Full factorial design applied to the synthesis of Pd-?Ag nanobars by the polyol method and the perspective for ethanol oxidation

Abstract

Full factorial design methodology was applied to the synthesis and optimization of Pd–Ag nanobars using
the polyol process as the reducer. The concentration of Br? ions, the temperature and the reaction time
were selected as factors to study, whereas the yield (% nanobars) was the response to be analyzed. The
nanoparticles were characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy,
transmission electron microscopy, high-resolution transmission electron microscopy and X-ray
photoelectron spectroscopy. The nanoparticles were also tested for the ethanol electro-oxidation
reaction by cyclic voltammetry in alkaline solution. The three factors had a positive effect on
the response: the nanobar yield increased as the level of the variables changed from ?1 to +1. The
temperature and reaction time were the most determinant variables (main and interacting) on the
nanobar yield, whereas the concentration of Br? influenced the yield to a lesser extent. After designing
three optimum experiments, a maximum nanobar yield of 47.3% was obtained. The more negative
electro-oxidation onset, higher current density and more negative current peak potential show that the
incorporation of Ag into Pd nanobars improves the kinetic and thermodynamic behavior towards the
ethanol electro-oxidation reaction compared with that obtained with nanometrically pure Pd nanobars.
This improvement is the result of surface modification caused by the incorporation of Ag in the
formation of Pd–Ag bimetallic nanobars with (200) surfaces.

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Identifiers

ORCID for Carlos Ponce de Leon: orcid.org/0000-0002-1907-5913

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