RESUMEN
Chronoamperometry was used to study the dynamics of Pt nanoparticle (NP) collision with an inert ultramicroelectrode via electrocatalytic amplification (ECA) in the hydrogen evolution reaction. ECA and dynamic light scattering (DLS) results reveal that the NP colloid remains stable only at low proton concentrations (1.0â mm) under a helium (He) atmosphere, ensuring that the collision events occur at genuinely single NP level. Amperometry of single NP collisions under a He atmosphere shows that each discrete current profile of the collision event evolves from spike to staircase at more negative potentials, while a staircase response is observed at all of the applied potentials under hydrogen-containing atmospheres. The particle size distribution estimated from the diffusion-controlled current in He agrees well with electron microscopy and DLS observations. These results shed light on the interfacial dynamics of the single nanoparticle collision electrochemistry.
RESUMEN
Carbon supported PtSn catalyst (PtSn/C) was prepared by a modified polyol method and characterized by means of XRD. It was showed that the metal particle size was 2.2 nm and the unit cell parameter increased compared with Pt/C. In situ time-resolved Fourier transform infrared spectroscopy (TRFTIRS) was used to study the electrooxidation of ethanol on PtSn/C catalyst. COL was the main poison species adsorbed on the active sites to inhibit the further reaction of ethanol electrooxidation. Acetaldehyde and acetic acid were found to be the products of ethanol electrooxidation as competing reactions with ethanol dissociation when the potential was up to 0.3 V, which reduced the poisoning effect. The selectivity of acetic acid among the products was improved with the increase in the potential and reaction time. CO2, which appeared at 0.4 V, was the final product and yielded from the oxidation of COL. The catalytic mechanism of PtSn/C towards ethanol electrooxidation was analyzed based on the results.
RESUMEN
Nanosized LnVO4:Eu (Ln = La, Gd, Y) with diameters ranging from 20 to 50 nm were synthesized by complex sol-gel technique. The structures and spectral properties of LnVO4:Eu were studied by X-ray powder diffraction (XRD), Fourier transform (FT-IR) spectroscopy, luminescence spectra and ultraviolet spectroscopy (UV). The experimental results show that YVO4:Eu and GdVO4:Eu have similar spectral properties because they both have the structure of xenotime, while the structure of LaVO4:Eu belongs to monazite, whose symmetry is inferior to the former vanadates. Consequently the spectral properties of LaVO4:Eu are obviously different from the other two luminescence materials, as the peaks of infrared spectrum and emission spectrum become wider and the number of peaks in UV-Vis spectrum increases.