Stabilising the Lattice Oxygen Oxidation Mechanism Through Iridium Single Atoms in Chromium-Doped Cobalt Iron Layered...

Transition metal hydroxides are among the most promising alkaline oxygen evolution reaction (OER) catalysts for anion exchange membrane water electrolysers (AEMWEs), owing to their high intrinsic activity originated from the kinetically favourable lattice oxygen oxidation mechanism (LOM). However, lattice oxygen participation often accelerates catalyst degradation through active-site dissolution, posing a major challenge to the long-term stability. Herein, we report a synergistic catalyst design that simultaneously promotes efficient LOM and improves durability through incorporating Ir single atoms (Ir_SAs) and Cr doping into CoFe layered double hydroxide (LDH). The resulting Ir_SAs/CoFeCr LDH exhibits low overpotential of 252 mV at 10 mA cm^-2 and maintains stable operation for over 100 h at 500 mA cm^-2. Combined experimental and theoretical analyses reveal that Ir and Co serve as primary OER-active sites, while Cr enhances the structural stability by enriching the electron density of neighbouring metal sites. This electronic modulation suppresses over-oxidation and facilitates lattice oxygen regeneration, while Ir incorporation strengthens the metal-oxygen covalency, enabling reversible lattice-oxygen participation. The AEMWE exhibits a low cell voltage of 1.61 V at 1 A cm^-2 and durability over 120 h with a negligible decay rate of 0.04 mV h^-1, highlighting the practical viability of the catalyst design for alkaline water electrolysis.