MnO₂/CNS Nanofilms Prepared By Layer-by-layer Assembly For Supercapacitor Application

Supercapacitor is a new energy storage device with higher power density,energy density,longer service life and pollution free compared with battery and traditional capacitor.Recently,scientists have employed biomaterial such as coffee ground,sugar cane bagasse,bacterium,fungi to prepare carbon materials,it has revealed vast application foreground in energy storage device because of their abundance,low-price and simple preparation.The layer-by-layer(LBL)technique is a simple,high-efficient,economic and effective approach to construct composite multilayers on substrates.Till now,the multi-functionalized nanomaterials prepared by layer-by-layer technique have been used as electrode materials and applied in energy storage device.The main contents for the thesis are as follows:In the first chapter,we introduced the important carbon nanomaterials and metallic oxide that were wide used recently.And we also described the basic conceptions and developments of layer-by-layer technique,and mainly introduced the types,application value and future prospect of supercapacitor.In the second chapter,to prepare highly activated carbon nanospheres(CNS),we used biomaterial-cocoon silk as the raw material.First,the porous carbon wires were prepared by calcination of silk at high temperature.Subsequently,the as-formed carbon wires were refluxed in nitric acid to form carbon nanospheres with good water-solubility and negatively charged groups on their surface.Good water-solubility is originated from the abundant carboxylic acid groups on the surface.CNS has an extremely broad application prospect in the construction of capacitors.In the third chapter,based on electrostatic adsorption,we assembled the amine-functionalized poly(allylamine hydrochloride)(PAH)and the carboxy-functionalized carbon CNS to fabricate thin film by LBL technique.In this process,the proppant is introduced into the PAH layer innovatively,then removed after the formation of thin film,by which a lot of nanopores can be generated in the as-formed nanofilm.Thus,the thin film prepared by this strategy has porous structure,good water-solubility,large specific surface and well solute transport capacity.Based on the above structural features of thin film,KMnO4 would successfully enter the inner pores of the thin film,and reduced to MnO2 owning to the reducibility of CNS.The specific capacitance of[PAH-CNS]20-MnO2 composite thin film can reach to 1134 F/g based on MnO2,The specific capacitance can remain 85.00%of the maximum value after continuous charge-discharge 1000 times.Obviously the[PAH-CNS]20-MnO2 nanofilm could be a promising supercapacitor electrode material.