High-density Ir single sites from rapid ligand transformation for efficient water electrolysis

The development of high-performance oxygen evolution reaction catalysts with low iridium content is the key to the scale-up of proton exchange membrane water electrolyzer (PEMWE) for green hydrogen production. Single-site electrocatalysts with maximized atomic efficiency are held as promising candidates but still suffer from inadequate activity and stability in practical electrolyzer due to the low site density. Here, we proposed a NaNO₃-assistant thermal decomposition strategy for the preparation of high-density Ir single sites on MnO₂ substrate (NaNO₃-H-Ir-MnO₂). Direct spectroscopic evidence suggests the inclusion of NaNO₃ accelerates the transformation of Ir-Cl to Ir-O coordination, thus generating uniform dispersed high-density Ir single sites in the products. The optimized H-Ir-MnO₂ demonstrates not only high intrinsic activity in a three-electrode set-up but also boosted performance in scalable PEMWE, requiring a cell voltage of only 1.74 V to attain a high current density of 2 A cm^‒2 at a low Ir loading of 0.18 mg_Ir cm^‒2. This work offers a new insight for enhancing the industrial practicality of Ir-based single site catalysts.