Abstract
Three types of carbon nanofibers (pyrolytically stripped carbon nanofibers (PS), low-temperature heat treated carbon nanofibers (LHT), and high-temperature heat treated carbon nanofibers (HHT)) with different graphitization degrees and surface chemistry have been used as support for Au, Pd, or bimetallic AuPd alloy nanoparticles (NPs). The carbon supports have been characterized using Raman, X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). Moreover, the morphology of the metal nanoparticles was investigated using transmission electron microscopy (TEM) and CV. The different properties of the carbon-based supports (particularly the graphitization degree) yield different electrochemical behaviors, in terms of potential window widths and electrocatalytic effects. Comparing the electrochemical behavior of monometallic Au and Pd and bimetallic AuPd, it is possible to observe the interaction of the two metals when alloyed. Moreover, we demonstrate that carbon surface has a strong effect on the electrochemical stability of AuPd nanoparticles. By tuning the Au-Pd nanoparticles’ morphology and modulating the surface chemistry of the carbon support, it is possible to obtain materials characterized by novel electrochemical properties. This aspect makes them good candidates to be conveniently applied in different fields.
Highlights
Over the last decades, many studies have focused on metal nanoparticles, thanks to their excellent catalytic, electrocatalytic, optical, and magnetic properties, that often differ from the ones of their correspondent bulk metals [1,2,3]
Morphology of the catalysts was characterized by high angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM), and its composition information was acquired by EDAX S-UTW EDX detector in an FEI Titan 80−300 microscope operating (Thermo Fisher Scientific, Waltham, MA, USA) at 300 kV
Raman spectroscopy has been used to investigate the graphitization degree of carbon nanofibers (CNFs) treated at different temperatures
Summary
Many studies have focused on metal nanoparticles, thanks to their excellent catalytic, electrocatalytic, optical, and magnetic properties, that often differ from the ones of their correspondent bulk metals [1,2,3]. There has been interest in bimetallic nanosystems, because of the possibility to create new materials characterized by specific and innovative properties due to synergistic effects among precursors [4,5,6,7] These effects reflect a general enhancement of the performances of the final products with respect to their monometallic components. The results highlight how the bimetallic samples behave differently with respect to the relative Au and Pd monometallic systems, underlying the presence of an intimate contact between the two metals, which provides new materials, completely different from the original ones. This aspect makes them good candidates to be conveniently applied in many different applications
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