Methanol electrocatalytic oxidation

Electrocatalysis Electrocatalysis of methanol, Electrocatalytic oxidation of nitric oxide at Ti02-Au nanocomposite. Electrochemical wastewater treatment [351-356]... 

The electrocatalytic oxidation of methanol has been widely investigated for exploitation in the so-called direct methanol fuel cell (DMFC). The most likely type of DMFC to be commercialized in the near future seems to be the polymer electrolyte membrane DMFC using proton exchange membrane, a special form of low-temperature fuel cell based on PEM technology. In this cell, methanol (a liquid fuel available at low cost, easily handled, stored, and transported) is dissolved in an acid electrolyte and burned directly by air to carbon dioxide. The prominence of the DMFCs with respect to safety, simple device fabrication, and low cost has rendered them promising candidates for applications ranging from portable power sources to secondary cells for prospective electric vehicles. Notwithstanding, DMFCs were... 

Interest in fuel cells has stimulated many investigations into the detailed mechanisms of the electrocatalytic oxidation of small organic molecules such as methanol, formaldehyde, formic acid, etc. The major problem using platinum group metals is the rapid build up of a strongly adsorbed species which efficiently poisons the electrodes. 

The electrocatalytic oxidation of methanol has been thoroughly investigated during the past three decades (see reviews in Refs. 21-27), particularly in regard to the possible development of DMFCs. The oxidation of methanol, the electrocatalytic reaction, consists of several steps, which also include adsorbed species. The determination of the mechanism of this reaction needs two kinds of information (1) the electrode kinetics of the formation of partially oxidized and completely oxidized products (main and side products) and (2) the nature and the distribution of intermediates adsorbed at the electrode surface. 

Perhaps the most important paradigm in research on the mechanism of the electrocatalytic oxidation of small organic molecules is the dual pathway mechanism introduced in Capon and Parsons [1973a, b], and reviewed in Parsons and VanderNoot [1988]. In terms of methanol oxidation, the dual pathway may be summarized in a simplified way by Fig. 6.1. The idea is that the complete oxidation of methanol to carbon dioxide may follow two different pathways ... 

Kabbabi A, Faure R, Durand R, Beden B, Hahn F, Leger JM, Lamy C. 1998. In situ FTIRS study of the electrocatalytic oxidation of carbon monoxide and methanol at platinum-ruthenium bulk alloy electrodes. J Electroanal Chem 444 41-53. 

Attwood PA, McNicol BD, Short RT. 1980. Electrocatalytic oxidation of methanol in acid electrolyte—Preparation and characterization of noble-metal electrocatalysts supported on pretreated carbon-fiber papers. J Appl Electrochem 10 213-222. 

Clavilier J, Lamy C, Leger JM. 1981a. Electrocatalytic oxidation of methanol on single-crystal platinum-electrodes—Comparison with polycrystalline platinum. J Electroanal Chem 125 (1) 249-254. 

The electrocatalytic oxidation of methanol was discussed on page 364. The extensively studied oxidation of simple organic substances is markedly dependent on the type of crystal face of the electrode material, as indicated in Fig. 5.56 for the oxidation of formic acid at a platinum electrode. 

Wu, B., et al., Functionalization of carbon nanotubes by an ionic-liquid polymer Dispersion ofPt and PtRu nanoparticles on carbon nanotubes and their electrocatalytic oxidation of methanol. Angewandte Chemie International Edition, 2009. 48(26) p. 4751-4754. 

The methanol oxidation current increases because Pt-OH helps electrocatalytic oxidation of methanol, but decreases again once the siurface is completely covered with Pt-OH. This causes an oxidation ciurent peak at 850 mV. The oxidation current increases again after the potential is high enough (1200 mV) to oxidixe methanol on Ptr-OH surface. 

J. Luo, M. M. Maye, N. N. Kariuki, L. Wang, P. Njoki, Y. Lin, M. Schadt, H. R. Naslund, and C. J. Zhong, Electrocatalytic oxidation of methanol Carbon-supported gold-platinum nanoparticle catalysts prepared by two-phase protocol, Catal. Today 99, 291-297 (2005). 

Platinum carbonylate anion clusters like [Pt3(CO)6] can be obtained by alkaline reduction of [PtCh] in a CO atmosphere. From [Pt3(CO)s] other higher nuclear-ity anions can be obtained. In this context, several examples have been reported in which this type of anionic cluster is used in the preparation of catalysts by impregnation or exchange methods. Salts of [Pt3 (CO)6 ] (n = 3, 5) have been used to prepare, by impregnation, dispersed platinum on ZnO and MgO [49] and, by ion exchange methods, to prepare Pt3 /C electrodes for the electrocatalytic oxidation of methanol [50]. A salt of [Pti2(CO)24] has recently been used to prepare... 

