In Situ Synthesis of Cu x O/N Doped Graphdiyne with Pyridine N Configuration for Ammonia Production via Nitrate Reduction.

Electroreduction of nitrate to ammonia provides an interesting pathway for wastewater treatment and valorization. Cu-based catalysts are active for the conversion of NO 3 - to NO 2 - but suffer from an inefficient hydrogenation process of NO 2 - . Herein, Cu x O/N-doped graphdiyne (Cu x O/N-GDY) with pyridine N configuration are in situ prepared in one pot. Benefiting from the synergistic effect of pyridinic N in GDY and Cu x O, the prepared Cu x O/N-GDY tested in a commercial H-cell achieved a faradaic efficiency of 85% toward NH 3 at -0.5 V versus RHE with a production rate of 340 µmol h -1  mg cat -1 in 0.1 M KNO 3 . When integrating the Cu x O/N-GDY in an anion exchange membrane flow electrolyzer, a maximum Faradaic efficiency of 89% is achieved at a voltage of 2.3 V and the production rate is 1680 µmol h -1  mg cat -1 at 3.3 V in 0.1 M KNO 3 at room temperature. Operation at 40 °C further promoted the overall reaction kinetics of NO 3 - to NH 3 , but penalized its selectivity with respect to hydrogen evolution reaction. The high selectivity and production rate in this device configuration demonstrate its potential for industrial application.