Mechanisms for Stability, Degradation, and Regeneration of Ni(Oxy)Hydroxide for Oxygen Evolution Electrocatalysis and Photocatalysis

There is a global annual increase in energy consumption and a corresponding global increase in harmful carbon emissions and greenhouse gases into Earth’s atmosphere. Anthropogenic greenhouse gases in our atmosphere are the major contributor to global warming, where CO2 emissions from the use of fossil fuels is the primary factor. Chapter I of this dissertation reviews these statistics in the context of energy consumption by the U.S. and globally, with an emphasis on commercial sectors with the greatest impact on these statistics. Chapter I introduces photoelectrochemical cells (PEC) for water splitting as a promising possibility for alternative renewable energy. Chapter II introduces the material Ni (oxy)hydroxide (NiOxHy), a widely used and studied electrocatalysts for water electrolysis, namely the oxygen evolution reaction (OER) half-reaction. The physical, structural, and electrochemical properties of the material are reviewed. Chapter III presents a new analysis on the structure-stability relationship of Ni (oxy)hydroxide during and after prolonged OER catalysis. Chapter IV evaluates the NiOxHy material with Fe-incorporation; Ni(Fe)OxHy is one of the most active known catalyst for OER. The role of dynamic Fe incorporation/exclusion during operation and the potential role it plays in the high activity and stability of Ni(Fe)OxHy is investigated. Chapter V of this work presents an electrode-level-approach to using Ni(Fe)OxHy for PEC applications. In this chapter a full fabrication scheme is presented for photoanodes utilizing Ni(Fe) (oxy)hydroxide as a catalyst. This work builds on the fundamental studies of the catalyst stability and broadens the scope to full photoanode stability for OER catalysis