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

Abstract

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 NH3 synthesis research. Electroreduction of contaminant nitrate ions back to NH3 is an effective complement but is still limited by low NH3 yields and nitrate-to-NH3 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 NH3 production rate of 13.8 mol gcat -1 h-1 and NO3 - -to-NH3 faradaic efficiency (FE) of 95.5 % at -1.0 V. Cu-N-C catalyst can sustain continuous 120 h NTRR test in the simulated NH3 synthesis scenarios with large current density (about 200 mA cm-2 ) and amplified volume of NO3 - solution (9 times). Theoretical calculations reveal that atomically dispersed Cu1 -N4 sites reduce the energy barrier of potential-determining step in NTRR and promote the decomposition of primary intermediate in NO3 - -to-N2 process. These findings provide a guideline for the rational design of highly active, selective and durable electrocatalysts for the NTRR.