Electrochemical Characterization of Shape-Controlled Pt Nanoparticles in Different Supporting Electrolytes

The voltammetric profile of preferentially shaped platinum nanoparticles has been used to analyze the different sites present on the surface. For the first time, this analysis has been made in NaOH solutions and revisited in sulfuric and perchloric acid media. The comparison with the voltammetric profiles of the model surfaces, that is, single-crystal electrodes, allows assigning the different signals appearing in the voltammograms of the nanoparticle to specific sites on the surface. A good correlation between the shape of the nanoparticle determined by TEM and the voltammetric profile is obtained. For the nanoparticles characterized in alkaline media, the adsorbed species on the surface have been characterized, and three major regions can be identified. Below 0.2 V, the major contribution is due to hydrogen adsorption, whereas above 0.6 V, adsorbed OH is the main species on the surface. Between those values, the signals are due to the competitive adsorption/desorption process of OH/H. New criteria for determining the active area in NaOH solutions has been proposed. In this medium, the total charge density measured between 0.06 and 0.90 V stands for 390 μC cm–2. The areas measured are in perfect agreement with those measured in acid media. Once the nanoparticles have been characterized, the behavior of the nanoparticles toward CO oxidation is analyzed and compared with that observed for single-crystal electrodes.

Characterization and electrochemical properties of conducting nanocomposites synthesized from p-anisidine and aniline with titanium carbide by chemical oxidative method

A novel polymer/TiC nanocomposites “PPA/TiC, poly(PA-co-ANI)/TiC and PANI/TiC” was successfully synthesized by chemical oxidation polymerization at room temperature using p-anisidine and/or aniline monomers and titanium carbide (TiC) in the presence of hydrochloric acid as a dopant with ammonium persulfate as oxidant. These nanocomposites obtained were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and thermogravimetric analysis (TGA). XRD indicated the presence of interactions between polymers and TiC nanoparticle and the TGA revealed that the TiC nanoparticles improve the thermal stability of the polymers. The electrical conductivity of nanocomposites is in the range of 0.079–0.91 S cm−1. The electrochemical behavior of the polymers extracted from the nanocomposites has been analyzed by cyclic voltammetry. Good electrochemical response has been observed for polymer films; the observed redox processes indicate that the polymerisation on TiC nanoparticles produces electroactive polymers. These nanocomposite microspheres can potentially used in commercial applications as fillers for antistatic and anticorrosion coatings.

Sn@Pt and Rh@Pt core–shell nanoparticles synthesis for glycerol oxidation

The development and optimization of electrocatalysts for application in fuel cell systems have been the focus of a variety of studies where core–shell structures have been considered as a promising alternative among the materials studied. We synthesized core–shell nanoparticles of Sn x @Pt y and Rh x @Pt y (Sn@Pt, Sn@Pt2, Sn@Pt3, Rh@Pt, Rh@Pt2, and Rh@Pt3) through a reduction methodology using sodium borohydride. These nanoparticles were electrochemically characterized by cyclic voltammetry and further analyzed by cyclic voltammetry studying their catalytic activity toward glycerol electro-oxidation; chronoamperometry and potentiostatic polarization experiments were also carried out. The physical characterization was carried out by X-ray diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The onset potential for glycerol oxidation was shifted in 130 and 120 mV on the Sn@Pt3/C and Rh@Pt3/C catalysts, respectively, compared to commercial Pt/C, while the stationary pseudo-current density, taken at 600 mV, increased 2-fold and 5-fold for these catalysts related to Pt/C, respectively. Thus, the catalysts synthesized by the developed methodology have enhanced catalytic activity toward the electro-oxidation of glycerol, representing an interesting alternative for fuel cell systems.