Highly Active Ir/TiO2 Electrodes for the Oxygen Evolution Reaction Using Atomic Layer Deposition on Ordered Porous Substrates

Nanostructured Ir/TiO2 electrodes are investigated toward the oxygen evolution reaction (OER) from water. The electrodes are prepared based on highly ordered TiO2 nanotubes grown from Ti foils with full geometric control. The tube walls are coated with iridium using atomic layer deposition (ALD), which allows for an accurate tuning of the amount deposited. The electrocatalytic performance of electrodes with different TiO2 tube lengths and iridium catalyst loadings toward OER is quantified by cyclic voltammetry and steady-state electrolysis. This study enables us to minimize the catalyst loading, and we reach a current density of 31.3 mA cm−2 at an overpotential η = 0.34 V for a tube length of L = 12 μm and a Ir coating thickness of t = 6 nm. The benchmark of 10 mA cm−2 is already achieved at a lower overpotential of η = 0.24 V.