Preparation Of Cobalt/Nickel Hydroxide And Co₃O₄ And Their Electrochemical Capacitive Properties

Super-capacitor is a new kind of energy storage devices with remarkable advantages. Electrode material is an important factor that affects the electrochemical performances. Therefore, the research and development of electrode materials has been a hot topic in both academic and industrial field in recent years. At present, Cobalt/nickel hydroxide and oxide have a potential application in the electrode materials of electrochemical capacitor due to their excellent electrochemical properties resulting from the good redox reaction activity and unique structure.This thesis was focused on the preparation ofα-Co(OH)₂,Co_xNi_1–x LDHs and Co₃O₄ and their applications as the electrode materials of electrochemical capacitors. Their morphologies, crystal structure and components were characterized by means of modern analysis techniques. The capacitive behaviors of the resultant materials were also measured by electrochemical skills. The main points of this thesis are summarized as follows:1. Sheet-likeα-Co(OH)₂ composed of the uniform nanoparticles was successfully prepared using cobalt chloride as the raw material and polyvinyl pyrrolidone as the dispersant by chemical precipitation method. The components of products were analyzed by FT-IR and the structure and morphology were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. The electrochemical performances were investigated by cyclic voltammetry and constant current charge/discharge techniques. The results show that an extraordinary high specific capacitance value of 1220 F/g was achieved, and theα-Co(OH)₂ is a promising electrode material for supercapacitor2. A novel cobalt nickel double hydroxides (Co_xNi_1–x LDHs) nanoparticles are synthesized by chemical co-precipitation route using cobalt chloride and nickel chloride as the raw material and polyvinyl pyrrolidone as the dispersant to obtain ultrahigh specific capacitances of supercapacitor electrode materials. The structural and morphological characterizations are performed using powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The component of the samples was measured by energy dispersed X-ray spectrometry (EDS), Fourier Transform Infrared (FT-IR) spectrometry. The electrochemical performances were investigated by cyclic voltammetry and constant current charge/discharge techniques. The results show the maximum specific capacitance of 2614 F/g is reached by the Co0.5441Ni0.4559 LDHs in 6 M KOH electrolyte. Furthermore, the Co_0.5441Ni_0.4559 LDHs electrodes exhibit good cyclability, and maintained 91% of the maximum value after 500 cycles at a current density of 5 A/g. The relationship between the chemical composition and the capacitance is discussed.3. The cobalt hydroxide carbonate with different morphology has been synthesized through hydrothermal method using Co(NO₃)₂·6H₂O as cobalt source and urea as precipitating agent in the presence of sodium dodecyl sulfates (SDS) or Polyvinylpyrrolidone (PVP). The components of products were analyzed by FT-IR. The structure and morphology were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. The results show that every one among the four samples displays an interesting and distinctive morphology. The Co₃O₄ powders were obtained when the precursor B was calcined by thermal decomposition methods. The components and morphology of Co₃O₄ product were characterized by FT-IR and field emission scanning electron microscopy (FESEM). The results show the shape and size of the precursor was maintained when treated at 300 oC. The electrochemical performances were investigated by cyclic voltammetry and constant current charge/discharge techniques. The results show that the obtained Co₃O₄ exhibits excellent capacitive properties, and the specific capacitance is as high as 263 F/g within a potential range of -0.4 to 0.55 V (versus Hg/HgO)...