Prussian Blue Derived High‐Entropy Alloy Catalysts for Enhanced Electrochemical Nitrate Reduction to Ammonia

Abstract Electrochemical nitrate reduction (NO₃RR) to ammonia is a promising method for treating nitrate pollutant and potentially replacing the Haber‐Bosch process for ammonia production. High‐entropy nanoalloys (HEAs) show significant potential in catalyzing NO₃RR due to their compositional diversity, which results in a unique “cocktail” effect beneficial for the multistep NO₃RR process. Herein, a high‐entropy alloy catalyst consisting of Co, Ni, Cu, Mn, and Fe elements is prepared through the pyrolysis of a high‐entropy Prussian blue precursor. After optimizing the elemental proportions, the Fe HEA catalyst exhibits exceptional NO₃RR activity with an NH₃ Faradaic efficiency (FE) of 92% and a yield rate of 3.25 mg h⁻¹ cm⁻². Moreover, the electrochemical hydrazine oxidation reaction (HzOR) is applied to construct a NO₃RR‐H_ZOR flow cell. This cell system not only produces NH₃, but also generates electricity, achieving a peak power density of 1.32 mW cm⁻². Theoretical investigations show that the excellent performance of HEA can be attributed to the “cocktail” effect induced by multi‐element composition, which results in a lower work function and a negative shifting of the d band center, thus favoring the charge transfer and hydrogenation process of NO₃RR. This work highlights the remarkable potential of HEAs for multistep chemical production and expands their applications in energy conversion and electrosynthesis.