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. This work guides the application of Cu3N enhanced regulation of the active site in the electrocatalytic synthesis of NH3 from NO3RR.