Synthesis And Capacitive Performance Of Bamboo-like Porous Carbon Nanotube And Its Composites

Tubular porous carbon materials have been widely applied in energy storage,gas adsorption,water purification and other fields because of their unique morphology,developed pore structure and large specific surface area.Meanwhile,the application in supercapacitors has already become the research hotspot.Considering the fact that inexpensive manganese dioxide has the advantage of relatively high capacitance,better capacitive performance can be obtained by complexing it with porous carbon material.In this thesis,bamboo-like porous carbon nanotubes with good capacitive properties were prepared and further complexed with manganese dioxide to improve their electrochemical properties.The main research contents were shown as follows:(1)Preparation and capacitive performance of bamboo-like porous carbon nanotubes.The bamboo-like,cross-linked polydivinylbenzene(PDVB)tubes are firstly synthesized by cationic polymerization of divinylbenzene.After a secondary cross-linking being imposed by Friedel-Crafts reaction,the obtained dual cross-linked,carboxylic acid functionalized PDVB tubes are directly subjected to pyrolysis,yielding bamboo-like,O-doped porous carbon tubes(BCTF).The obtained BCTF materials were characterized by SEM,TEM,XRD,XPS and BET techniques.The BCTF materials were also used as electrode supercapacitor materials for the test of the electrochemical properties.The BCTF-900 sample(pyrolyzed at 900 oC)prepared under optimal conditions exhibit a trimodal pore structure(micro-,meso-,and macropores)with a relatively high specific surface area of 595 m2 g-1 and a low total pore volume of 0.37 cm3 g-1.Such bamboo-like carbon tubes display good volumetric capacitive performance(254 F cm-3 at 0.5 A g-1),moderate volumetric energy density(12.9 Wh L-1 at 428 W L-1),and excellent cycling stability(the capacitance retention has remained at 96.9% after 10000 cycles at 2 A g-1).(2)Preparation and capacitive performance of BCTF@MnO2 composite.The composites of porous carbon nanotubes and manganese dioxide(BCTF@MnO2)were prepared by potassium permanganate in situ growth deposition using BCTF-900 as the precursor.The obtained BCTF@MnO2-1.0 composite with reaction time of 1 h has the best electrochemical performance.The obtained composites were studied by SEM,TGA,BET and electrochemical analysis.The BCTF@MnO2 composite was still retained a tubular structure with MnO2 nanoparticles mainly growing on the outer surface of the BCTF tubes.The specific surface area and total pore volume were decreased to 293 m2 g-1 and 0.30 cm3 g-1,respectively,after MnO2 deposition.The capacitance of the BCTF@MnO2-1.0 composite in 1 M Na2SO4 electrolyte is 127 F g-1,the energy density of the composite is as high as 28.9 Wh kg-1 at 478.7 W kg-1 power density,and the capacitance was maintained at 81.1% after 5000 cycles at 2 A g-1 current density.