Ultrafine-Grained Porous Ir-Based Catalysts for High-Performance Overall Water Splitting in Acidic Media

Iridium (Ir)-based materials are known to be state-of-the-art electrocatalysts for catalyzing the oxygen evolution reaction (OER) in proton-exchange membrane (PEM) water electrolysis. However, it remains challenging for Ir-based catalysts to simultaneously achieve high catalytic activity and good stability in a strongly acidic environment. Herein, we report the fabrication of self-supported nanoporous ultrafine-grained IrO2 electrodes (np-IrO2) through the electrochemical activation of melt-spun Ir12Al88 ribbons under the OER conditions in 0.5 M H2SO4. The as-obtained np-IrO2 needs only 240 mV to deliver 10 mA cm–2 and can sustain continuous OER electrolysis in strong acid at an unusually high current density of 100 mA cm–2 for 30 h without substantial degradation. Moreover, we find that the electrochemical activation of Ir12Al88 ribbons under the hydrogen evolution reaction (HER) conditions results in the formation of nanoporous IrAl alloy electrodes (np-IrAl), which show outstanding catalytic performance for HER in 0.5 M H2SO4. We further demonstrate that by using np-IrO2 as an anode and np-IrAl as a cathode, we can accomplish overall acidic water splitting at 10 mA cm–2 with a low voltage of 1.52 V. Remarkably, the np-IrO2∥np-IrAl electrode pair is able to split water stably in 0.5 M H2SO4 at a high current density of 100 mA cm–2 for up to 40 h, showing substantial promise for use in PEM water electrolysis.