ABSTRACT Activating lattice oxygen redox is essential for high‐efficiency water oxidation in anion exchange membrane water electrolyzers (AEMWEs), yet remains challenging due to elusive orbital reconstruction, instability from metal leaching, and reliance on theoretical predictions. Here, we introduce a phase engineering strategy that triggers and stabilizes the lattice oxygen evolution reaction (LOER) pathway by promoting orbital reconstruction and enhancing OH − adsorption, based on a series of AB 2 O 4 spinel oxides. In addition to an in‐depth discussion of the phase transition mechanism, we novelly provide direct spectroscopic evidence of d–p orbital hybridization using ultraviolet and inverse photoelectron spectroscopy (UPS/IPES), offering mechanistic insights into the OER pathway. The direct spectroscopic evidence is consistent with results from theoretical calculations. As a result, AEMWEs incorporating these spinel catalysts achieve over 1000 h of stable operation at 100 mA cm − 2 , surpassing benchmark RuO 2 and IrO 2 systems. These findings bridge theoretical predictions and experimental evidence, establishing a direct link between catalyst stability and electronic structure, while offering mechanistic insights into lattice oxygen activation.
Ma et al. (Wed,) studied this question.