Breaking the Performance Limit of Pure Metals for N

The electrocatalytic nitrogen reduction reaction (NRR) offers a sustainable pathway for ambient-condition ammonia synthesis, yet its efficiency is fundamentally limited by the low N2 concentration in aqueous systems and the competing strong adsorption of H2O/H intermediates on conventional bulk metal catalysts. Herein, we propose a universal micro/nanoengineering strategy to address these challenges by constructing three-phase-interface-optimized hollow fiber (HF) electrodes. This design simultaneously enhances local N2 enrichment and modulates the surface coverage of critical intermediates (*N2 versus *H), thereby shifting the reaction equilibrium toward NRR. As a proof of concept, Fe-based HF electrodes achieve a remarkable NH3 yield rate of 27.1 µg h-1 cm-2 and a Faradaic efficiency (FE) of 3.5% under ambient conditions-values dramatically enhanced by ∼60-fold and ∼35-fold, respectively, compared to planar Fe electrodes. Mechanistic studies reveal that the hierarchical porous architecture of HF electrodes promotes N2 diffusion and alters the adsorption hierarchy of intermediates, effectively suppressing hydrogen evolution while activating N≡N bond cleavage. Crucially, this strategy demonstrates broad applicability, as evidenced by significantly improved NRR performance across diverse metals (e.g., Cu, Ni), highlighting its potential as a general platform for advancing sustainable ammonia electrosynthesis.