Electroreduction of nitrogen to ammonia by single-atom catalysis with synergistic boron-carbon nitrogen nanotubes

Electrochemical nitrogen reduction reaction (NRR) to produce ammonia without CO2 emissions has the potential to solve energy problems and reduce greenhouse gas emissions. A daunting challenge for its applications at present is its low catalytic efficiency. Doping B and N atoms on the surface of carbon nanotubes can be used as a stable conductive carrier for single atom catalysis (SAC) to enhance productivity. In this work, we use density functional theory (DFT) to investigate the NRR catalytic performance of boron carbon nitrogen nanotubes (BCN NTs) containing defective vacancies embedded with transition metals (TMs). The result shows that for TMs of 3d, 4d, and 5d, delta G(max) gradually decreases as the number of outermost electrons increases because of the increase in the charge transferred from TM to N-2. Mn embedding exhibits the highest catalytic activity thanks to the lowest limiting potential (0.10 V) through a distal mode. It is mainly due to the d-pi* hybridization of the d orbitals of Mn with the antibonding pi* of N-2 reducing the reaction potential. This work contributes to the development and optimization of efficient TM-based B, C, and N atoms co-doped catalytic materials.