Synthesis, Physical Characterization, and Electrochemical Characterization of Zirconium-Iridium Mixed Oxide Electrocatalysts for the Oxygen Evolution Reaction in Acidic Media

Abstract

The kinetically sluggish oxygen evolution reaction (OER) is the limiting factor for the efficiency of water electrolyzers, requiring highly active and expensive catalysts such as iridium oxide. In this thesis, zirconium-iridium mixed oxides, as synthesized by ion beam sputter deposition of metallic films followed by thermal oxidation, were examined for their properties as OER catalysts. Electrochemical techniques such as cyclic voltammetry were applied to determine the catalytic activity of these materials in acidic conditions. To gain insights into the electronic, morphological, and structural features of the catalyst surface, X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy were used. It was found that this synthesis method does not completely oxidize iridium to the dioxide IrO\(_{2}\), with IrO\(_{2}\) yield depending on the synthesis conditions, but zirconium is completely oxidized as zirconium dioxide, ZrO\(_{2}\). The morphology and OER activity of the prepared catalysts depended heavily on the synthesis conditions. For selected synthesis parameters, the zirconium-iridium mixed oxide electrocatalysts outperformed the analogously prepared iridium oxide. However, iridium oxides and zirconium-iridium mixed oxides prepared using these methods suffer from substrate conduction problems. While this synthesis method cannot be recommended as-is, the insights gained can aid in the rational design of highly efficient, cost-effective, and durable OER catalysts.