Carbon-templated conductive oxide supports for oxygen evolution catalysis†
We present a novel route for the preparation of supported IrO2 catalysts for the oxygen evolution reaction in proton exchange membrane electrolyzers. It uses carbon soot as a nanostructure template, which is sequentially coated with a conductive niobium-doped titanium oxide (NTO) layer and an ultrathin, highly pure IrO2 catalyst layer by atomic layer deposition (ALD). The NTO acts as an oxidation-stable conductor between the metal current distributor and the catalyst. The highly controlled film growth by ALD enables the fabrication of electrodes with a very low noble metal loading. Nonetheless, these electrodes exhibit very high catalytic activity and good stability under cyclic and constant load conditions. At an IrO2 content of less than 10 percent by mass of the oxide material and an area-based Ir content of 153 μg cm−2, the nanostructured NTO/IrO2 electrode achieves an oxygen evolution current density of 1 mA cm−2 at an overpotential of ∼250 mV, which is significantly lower than the reported values for particulate NTO/IrO2 catalysts.