Electrodes consisting of Pt nanoparticles dispersed on thin films of niobium oxide were prepared onto titanium substrates by a sol-gel method. The physical characterization of these electrodes was carried out by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The mean size of the Pt particles was found to be 10.7 nm. The general aspects of the electrochemical behavior were studied by cyclic voltammetry in 1 mol L -1 HClO 4 aqueous solution. The response of these electrodes in relation to the oxidation of formaldehyde and methanol in acidic media was also studied.

PtFe/C nanocatalysts of different compositions and nearly constant particle size were prepared by a microemulsion method. Crystallite sizes and degree of alloying were determined by X-ray diffraction. Particle size and distribution were characterized by transmission electron microscopy and average composition was determined by energy dispersive X-ray analysis. Measurements of electrocatalytic activity for oxygen reduction were done using the rotating disk electrode technique in O2 saturated 0.5 mol L-1 sulfuric acid solutions, at room temperature. For all catalysts oxygen reduction begins at ~ 0.90V. Tafel plots show slopes of c.a. 60 and 120 mV dec-1 in the regions of low and high overpotentials, respectively. The best results for the ORR were obtained for the PtFe/C catalyst of composition Pt:Fe 70:30. This catalyst was also found to exhibit the largest methanol tolerance.

Electrodes consisting of Pt nanoparticles dispersed on thin films of niobium oxide were preparedonto titanium substrates by a sol-gel method. The physical characterization of these electrodes was carriedout by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The meansize of the Pt particles was found to be 10.7 nm. The general aspects of the electrochemical behavior werestudied by cyclic voltammetry in 1 mol L -1 HClO 4 aqueous solution. The response of these electrodes inrelation to the oxidation of formaldehyde and methanol in acidic media was also studied.