Lanthanum-assisted lattice anchoring of iridium in CoO for efficient oxygen evolution reaction in low-iridium water electrolysis.

The use of single-atom catalysts is an effective way to reduce the amount of iridium in proton exchange membrane water electrolysis (PEM-WE). However, conventional methods can only obtain surface-loaded single atoms or clusters which cannot meet the needs of high current density and stability. In this study, assisted by lanthanum-doping-induced ion exchange, we realize atomically anchoring iridium within the CoO lattice. The lattice anchored iridium in lanthanum-doped CoO exhibits higher atomic dispersion, a larger average coordination number, and an elevated oxidation state. This improvement stimulates the oxide path mechanism (OPM), resulting in enhanced activity (236 mV at 10 mA cm) and stability (1000 h at 10 mA cm). Impressively, our catalyst demonstrates notable performance in a PEM electrolyzer with an iridium mass loading of just 0.2 mg cm, achieving a low cell voltage of 1.61 V at 1.0 A cm and maintaining stable operation for over 1000 h. This work presents an effective strategy for fabricating low-noble-metal-loading catalysts with enhanced efficiency for PEM-WE.