Anodic Oxidation of Reductants in Electroless Plating

The anodic oxidat ion of reductants (hypophosphite, formaldehyde, borohydride, d imethylamine borane, and hydra-zine) was studied on different metal electrodes (Au, Pt, Pd, Ag, Cu, Ni, and Co) at various temperatures, with special in-terest in the catalytic aspect of electroless plating. The rate of the anodic oxidat ion strongly depended on the pH value, the concentrat ion of reductants, and the nature of the metal electrode. The catalytic activities of the metals for the anodic oxidat ion of different reductants were evaluated by the potentials at a reference current density. The order of the catalytic activity with metal varied depending on the nature of the reductants. The catalytic activity series thus obtained can be uti l ized for choosing the reductant suitable for the metal to be deposited. Arrhenius plots of the anodic currents on dif ferent metals at a reference potential yielded their respective straight lines. Some correlations were observed be-tween the catalytic activity and the activation energy. The catalytic activity series was discussed in connect ion with that for hydrogen electrode reaction. It is widely accepted that electroless plating proceeds along the electrochemical mechanism as the simultane-ous reaction of cathodic metal deposit ion and anodic oxi-dation of reductant (1-5). The electrochemical condit ions