Fabrication and investigation of high performance CNT-incorporated tin-oxide supercapacitor

In this paper, we have developed an inexpensive and simple method to realize high performance supercapacitor with high specific capacitance of 21 mF/cm² at a scan rate of 10 mV/s, which is among the highest areal capacitance values reported for SnO₂ based devices. Stainless steel foils, coated with a mixture of tin oxide (sol–gel) and multiwall carbon nanotube powder to act as the working electrode, have been employed as substrates for the fabrication of these supercapacitors. The use of hydrogen plasma at a moderate temperature of 300–600 °C has been found to be suitable to functionalize the tin-oxide layer and to incorporate deep porosity in its structure. The application of carbon nanotubes has been a critical step to improve the capacitance of the device and to add to its cycling stability. Comparing the results of tin-oxide with CNT-incorporated structures demonstrates more than two orders of magnitude improvement in the value of areal capacitance. The films have been analyzed using scanning and transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. The electrochemical properties of the electrodes have been examined using the cyclic voltammetry and galvanostatic measurements.