1D Monoclinic Ir x Ru 1‐x O 2 Solid Solution with Ru‐Enhanced Electrocatalytic Activity for Acidic Oxygen Evolution Reaction

The rutile phase IrO 2 , as a promising catalyst for oxygen evolution reaction (OER), still falls short of satisfactory activity. Here, a novel 1D monoclinic phase iridium‐ruthenium oxide solid solution (m‐Ir x Ru 1‐x O 2 ) is reported. For m‐Ir x Ru 1‐x O 2 with different metal proportions, the optimal m‐Ir 0.91 Ru 0.09 O 2‐δ catalyst exhibits excellent OER activity under acidic conditions with an overpotential of 180 mV at 10 mA cm −2 . As an anode catalyst in a proton exchange membrane electrolyzer, m‐Ir 0.91 Ru 0.09 O 2‐δ with a low catalyst loading (0.1 mg cm −2 ) can operate ≈256 h at 1.8 V with a high current density over 900 mA cm −2 at room temperature. Such a satisfied stability may have originated from the specific morphology and crystal structure, which is confirmed by the transient potential scanning test. Density functional theory calculations show that the Ru in the m‐Ir x Ru 1‐x O 2 facilitates decreasing the OER overpotentials due to the electron transfer from Ru to Ir.