No abstract

This work examines the effect of the degree of surface oxidation of carbon fibers on the anchoring of hydroxyl- terminated dendrimers that encapsulate platinum nanoparticles. Several methods of electrochemical pretreatment were investigated for the preparation of the carbon-fiber surfaces to obtain electrodes with functional groups of varying characteristics. The resulting carbon-fiber surfaces were modified with platinum-encapsulating dendrimers by means of ether linkages. The coverage of active groups on the oxidized carbon surfaces as well as the active area of the dendrimer-encapsulated platinum (G4OHPt) were evaluated with respect to the pretreatment method. The results showed that cyclic voltammetry as the pretreatment method immobilizes a significant amount of dendrimer- encapsulated platinum on the carbon-fiber surface. Accordingly, kinetic parameters obtained for the oxygen-reduction reaction on this surface indicate acceptable catalytic activity.

Bimetallic nanoparticles are of special interest for their potential applications to fuel cells, among the bimetallic systems, AuPd bimetallic nanoparticles have received great interest as they can be widely used as effective catalysts for various electrochemical reactions. Monodisperse AgPd alloy nanoparticles were synthesized by polyol method using silver nitrate and potassium tetrachloropalladate(II) in ethylene glycol as the reducing agent at 160°C. Structural, compositional and electrochemical characterizations of synthesized bimetallic nanoparticles were investigated. High-angle annular dark field scanning/transmission electron microscopy (HAADF-STEM) images and parallel beam X-ray diffraction (XRD) of the bimetallic nanoparticles were obtained. XRD and the contrast of the HAADF-STEM images show that the bimetallic nanoparticles have an alloy structure. Cyclic voltammetry was carried out in order to confirm the electrochemical responses of the AgPd/C electrocatalysts for methanol oxidation. Thanks to the narrow size distribution of the AgPd alloy bimetallic nanoparticles (9.15 nm) the supported AgPd/C electrocatalysts have high catalytic activity toward methanol electro-oxidation.