Efficient ammonia synthesis from the air using tandem non-thermal plasma and electrocatalysis at ambient conditions.

While electrochemical N 2 reduction presents a sustainable approach to NH 3 synthesis, addressing the emission- and energy-intensive limitations of the Haber-Bosch process, it grapples with challenges in N 2 activation and competing with pronounced hydrogen evolution reaction. Here we present a tandem air-NO x -NO x - -NH 3 system that combines non-thermal plasma-enabled N 2 oxidation with Ni(OH) x /Cu-catalyzed electrochemical NO x - reduction. It delivers a high NH 3 yield rate of 3 mmol h -1  cm -2 and a corresponding Faradaic efficiency of 92% at -0.25 V versus reversible hydrogen electrode in batch experiments, outperforming previously reported ones. Furthermore, in a flow mode concurrently operating the non-thermal plasma and the NO x - electrolyzer, a stable NH 3 yield rate of approximately 1.25 mmol h -1  cm -2 is sustained over 100 h using pure air as the intake. Mechanistic studies indicate that amorphous Ni(OH) x on Cu interacts with hydrated K + in the double layer through noncovalent interactions and accelerates the activation of water, enriching adsorbed hydrogen species that can readily react with N-containing intermediates. In situ spectroscopies and density functional theory (DFT) results reveal that NO x - adsorption and their hydrogenation process are optimized over the Ni(OH) x /Cu surface. This work provides new insights into electricity-driven distributed NH 3 production using natural air at ambient conditions.