Particle size effect of silver nanoparticles decorated single walled carbon nanotube electrode for supercapacitors

Abstract

Well dispersed silver nanoparticles (AgNPs) of different sizes (1–13 nm) on single walled carbon nanotubes (SWCNTs) were synthesized by a facile room-temperature deposition–precipitation process. The morphology and microstructure of samples examined by the transmission electron microscopy showed a monodispersed silver particle decorated SWCNT of 2 wt % as determined by the Rietveld phase analysis of powder X-ray diffraction patterns. The chemical state of silver determined from the binding energies of high resolution Ag 3d peaks from X-ray photoelectron spectroscopy revealed a silver (Ag0) oxidation state. Electrochemical properties were studied using cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance studies. Silver decorated SWCNTs demonstrated to be effective bifunctional charge collectors and active electrode materials for a supercapacitor, exhibiting a higher specific capacitance (106 F g−1) compared to pristine SWCNT (47 F g−1). An enhancement observed with AgNP decoration is highly size-dependent and is related to the improved intertube contact resistance, electroactive surface considerations, as well as the participation of Ag in a faradaic reaction induced pseudocapacitance. Decorating the SWCNT with 1 nm AgNP doubled the energy density of the device, which on charge–discharge cycling retained 84% of the initial capacitance at the end of 8000 cycles.