Voltammetric characterization of Pt-TiO{sub}2 composite nanomaterials prepared by metal organic chemical vapour deposition (MOCVD)

摘要

The voltammetric behaviour of the Ru(NH{sub}3){sub}6{sup}(3 + /2+ ) redox couple was studied on Pt-TiO{sub}2-coated stainless steel and gold electrodes. The Pt-TiO{sub}2 coatings were prepared by metal organic chemical vapour deposition in the Pt:Ti composition range 1:10 to 1:80 atomic ratio. These electrodes behaved as ensembles of nanoelectrodes in which the Pt particles acted as active sites, whereas the TiO{sub}2 matrix was inactive. The voltammetric patterns recorded with all the electrodes in Ru(NH{sub}3)6C1{sub}3 solutions displayed quasi-reversible character. Peak current and peak-to-peak separation △E{sub}p were examined as a function of scan rate. From the △E{sub}p values the apparent heterogeneous kinetic rate constant of the Ru(NH{sub}3){sub}6{sup}(3 + /2+ ) redox couple was evaluated with the various electrodes. From these values the fractional surface covered by active Pt or inactive TiO{sub}2 was calculated. The active surface area was in all cases less than 0.06%. From X-ray diffraction measurements the Pt crystallite dimension was calculated to be 6 nm for Pt:Ti 1:10 ratio, and less than 3 nm for lower Pt:Ti ratios.