Publications internationales
Résumé: Cobalt ferrite magnetic nanoparticles (CoFe2O4-MNPs) were synthesized by hydrothermal and co-precipitation methods using different precursors such as nitrates, chlorides, and acetates, at different concentrations with/without surfactant under different growth conditions. The structural and morphological analyses reveal the formation of a single-phase CoFe2O4 in nanoplatelet-shaped NPs with average particle size between 11 and 26 nm depending on synthesis condition. The specific surface area of these NPs obtained by hydrothermal method was ~ 34 m2 g−1. Electrochemical performances of the obtained nanoparticles in a three-electrode configuration with a 6 M KOH electrolyte revealed a specific capacitance (C s) of 429 F/g at 0.5 A/g, with excellent capacitance retention of 98.8% after 6000 cycles at 10 A/g for the electro-active NPs synthesized by hydrothermal method at 200 °C for 18 h.
Résumé: In this study, a facile and low cost free-template hydrothermal precipitation method was used to synthesize mesoporous Ni-Co based bimetallic carbonates (CO3)2- and/or hydroxides (OH)−micro/nanostructures with different morphologies (1D, 2D and 3D) based on variant stoichiometric compositions. The effect of the growth temperature, synthesis time as well as the Ni/Co-precursors ratio on the physico-chemical properties and faradic electrochemical behavior of these products was investigated. The as-obtained bi-phase nanohybrids were characterized extensively structurally and morphologically. The textural analysis results confirmed the presence of mesoporous products with a BET-SSA ∼50 m2 g−1 (0.52 cm3 g−1 pore volume) for the 3D urchin-like structure and a BET-SSA ∼ 47.14 m2 g−1 (0.31 cm3 g−1 pore volume) was obtained for the 2D nanoflakes structure. The electrochemical measurements performed in a 6.0 MKOH aqueous electrolyte depicted excellent electrochemical performance ascribed to the optimized composition of Ni-Co LDH (or α-Ni(OH)2) with Co2(OH)3Cl and their unique hierarchical mesoporous nanoflake and urchin-like architectures. In addition, an exceptionally notable specific capacitances (capacities) of 1700 F g−1 (161 mAh.g−1) and 1379 F g−1 (192 mAh.g−1) were obtained for both structures at 5 mV s−1 scan rate (0.5 A g−1 gravimetric current density) respectively. These are much better than mono - hydroxides synthesized in same conditions with 351 F g−1 (90 mAh.g−1) for Ni and 216 F g−1 (21.5 mAh.g−1) for Co. A good cyclic stability of ∼98% after 2000 charge-discharge cycles at 30 A g−1 was recorded depicting their potential as suitable materials for energy storage devices.