17 research outputs found
Binary FeāCo Alloy Nanoparticles Showing Significant Enhancement in Electrocatalytic Activity Compared with Bulk Alloys
Microemulsion-based synthesis of FeāCo alloy nanoparticles has been reported for the first time. Spherical, uniform, and highly monodisperse nanoparticles of Fe75Co25, Fe67Co33, Fe50Co50, and Fe33Co67 with an average size of 20, 25, 10, and 40 nm, respectively, were synthesized. These nanoparticles crystallize in a body-centered cubic cell. A higher cobalt content led to the formation of biphasic mixtures. Energy-dispersive X-ray spectroscopy studies confirmed the Fe/Co ratios. Nanoparticles of the Fe33Co67 alloy show higher hydrogen and oxygen evolution efficiencies (over 100 times) compared with other FeāCo alloys of nanocrystalline or bulk form. The FeāCo alloy nanoparticles also show ferromagnetism
Enhanced Electrocatalytic Activity of Copper-Cobalt Nanostructures
Novel coreāshell nanostructures containing Cu and Co have been synthesized using the microemulsion method at 700 Ā°C. The core consists of CuāCo composite particles, whereas the shell is composed of CuāCo alloy particles (shell thickness 12 nm). It is to be noted that in bulk CuāCo binary system there is practically no miscibility. TEM studies show formation of spherical-shaped nanoparticles of coreāshell structures. The composition of the core (CuāCo composite) and shell (CuāCo alloy) were confirmed by XPS studies. The formation of the CuāCo alloy as the shell is mainly driven by surface energy considerations. We have also obtained CuāCo nanocomposites (by controlling the concentration of reducing agent) with particle size in the range of 40ā200 nm. These CuāCo nanostructures show ferromagnetic behavior at 4 K. The saturation magnetization of the coreāshell (CuāCo composite @ CuāCo alloy) nanostructure (125 emu/g) is found to be higher than that of pure CuāCo nanocomposite or alloy, which may be useful for applications as a soft magnet. Electrochemical studies of these nanocrystalline CuāCo particles show higher hydrogen evolution efficiencies (5 times) compared to bulk (micrometer-sized) CuāCo alloy particles