Identifying the Dominant Role of Pyridinic-N-Mo Bonding in Synergistic Electrocatalysis for Ambient Nitrogen Reduction.

Abstract

For electrochemical nitrogen reduction reaction (NRR), hybridizing transition metal (TM) compounds with nitrogen-doped carbonaceous materials has been recognized as a promising strategy to improve the activity and stability of electrocatalysts due to the synergistic interaction from the TM-N-C active sites. Nevertheless, up to date, the fundamental mechanism of this so-called synergistic electrocatalysis for NRR is still unclear. Particularly, it remains ambiguous which configuration of N dopants, either pyridinic N or pyrrolic N, when coordinated with the TM, predominately contributes to this synergy. Herein, a self-assembled three-dimensional 1T-phase MoS₂ microsphere coupled with N-doped carbon was developed (termed MoS₂/NC), showing an impressive NRR performance in neutral medium. The hybridization of MoS₂ and N-doped carbon can synergistically enhance the NRR efficiency by optimizing the electron transfer of catalyst. Acidification/blocking/poisoning experiments reveal the decisive role of pyridinic-N-Mo bonding, rather than pyrrolic-N-Mo bonding, in synergistically enhancing NRR electrocatalysis. The electrochemical-based <i>in situ</i> Fourier transform infrared spectroscopy (<i>in situ</i> FTIR) technology provides deep insights into the substantial contribution of pyridinic-N-MoS₂ sites to NRR electrocatalysis and further uncover the underlying mechanism (associative pathway) at a molecular level.