High-Yield Ammonia Production from Al-Nitrate Battery via Anodic Al&NO₃ ^- Spontaneous Reaction Driven Cathodic Nitrate Reduction Reaction.

Abstract

The electrocatalytic nitrate reduction reaction (NIRR) offers a sustainable alternative for ammonia (NH₃) synthesis, addressing the limitations of the energy-intensive Haber-Bosch process. This study introduces a novel aluminum-nitrate (Al-NO₃ ^-) battery system that integrates anodic Al and NO₃ ^- (Al&NO₃ ^-) spontaneous reactions with cathodic NO₃ ^- reduction, enabling simultaneous NH₃ production and electricity generation. The CuNi alloy films, synthesized via pulse laser confined bombardment (PLCB) technology, serve as efficient NIRR cathodes with tandem catalytic sites, delivering an NH₃ production rate of ≈58.04 mg h^-1 cm^-2 with a Faradaic efficiency (FE) of 99.40% at -1.3 V vs. Hg/HgO. The Al-NO₃ ^- battery system, incorporating NO₃ ^- in both anodic and cathodic electrolytes, suppresses hydrogen evolution at the anode, and achieves an apparent FE exceeding 100% due to NO₃ ^- consumption for NH₃ production through both cathodic NIRR and the spontaneous anodic Al&NO₃ ^- reaction. Extended stability studies indicated continuous operation exceeding 50 h, with peak apparent FE reaching ≈183.60%. This system demonstrates a high NH₃ yield of over 10.0 mg h^-1 cm^-2 at a current density of 40 mA cm^-2. The findings highlight the potential of Al&NO₃ ^- spontaneous reactions to drive cathodic NO₃ ^- reduction, offering a sustainable pathway for NH₃ synthesis from NO₃ ^--rich wastewater while generating electrical energy.