Synergistic Design of Supports and Electronic Structures for Effective Nitrate-to-Ammonia Conversion

The electrochemical nitrate reduction reaction (NO3–RR) offers a sustainable pathway for green ammonia production, but it remains challenged by sluggish proton-coupled electron transfer and limited activation of catalytic sites. Herein, we develop a dual-modulation strategy to construct an Fe2O3/Fe-doped MOF composite (Fe2O3/Fe-ZIF-8-H) via Fe doping and support structure engineering. This design enhances the Fe2O3 dispersion and introduces active Fe centers, significantly boosting the reaction kinetics. Fe2O3/Fe-ZIF-8-H demonstrates remarkable NO3–RR performance, with up to 97.7% NH4+-N Faraday efficiency, nearly 100% NH4+-N selectivity, a high kinetic constant of 0.094 h–1, stable operation over 16 cycles, and low energy consumption (0.17 kWh/mol NH3) at −0.78 V vs RHE in 1000 mg/L NO3–-N and the 0.1 M Na2SO4 electrolyte. Experimental and theoretical analyses reveal the mechanisms underlying the performance enhancement: (i) the MOF support structure alters the agglomeration state of Fe2O3 and increases the electrochemically active surface area by 9.5 times compared to bare Fe2O3 and (ii) Fe doping induces active sites and optimizes the atomic hybridization state, thereby lowering the reaction energy barrier (ΔGmax: 4.35 eV → 2.72 eV). This study proposes a catalyst design methodology that combines support structure design with electronic modulation for simultaneous high-performance and low-energy ammonia production, providing new opportunities for advancing energy-efficient, clean energy production.