Abstract
Developing multifunctional nanoparticles (NPs) for magnetic and catalytic purposes is crucial for controlling magnetic properties and reducing production costs. We synthesized Co and low Pt loaded CoPt NPs by the modified polyol process. Co and CoPt NPs exhibited coexist fcc and hcp phases which are confirmed with x-ray diffraction and Rietveld refinement analysis. Scanning electron microscopy images revealed the average size of the NPs smaller than 9 nm with a narrow distribution. An irreversible magnetization-temperature behavior of the particles is observed in the modes of zero-field cooled and field cooled with a strong ferromagnetic signal close to 350 K. The field-dependent magnetization up to ±5 T was investigated to determine coercive field ( H c ), exchange bias ( H E ), saturation magnetization ( M s ), remanent magnetization ( M r ), and the ratio of remanent magnetization to saturation magnetization ( M r /M s ). There is a general decrease in magnetic values due to an increase of both the temperature and the Pt ratio in Co nanoparticles. When the Pt/Co ratio drops to 1%, the sample was measured with the highest H c value of 648.5 Oe and M s value of 100 emu/g at 5 K. On the contrary, increasing the concentration of Pt to 10% resulted in a reduction for the M s value below 40 emu/g. Besides, cyclic voltammetry measurements showed apparent hydrogen reduction in the potential range of −0.91 V and −0.96 V (vs Ag/AgCl) and 10% Pt loaded CoPt NPs exhibits the highest activity after 10th cycles and increase the activity up to 15.80 mA cm −2 at −1.2 V due to the surfactant. • Co and CoPt NPs synthesized by modified polyol method exhibited coexist fcc and hcp phases. • Large particle size resulted increased magnetic properties with a strong ferromagnetic signal. • Increasing Pt ratio to 10% results in reduce in magnetization although all samples magnetically separable from environment. • CV measurements showed apparent hydrogen reduction in the potential range of −0.91 V and −0.96 V (vs Ag/AgCl). • Maximum activity is observed as 15.80 mA cm −2 for 10% Pt loaded CoPt NPs.
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