Oxidation of Methanol and Other Low-Molecular-Weight Alcohols on the RuNi Catalysts in an Alkaline Environment

The results of investigations of the RuNi catalysts, which are designed for the electrooxidation of methanol and other low-molecular-weight alcohols in alkaline solutions, are presented. It is shown that the maximum catalytic activity in this reaction is exhibited by a catalyst, which was synthesized thermochemically on acetylene black AD100 containing 15 wt % RuNi at a 68 : 32 atomic ratio (in at. %) between the metals. The structure of the synthesized catalysts is studied by the methods of x-ray photoelectron spectroscopy and x-ray diffraction analysis (XRDA). The area of the metal surface is determined on the basis of the magnitude of the adsorption of CO from the voltammetric curves. An analysis of the data obtained in this work leads to the conclusion that ruthenium in the composition of the catalyst exists in metallic and partially oxidized states and nickel exists in the form of a nonstoichiometric oxide. In addition it is found that the insertion of nickel into the system leads, as follows from the XRDA data, to the dispersion of ruthenium and, as follows from the voltammetric curves, to a decrease in the specific surface area accessible to the adsorption of CO. This is probably connected with the decoration and blockade of a portion of the ruthenium surface by some nickel oxides. Data on the influence, which is exerted by the concentration of methanol, alkali, and temperature on the electrocatalytic activity of the AD100 + 15 wt % RuNi catalyst at a 68 : 32 atomic ratio (in at. %) between the components, are presented. Rates of the oxidation of methanol, ethanol, n-butanol, and ethylene glycol in identical conditions on the catalyst AD100 + 15 wt % RuNi (68 : 32 at. %) between the metals are compared with one another. The oxidation currents, which are observed at a potential of 0.3 V, are equal to 5.48, 2.67, 0.48, and 0.47 A per gram of the catalyst for ethanol, ethylene glycol, methanol, and n-butanol, respectively.__________Translated from Elektrokhimiya, Vol. 41, No. 7, 2005, pp. 829–839.Original Russian Text Copyright © 2005 by Tarasevich, Karichev, Bogdanovskaya, Kapustin, Lubnin, Osina.