Precise Vacancy Fitting of Horizontal Dinitrogen for Ammonia Synthesis

Area of Science:

• Catalysis and Materials Science
• Sustainable Chemistry
• Chemical Engineering

Background:

• Efficient ammonia synthesis under mild conditions is a critical challenge.
• Chemical looping ammonia synthesis (CLAS) offers a sustainable pathway for ammonia production at near-ambient pressures.
• Traditional CLAS catalysts often face limitations in activity and stability.

Purpose of the Study:

• To introduce and investigate a novel "horizontal N2" approach for chemical looping ammonia synthesis.
• To explore the potential of barium carbide (BaC2) as a catalyst support for enhanced nitrogen activation.
• To develop a more efficient and stable catalytic system for ammonia production under mild conditions.

Main Methods:

• Utilized barium carbide (BaC2) as a model material with loaded Ni nanoparticles.
• Employed a "horizontal N2" strategy for nitrogen molecule incorporation into the catalyst surface.
• Conducted resonant inelastic X-ray scattering (RIXS) analysis and computational calculations to study reaction mechanisms.

Main Results:

• The surface dianion vacancy sites on BaC2 facilitated optimal N2 activation, while Ni nanoparticles activated H2.
• The rate-determining step was identified as the hydrogenation of *HNNH, significantly reducing activation energy.
• The Ni/BaC2 catalyst demonstrated an order of magnitude higher NH3 production rate than conventional CLAS catalysts and superior stability over 20 hours.

Conclusions:

• The "horizontal N2" approach with Ni/BaC2 offers a highly efficient and stable method for ammonia synthesis under mild conditions.
• Surface vacancy sites play a crucial role in the CLAS reaction cycle, enabling effective N2 activation.
• This study presents a new catalyst design concept for developing earth-abundant catalysts for sustainable ammonia production.