Developing active and durable air cathodes for oxygen reduction reaction (ORR) is pivotal for rechargeable aqueous Zn-air battery (A-ZAB) and chlor-alkali electrolysis. Fe-N-C single-atom catalysts have shown great promise, yet the critical role of the carbon support structure remains underexplored. Herein, we report the Fe single-atom on hierarchically ordered porous carbon (Fe-N-HOC) with an inverse opal structure. Fe-N-HOC features high-density Fe-N₄ sites and delivers highly active ORR performance in alkaline media, attaining substantially enhanced half-wave potential (E_1/2) of 0.90 V. Density functional theory (DFT) calculations manifest that the curved configuration Fe-N₄ enhances electron transfer, weakens the binding strength of oxygen intermediates, and reduces the energy barrier of *OH desorption significantly by 0.79 eV relative to planar analogues, boosting ORR kinetics. Consequently, Fe-N-HOC delivers excellent durability, with only 8 mV loss in E_1/2 after 50,000 cycles. In practical applications, A-ZAB with Fe-N-HOC achieves remarkable cycling for 1600 h at 5 mA cm⁻². Fe-N-HOC-based quasi-solid-state ZAB (QSS-ZAB) also exhibits large peak power density of 216.7 mW cm⁻² and extended cycle life (>130 h) across the current densities of 0.5−2.0 mA cm⁻². Furthermore, in chlor-alkali electrolysis, the Fe-N-HOC||RuO₂ system operates at 1.62 V for large current density of 300 mA cm⁻² with minimal performance decay. This work presents a multi-dimensional modification strategy encompassing morphology control, element doping, and electronic tuning, providing crucial guidance for the development of efficient catalysts in energy conversion and storage systems.

Developing noble-metal-free oxygen evolution reaction (OER) electrocatalysts with stable performance at large working current is an imperative and yet formidable challenge for practical large scale water splitting. In this study, by inheriting hierarchical nanostructure and elemental homogeneity of Prussian blue analogues, a series of medium entropy transition metal phosphides (METMP) OER catalysts with high cost-effectivity, efficiency and stability were precisely prepared. Specifically, the METMP-based ((FeCoNi)P/Ni₂P-NF) catalyst demonstrates exceptional performance with an overpotential of only 232 mV at 50 mA·cm⁻² and a Tafel slope of 52.7 mV·dec⁻¹, significantly superior to its less entropy counterparts and commercial RuO₂. Moreover, it even maintains stability at the industrial standard current density of 500 mA·cm⁻² for over 200 h. Density functional theory (DFT) calculations indicates that the synergistic effect of Fe, Co, Ni modulates electronic structure of METMPs, which effectively reduces the energy barrier for the rate-determining HOO* formation step, thereby considerably enhancing catalytic activity. This work not only contributes to the fundamental understanding of the role of medium/high entropy in catalysis but also paves the way for the development of next-generation electrocatalysts for energy-related applications.