Carbon-templated conductive oxide supports for oxygen evolution catalysis

Abstract

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.