Synthesis of High-Performance Supercapacitor Electrodes using a CNT-ZIF-8-MoS2 Framework

Abstract

Supercapacitors are an emerging energy storage device that have gained attention because of the large specific power, at a reasonable specific energy, that they exhibit. These energy storage devices could be used alongside of or in the place of traditional electrochemical battery technologies to power reliable electrical devices. The performance of supercapacitorsis largely determined by electrode properties including the surface area to volume ratio, the electrical conductivity, and the ion diffusivity. Nanomaterial synthesis has been proposed as a method of enhancing the performance of many macroscopic supercapacitor electrodes due to the high surface area to volume ratio and unique tunable properties that are often size or thickness dependent for many materials. Specifically, carbon materials (such as carbon nanotubes), metal organic frameworks, (such as ZIF-8), and transition metal dichalcogenides (such as molybdenum disulfide) have been of interest due to their conductivity, large surface area, and ion diffusivity that they exhibit when one or more of their characteristic lengths is on the order of several nanometers.For the experiments, a carbon nanotube-/ZIF-8-/MoS2framework was synthesized into an electrode material. This process involved first dispersing the carbon nanotubes in DMF using ultrasonication and then modifying the structure with polydopamine to create a binding site for the ZIF-8 to attach to the carbon nanotubes. The ZIF-8 was synthesized by combining 1,2,4-Triazole-3-thiol and ZnCl under 120 degrees Celsius. Afterwards, the MoS2was associated with the carbon nanotube and ZIF-8 framework by a disulfide bond with the sulfur vacancy of the MoS2andthe sulfide group of the ZIF-8. Finally, the sample solution was filtered by vacuum filtration and then annealed at 110 degrees Celsius before being deposited on a nickel foam substrate and tested in a 3-electrode electrochemical cyclic voltammetry study.The resulting materials were found to have a capacitance of 262.15 F/g with corresponding specific energy and specific power values of 52.4Whr/kg and 1572W/kg. Compared to other supercapacitor research materials, this electrode shows a much larger capacitance than other exclusively carbon materials, and comparable capacitance values to the ZIF-8 and MoS2materialswith the added benefits of an easier and faster manufacturing process. Overall, the electrodes developed in this study, could potentially reduce the cost per farad of the supercapacitor to be more competitive energy storage devices