Electrochemical Deposition of Pt–RuO x ⋅nH2O Composites on Conductive Diamond and Its Application to Methanol Oxidation in Acidic Media

Abstract

Boron-doped diamond (BDD) films were used as substrates for the electrochemical deposition of a platinum–hydrous ruthenium oxide (Pt–RuO x ⋅nH2O) composite with promising electrocatalytic activity for methanol oxidation. The influence of the BDD surface termination was checked, and it was found that oxidized diamond (BDD-O) not only allows more efficient RuO x ⋅nH2O deposition but also enables a higher surface concentration of oxygenated carbon species. Scanning electron microscopy (SEM) and cyclic voltammetry experiments have shown that, with a BDD-O support, an increase of the oxide loading from ca. 3 to ca. 140 μg cm−2 results in an enhancement of approximately six times of the specific surface area of deposited Pt particles, with beneficial effects on the electrocatalytic activity for methanol oxidation. However, in terms of resistance to fouling, a lower amount of RuO x ⋅nH2O appeared to be more advantageous, probably due to the fact that, as evidenced by X-ray photoelectron spectroscopy (XPS), it allows higher surface concentration of oxidized species of both carbon and platinum. These species could act as oxygen donors and may facilitate further oxidation of carbon monoxide to CO2.