IrO2-TiO2: A High-Surface-Area, Active, and Stable Electrocatalyst for the Oxygen Evolution Reaction

The utilization and development of efficient water electrolyzers for hydrogen production is currently limited due to the sluggish kinetics of the anodic process - the oxygen evolution reaction (OER). Moreover, state of the art OER catalysts contain high amounts of expensive and low-abundance noble metals such as Ru and Ir, limiting their large-scale industrial utilization. Therefore, the development of low-cost, highly active, and stable OER catalysts is a key requirement toward the implementation of a hydrogen-based economy. We have developed a synthetic approach to high-surface-area chlorine-free iridium oxide nanoparticles dispersed in titania (IrO₂-TiO₂), which is a highly active and stable OER catalyst in acidic media. IrO₂-TiO₂ was prepared in one step in molten NaNO₃ (Adams fusion method) and consists of ca. 1-2 nm IrO₂ particles distributed in a matrix of titania nanoparticles with an overall surface area of 245 m² g^-1. This material contains 40 mol_M % of iridium and demonstrates improved OER activity and stability in comparison to the commercial benchmark catalyst and state of the art high-surface-area IrO₂. Ex situ characterization of the catalyst indicates the presence of iridium hydroxo surface species, which were previously associated with the high OER activity. Operando X-ray absorption studies demonstrate the evolution of the surface species as a function of the applied potential, suggesting the conversion of the initial hydroxo surface layer to the oxo-terminated surface via anodic oxidation (OER regime).