Silica veils-conductive diamond powder composite as a new propitious substrate for platinum electrocatalysts

Abstract

An innovative composite was obtained by a straightforward sol-gel procedure, involving boron-doped diamond powder (BDDP) incorporation into a SiO2 veil (SiO2V) matrix. Composite-coated glassy carbon plates were used as substrate for Pt electrochemical deposition, and the electrodes thus obtained (Pt/BDDP–SiO2V) were compared on a relative basis with those prepared in the absence of the silica matrix (Pt/BDDP). SEM measurements have shown that a BDDP substrate promotes Pt cluster formation, whereas on BDDP–SiO2V, particles are much smaller (ca. 45 nm to ca. 140 nm). The activity for CH3OH oxidation was checked by cyclic voltammetry, and it was found that at Pt/BDDP–SiO2V, the main anodic peak is shifted with ca. 0.35 V toward lower potentials, indicating a considerable improvement in the overall process kinetics. Stripping experiments together with long-term polarization measurements demonstrated that when deposited on the BDDP–SiO2V support, Pt particles are less susceptible to CO poisoning and this behavior was tentatively ascribed to the presence of a higher relative surface concentration of more stable, oxidized platinum species, as evidenced by XPS.