High‐Entropy Porous Hollow Spinel Oxides via Lattice Oxygen Activation for Efficient and Stable Oxygen Evolution

High‐entropy oxides (HEOs) are promising electrocatalysts for the sluggish oxygen evolution reaction (OER). The lattice oxygen mechanism (LOM) offers a lower thermodynamic barrier than the conventional adsorbate evolution mechanism (AEM). However, maintaining structural integrity while activating lattice oxygen during prolonged electrolysis remains a significant challenge. Herein, we report a dual sacrificial template strategy to synthesize single‐crystalline porous hollow high‐entropy ZnVCrMoMn spinel oxides (ZnVCrMoMn‐HHESOs). Chemical probe, in situ spectroscopic, and isotope‐labeling experiments demonstrate that multicomponent electronic interactions synergistically enhance lattice oxygen activation and promote a dominant LOM pathway with high structural stability. Density functional theory calculations reveal that high‐valent cation incorporation induces electron redistribution, upshifts the O 2p‐band center toward the Fermi level, and strengthens metal–oxygen covalency, facilitating lattice oxygen participation in the OER. Consequently, ZnVCrMoMn‐HHESOs delivers an ultralow overpotential of 218 mV at 10 mA·cm −2 and outstanding stability over 400 h. In a lab‐scale electrolyzer, it achieves 774 mA·cm −2 at 1.7 V and operates stably at 500 mA·cm −2 for over 500 h with a voltage degradation rate of merely 0.07 mV·h −1 . This work demonstrates the rational design of hollow high‐entropy spinel oxides as an effective strategy for developing highly active and stable LOM‐based OER electrocatalysts.