Microemulsions as Reaction Media for the Synthesis of Bimetallic Nanoparticles: Size and Composition of Particles

Abstract

This paper describes the synthesis of intermetallic Pt/Bi and Pt/Pb nanoparticles (NPs) using waterin-oil (w/o) microemulsions (μe) as template. For that purpose, w/o-microemulsions containing H 2 PtCl 6 þ Pb(NO 3 ) 2 and H 2 PtCl 6 þBi(NO) 3 , respectively, were mixed either with a w/o-microemulsion containing the reducing agent (NaBH 4 ) or with solid NaBH 4 . A variation of the amount of reducing agent led to different particle compositions and sizes, while different ratios of the two metal salts only affected the composition but not the size of the resulting NPs. The size and structure of the microemulsion droplets were studied via small angle X-ray scattering (SAXS), and the intermetallic NPs were characterized by high resolution transmission electron microscopy (HRTEM) in combination with energy dispersive X-ray spectroscopy (EDX) and selected area electron diffraction (SAED). The results revealed that it is indeed possible to synthesis Pt/Pb and Pt/Bi intermetallic nanoparticles of ∼3-8 nm in diameter at low temperatures.

Catalytic Activity of Mono- and Bi-Metallic Nanoparticles Synthesized via Microemulsions

“…The synthesis of the mono-and bi-metallic nanoparticles via the microemulsion route has been described elsewhere [13,14] and will thus not be explained. Furthermore, a detailed characterization of the composition of the bimetallic PtBi and PtPb nanoparticles has been previously published [13,14].…”

“…The synthesis of the mono-and bi-metallic nanoparticles via the microemulsion route has been described elsewhere [13,14] and will thus not be explained. Furthermore, a detailed characterization of the composition of the bimetallic PtBi and PtPb nanoparticles has been previously published [13,14]. The main results of this study are as follows: (1) using the microemulsion route, it is possible to synthesize bimetallic nanoparticles, rather than core-shell structures, even of metals with great differences in the reduction potentials of their respective metal salts; (2) it is possible to influence their composition via a variation in the metal salt ratio, as well as the amount of reducing agent; and (3) the resulting nanoparticles consist of a mixture of phases rather than of a single bimetallic phase, including oxide phases.…”

“…Although it is well known in the literature that intermetallic PtBi and PtPb electrodes are less affected by CO poisoning compared to monometallic Pt electrodes [5,6,9,[21][22][23], it is interesting to find out whether the mixture of phases present in our nanoparticles [13,24] has an effect on the activity and selectivity of the electrochemical reaction. For this purpose, we compare the ratios discussed above with the ratios calculated from the literature.…”

“…In previous work, it has been shown that it is possible to synthesize monometallic and bimetallic nanoparticles in microemulsions at room temperature [13][14][15]. Measurements have proven that it is possible to control the size of the NPs by varying the size of the microemulsion droplet prior to the synthesis [15].…”

“…Measurements have proven that it is possible to control the size of the NPs by varying the size of the microemulsion droplet prior to the synthesis [15]. It is further possible to change the composition of the NPs by changing the concentration of the reducing agent and or the metal salt ratios [13].…”