Modulating the Leverage Relationship in Nitrogen Fixation Through Hydrogen-Bond-Regulated Proton Transfer

In the electrochemical nitrogen reduction reaction (NRR), a leverage relationship exists between NH3-producing activity and selectivity because of the competing hydrogen evolution reaction (HER), which means that high activity with strong protons adsorption causes low product selectivity. Herein, we design a novel metal-organic hydrogen bonding framework (MOHBF) material to modulate this leverage relationship by a hydrogen-bond-regulated proton transfer pathway. The MOHBF material was composited with reduced graphene oxide (rGO) to form a Ni-N₂O₂ molecular catalyst (Ni-N₂O₂/rGO). The unique structure of O atoms in Ni-O-C and N-O-H could form hydrogen bonds with H₂O molecules to interfere with protons being directly adsorbed onto Ni active sites, thus regulating the proton transfer mechanism and slowing the HER kinetics, thereby modulating the leverage relationship. Moreover, this catalyst has abundant Ni-single-atom sites enriched with Ni-N/O coordination, conducive to the adsorption and activation of N₂. The Ni-N₂O₂/rGO exhibits simultaneously enhanced activity and selectivity of NH3 production with a maximum NH₃ yield rate of 209.7 μg h^-1 mg_cat.^-1 and a Faradaic efficiency of 45.7 %, outperforming other reported single-atom NRR catalysts.

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