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 FE_NH3 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 % FE_NH3, 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.