UC Santa Cruz

Climate change has made the severity of the impact humanity has on the environment in which we live clear. The production of energy and waste are major contributors to our effect on the environment. Electrochemical technologies have drawn interest as tools to lessen the impact on the environment. Two such tools include proton exchange membrane fuel cells (PEMFCs) and the electrochemical production of H2O2. Both technologies are built on the oxygen reduction reaction (ORR). PEMFCs rely on thermodynamically favorable conversion of O2 to H2O via a 4-electron multistep pathway, while the electrochemical production of H2O2 involves the conversion of O2 to H2O2 via the 2-electron pathway. The kinetic limitations of the ORR necessitate the use of precious metal catalysts. Unfortunately, these precious metals are unsustainable, rare, and expensive and continued reliance on these metals in catalysts for the ORR limit the scalability of any technology which takes advantage of the ORR. There has been much research on the use of heteroatom and/or metal doped carbon nanostructures as an alternative to precious metal catalysts. The selection of metal dopants can be chosen to affect the pathway selectivity of the ORR catalyst. Additionally, the morphology of the catalyst is vital in the pursuit of optimal activity. Inert atmosphere pyrolysis has been used to carbonize organic precursors in the engineering of electrocatalysts. Different strategies exist to arrange these carbon rich precursors to control the morphology and arrangement of dopant materials in the designed catalyst. One such strategy is the use of metal organic frameworks (MOFs) as a self-templating carbonization precursor. MOF derived carbon materials often retain some of the high surface area, extensive porosity, heteroatoms, and metal centers of the original MOF allowing for catalyst design through careful design of that MOF. Chapter 2 will feature a Fe3C nanoparticle containing mesoporous carbon material derived from a Fe/Zn MOF as an ORR catalyst selective of the 4-electron pathway through pore size and distribution optimization through the tuning of the Fe:Zn ratio. Chapter 3 will focus on a Cu-Nx/CuO carbon-based ORR catalyst derived from a Cu MOF whose selectivity for the 2-electron pathway was improved through the subjugation of the catalyst to voltametric cycling.