Ir single-atom sites stabilized by Ir-O-Ce4-δ coordination for high-efficiency PEMWE

Developing efficient and stable single-atom catalysts (SACs) for acidic oxygen evolution reaction (OER) offers a promising direction toward achieving economical and sustainable development of proton exchange membrane water electrolysis (PEMWE). However, their widespread application remains hindered by intrinsic stability challenges. Herein, we engineered an m-Ir SA -CeO 2 catalyst featuring an Ir-O-Ce 4-δ (0 < δ <1) coordination that delivered exceptional efficiency and stability in PEMWE. In this configuration, low-valent Ce species stabilized high-valent Ir active sites through lattice charge compensation, significantly enhancing catalyst activity and durability. X-ray photoelectron spectroscopy, X-ray absorption fine structure spectroscopy, and theoretical calculations revealed electron transfer from Ir to Ce through the Ir-O-Ce 4-δ coordination, which optimized oxygen intermediate adsorption in the adsorbate evolution mechanism and reduced the ionic character of Ir O bonds to boost intrinsic activity and structural stability. The m-Ir SA -CeO 2 achieved a 267 mV overpotential with >500 h stability at 10 mA cm −2 in 0.1 M HClO 4 . Furthermore, the PEMWE electrolyzer employing the m-Ir SA -CeO 2 anode catalyst maintained stable operation at 100 mA cm −2 for >1000 h with an ultralow Ir loading of 0.12 mg cm −2 .