Effective Nitrate Electroconversion to Ammonia Using an Entangled Co₃O₄/Graphene Nanoribbon Catalyst

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Nitrate (NO3-) reduction to ammonia (NH4+) is crucial for fertilizer and fuel production.
• Developing highly selective and stable electrocatalysts is essential for this complex eight-electron reaction.
• Existing electrocatalysts often struggle with selectivity and efficiency, necessitating new material development.

Purpose of the Study:

• To develop and evaluate novel Co3O4/GNR electrocatalysts for efficient nitrate electroreduction to ammonia.
• To investigate the catalytic performance, selectivity, and stability of the synthesized Co3O4/GNR materials.
• To elucidate the reaction mechanism and understand the role of catalyst structure in performance.

Main Methods:

• Synthesis and characterization of Co3O4/GNR electrocatalysts.
• Electrochemical evaluation including yield rate, Faradaic efficiency (FE), conversion efficiency, and selectivity measurements.
• In situ FTIR and Raman spectroscopy for intermediate identification.
• Density Functional Theory (DFT) calculations to study reaction pathways and energetics.

Main Results:

• Co3O4/GNR electrocatalysts demonstrated high NH4+ yield rates (up to 42.11 mg h-1 mgcat-1) and 100% selectivity.
• Achieved excellent Faradaic efficiency (FE) of 98.7% and nitrate conversion efficiency of 14.71%.
• Catalyst performance was linked to high electrochemically active surface area (ECSA), low charge transfer resistance (Rct), and specific structural features, including a complex cobalt structure and GNR entanglement.

Conclusions:

• Co3O4/GNR electrocatalysts are highly effective for selective nitrate-to-ammonia reduction.
• The catalyst's structure, including GNR integration and unique cobalt complexes, significantly enhances performance.
• The findings provide a pathway for developing advanced electrocatalysts for sustainable ammonia synthesis.