The role of a bimetallic catalyst in enhancing the electro-catalytic activity towards methanol oxidation

Nickel and ruthenium dispersed on graphite electrode showed a catalytic activity towards methanol oxidation in KOH solution. Various modified graphite electrodes of different Ni-Ru ratios were prepared by the electro-deposition of Ni and Ru from their salt solutions by changing the relative concentration of each metal ion in the deposition bath. Results of the electrochemical measurements revealed that simultaneous deposition of the binary metals is the best method to prepare the catalyst. The relative distribution of Ni-Ru deposits on the graphite electrode depends on the method of deposition as shown by optical microscope analysis. The catalytic activity of the bimetallic catalyst C/(Ni-Ru) towards methanol oxidation was found to vary with the amount of electrodeposited Ni and Ru. However, the catalytic activity increases with increasing the Ni content relative to Ru in the electrode. The dependence of the oxidation current on methanol concentration and the upper- and lower-potential limits was discussed. It was concluded from the electrochemical measurements that methanol oxidation begins at the potential value of NiOOH production with the formation of intermediate products. The presence of perruthenate species on the electrode surface is responsible for the complete oxidation of the intermediate species. (C) 2004 Elsevier B.V. All rights reserved.