Alcohol oxidation cyclic voltammetry

It is concluded that the occupation of the step and kink sites plays a crucial role in the promotion of the Pt catalyst. The cyclic voltammetry results can be used to explain the conversion trends observed in Figure 2. For unpromoted 5%Pt/C the Pt step and kink sites are unoccupied and available for adsorption of reactant and oxidant species. During reaction these sites facilitate premature catalyst deactivation due to poisoning by strongly adsorbed by-products (5) and (or) the formation of a surface oxide layer (6). The 5%Pt,0.5%Bi/C catalyst has a portion of these Pt step and kink sites occupied and the result is a partial reduction in the catalyst deactivation and a consequent increase in alcohol conversion. As the Bi level is increased to lwt.% almost all of the Pt step and kink sites are occupied and the result is a catalyst with high activity. As more Bi is introduced onto the catalyst surface a bulk Bi phase is formed. Since the catalyst activity is maintained it is speculated that the bulk Bi phase is not involved in the catalytic cycle. 

A report was concerned with the ability of nitroxyl radicals, such as TEMPO and other related structures, to act as catalysts in the asymmetric oxidation of alcohols. Cyclic voltammetry was used to measure the oxidation potentials of the nitroxyl... 

Electrochemically generated nickei(lll) oxide, deposited onto a nickel plate, is generally useful for the oxidation of alcohols in aqueous alkali [49]. The immersion of nickel in aqueous alkali results in the formation of a surface layer of nickel(ll) oxide which undergoes reversible electrochemical oxidation to form nickel(lll) oxide with a current maximum in cyclic voltammetry at 1.13 V vj. see, observed before the evolution of oxygen occurs [50]. This electrochemical step is fast and oxidation at a prepared oxide film, of an alcohol in solution, is governed by the rate of the chemical reaction between nickel oxide and the substrate [51]. When the film thickness is increased to about 0.1 pm, the oxidation rate of organic species increases to a rate that is fairly indifferent to further increases in the film thickness. This is probably due to an initial increase in the surface area of the electrode [52], In laboratory scale experiments, the nickel oxide electrode layer is prepared by prior electrolysis of nickel sulphate at a nickel anode [53]. It is used in an undivided cell with a stainless steel cathode and an alkaline electrolyte. 

The correlation between the coverage of surface platinum atoms by bismuth adatoms (Ggi) and the measured rate of 1-phenylethanol oxidation was studied on unsupported platinum catalysts. An electrochemical method (cyclic voltammetry) was applied to determine G i and a good electric conductivity of the sample was necessary for the measurements. The usual chemisorption measurements have the disadvantage of possible surface restructuring of the bimetallic system at the pretreatment temperature. Another advantage of the electrochemical polarization method is that the same aqueous alkaline solution may be applied for the study of the surface structure of the catalyst and for the liquid phase oxidation of the alcohol substrate. 

Fleischmann et al. [549] studied the electro-oxidation of a series of amines and alcohols at Cu, Co, and Ag anodes in conjunction with the previously described work for Ni anodes in base. In cyclic voltammetry experiments, conducted at low to moderate sweep rates, organic oxidation waves were observed superimposed on the peaks associated with the surface transitions, Ni(II) - Ni(III), Co(II) -> Co(III), Ag(I) - Ag(II), and Cu(II) - Cu(III). These observations are in accord with an electrogenerated higher oxide species chemically oxidizing the organic compound in a manner similar to eqns. (112) (114). For alcohol oxidation, the rate constants decreased in the order kCn > km > kAg > kCo. Fleischmann et al. [549] observed that the rate of anodic oxidations increases across the first row of the transition metals series. These authors observed that the products of their electrolysis experiments were essentially identical to those obtained in heterogeneous reactions with the corresponding bulk oxides. 

Different organic compounds have been investigated at BDD and BDD/Ir02 electrodes by cyclic voltammetry and preparative electrolysis. As model organic compounds, simple alcohols (methanol, ethanol, n-propanol, isopropanol, and ter-butanol) and simple carboxylic acids (formic acid, oxalic acid, and maleic acid) have been investigated. Two mechanisms can be distinguished for the organics oxidation ... 

PtSn/C electrocatalysts with R Sn atomic ratios of 50 50 and 90 10 were prepared by alcohol-reduction process, using ethylene glycol as solvent and reducing agent, and by borohydride reduction. The electrocatalysts were characterized by EDX, XRD and cyclic voltammetry. The electro-oxidation of ethanol was studied by cyclic voltammetry using the thin porous coating technique. The electrocatalysts performance depends greatly on preparation procedures and R Sn atomic ratios. 

The product of nucleophilic attack of water on the diimine primary product of electrochemical oxidation of uric acids is an imine-alcohol (see Figure 25). This species is characterized in the case of uric acid in terms of its reduction peak lie observed under cyclic voltammetric conditions and its uv absorption spectrum under thin-layer spectroelectrochemical conditions. Reduction peak lie niay be observed on cyclic voltammetry of all uric acid derivatives. The general reaction involved in forming the imine-alcohol intermediate from neutral or anionic diimines in the case of the group I uric acids is shown in Figure 25. In the case of the positively charged diimines formed upon oxidation of the group II uric acids, the reaction scheme is illustrated in Eq. (17). That... 

The general reactivity of oxidized Ni anodes in various f-butanol/H20 mixtures was followed by cyclic voltammetry. " The coulombic and organic product yields of aldehyde and acid were determined for various primary alcohol derivatives. Substituent effect on the anodic oxidation rates of a series of benzyl alcohols were evaluated. Attempts were made to relate the oxidation rates to the Hammett cr parameter for substituent properties. 

ABSTRACT. The electrochemical behaviour of tetraazamacrocyc-lic Ni(II) complexes containing a pendant amino group has been studied by cyclic voltammetry at glassy carbon electrodes in function of pH and kind of solvent. The internal pH-dependent equilibrium between the open and chelated form of the pendant arm, the influence of solvent on the heterogenous kinetics of Ni(III)/Ni(II) redox couple in these complexes, formation of the modified electrode in strongly alkaline solutions and its application to the electrocatalytic oxidation of simple alcohols have been studied and discussed. 

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