Two‐Dimensional Amorphous Iridium Oxide for Acidic Oxygen Evolution Reaction

Abstract The increasing popularity of proton exchange membrane electrolysis technology for hydrogen production has brought attention to the electrolytic water reaction. However, the slow kinetics of the oxygen evolution reaction (OER) at the anode have great influence on the overall efficiency of the reaction. While iridium oxide shows excellent stability under acidic conditions, its OER activity still needs to be improved. Here, we synthesized two‐dimensional amorphous iridium oxide (Am−IrO 2 ) nanosheets with the thickness of only 6 nm by a mixed molten salt method. Such nanosheets show an ultralow overpotential of only 230 mV at 10 mA cm −2 in 0.5 M H 2 SO 4 . The overpotential increases only 40 mV after 90 hours of the stability test at this current density. Am−IrO 2 can maintain the current density of ~400 mA cm −2 after 120 hours of test at 1.8 V in the PEM device, demonstrating good industrial prospects. Density functional theoretical calculations show that the oxygen vacancies, together with the upshift of the O 2p band center, are responsible for the improvement of OER in Am−IrO 2 .