Highly Active IrO_x Formation on Strontium Manganite for Acidic Oxygen Evolution

Iridium-based oxides are considered the most effective catalysts for the acidic oxygen evolution reaction (OER) due to their superior stability and high activity. However, the high Ir content required poses a significant barrier to their commercial application. Enhancing OER activity and durability while simultaneously reducing the Ir loading remains a significant challenge. Here, porous strontium manganate nanofibers are synthesized via electrospinning and the element leaching behavior is exploited during hydrothermal synthesis to load short-range ordered IrO_x with high activity. In situ characterizations, including X-ray absorption spectroscopy and Raman spectroscopy, confirm the structural stability of the short-range ordered IrO_x during the OER process. Complementary theoretical calculations, differential electrochemical mass spectrometry, and in situ synchrotron-radiation infrared spectroscopy reveal that Mn suppresses the lattice oxygen mechanism, enabling the catalyst to stabilize OER through the adsorbate evolution mechanism. The synthesized low-Ir-loading catalyst exhibits high OER activity (221 mV overpotential at 10 mA cm^-2) and robust stability (≈1000 h).