The Influence Of Zeolite Structure On The Specific Capacitance Of Zeolite/Ni(OH)₂ Composite As Supercapacitor Electrode Materials

In this thesis,the newest development in research of ultra-stable Y zeolite/metal hydroxide composite materials as the electrode material of supercapacitor devices has been reviewed.Relevant electrode materials in this kind of devices were prepared and their electrochemical characteristics were explored in detail.The microstructures and morphologies of these materials were investigated by XRD and TEM measurements. The electrochemical performance has been evaluated by galvanostatic charge-discharge,cyclic voltammetry(CV) and electrochemical impedance spectra (EIS).The main result is the following:1.Different kinds of ultra-stable Y zeolite were successfully synthesized by repeated sodium exchange of NaY zeolite with different NH₄Cl concentration and then steamed at different temperature.The results indicate that with the increasing of NH₄Cl concentration,the crystal cell constant decreased,whereas the crystal cell constant increased with increasing the steam temperature.The Si/Al ratio of the USY sample increases with the increaseing of NH₄Cl concentration at low concentration. The Si/Al ratio reached a maximun value when NH₄Cl concentration is at 2 M and then decreased with further increasing the concentration of NH₄Cl.The Si/Al ratio increase almost linearly with increasing the steam temperature.2.Nickel hydroxide was successfully synthesized by a facile chemical precipitation reaction between NiCl₂·6H₂O and NH₃·H₂O.Structure characterizations indicate that a flower-like structure with low erystallinity for the nickel hydroxide samples was obtained.A maximum specific capacitance of 2055 F/g could be achieved in 2 M aqueous KOH with the potential range from 0 to 0.4 V(vs.SCE) in a half-cell setup configuration for the Ni(OH)₂ electrode,suggesting its potential application in electrochemical capacitors.The Ni(OH)₂/USY composite were synthesized by a liquid-precipitated method,which used the ultra-stable Y zeolite as the template,and these materials have been applied in the supercapacitor fields.The microstructures, morphologies and electrochemical characteristics of these materials were systemically investigated.The results have shown that the materials have a loosely packed microstructure in the nanometer scale.The special microstructure can accommodate the electroactive species not only on the surface but also in the solid bulk.which is very helpful for making full use of the electroactive sites to take place the faradic reaction,and contributed to the increase of the specific capacitance of the material. 3.Different kinds of Ni(OH)₂/USY composites were synthesized by use different USY zeolite as the template.The microstructures,morphologies and electrochemical characteristics of these Ni(OH)₂/USY composites have been studied in detail. Furthermore,the effect of NH₄Cl concentration,the steam temperature and the load of Ni(OH)₂ on the specific capacitance of the composite has also been systemically explored.