Abstract

Electrochemical nitrate reduction reaction (ENR) provides an eco-friendly route to ammonia (NH 3) synthesis, positioning it as a viable substitute to the traditional Haber–Bosch method.

However, accomplishing high efficiency and selectivity is challenging because of competing hydrogen production and reaction instability. Herein, we present phase-stabilized NiFe 2O 4@CoFe 2O 4 (NFCO) core@shell nanocages synthesized via a controlled annealing process using Prussian blue analogs. These analogs are self-assembled from divalent Ni and Co species within a trivalent Fe–CN framework, which serves as a sacrificial template. These nanocages impressively enhanced the ENR to NH 3 with a Faradaic efficiency of 95% at −0.4 V vs. RHE via a direct eight-electron N-end reduction pathway. The NiFe 2O 4 core facilitates rapid charge transfer, while the CoFe 2O 4 shell boosts NO 3− adsorption and stabilizes reaction intermediates, effectively suppressing hydrogen evolution. Theoretical calculations and in situ Raman spectroelectrochemistry unveil ENR sites. Beyond the ENR, integrating NFCO into a Zn–NO 3 mechanisms and possible limiting steps on NFCO − battery enables simultaneous energy generation and stable NH 3 production, demonstrating an open-circuit voltage of 1.4 V and a power density of 1.54 mW cm −2 . This approach advances the design of competent, stable catalysts for large-scale, sustainable NH 3 production and nitrate removal, with promising environmental applications.