RESUMO
Supercapacitors are irreplaceable energy-storage devices for high power output and rapid charge/discharge of electrical energy. In this study, the laser-based fabrication of reduced graphene oxide (rGO) electrodes for supercapacitors is demonstrated with several new features of laser irradiation. A conventional CO2 laser irradiation system is equipped with (1) a nitrogen blower to avoid combustion of the GO paper, (2) a cylindrical lens for producing a wide line beam, and (3) an optical chopper system for generating an intensity-modulated laser beam. Scanning of the intensity-modulated line beam transforms an extended area of GO into chemically reduced and physically porous graphene. The effects of the laser beam modifications and scanning parameters on the electrochemical performance of the rGO electrode are investigated. The rGO electrode exhibits a high specific capacitance (up to â¼130 F/g) at a current density of 1 A/g. This work can serve as a reference for the process optimization of laser-induced GO reduction.
RESUMO
We investigate the thermal stability of alumina supporting layers sputtered at different conditions and its effect on the growth of aligned single-walled carbon nanotube arrays. Radio frequency magnetron sputtering of alumina under oxygen-argon atmosphere produces a Si-rich alumina alloy film on a silicon substrate. Atomic force microscopy on the annealed catalysts reveals that Si-rich alumina films are more stable than alumina layers with low Si content at the elevated temperatures at which the growth of single-walled carbon nanotubes is initiated. The enhanced thermal stability of the Si-rich alumina layer results in a narrower (< 2.2 nm) diameter distribution of the single-walled carbon nanotubes. Thanks to the smaller diameters of their nanotube pores, membranes fabricated with vertically aligned nanotubes grown on the stable layers display improved ion selectivity.