Highly Active IrO_x Formation on Strontium Manganite for Acidic Oxygen Evolution

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Iridium-based oxides are effective oxygen evolution reaction (OER) catalysts but require high iridium (Ir) content, hindering commercial use.
• Reducing Ir loading while maintaining high activity and durability is a critical challenge in OER catalysis.

Purpose of the Study:

• To synthesize a low-Ir-loading catalyst with enhanced OER activity and stability.
• To investigate the mechanism behind the catalyst's performance using advanced characterization and theoretical calculations.

Main Methods:

• Electrospinning of porous strontium manganate nanofibers.
• Hydrothermal synthesis to load short-range ordered Iridium oxide (IrO_x).
• In situ characterizations (X-ray absorption spectroscopy, Raman spectroscopy, differential electrochemical mass spectrometry, synchrotron-radiation infrared spectroscopy) and theoretical calculations.

Main Results:

• Successfully synthesized low-Ir-loading porous strontium manganate nanofibers decorated with short-range ordered IrO_x.
• Confirmed structural stability of IrO_x during OER using in situ techniques.
• Demonstrated that Manganese (Mn) suppresses the lattice oxygen mechanism, favoring the adsorbate evolution mechanism for OER stabilization.

Conclusions:

• The synthesized catalyst exhibits high OER activity (221 mV overpotential at 10 mA cm^-2) and excellent stability (≈1000 h) with significantly reduced Ir loading.
• The findings offer a promising strategy for developing cost-effective and high-performance OER catalysts.