Platinum, lead modified acids

P. C. C. Smits, B. F. M. Kuster, K. Van der Wiele, and H. S. Van der Baan, The selective oxidation of aldoses and aldonic acids to 2-ketoaldonic acids with lead-modified platinum-on-carbon catalysts, Carbohydr. Res., 153 (1986) 227-235. 

Zhang M, Wilde CP (1995) The influence of organic adsorbates on the UPD process. Oxidation of formic acid at UPD lead-modified platinum electrodes. J Electroanal Chem 390 59-68... 

The direct electrooxidation of aqueous E>-g]uconic acid to l>arabinose on graphite has been performed in a very simple apparatus which may be suitable for practical application. The electrocatalytic oxidation of sucrose on smooth, lead-modified platinum electrodes has been examined with a view to finding experimental conditions for the selective electrosynthesis of value-added compounds. A paper in Bulgarian on the electrooxidation of diacetone-L-sorbose at low current densities in a nickel oxide electrolizer has been publi ed. The influence of the rize of palladium particles and their location on the support on their activity in the oxidation of glucose has been examined. An investigation of the effect of tonperature and pH on the platinum-catalysed oxidation of sucrose showed that changes in temperature affect mainly the reaction rate, where changes in pH alter the selectivity. ... 

The electrochemical oxidation of methanol has been extensively studied on pc platinum [33,34] and platinum single crystal surfaces [35,36] in acid media at room temperature. Methanol electrooxidation occurs either as a direct six-electron pathway to carbon dioxide or by several adsorption steps, some of them leading to poisoning species prior to the formation of carbon dioxide as the final product. The most convincing evidence of carbon monoxide as a catalytic poison arises from in situ IR fast Fourier spectroscopy. An understanding of methanol adsorption and oxidation processes on modified platinum electrodes can lead to a deeper insight into the relation between the surface structure and reactivity in electrocatalysis. It is well known that the main impediment in the operation of a methanol fuel cell is the fast depolarization of the anode in the presence of traces of adsorbed carbon monoxide. 

Joo and co-workers [22] have discussed a new type of composite membrane, consisting of functionalised carbon nanotubes (CNT) and sulfonated polyarylene sulfone (sPAS) for direct methanol fuel cell applications. The CNT modified with sulfonic acid or platinum-rubidium (PtRu) nanoparticles were dispersed within the sPAS matrix by a solution casting method to give SOs-CNT-sPAS or PtRu-CNT-sPAS composite membranes, respectively. Characterisation of the composite membranes revealed that the functionalised CNT were homogeneously distributed within the sPAS matrix and the composite membranes contained smaller ion clusters than the neat sPAS. The composite membranes exhibited enhanced mechanical properties in terms of tensile strength, strain and toughness, which leads to improvements in ion conductivity and methanol permeability compared with the neat sPAS membrane, which demonstrates that the improved properties of the composite membranes induce an increase in power density. The strategy for CNT-sulfonated composite membranes in this work can potentially be extended to other CNT-polymer composite systems. 

In this way, a catalytic eff t of Pb on die electro-oxidation of formic acid was clearly observed when its respcmse was compared with the response obtained with the respective Pt/Polymer-Pt electrode under the same conditions. A noticeable increase in the curratit peaks associated with die direct oxidation of the substrate is observed in the tfam cases along with a clear decrease in the charge assigned to the oxidation of strongty adsorbed intermediates near 0.74 V. This observation confirms that the presence of lead precludes the fixation of poisoning intermediate species on platinum. It is necessaiy to emphasize that the presence of Pb(U) in die electrolyte is not required to obtain the j-t response for these modified electrodes. 

Palladium was electrodeposited on gold electrodes constructed from recordable CDs and was utilized for dipyrone quantification under flow injection analysis. The limit of detection attained was 1 x 10 mol the volume utilized in the ElA was only 100 pL, and the time required for each analysis was 40 s. Arrays of microelectrodes modified by electrodeposition of palladium, platinum, and a mixture of platinum -i- palladium were utilized for the quantification of the components of a mixture containing ascorbic acid, dopamine, epinephrine, and dipyrone. Lead... 

---