Preparation And Electrochemical Properties Of Nitrogen - Doped Porous Carbon Materials Based On ZIF-8

With the increasingly serious problem of fossil energy crisis and environmental pollution,supercapacitor as a new type of energy storage element has been widely used for it's long cycle life,high safety performance and can be operated in a wide temperature range.Electrode material is the current research focus which plays a key role in the electrochemical performance of supercapacitors.Until now,the electrode materials mainly include carbon materials,conductive polymers and metal oxides.Metal organic frameworks?MOFs?,as a new type of multifunctional porous material,have many advantages,such as large specific surface area and controllable pore structure,which have shown great applications in catalysts,sensors and luminescent materials.In this paper,ZIF-8 as the precursor,have been prepared by a simple precipitation method.Then,we have prepared nitrogen-doped porous carbon materials based on ZIF-8 through the direct carbonization.In addition,we also have synthesised nitrogen-doped porous carbon composite by combining the as-prepared porous carbon material through the method of in situ growth.Some symmetric supercapacitors with a high operating voltage had been designed and assembled.The practical value and electrochemical properties of two-electrode systems were systematic evaluated.The main contents are as follows:Nitrogen-doped porous carbon materials based on ZIF-8?HPNCs?have achieved through the direct carbonization method,and systematically studied the effect of the different sources of Zn²⁺on the structure morphology and electrochemical performance of HPNCs.The electrochemical performance of nitrogen-doped porous carbon materials?HPNCs-C8?from the zinc acetate is better than nitrogen-doped porous carbon materials?HPNCs-N8?containing zinc nitrate.The specific capacitance of HPNCs-C8 at the current density of 0.25A/g is 300 F/g,showing a good multiplier performance.And the assembled HPNCs-C8//HPNCs-C8 symmetric supercapacitor delivers a high power density of 0.79 kW/kg at energy density of 24.8 Wh/kg in the voltage window of 0-1.8 V.In order to decrease the agglomeration of HPNCs,we have used the 3D interconnected honeycomb-like structure carbon sphere which made of natural lotus powder as the carbon source and the template,compositing with HPNCs to successfully synthesize nitrogen-doped porous carbon materials?HPNCs/CS?by a simple static method.The specific capacitance of HPNCs/CS at a current density of 1 A/g is 280 F/g,which compared with HPNCs suggesting a good electrochemocal performance.Moreover,the assembled symmetrical supercapacitor exhibits that the gravimetric energy density of HPNCs/CS//HPNCs/CS is 16.2 Wh/kg at the power density of 0.45 kW/kg in the voltage window of 0-1.8 V.We have substituted the reduced oxide graphite for hollow interconnected carbon spheres,which composite with HPNCs to prepare nitrogen-doped porous carbon based on ZIF-8 and the reduced oxide graphite composites?HPNCs/rGO?.Effects of activation temperature and the quantity of graphite were systematically studied on the morphology and electrochemical performances of HPNCs/rGO.HPNCs/rGO-800,which have prepared from 8mg GO and the carbonization temperature at 800°C,show a better electrochemical performance.HPNCs/rGO-800 exhibite the specific capacitance of 298 F/g at the current density of 0.5 A/g.Assembled into a symmetric supercapacitor,the energy density of HPNCs/rGO-800//HPNCs/rGO-800 is 18 Wh/kg when the power density is 475 W/kg in the voltage window of 0-1.8 V.