Enhanced Activity for Methanol Oxidation of Platinum Particles Supported on Iridium Oxide Modified Boron-Doped Diamond Powder

摘要

Electrocatalytic activity toward methanol oxidation in alkaline media of platinum nanoparticles supported on iridium oxide modified boron-doped diamond powder (Pt/IrO2/BDDP) was assessed, and was compared with that of Pt deposited on bare diamond particles (Pt/BDDP). Cyclic voltammetry attests that the presence of the iridium oxide intermediary layer promotes methanol oxidation and provides a more efficient reactivation of Pt particles. Linear sweep voltammetric experiments performed in methanol-free solution indicated that, at Pt/IrO2/BDDP, oxygen evolution is preceded by the formation, within the potential range of CH3OH oxidation, of adsorbed oxygenated species. As expected, the presence in close proximity of Pt particles of such species and of an important amount of IrOx(OH)(y) (evidenced by XPS) assists in the oxidative desorption of CO species adsorbed on Pt active sites. Steady-state polarization measurements carried out in a floating configuration with Pt/IrO2/BDDP gas-diffusion-type electrodes yielded for methanol oxidation overall process Tafel slope values of ca. 120 mVdecade(-1), which compare well with those reported for traditional electrocatalysts.