Date of Award
Spring 5-12-2018
Document Type
Thesis
Degree Name
Master of Science in Chemistry (MSChem)
Department
Chemistry
First Advisor
Dr. Ram Gupta, rgupta@pittstate.edu
Second Advisor
Dr. Khamis Siam, ksiam@pittstate.edu
Third Advisor
Dr. Pawan Kahol, Pkahol@pittstate.edu
Fourth Advisor
Dr. John Franklin, jfranklin@pittstate.edu
Keywords
Fuel cells, Pseudocapacitors, Oxygen evolution reaction, Hydrogen evolution reaction, Cyclic Voltammetry, Tafel slope
Abstract
In recent years, the increasing demands for clean, efficient, and renewable energy have triggered researchers to increase their effort to develop multi-functional materials for energy applications. Supercapacitors, among the comparative energy storage devices, have attracted considerable attention due to their high energy storage capacity, fast charge-discharge capability, long cycle life, and high power density. Transition metal oxides and sulfides are being used as materials for supercapacitor applications due to their excellent conductivity, high electrochemical properties, and large theoretical energy storage capacitance. On the other hand, among the numerous energy techniques, water splitting has become one of the most important technologies recently due to its ability to produce hydrogen and oxygen as renewable and clean fuels in a sustainable way. Transition metal oxides are one of the most promising alternative candidates for noble metal due to its interesting properties in water splitting fields. In this regard, we have used a facile hydrothermal method to synthesize nanostructured nickel hydroxide, nickel oxide, and nickel sulfide in presence of cetyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVP) on nickel foams using a binder-free approach. These synthesized nanostructured materials are used for both supercapacitor applications and as catalysts for water splitting. The structures, morphologies, and electrochemical performances of the synthesized nickel compounds (nickel hydroxide, nickel oxide, and nickel sulfide) were analyzed and characterized using a variety of techniques. For the structural characterizations, the X-ray diffraction, and scanning electron microscopy were used. The XRD patterns confirmed the phase purity of all the synthesized samples. The average crystallite size of all the samples was also estimated using the Scherrer equation based on the most intense peak. The morphological structure and the size of the samples were analyzed via SEM, and they were observed to depend on the growth condition and presence of CTAB and PVP.
The electrochemical performances of the samples toward supercapacitors and catalysts applications were performed in a standard three-electrode system using potassium hydroxide as an electrolyte, a Pt wire as a counter electrode, a saturated calomel electrode as a reference electrode, and the synthesized electrodes as a working electrode. The potential applications for supercapacitors and catalysts were investigated via cyclic voltammetry, galvanostatic charge-discharge measurements, electrochemical impedance spectroscopy, and linear sweep voltammetry. The electrochemical performance of the synthesized nanostructured materials revealed that their properties depend on the presence of CTAB and PVP during synthesis. The areal capacitance was observed to be 67, 859, and 2,633 mF/cm2 for NiO, Ni(OH)2, and NiS2, respectively. On the other hand, the electrocatalytic performances toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) were investigated. The NiS2-CTAB electrode showed the lowest OER overpotential of 298 mV at 10 mA/cm2 and relatively a low Tafel slope of 111 mV/dec. The lowest HER overpotential of 177 mV at 10 mA/cm2 was observed for the Ni(OH)2-PVP electrode. Our results suggest that nickel-based nanostructured materials could be used as bi-functional materials for energy storage and generation applications.
Recommended Citation
Albeladi, Nawaf, "A FACILE METHOD TO SYNTHESIZE BI-FUNCTIONAL NANOSTRUCTURED NICKEL COMPOUNDS FOR ENERGY STORAGE AND WATER SPLITTING APPLICATIONS" (2018). Electronic Theses & Dissertations. 243.
https://digitalcommons.pittstate.edu/etd/243