Oxidation of Alcohols in a Direct Alcohol Fuel Cell The electrocatalytic oxidation of an alcohol (methanol, ethanol, etc.) in a direct alcohol fuel cell (DAFC) will avoid the presence of a heavy and bulky reformer, which is particularly convenient for applications to transportation and portable electronics. However, the reaction mechanism of alcohol oxidation is much more complicated, involving multi-electron transfer with many steps and reaction intermediates. As an example, the complete oxidation of methanol to carbon dioxide ... 

This section addresses the role of chemical surface bonding in the electrochemical oxidation of carbon monoxide, CO, formic acid, and methanol as examples of the electrocatalytic oxidation of small organics into C02 and water. The (electro)oxidation of these small Cl organic molecules, in particular CO, is one of the most thoroughly researched reactions to date. Especially formic acid and methanol [130,131] have attracted much interest due to their usefulness as fuels in Polymer Electrolyte Membrane direct liquid fuel cells [132] where liquid carbonaceous fuels are fed directly to the anode catalyst and are electrocatalytically oxidized in the anodic half-cell reaction to C02 and water according to... 

The electrocatalytic oxidation of many small organic molecules was carried out at Pt-based catalysts dispersed in an ECP, particularly that of Cl molecules (formic acid, formaldehyde, and methanol). 

Janik, M.J., Taylor, C.D. and Neurock, M. (2007) First principles analysis of the electrocatalytic oxidation of methanol and carbon monoxide. Top. Catal., 46, 306-319. 

Intensive research is currently being carried out to obtain efficient catalysts for this reaction. Most of the research is devoted to different metal (Pt, in particular)-based materials, but several approaches include porous materials such as Ni-impregnated zeolites, obtained from soaking of zeolites in, for instance, NiSO4 solutions (Abdel Rahim et al., 2006). The performance of gold-zeolite-modified electrodes toward electrocatalytic oxidation of ethanol, an alternative to methanol fuel, has been recently reported by Ouf et al. (2008). 

With the development of fuel cells, electrocatalytic oxidation of small organic molecules, such as methanol or formic acid, has attracted great interest recently (Rice et al., 2003). Ethanol oxidation to acetaldehyde can be performed by means of the reactions ... 

The electrocatalytic oxidation of the primary alcohol (in C6 position) is similar to the reaction mechanism that is well known for methanol. Therefore, the transformation of gluconic acid into glucaric acid can be written as follows ... 

Electrocatalytic oxidation of methanol on platinum based catalysts... 

Electrocatalytic oxidation of methanol was conducted over Pt and Pt-Ru-WOs deposited graphite electrodes in H2SO4 medium. Hydrogen adsorption experiment was conducted with H2SO4 in absence of methanol. XPS analysis was done to confirm existence of Pt, Ru and WO3 on electrodes. Constant potential oxidation was used to monitor the activity of electrodes with respect to time. 

Pt-Ru-WOs deposited graphite electrode shows better activity than pure Pt deposited graphite electrode. Presence of WO3 with Pt prevents the measurement of real surface area of platinum on the electrode. Increase of both H2SO4 and methanol concentration increases methanol oxidation. Potential around 0.5-0.6 V vs SCE appears to be the best for electrocatalytic oxidation of methanol. At all potentials Pt-Ru-WOs/C shows higher activity than Pt/C during long term polarisation. 

In general, a complex structure is designed toward a particular end, perhaps to facilitate an electrode process (such as the electrocatalytic oxidation of methanol), or to inhibit a reaction (such as metallic corrosion), or to produce selectivity toward a particular process (such as the enzyme-catalyzed oxidative determination of glucose in whole blood). The end is... 

In order to improve the electrocatalytic properties of methanol electrodes, and to reduce the poisoning phenomenon usually observed with bulk platinum, different platinum based alloys were considered such as Pt-Ru, and Pt-Sn, etc. [153]. Therefore such alloys were also dispersed into electron conducting polymers. Hable et al. [53] were apparently the first authors to disperse Pt-Sn catalyst particles in a polyaniline matrix, in order to activate the oxidation of methanol. They evaluated the Pt/Sn ratio by X-ray Photoelectron Spectroscopy and found that small amounts of Sn (e.g. Pt/Sn ratios of 10/1) were sufficient to enhance the electrocatalytic oxidation of methanol. Pt was found to be in the Pt(0) state whereas Sn was in an oxidized form. Similar observations concerning the enhanced electrocatalytic activity of Pt-Sn particles incorporated in PAni films were made by Laborde et al. [154]. Such Pt-Sn alloys are also very active for the electrocatalytic oxidation of ethanol [68,154]. 

The electrocatalytic oxidation of alcohols is possible by using modified conductive polymer electrodes. One of the most interesting examples of such a reaction is the electro-oxidation of methanol with highly dispersed platinum-based particles inserted in a polymeric matrix. 

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