دانلود رایگان مقاله انگلیسی عملکرد الکتروشیمایی بهبود یافته پلی اتیلن (amidographene) - الزویر 2019

Abstract

We report a facile route for the synthesis of hyperbranched polyamido-graphenes (HBP(A-G)) as non-metallic high capacity electrodes for charge storage in supercapacitors. HBP(A-G) were synthesized by Michael addition of polyamines, ethylene diamine (EDA), diethylene triamine (DETA), triethylene tetraamine (TETA), to acrylamide grafted graphene oxide, followed by reduction in situ. A 3D network of stiff graphene sheets connected by flexible polyamine chain was formed. Hyperbranching increased d-spacing and BET surface area of graphene stacks, which enhanced accessibility of sites for ion storage, and prevented restacking. HBP(A-G) electrodes displayed electric double layer capacitance behaviour with excellent specific capacitance. The charge storage capacity of the electrodes increased with an increase in the amine chain length. Specific capacitance of electrodes containing HBP(TETA-G) was found to be 269 F g-1 in a symmetric two electrode electrochemical cell, using 1 M H2SO4 electrolyte at a current density of 1 A g-1 for voltage range of 0- 1 V. An increase in the length of amine chains improved ion mobility, lowered equivalent distributed resistance and time constant of the electrodes. The time constant of HBP(TETA-G) capacitor was only 538 ms. Hydrophilic amine linkages on graphene backbone provided stability against electrode volume changes during charging and discharging and gave 89 % capacity retention over 10,000 cycles at 10 A g-1 current density for HBP(TETA-G) electrodes. HBP(A-G) electrodes demonstrated superior performance as electrodes for supercapacitors and has shown potential for use in other electrochemical applications. Graphical abstract Symmetric supercapacitor fabricated using hyperbranched poly(amidographene)s, synthesized via novel route by Michael addition of polyamines to acrylamide-grafted-graphene oxide followed by in situ reduction to graphene, gave high specific capacitance with good energy density.

Electrochemical measurements

Supercapacitor electrodes with an effective area of 0.785 cm2 were prepared by drop-casting sonicated suspension of HBAG in ethanol (3 g/L) on graphite paper followed by drying at room temperature. The increase in mass of the graphite sheet gave the exact amount of HBAG deposited on the electrode. Supercapacitor was assembled in a Swagelok cell using two identical HBAG coated electrodes separated by filter paper. Electrochemical measurements such as cyclic voltammetry, galvanostatic charge/discharge analysis, electrochemical impedance spectroscopy (EIS) were carried out using two electrode method on an electrochemical workstation (μAutolab Type III, Metrohm) with 1 N H2SO4 as electrolyte between 0-1 V. EIS curves were fitted to circuit model using Nova 1.11 software.