Building hydrogen bonds on graphitic carbon nitride for dramatically enhanced ammonia synthesis

Abstract

N2 electrochemical reduction (NRR) suffers from weak activity and fierce competition of hydrogen evolution reaction (HER). Herein, we propose a strengthened activating strategy for N2 fixation via hydrogen bonds. To this end, amino functionalized graphitic carbon nitride (NHx-gCN) is designed. Through the NH⋯N hydrogen bonds between amino groups and N2 as well as NRR intermediates of NxHy, NHx-gCN presents dramatically enhanced NRR performance, with NH3 yield rate of 56.38 µg mg−1cat h−1 and Faradaic efficiency of 27.00 % at −0.73 V (vs RHE). Theoretical calculations certify through hydrogen bonds the adsorption of N2 and NxHy on NHx-gCN is enhanced and the dissociation of N2 into *N2H and *N2H2 is greatly facilitated. Besides, hydrogen bonding interactions between amino groups and heptazine can suppress the HER by inhibiting adsorption of proton H. This work delivers a new hydrogen-bond strategy to optimal NRR performance with both high NH3 production and high Faradaic efficiency.