PREPARATION OF PLATINUM CLUSTER-DERIVED ELECTRODES FROM METAL-CARBONYL-COMPLEXES AND THEIR ELECTROCATALYTIC PROPERTIES FOR ANODIC-OXIDATION OF METHANOL

Platinum and platinum-based bimetallic carbonyl cluster complex anions, [Pt3n(CO)6n]2- (n = 3, 5), [Pt3Fe3(CO)15]2-, [PtCl2(SnCl3)2]2- and [Pt3Sn8Cl20]4-, were introduced by an ion exchange technique on graphite disks, treated beforehand with an organosilane reagent of quarternary ammonium chloride, or on anion exchange membranes to prepare metal cluster-attached electrodes. The Auger electron spectra showed that platinum species were indeed attached on the electrodes. Except for the Pt-Sn electrodes, the redox voltammograms due to H+/H(a) in the potential range 0.05-0.40 V (RHE) were clearly observed in 0.5M H2SO4 solution, which are very similar as those observed on Pt electrodes-prepared by vacuum evaporation. Dependence of the electrocatalytic activity for the anodic oxidation of methanol on the cluster size indicated that the activity becomes significant on electrodes with the precursor unit size of above Pt9. Particularly, the Pt-15-derived electrodes, following by heating in H-2 or air at 373-573 K, were found to be highly active for the anodic oxidation of methanol.