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

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• The electrochemical nitrogen reduction reaction (NRR) faces challenges due to competing hydrogen evolution reaction (HER), limiting ammonia (NH₃) production activity and selectivity.
• High proton adsorption on active sites often leads to low product selectivity in NRR.

Purpose of the Study:

• To design a novel metal-organic hydrogen bonding framework (MOHBF) material to modulate the trade-off between NRR activity and selectivity.
• To regulate the proton transfer pathway via hydrogen bonding to suppress HER kinetics.
• To enhance nitrogen (N₂) adsorption and activation for improved NH₃ synthesis.

Main Methods:

• Fabrication of a Ni-N₂O₂ molecular catalyst composited with reduced graphene oxide (Ni-N₂O₂/rGO) using MOHBF.
• Utilizing the hydrogen-bonding interactions of oxygen atoms in the catalyst structure with water molecules to interfere with proton adsorption.
• Characterization of the catalyst's structure, coordination environment (Ni-N/O), and performance in electrochemical NRR.

Main Results:

• The Ni-N₂O₂/rGO catalyst effectively modulated proton transfer, slowing HER kinetics and improving the NRR activity-selectivity relationship.
• The catalyst demonstrated abundant Ni-single-atom sites with Ni-N/O coordination, facilitating N₂ adsorption and activation.
• Achieved a maximum NH₃ yield rate of 209.7 μg h^-1 mg_cat.^-1 and a Faradaic efficiency of 45.7%, surpassing other single-atom NRR catalysts.

Conclusions:

• The developed MOHBF-based Ni-N₂O₂/rGO catalyst offers a promising strategy for enhancing electrochemical ammonia synthesis.
• Hydrogen-bond-regulated proton transfer is an effective method to overcome the activity-selectivity limitations in NRR.
• The catalyst's design showcases superior performance for NRR, paving the way for efficient nitrogen fixation technologies.