Embedded Fe-Cu Pairs Enable Tandem Nitrate-to-Ammonia Electroreduction

Abstract

Electrochemical nitrate reduction (e-NO3RR) to ammonia (NH3) represents a transformative technology that seamlessly integrates environmental remediation with resource regeneration. This approach is crucial for restoring equilibrium in the global nitrogen cycling, advancing green chemistry, and accelerating the transition toward a sustainable circular economy. However, under pH-neutral conditions, the simultaneous occurrence of two competing reactions (Hydrogen Evolution Reaction and NO3RR) at the same active sites results in considerable interference, significantly limiting the catalytic efficiency and selectivity. Here a Fe-Cu pair (Cu-N3/Fe3-N8) electrocatalyst is meticulously designed, achieving a NH3 production rate of 18.83 mg∙h‒1∙mgcat‒1 at −0.65 V versus the reversible hydrogen electrode (RHE), accompanied with a Faradaic efficiency of 97.1%. This as-prepared Fe-Cu pair overcomes the limitations of conventional bimetallic catalysts, which typically rely on direct atomic coupling. The electron-deficient region formed by Cu–N3 enhances the adsorption of nitrate, while the electron-rich domain generated by the Fe3–N8 cluster facilitates the adsorption of nitrite and promotes water activation. The spatially separated charge gradient optimizes the adsorption energies of multi-step reaction intermediates, thereby establishing a relay mechanism. The work provides valuable insights into the design of multi-active-site electrocatalysts and offers a promising approach to addressing critical challenges in nitrogen resource conversion.