Ternary Heteroatom-Doped Carbon As a High-Performance Metal-Free Catalyst for Electrochemical Ammonia Synthesis

The electrochemical nitrogen reduction reaction (NRR) has garnered much attention, but the major challenge remains with efficient electrocatalysts. Metal-free carbonaceous materials, doped with heteroatoms and structural defects, present a promising alternative to metal-based catalysts. This study introduces a novel strategic stepwise synthesis strategy of defective nitrogen-doped carbon material, further doped with secondary heteroatoms boron and fluorine (FBDG). These secondary atoms in combination create additional active sites for nitrogen adsorption and activation and suppress the hydrogen evolution reaction (HER). The synergistic effect of three heteroatoms and induced defects in the catalyst enhances electron-donor behavior, improving π bonding within the carbon framework and facilitating the electron transfer processes during NRR, resulting in a significantly high Faradaic efficiency of 38.1% in the case of metal-free electrocatalysts. The theoretical calculation reveals that FBDG possesses a sufficient charge density to reduce nitrogen at a low overpotential following an alternating free energy pathway. The reaction intermediates are thereby identified by in situ ATR-FTIR studies. For the rapid screening of ammonia, we used a rotating ring disk system (RRDE) and did a kinetic study. The high efficiency, stability, and cost-effectiveness of FBDG position it as a strong contender for sustainable ammonia production and pave the way for future advancements in NRR.