The size effect of Pt/C nanoparticles with diameters ranging from 2 to 28 nm have been studied using X-ray diffraction.

Carbon-supported Pt catalysts prepared by the impregnation method in water−dimethyl sulfoxide (DMSO) solutions were investigated. Using X-ray diffraction (XRD) technique for estimation of the particle size and shapes, we show that morphology of the Pt/C catalysts depends strongly on the DMSO content in the solutions. The average particles size reduces and a shape of the Pt nanocrystals changes from a truncated octahedron to a cuboctahedron and eventually to a truncated cube with increasing DMSO concentration in the reaction mixture. Antibate effects of the size and shape cause nonmonotonic dependence of the catalytic activity for the oxygen reduction reaction (ORR) with electric current maximum at an average particle size of 2.7 nm.

No abstract

No abstract

International audiencePt-Co/C electrocatalysts with Pt loadings near 30 wt. % prepared by the impregnation method in water - ethylene glycol solutions were investigated by X-ray diffraction and correlated with electrochemical measurements. We show that the composition of the binary solvent controls the average particle size and its distribution. The unit cell parameter of the Pt3Co alloy decreases nonlinearly with decreasing particle size. The ORR activity of the prepared Pt-Co/C catalysts in H2SO4 solution enhances with decreasing particle size and unit cell parameter as well as with narrowing of the particle size distribution. Corrosion treatment of the synthesized Pt-Co/C materials causes an increase of ca. 1 nm in average particles size accompanied by broadening of the particle size distribution and decreasing Co content in the Pt-Co alloy. All of the synthesized Pt-Co/C materials show higher ORR activities than do the commercial Pt/C electrocatalysts

No abstract

No abstract

We investigated the effect of huge electric field up to E=55 MV/m on tetragonal ferroelectric phase of BaTiO3 single crystal. Both lattice parameters and the dielectric susceptibility along the polar axis were determined. The induced polarization shows a continuous increase up to 20% of the spontaneous polarization. The longitudinal d33 and transverse d31 piezoelectric coefficients were also determined. The experimental data are described by a phenomenological approach. Interestingly, an intermediate critical electric field value of E∼25 MV/m was evidenced suggesting that the physics below and above this value are different.