IMPROVING THE ELECTROCHEMICAL PROPERTIES OF MnO2 BY DOPING WITH Fe FOR WATER SPLITTING AND SUPERCAPACITOR APPLICATION

An Abstract of the Thesis by Joseph Okwe These days when the issue of energy is talked about, it is usually more than just the usefulness of different types of energy. This topic now encompasses ways of generating and storing energy in the most efficient and sustainable way. For this reason, various research has shown that materials that are fabricated for the purpose of energy storage and conversion also find applications in other areas such as water splitting and supercapacitors. And so certain materials, when synthesized, can serve more than one purpose in either generating or storing energy. This project reports on the fabrication of electrodes by doping MnO2 with different percentages of Fe to get five sample electrodes namely, MnO2, Mn0.98Fe0.02O2, Mn0.95Fe0.05O2, Mn0.90Fe0.10O2 and Mn0.88Fe0.12O2 which were synthesized through hydrothermal method and deposited on a Ni-foam that serves as a substrate. These samples were examined by testing them for possible application as electrocatalyst for water splitting process and as electrodes for supercapacitors. When tested for electrocatalytic applications for hydrogen evolution reaction, of all the five samples Mn0.95Fe0.05O2 has the least overpotential value ­­of 235 mV at 10 mA/cm­­2and a Tafel slope value of 171 mV/dec making it the best sample. Similarly, for oxygen evolution reaction, Mn0.95Fe0.05O2 has the least overpotential value ­­of 278 mV at 10 mA/cm­­2 and a Tafel slope value of 44 mV/dec. All five electrodes show great stability for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) for over 1000 cycles. When tested for energy storage as supercapacitors, Mn0.88Fe0.12O2 performed best with a specific capacitance value of 65 F/g.