Introducing High‐Valence Iridium Single Atoms into Bimetal Phosphides toward High‐Efficiency Oxygen Evolution and Overall Water Splitting

Single atoms are superior electrocatalysts having high atomic utilization and amazing activity for water oxidation and splitting. Herein, this work reports a thermal reduction method to introduce high‐valence iridium (Ir) single atoms into bimetal phosphide (FeNiP) nanoparticles toward high‐efficiency oxygen evolution reaction (OER) and overall water splitting. The presence of high‐valence single Ir atoms (Ir4+) and their synergistic interaction with Ni3+ species as well as the disproportionation of Ni3+ assisted by Fe collectively contribute to the exceptional OER performance. In specific, at appropriate Ir/Ni and Fe/Ni ratios, the as‐prepared Ir‐doped FeNiP (Ir25‐Fe16Ni100P64) nanoparticles at a mass loading of only 35 µg cm−2 show the overpotential as low as 232 mV at 10 mA cm−2 and activity as high as 1.86 A mg−1 at 1.5 V versus RHE for OER in 1.0 m KOH. Computational simulations confirm the vital role of high‐valence Ir to weaken the adsorption of OER intermediates, favorable for accelerating OER kinetics. Impressively, a Pt/C||Ir25‐Fe16Ni100P64 two‐electrode alkaline electrolyzer affords a current density of 10 mA cm−2 at a low cell voltage of 1.42 V, along with satisfied stability. An AA battery with a nominal voltage of 1.5 V can drive overall water splitting with obvious bubbles released. This work introduces high‐valence Ir single atoms into the bimetal phosphide nanoparticles through a facile thermal reduction method to achieve high catalytic efficiency in terms of low overpotential and high activity at a low mass loading on the electrode for OER and overall water splitting in an alkaline electrolyte.