Electrochemical measurements of 1D/2D/3DNi-Co bi-phase mesoporous nanohybrids synthesized using free-template hydrothermal method

Highlights: • Ni/Co-precursor ratio effect on the template-free hydrothermal growth of carbonate and/or hydroxide nanocomposites. • Ni/Co-content ratio effect on electrochemical performance of Ni-Co based multiphase nanocomposites. • D/2D/3D architecture microstructures of Ni-Co bi-phase nanohybrids as promising candidates for electrodes in supercapacitor application. 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.