(562f) Electrochemical Reduction of N2 into NH3 By High Efficiency Molecule-Level Bi-C3N4 Electrocatalysts

Ammonia as a basic chemical plays an important role in the industry and agriculture. The synthesis of ammonia is mainly relying on the Haber-bosch process in the industry, but the hard reaction conditions and the high energy consumption are the concerning problems. Electrochemical nitrogen reduction reaction (ENRR) is a promising process to achieve the ammonia synthesis environmentally and efficiently. Most metal nitrides and metal-nitrogen/carbon (M-N/C) electrocatalysts have proved activity towards ENRR, but the efficiency is limited. Here, we developed a molecular electrocatalyst (Bi-C₃N₄) that coordinate the heavy metal bismuth to the graphitic carbon nitride (g-C₃N₄) for the ENRR, which has defined active sites to allow the mechanism-based analysis. The Bi-C₃N₄ is immobilized on the carbon nanotubes (CNT) to improve the electrical conductivity of the catalysts by one-step calcination process.

Theoretical and experimental evaluations were conducted on this type of M-N/C catalysts. The results show the Bi-C₃N₄ performance better than the bismuth nitrides and the Bi-N/C electrocatalysts. Faradaic efficiency is higher than 20 percent and the current density is greater than 10mA/cm² at −0.9V with respect to the reversible hydrogen electrode in acid electrolyte. The high ENRR performance is attributes to the M-N coordination exist in g-C₃N₄. This proposed molecular catalyst as a class of the M-N/C complexes provides a new strategy for the high activity and selectivity catalysts design towards the ENRR.