Stabilizing high-efficiency iridium single atoms via lattice confinement for acidic oxygen evolution

Stable and efficient single atom catalysts (SACs) are highly desirable yet challenging in catalyzing acidic oxygen evolution reaction (OER). Herein, we report a novel iridium single atom catalyst structure, with atomic Ir doped in tetragonal PdO matrix (Ir_SAs-PdO) via a lattice-confined strategy. The optimized Ir_SAs-PdO-0.10 exhibited remarkable OER activity with an overpotential of 277 mV at 10 mA·cm⁻² and long-term stability of 1000 h in 0.5 M H₂SO₄. Furthermore, the turnover frequency attains 1.6 s⁻¹ at an overpotential of 300 mV with a 24-fold increase in the intrinsic activity. The high activity originates from isolated iridium sites with low valence states and decreased Ir–O bonding covalency, and the excellent stability is a result of the effective confinement of iridium sites by Ir–O–Pd motifs. Moreover, we demonstrated for the first time that SACs have great potential in realizing ultralow loading of iridium (as low as microgram per square center meter level) in a practical water electrolyzer.