Alkali Metal Iridates as Oxygen Evolution Catalysts Via Thermal Transformation of Amorphous Iridium (oxy)hydroxides.

Efficient water-splitting is severely limited by the anodic oxygen evolution reaction (OER). Iridium oxides remain one of the only viable catalysts under acidic conditions due to their corrosion resistance. We have previously shown that heat-treating high-activity amorphous iridium oxyhydroxide in the presence of residual lithium carbonate leads to the formation of lithium-layered iridium oxide, suppressing the formation of low-activity crystalline rutile IrO₂. We now report the synthesis of Na-IrO_x and K-IrO_x featuring similarly layered crystalline structures. Electrocatalytic tests confirm Li-IrO_x retains similar electrocatalytic activity to commercial amorphous IrO₂ ⋅ 2H₂O and with increasing size of the intercalated cation, the activity towards the OER decreases. However, the synthesised electrocatalysts that contain layers show greater stability than crystalline rutile IrO₂ and amorphous IrO₂ ⋅ 2H₂O, suggesting these compounds could be viable alternatives for industrial PEM electrolysers where durability is a key performance measure.