A highly active and stable IrO _x /SrIrO ₃ catalyst for the oxygen evolution reaction

Oxygen electrochemistry plays a key role in renewable energy technologies such as fuel cells and electrolyzers, but the slow kinetics of the oxygen evolution reaction (OER) limit the performance and commercialization of such devices. Here we report an iridium oxide/strontium iridium oxide (IrO _x /SrIrO ₃ ) catalyst formed during electrochemical testing by strontium leaching from surface layers of thin films of SrIrO ₃ . This catalyst has demonstrated specific activity at 10 milliamps per square centimeter of oxide catalyst (OER current normalized to catalyst surface area), with only 270 to 290 millivolts of overpotential for 30 hours of continuous testing in acidic electrolyte. Density functional theory calculations suggest the formation of highly active surface layers during strontium leaching with IrO ₃ or anatase IrO ₂ motifs. The IrO _x /SrIrO ₃ catalyst outperforms known IrO _x and ruthenium oxide (RuO _x ) systems, the only other OER catalysts that have reasonable activity in acidic electrolyte.