Amino-functionalized silica anchored to multiwall carbon nanotubes as hybrid electrode material for supercapacitors

Abstract

Silica particles (SiO2) have been prepared by using sol-gel synthesis technique and are amino functionalized by treating with (3-Aminopropyl)triethoxysilane followed by composite formation using acid-functionalized multiwall carbon nanotubes (MWCNTs). The synthesized materials are characterized using morphological and structural techniques like SEM, TEM, XRD, TGA, and FTIR. The MWCNTs with large active surface area and good conductivity present several sites for the growth of spherical SiO2 particles of ∼200 nm diameter. The composite electrode is studied for supercapacitor application between −0.2 to +0.8 V and the electrochemical studies of sample electrodes have been done using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance analysis. The specific capacitance, power density and energy density have been compared at various current rates. The MWCNTs electrode exhibit max specific capacitance of 128.4 F g−1 with a power density of 1000 W kg−1 and energy density of 17.8 Wh kg−1 at 2 A g−1 compared to 11.8 F g−1, 1.64 Wh kg−1 and 1000 W kg−1, respectively for SiO2/MWCNTs electrode at the same current rate. High charge propagation is observed for MWCNTs electrode due to conducting and mesoporous nature along with good resilience. Apparently, the MWCNTs electrode displays lower internal resistance with higher capacitive performance compared to SiO2/MWCNTs composite electrode. It has been observed that the power density of electrodes is strongly dependent on current density and reaches up to 1000 W kg−1 for SiO2/MWCNTs composite as current density is increased up to 2 A g−1. Keywords: Multiwall carbon nanotubes, Functionalization, SiO2, Supercapacitor