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.