As fossil fuels become scarce, supercapacitors are a potential solution for storing energy from renewable sources, e.g. wind and sunlight for future use. The progression of supercapacitors necessitates the use of economical, plentiful, eco-friendly, and long lasting electrode materials. Previous research has investigated the use of carbon obtained from different biomasses (basswood, biogas slurry, cow dung, rotten carrots, etc.) as electrode materials, as well as metal oxides (iron-based, cobalt-nickel-based, manganese-based, and vanadium-based electrode materials). This research work makes a significant contribution to the development and evaluation of activated carbon and new composite materials for supercapacitor electrodes as well as the preparation methods thereof. The conversion of cattle blood waste into activated carbon materials in this study provides an economical and feasible method to produce electrode materials for electric double layer (EDLC) and pseudo-supercapacitors. To generate activated carbon materials, cattle blood waste was dried, followed by carbonization under N2 atmosphere and the resultant samples were chemically activated using KOH. The effect of physiochemical parameters of electrode materials on electrochemical performance was investigated. X-ray diffractometry showed that, samples lost their crystallinity, resulting in amorphous/turbostratic carbon materials with increase in activation ratio, time, and temperature. Raman spectroscopy showed that introducing KOH to carbonised materials induces structural defects. Using nitrogen sorption studies portray a decrease in pore volumes from 0.19 to 0.08 cm3 g-1 and surface area from 340 to 140 m2 g-1 as the activation KOH ratio increased from 1 to 3. Cyclic voltammetry (CV), cyclic charge-discharge (CCD), and electrochemical impedance spectroscopy (EIS) measurements were used to assess the capacitive properties of the electrode materials. Electrochemical measurements performed under three-electrode system revealed that the charge-discharge time and specific capacitances increased with decrease in carbonisation and activation temperature, time, and activation ratio. A sample carbonised at 800 °C for 60 min and activated with KOH ratio 1:1 at 600 °C for 30 min attained specific capacitance of 162.51 and 204 F g-1 at 5 mV s-1 scanning rate and current density of 0.5 A g-1, respectively. The presence of micropores in the carbon framework showed a significant contribution to the specific capacitance of supercapacitor electrodes. When tested in a symmetric real device for supercapacitors, the above electrode exhibited ideal capacitive behaviour with an energy density of 20 Wh kg-1 and a power density of 4000 W kg-1 using 6 M KOH as electrolyte. All samples exhibited significantly low solution resistance, Rs, of 0.20 ohms, which improved electrolyte ion diffusion in the electrode’s outer shell resulting in high power density. The electrode demonstrated displayed impressive cyclic vstability at 0.2 A g-1 after being cycled 5000 times with capacitance retention and coulombic efficiency of 91 percent and 100 percent, respectively. Furthermore, nickel-cobaltite (NiCo2O4) nanomaterial was incorporated into the optimum activated carbon, namely, ACBW11600_30, yielding an optimum composite with substantial specific capacitances of 431 F g-1 and 554 Fg-1 at 5 mV s-1 and 0.5 A g-1, respectively. NiCo2O4 is not only non-toxic and environmentally user-friendly, and it is also inexpensive to produce due to its abundant constituent metals. Finally, the use of blood waste provides a green synthetic method for activated carbon nanomaterials and has the potential to increase the economic value of slaughterhouse blood.

Thesis (MSc of Chemical and Forensic Sciences)---Botswana International University of Science and Technology, 2023