Date of Award
Fall 11-12-2020
Document Type
Thesis
Degree Name
Master of Materials Science and Engineering (MMatSE)
Department
Materials Science
First Advisor
Dr. Ram Gupta
Second Advisor
Dr. Khamis Siam
Third Advisor
Dr. Seif Uran
Keywords
Bio-waste, Soybean, Shell, Leaf, Stem, Supercapacitor
Abstract
In this era of rising energy consumption, people are demanding high-performance and environment friendly energy storage devices. To meet these needs, there are many efforts to develop high performance supercapacitor using biomass. In this study, soybean shell, leaf, and stem was used as a source of carbon via chemical activation with an KOH activating agent. The activating agent KOH was mixed in several proportions ranging from 1:0.125 to 1:1, and all samples exhibited the tendency to increase the surface area and porosity as the activating agent ratio increased. Samples mixed with KOH in a 1:1 ratio showed not only the largest surface areas of 2254, 2114, and 1991 m2/g for soybean shell, leaf, and stem, but also high porosity. All samples were used to make working electrodes, and electrochemical investigation was performed using conventional three-electrode system. Activated carbon electrodes derived from various parts of soybean mixed with KOH in a 1:1 ratio delivered a high specific capacitance of 513, 494, 651 F/g at a scan rate of 2 mV/s from the cyclic voltammetry test, and a high specific capacitance of 288, 332, 470 F/g at a current density of 1 A/g from the galvanostatic charge–discharge measurements for shell, leaf, and stem, respectively. Soybean stem mixed with KOH in a 1:1 ratio, which showed the highest energy performance, was used as an electrode in the symmetric supercapacitor devices, and three different aqueous electrolytes (KOH, LiOH, NaOH) were employed in each device. KOH electrolyte which has the smallest hydrated ions showed the highest energy storage properties, exhibiting the maximum energy and power density of 21 Wh/kg and 9684 W/kg, respectively. All devices showed over 90 % retention of initial specific capacitance, along with 100% coulombic efficiency even after 10,000 cycles. Moreover, the voltage increased by three times when each three devices were connected in series, demonstrating the possibility that it could be used for real application requiring high voltages. This work showed that eco-friendly and abundant material soybean shell, leaf, and steam can be used for efficient energy storage applications.
Recommended Citation
Choi, Jonghyun, "SOYBEAN: GOOD SOURCE FOR HIGH-PERFORMANCE SUPERCAPACITORS" (2020). Electronic Theses & Dissertations. 719.
https://digitalcommons.pittstate.edu/etd/719
