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

Abstract

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 ~50m2 g 1 (0.52 cm3 g 1 pore volume) for the 3D urchin-like structure and a BET-SSA ~ 47.14m2 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 a-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 (161mAh.g 1) and 1379 F g 1 (192 mAh.g 1) were obtained for both structures at 5mV 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.