Ethanol\nElectrooxidation Catalyzed by Tungsten Core@Palladium\nShell Nanoparticles

Abstract

Bimetallic nanostructures\nrepresent effective electrocatalysts\ntoward a number of important reactions. In the present study, carbon-supported\npalladium–tungsten alloy nanoparticles with a quasi-tungsten\ncore@palladium shell structure (W@Pd/C) were synthesized by a galvanic\nreplacement reaction of amorphous tungsten nanoparticles with Pd­(II)\nat different temperatures (0, 25, and 50 °C), and exhibited apparent\nelectrocatalytic activity toward ethanol oxidation reaction (EOR).\nWhen the sample was prepared at 0 °C, large amorphous tungsten\nnanoparticles were etched off and much smaller W@Pd nanoparticles\nwere formed and dispersed rather evenly on the carbon surface whereas\nat higher reaction temperatures (25 and 50 °C), the W@Pd nanoparticles\nbecame agglomerated. The structures of the obtained samples were characterized\nby a range of experimental tools, including (scanning) transmission\nelectron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy,\nand electrochemical methods. Among the series, the W@Pd/C sample prepared\nat 0 °C was observed to exhibit the best EOR performance, with\na mass activity (9535.5 mA mg_Pd^–1) over three times better than that\nof commercial Pd/C and markedly enhanced stability.