Catalyst Development for Electrochemical Water Splitting

The world population is growing at a rate untenable for our current energy resources to keep up with. This combined with the factors of depleting nonrenewable energy sources, i.e. fossil fuels, and environmental impacts of obtaining and utilizing these resources has created an urgent demand for new alternative clean energy sources. Hydrogen has shown promise as a potential fuel to help alleviate the use of these destructive energy sources. The use of hydrogen in a fuel cell cars is rated as a zero emissions fuel. However, a challenge associated with using hydrogen is the current means of production. Today, almost all hydrogen is produced through steam reformation, at high temperatures and pressures requiring excess energy, and which also produces carbon dioxide. The emissions of carbon dioxide at the production step essentially offsets the zero emissions at the tailpipe. Water electrolysis has been at the forefront to address this concern. Previously this technique was not commercially viable due to costly materials and operational requirements. With recent advancements in research this technology is becoming increasingly feasible. To continue to improve this process and lower costs, a main factor is the development of electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in splitting water. It has been particularly difficult to balance an active electrocatalyst with operation conditions. Typically, these catalysts were comprised of expensive, rare metals that would not be practical for large scale production. For the HER, platinum is the leading catalyst in acid. Acidic conditions with the abundance of protons is preferred for the HER. Unfortunately, this is hard to implement due to the corrosive nature of acids and scarcity of platinum. OER on the other hand is suited for alkaline conditions. The OER is also especially complicated due to the four electron/four proton transfer reaction. For these reasons, the OER in alkaline conditions is where this thesis commenced. The purpose of this thesis is to search for a reasonably priced and accessible electrocatalyst for both the OER and HER that is highly active and porous in structure. Utilizing a microwave-assisted synthesis technique, electrocatalysts comprised of FeNi for OER and 80/20 Co/Ni for HER resulted in the lowest overpotentials. These low overpotentials mean the reactions are closer to thermodynamic equilibrium potentials and would require less electricity to split the water. With this electrocatalyst, the next goal is to further improve performance by fabricating an electrode with a 3D, porous, high surface area in order to increase mass transfer to the active sites. This was accomplished by using a nickel foam support for both OER and HER. Finally by adjusting the electrolytic solution from 1 M NaOH to 3 M NaOH we were able to complete OER using an FeNi and HER using 80/20 Co/Ni nanoamorpohous electrocatalysts electrophoretically deposited on nickel foam to reach overpotentials of 194 mV and 120 mV respectively at 10 mA cm^(-2). Ultimately, if fueled by renewable electricity such as wind, solar, hydroelectric, and with the use of highly active electrocatalysts the widespread implementation of water electrolysis could be in the near future.