In-situ reduced Cu3N nanocrystals enable high-efficiency ammonia synthesis and zinc-nitrate batteries.

Nitrate reduction reaction (NO3RR) involves an 8-electron transfer process and competes with the hydrogen evolution reaction process, resulting in lower yields and Faraday efficiency (FE) in the process of NH3 synthesis. Especially, Cu-based catalysts (Cu0 and Cu+) have been investigated in the field of NO3RR due to the energy levels of d-orbital and the least unoccupied molecular orbital (LUMO) π* of nitrate's orbital. Based on the above, we synthesized a Cu-based compound containing Cu3N (Cu+) through a simple one-step pyrolysis method, applied it to electrocatalytic NO3RR, and tested the performance of the Zn-NO3- battery. Through various characterization analyses, Cu-based catalysts (Cu+) are the key active sites in reduction reactions, making Cu3N a potential catalyst for ammonia synthesis. The research results indicate the application of Cu3N catalyst in NO3RR shows the best NH3 yield of 173.7 μmol h-1 cm-2, with FENH3 reaching 91.0% at -0.3 V vs. RHE, which is much higher than that of Cu catalyst without N. In addition, the Zn-NO3- battery based on Cu3N electrode also exhibits an NH3 yield of 39.8 μmol h-1 cm-2, 63.0% FENH3, and a power density of 2.7 mW cm-2, as well as stable cycling charge-discharge stability for 5 hours.