Interstitial Lithium Doping Activates Lattice Oxygen in High‐Entropy LDHs for Enhanced and Durable Water Oxidation

ABSTRACT High‐entropy layered double hydroxides (HE‐LDHs) are promising OER catalysts, but their activity and long‐term durability require significant improvement. We propose a novel strategy to boost their performance by introducing interstitial lithium (Li) doping into MnFeCoNiCu HE‐LDHs. The optimized catalyst achieved a remarkably low overpotential of 195 mV at 10 mA cm −2 and maintained outstanding stability for 300 h at 300 mA cm −2 . Crucially for practical application, it achieved a low cell voltage of 1.83 V at an industrial current density of 1 A cm −2 in an alkaline exchange membrane water electrolyzer (AEMWE) device, demonstrating robust 200 h stability. X‐ray absorption fine structure (XAFS) spectroscopy and theoretical calculations confirmed that Li is stably embedded in the lattice as an interstitial dopant. The introduction of interstitial Li impurities activates the lattice oxygen in the HE‐LDHs, promoting a change in the OER mechanism from the adsorbate evolution mechanism (AEM) to the highly efficient lattice oxygen oxidation mechanism (LOM) pathway. Density functional theory (DFT) calculations further revealed that interstitial Li doping induces the formation of a non‐bonding state band in the O 2p orbital. This electronic reconstruction is key to activating the lattice oxygen, ensuring excellent long‐term stability.