Bi-directional strains increase the performance of iridium oxide nanoparticles towards the acidic oxygen evolution reaction in proton exchange membrane electrolyzers

Abstract

The challenge of achieving high-performance iridium-based catalysts towards the oxygen evolution reaction (OER) in proton exchange membrane (PEM) electrolyzers remains unresolved due to the highly acidic catalyst/PEM interface and oxidation conditions. To address this issue, we introduce core–shell structured Sb_0.3Ir_0.7O_x@TB-IrO_x nanocatalysts featuring twin boundaries (TBs) with bi-directional (shear and axial) strains that exhibit a remarkably low overpotential of 201 mV at 10 mA cm⁻² towards the OER in 0.5 M H₂SO₄. Moreover, Sb_0.3Ir_0.7O_x@TB-IrO_x displays outstanding mass activity of 3.16 A mg per Ir (η = 270 mV), which is 26.2 times better than that of commercial IrO₂. The enhanced catalytic activity is attributed to the tuned Ir–O bond lengths along the bi-directional strains, caused by twin boundaries and the core–shell structure, optimizing oxygen intermediate adsorption energy, as supported by microscope characterization and theoretical calculations. Furthermore, a PEM electrolyzer employing the Sb_0.3Ir_0.7O_x@TB-IrO_x nanocatalyst maintains a cell voltage of 2.03 V at 2.0 A cm⁻² and exhibits negligible decay in efficiency even after 500 hours of continuous operation.