Abstract
Bimetallic nanoparticles are of special interest for their potential applications for fuel cells, mainly for portable power applications. Among the bimetallic systems, Pt-Pd bimetallic nanoparticles have received great interest as they can be widely used as effective catalysts for various electrochemical reactions. In this work, Pt-Pd alloy bimetallic nanoparticles were synthesized through a chemical reduction method. The nanoparticles were characterized using aberration-corrected scanning/transmission electron microscopy (STEM). Also, parallel beam X-Ray diffraction analysis was carried out to evaluate the crystallographic structure. High-angle annular dark field (HAADF)-STEM images of the Pt-Pd bimetallic nanoparticles were obtained. The contrast of the images shows that the nanoparticles have an alloy structure with an average size of 7.15 nm. To understand the properties of the bimetallic nanoparticles, it is necessary to know the distribution of the elements in the nanostructure. We have used a semi-quantitative method to analyze the HAADF-STEM images, which allowed us to measure the total intensity of the scattered electrons for each atomic column. HAADF-STEM images of the Pt-Pd bimetallic nanoparticles were compared directly with image simulations, good agreement between simulation and experimental images was found. Cyclic voltammetry studies were carried out to analyze the electrochemical behavior of the bimetallic nanoparticles.
Highlights
In recent years, there has been much interest in improving the physicochemical properties of multimetallic nanoparticles
Pt-Pd alloy bimetallic nanoparticles were characterized as colloidal solution and as nanoparticles supported on Vulcan carbon
The samples were characterized by scanning electron microscopy (SEM) using the Hitachi SU8230 cold field emission (CFE) SEM/scanning/transmission electron microscopy (STEM) microscope, which is equipped with detectors that allow the simultaneous recording of various electron signals and energies
Summary
There has been much interest in improving the physicochemical properties of multimetallic nanoparticles. Bimetallic nanoparticles (NPs) are of interest since they lead to many interesting electrical, chemical, catalytic, and optical properties[1]. It is important to carry out images simulations based on the dynamical theory of electron diffraction for the quantitative interpretation of experimental HAADF-STEM images. When HAADF-STEM image simulations are carried out, all the experimental conditions of the electron microscope are taken into account, such as: acceleration voltage, defocus, coma, astigmatism, spherical aberration, chromatic aberration, probe size, convergence angle, annular detector range, and specimen thickness. A semi-quantitative method to analyze HAADF-STEM images was used, which allowed us to measure the total intensity of the scattered electrons for each atomic column and to know the distribution of the elements in the nanoparticle. Electrochemical properties of the as-prepared nanoparticles were measured using cyclic voltammetry
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