Unlocking a Water Coordination Environment in Co-Based Metal-Organic Frameworks for Advanced Nitrate-to-Ammonia...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Electrochemical nitrate reduction to ammonia (e-NO3RR) is a sustainable alternative to Haber-Bosch for decentralized ammonia production.
• Current e-NO3RR methods face limitations due to sluggish kinetics, high activation energy, poor mass transport, and weak catalyst adsorption.

Purpose of the Study:

• To design and synthesize a novel metal-organic framework (MOF) catalyst for efficient electrochemical nitrate reduction to ammonia.
• To investigate the role of framework water coordination in enhancing catalytic activity.

Main Methods:

• Synthesis of a 3D cobalt-based MOF (HUST-38) with water coordination.
• Electrochemical performance testing of HUST-38 for e-NO3RR.
• In situ measurements and theoretical calculations to elucidate the reaction mechanism.

Main Results:

• HUST-38 achieved a high NH3 Faradaic efficiency of 95.7% and a yield rate of 13.38 mg h-1 mgcat-1 at -0.6 V vs RHE.
• The water coordination in HUST-38 promoted water accessibility to active sites, enhancing localized *H enrichment and nitrate reduction.
• Performance significantly surpassed the control sample (HUST-39) and other reported catalysts.

Conclusions:

• The labile water coordination in HUST-38 is crucial for its superior electrocatalytic performance.
• Metal coordination microenvironments in MOFs can be tailored to optimize reaction pathways and improve e-NO3RR efficiency.
• This study provides a framework for designing MOFs as efficient electrocatalysts for sustainable ammonia synthesis.