Fabrication And Supercapacitive Properties Evaluation Of Porous Metal Oxide Electrode Materials

In this thesis, the newest development in research of electrode material of supercapacitors have been reviewed. Meanwhile, porousα-Co(OH)2 thin films have been successfully electrodeposited on nickel foam from 0.1 M cobalt nitrate electrolyte. Besides, cauliflower-like Co3O4 and hierarchical porousβ-Ni(OH)₂ electrode materials have been fabricated by a facile chemical precipitation method. The microstructures and morphologies of synthesized electrode materials were investigated by XRD, SEM, and BET measurements. The electrochemical properties of these electrode materials were evaluated by cyclic voltammetry (CV), galvanostatic charge-discharge, and electrochemical impedance spectra (EIS). The main content of this thesis is show as following:Porousα-Co(OH)2 thin films have been successfully electrodeposited on nickel foam from 0.1 M cobalt nitrate electrolyte. The result of XRD measurement show that the prepared Co(OH)2 corresponds to theα-Co(OH)2. The SEM photographs of porousα-Co(OH)2 thin films indicate that a network microstructure consisting of many interlaced Co(OH)2 leaves have been obtained. Electrochemical measurements show that porousα-Co(OH)2 thin films have excellent electrochemical capacitive behavior. The highest specific capacitance of 1472 F g-1 was reached, and the capacitance value remains 88% of the early cycle after continuous 1000 cycles. The effects of electrodeposition time, deposition potential and different substrates on the specific capacitance and microstructure of prepared porousα-Co(OH)2 thin film were systematically studied. Finally, the growth mechanism of porousα-Co(OH)2 thin film was proposed.Cauliflower-like cobalt oxide was successfully synthesized by a facile chemical precipitation reaction between Co(NO3)2?6H2O and NaOH using air as a mild oxidizing agent, CTAB was served as template to obtain cauliflower-like structure. The effect of vaious discharging current and annealing temperatures on the electrochemical capacitance characteristics has also been systemically explored. The results indicate that cauliflower-like Co3O4 electrode has a highest specific capacitance of 250 F g-1, the attenuation of the specific capacitance after 1000 cycles was only 16%. The mass of CTAB template has apparent effect on specific capacitance of Co3O4 electrode and the optimum value of mass between CTAB and Co(NO3)2?6H2O is 1:2. Hierarchical porousβ-Ni(OH)₂ was successfully synthesized by a facile chemical precipitation reaction between Ni(NO3)2?6H2O and NaOH using CTAB as template. XRD test indicate that the prepared Ni(OH)₂ wasβ-Ni(OH)₂. SEM photographs show thatβ-Ni(OH)₂ was composed of many nanoparticles, and have hierarchical porous microstructure. Electrochemical measurements indicating its excellent electrochemical capacitive behavior, the highest specific capacitance is 2164 F g-1. The capacitance remains 88.3% of the first cycle after 1000 cycles, exhibiting its excellent cycle stability in alkaline solution. Meanwhile, effects of the mass of CTAB, PH value and the crystallinity ofβ-Ni(OH)₂ on specific capacitance were systemically explored. The mass of CTAB template has apparent effect on specific capacitance ofβ-Ni(OH)₂ electrode and the optimum value of mass between CTAB and Ni(NO3)2?6H2O is 1:2. Excessive NaOH and lower crystallinity ofβ-Ni(OH)₂ is useful for improve electrochemical capacitive behavior ofβ-Ni(OH)₂ electrode.