deep destruction of the methanol molecule. 

Types of aging processes such as those described for the adsorption of oxygen and methanol on platinum are also characteristic of the adsorption of other substances and of adsorption on other electrodes. In some cases these changes manifest themselves as a change (mostly an increase) in the adsorption energy with time. In... 

Gilman S. 1964. The mechanism of electrochemical oxidation of carbon monoxide and methanol on platinum. II. The reactant-pair mechanism for electrochemical oxidation of carbon monoxide and methanol. J Phys Chem 68 70-80. 

Henero E, Femandez-Vega A, Feliu JM, Aldaz A. 1993. Poison formation reaction from formic acid and methanol on platinum (111) electrodes modified by irreversibly adsorbed bismuth and arsenic. J Electroanal Chem 350 73-88. 

Iwasita T, Vielstich W. 1988. New in-situ IR results on adsorption and oxidation of methanol on platinum in acidic solution. J Electroanal Chem 250 451-456. 

Okamoto H, Kon W, Mukouyama Y. 2005. Five current peaks in voltammograms for oxidations of formic acid, formaldehyde, and methanol on platinum. J Phys Chem B 109 15659-15666. 

Watanabe M, Motoo S. 1975b. Electrocatalysis by ad-atoms. Part I. Enhancement of the oxidation of methanol on platinum and palladium by gold ad-atoms. J Electroanal Chem 60 259-266. 

Gloaguen F, Leger JM, Lamy C. 1997. Electrocatal3ftic oxidation of methanol on platinum nanoparticles electrodeposited onto porous carhon substrates. J Appl Electrochem 27 ... 

In Fig. 2.12 characteristic IR reflectance spectra of concentrated (3 M) methanol on platinum at potentials between 0.45 V and 1.3 V are shown. The single beam spectrum at 0 mV was taken as background. The following characteristic bands allow the identification of bulk products ... 

Electrochemical infrared spectroscopy can be used on all kinds of electrodes and for all substances that are IR active. It is particularly useful for the identification of reaction intermediates, and has been used extensively for the elucidation of the mechanisms of technologically important reactions. A case in point is the oxidation of methanol on platinum, where linearly bonded = C = O (i.e., CO bonded to one Pt atom) has been identified as an intermediate Figs. 15.7 and 15.8 show EMIRS [6c] and IRRAS [8] spectra of this species. Near 2070 cm-1 the EMIRS spectrum shows the typical form produced by a peak that shifts with potential. This shift can be followed in the IRRAS spectrum... 

Figure 6. Comparison of various in situ techniques for the chemisorption of methanol on platinum.

ELECTROCHEMICAL OXIDATION OF METHANOL ON PLATINUM AND PLATINUM BASED ELECTRODES... 

The goal of this thesis is to achieve a deeper understanding of the mechanisms and their features of electrochemical oxidation of methanol on platinum and platinum based electrodes. This understanding will be helpful as a guide when searching for new catalysts and trying to improve the activities. 

There is no doubt that this reaction is made up of several series and/or parallel reactions. Mass spectroscopic measurement showed that formaldehyde and formic add are produced during the oxidation of methanol on platinum in add solution. Using gas chromatography, methylformate... 

CH00CH3)t carbon dioxide (C02>. formic acid (HCOOH), and formaldehyde (HCHO) are detected in the solution during the oxidation of methanol on platinum in sulfiiric add. While these are stable and detached spedes, spedes that are unstable or adsorbed on the electrode surface are also expected to be formed. 

In this chapter, electrochemical oxidation of methanol on platinum was investigated using electrochemical techniques, e.g. FTIR and on-line mass spectrometric techniques. Effects of types and concentration of adds, temperature and morpholo of platinum were studied. 

Several experimental approaches have been used to obtain information concerning the identity, concentrations, and reactivities of intermediates in catalytic reactions. Tamaru 136), during measurements of catalytic activity, concurrently determined the total quantity of gas adsorbed. One possible limitation to this method is that a proportion of the material bonded to the surface may not be involved in the surface reactions (57), The use of labeled reactants and monitoring the radioactivity in the region of the active solid may (95) provide a potentially useful technique for the estimation of Cj and/or c2. An alternative, and perhaps complementary, approach is through the individual investigation of the kinetics of product formation from reactions of known amounts of adsorbed material. This method has been used to elucidate some of the elementary steps in the breakdown of methanol on platinum (80). The independent preparation of a postulated intermediate,... 

Consider the following information on the electrochemical oxidation of methanol on platinum It is known that upon adsorption of CH3OH upon platinum, dehydrogenation occurs. The final product is C02. Several analyses made on the basis of potentiodynamic sweep data suggest the presence on the electrode surface of c -OH. However, further spectroscopic work, particularly that in potentiostatic work in steady state finds linear CO, i.e., S=0, the intermediate. The Tafel slope is 60 mV at low current densities and 120 mV at higher values of the current. Potentiodynamic profiles show that the overall number of electrons in the oxidation is 1.2—1.5 (i.e., two kinds of CO radicals of somewhat different character as to their adsorption are on the surface). 

Spectroscopic evidence obtained recently indicates that the electrosorption of methanol on platinum is probably a very complex process, in which several different partially oxidized species may be formed, in ratios that depend both on the potential and on the bulk concentration of methanol. 

J. Munk, P.A. Christensen, A. Hamnett, E. Skou, The electrochemical oxidation of methanol on platinum and platinum plus ruthenium particulate electrodes studied by insitu FTIR spectroscopy and electrochemical mass spectrometry. J. Electroanal. Chem. 1996, 401(1-2), 215-222. 

M. Watanabe, Y. Genjima, K. Turumi, Electrochemical oxidation of methanol on platinum electrodes with ruthenium ad-atoms in hot phosphoric acid. Denki Kagaku, 1996, 64(6), 462-463. 

K. Lasch, L. Jorissen, J. Garche, The effect of metal oxides as co-catalysts for the electro-oxidation of methanol on platinum-ruthenium. J. Power Sources 1999, 84, 225-230. 

A.V. Tripkovic, K.D. Popovic, Oxidation of methanol on platinum single crystal stepped electrodes from [110] zone in acid solution. Electrochim Acta 1996, 41(15), 2385-2394. 

The bulk electrooxidation of methanol on platinum single crystals has been extensively studied since the late 1980s. The electrochemical profile of the reaction on Pt(l 11) in acid media is depicted in Figure 2.2 ... 

Electrocatalytic oxidation of methanol on platinum based catalysts... 

A detailed mechanism for the electro-oxidation of methanol on platinum electrodes in acidic media is shown in Scheme 2. The important features of the reaction mechanism include the formation of reactive intermediates, such as (CHO)a 5, which form on the electrode surface and are further oxidized to either (CO)ads, which leads to the poisoning species, or the adsorbed formyl species is oxidized to (COOH)ads or directly to COj. The mechanistic pathways described... 

P.O. Esteban, J.M. Leger, C. Lamy, and E. Genies, Electrocatalytic oxidation of methanol on platinum dispersed in polyaniline conducting polymers, J. Appl. Electrochem., 19, 462-464 (1989). 

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