Atomically Dispersed Cu Sites on Dual-Mesoporous N-Doped Carbon for Efficient Ammonia Electrosynthesis from Nitrate.

The industrial Haber-Bosch process for ammonia synthesis is extremely important in modern society. However, it is energy intensive and leads to severe pollution, which has motivated eco-friendly NH 3 synthesis research. Electroreduction of contaminant nitrate ions back to NH 3 is an effective complement but is still limited by low NH 3 yields and nitrate-to-NH 3 selectivities. In this study, the electrochemical nitrate reduction reaction (NTRR) is carried out over a single-atom Cu catalyst. Atomically dispersed Cu sites anchored on dual-mesoporous N-doped carbon framework display excellent NTRR performance with NH 3 production rate of 13.8 mol NH 3  g cat -1  h -1 and NO 3 - -to-NH 3 faradaic efficiency (FE) of 95.5 % at -1.0 V. Cu-N-C catalyst can sustain continuous 120 h NTRR test in the simulated NH 3 synthesis scenarios with large current density (about 200 mA cm -2 ) and amplified volume of NO 3 - solution (9 times). Theoretical calculations reveal that atomically dispersed Cu 1 -N 4 sites reduce the energy barrier of potential-determining step in NTRR and promote the decomposition of primary intermediate in NO 3 - -to-N 2 process. These findings provide a guideline for the rational design of highly active, selective and durable electrocatalysts for the NTRR.