Nickel impregnated silicalite-1 as an electro-catalyst for methanol oxidation

Nickel impregnated zeolite-modified electrodes were prepared by mixing Ni-silicalite-1 with conducting carbon black in different rations. Using the cyclic voltammetric technique the electrochemical oxidation of methanol at such electrodes was investigated. Experiments on silicalite-1 (S-1) and nickel-silicalite-1 (Ni-S-1) show that they are not electrochemically active towards methanol oxidation in KOH solution. The presence of nickel ions in the zeolite matrix, by soaking the electrode in an aqueous NiSO4 solution, markedly enhances the electrocatalytic activity which was found to depend on the nickel content. On the other hand, the presence of zeolite and/or Ni metals in the catalyst is essential, however, the electro-catalytic activity depends on the Ni-S-1:carbon black ratio. Electrodes with Ni-S-1:carbon black ratio of 1:3, show the maximum electro-catalytic activity. The importance of impregnated Ni metal in the zeolite matrix is discussed on the basis of the experimental results. A weak dependence on bulk methanol concentration was observed. SEM analysis was used to characterize the Ni-S-1 catalyst. Dependence of methanol electro-oxidation on methanol concentration was discussed. (c) 2005 Elsevier B.V. All rights reserved.