Tungsten Modified Nickel Oxides and Carbides for Potential Use in Electrochemical Capacitors
University of Delaware
Capacitors are electrochemical devices that store charge and energy. Capacitors compliment other power storage devices, such as fuel cells and batteries, in that they have advantages in power density and rapid discharge and recharge rates. Two main pathways are followed to obtain this capacitance; pseudocapacitance and double layer capacitance. Pseudocapacitance is required to obtain the high specific power per specific energy that normal double layer capacitance is unable to attain. Current materials for pseudocapacitance, such as ruthenium oxide, are expensive and economically unviable. The goal of this research is to combine a cheap, nickel oxide capacitor that provides relatively high capacitance over a small range of voltages with a more stable tungsten capacitor that might increase the overall performance. This thesis investigates capacitance from both carbon-carbon capacitance and pseudocapacitance from transition metal oxides in nickel oxide and tungsten modified nickel oxides. The addition of carbon substrate is incorporated to investigate a possible enhancement of overall capacitance by including both double layer capacitance and pseudocapacitance. Individual and bimetallic oxides are investigated as well as tungsten carbide supported on Ketjen carbon black for a more comprehensive understanding of the system in question. Samples are analyzed for bulk composition using XRD and phase purity is determined for all samples. Cyclic voltommetry is used to test capacitive behavior, and results are analyzed using standard equations from literature. Due to the nature of the synthesis of most samples, low capacitance is observed with little to no pseudocapacitance in addition to trivial double layer capacitance.