Preparation By A Simple Template-free Growth Method And Electrochemical Performance Research Of Cobalt Compounds

Compounds of cobalt is a member of important transition metal compounds, they have many functional applications, especially in electrochemical aspects. For example, They can be used as fuel cell catalysts, cathode materials of nickel-metal hydride battery and anode materials of supercapacitor. In this paper, CoS and Co?OH?₂ electrodes are prepared by a simple template-free growth method. The as-prepared electrodes were characterized by X-rays diffraction ?XRD? and scanning electron microscopy ?SEM?. The electrochemical hydrogen storage performance as MH/Ni battery cathode and the capacitance performance supercapacitor anode were investigated by some electrochemical measurement technologies,such as Chronpotentiometry?CP?, Cyclic Voltammetry?CV? and Electrochemical impedance spectro-scopic ?EIS?.The electrochemical hydrogen storage performance of CoS and Co?OH?₂ electrodes was investigated in the alkali electrolyte respectively. The discharge/charge curves both show two discharge voltage platforms. The results of the cycling performance under the current density of 60 mA·g^-1 show that the discharge capacity of Co?OH?₂ electrode is 319.32 mAh·g^-1 at the first circle, then the discharge capacities decays quickly with the rate of 53.84% after 20 circles. Meanwhile, the first circle discharge capacity of CoS electrode is 220.15 mAh·g^-1 at the same condition and remains 145.66 mAh·g^-1 after 20 circles. The cycling performance of the electrodes was tested under different current densities. The results show that the electrodes both have the best cycle performance under the current density of 100 mA·g^-1.The capacitance performance of CoS and Co?OH?₂ electrodes were investigated in the alkali electrolyte respectively, too. The Co?OH?₂ electrode exhibits a speccific capacitance of 1136 F·g^-1 at a charge/discharge current density of 20 mA/cm² and the specific capacitance is retained 48% at a charge/discharge current density of 100 mA/cm². As to the CoS electrode, its speccific capacitance is 1625 F·g^-1 at a charge/discharge current density of 2mA/cm² and the specific capacitance is retained 61% at a charge/discharge current density of 100mA/cm².The asymmetric supercapacitors of CoS and Co?OH?₂ could be cycled reversibly in the high-voltage region of 0?1.6 V and Co?OH?₂ asymmetric supercapacitor displays a specific capacitance of 77 F/g and high energy density of 28 Wh/kg at a charge/discharge current density of 10 mA/cm², while CoS asymmetric supercapacitor displays a specific capacitance of 114 F/g and high energy density of 40 Wh/kg at a charge/discharge current density of 2 mA/cm². Furthermore, Co?OH?₂ asymmetric supercapacitor device exhibits an excellent long cycle life along with 80% specific capacitance retained after 10000 cycles at at a charge/discharge current density of 10 mA/cm² and the rate of CoS is 90% after 10000 cycles at at a charge/discharge current density of 5 mA/cm².