Enzyme‐Mimicking Metal–Phosphide Tandem Catalytic Centers for Efficient Electrochemical Nitrate‐to‐Ammonia Conversion and Zinc–Nitrate Battery

Abstract

ABSTRACT Achieving spatially coupled and functionally complementary active sites in synthetic catalysts remains a significant challenge. Inspired by the enzymatic cascade involving nitrate reductase and nitrite reductase, we report a nanozyme comprising iron clusters and iron‐doped nickel phosphide nanoparticles on CeO 2 nanorods (Fe–Fe x Ni 2−x P/CeO 2 ) in proximity for efficient electrocatalytic nitrate‐to‐ammonia conversion and Zn–NO 3 − battery. The Fe clusters serve as nitrate reductase mimics, promoting the deoxygenation step of NO 3 − to NO 2 − , while the adjacent Fe x Ni 2−x P nanoparticles serve as nitrite reductase mimics, accelerating the subsequent hydrogenation steps to NH 3 . The CeO 2 nanorods stabilize the dual active sites and function as proton reservoirs to suppress the hydrogen evolution reaction. Thus, the nanozyme delivers exceptional performance in NH 3 electrosynthesis, achieving a high yield rate of 43.5 mg h −1 cm −2 with a Faradaic efficiency (FE) of 91.2% at –0.7 V versus RHE in an H‐type cell and an industrial‐level current density of 800 mA cm −2 for over 100 h under flow‐cell conditions (FE NH3 > 90%) at the same potential. When employed Fe–Fe x Ni 2−x P/CeO 2 as a cathode in a rechargeable Zn–NO 3 − battery, it enables simultaneous NH 3 production and power generation, delivering a peak power density of 21.1 mW cm −2 and an NH 3 yield rate of 1.9 mg h −1 cm −2 .