Enabled Efficient Ammonia Synthesis and Energy Supply in a Zinc-Nitrate Battery System by Separating Nitrate Reduction Process into Two Stages.

The aqueous electrocatalytic reduction of NO 3 - into NH 3 (NitrRR) presents a sustainable route applicable to NH 3 production and potentially energy storage. However, the NitrRR involves a directly eight-electron transfer process generally required a large overpotential (<-0.2 V versus reversible hydrogen electrode (vs. RHE)) to reach optimal efficiency. Here, inspired by biological nitrate respiration, the NitrRR was separated into two stages along a [2+6]-electron pathway to alleviate the kinetic barrier. The system employed a Cu nanowire catalyst produces NO 2 - and NH 3 with current efficiencies of 91.5 % and 100 %, respectively at lower overpotentials (>+0.1 vs. RHE). The high efficiency for such a reduction process was further explored in a zinc-nitrate battery. This battery could be specified by a high output voltage of 0.70 V, an average energy density of 566.7 Wh L -1 at 10 mA cm -2 and a power density of 14.1 mW cm -2 , which is well beyond all previously reported similar concepts.