Ru Single Atom and Nanoparticle Tandem Catalyst Unlocking High-Efficiency Ammonia Synthesis under Mild Conditions.

Area of Science:

• Catalysis
• Materials Science
• Chemical Engineering

Background:

• Haber-Bosch ammonia synthesis traditionally requires harsh conditions.
• Achieving efficient ammonia synthesis under mild conditions is hindered by competitive N2 and H2 adsorption on active sites.
• Balancing N2 activation and H2 hydrogenation is crucial for catalyst design.

Purpose of the Study:

• To design a novel ruthenium (Ru) tandem catalyst for efficient ammonia (NH3) synthesis under mild conditions.
• To leverage cascade hydrogen catalysis between distinct Ru sites (single atom and nanoparticle) for improved performance.
• To overcome the trade-off in N2 and H2 activation dynamics.

Main Methods:

• Fabrication of a Ru tandem catalyst combining Ru single atoms (Ru1) and Ru nanoparticles (RuNP) on CeO2 nanoislands.
• Investigation of hydrogen spillover mechanism between RuNP and Ru1 sites.
• Evaluation of catalytic performance for NH3 synthesis under mild conditions (400 °C, 1 MPa).

Main Results:

• RuNP sites were found to be susceptible to hydrogen poisoning, while Ru1 sites selectively adsorbed N2.
• Hydrogen spillover from RuNP to Ru1 sites facilitated N2 dissociation and hydrogenation.
• The tandem catalyst achieved a high NH3 synthesis rate of 59.0 mmol gcat−1 h−1 with 600 h stability.
• Exceptional specific rates were observed compared to other Ru-based catalysts.

Conclusions:

• The Ru single atom and nanoparticle tandem catalyst design effectively addresses the challenges of N2/H2 activation for NH3 synthesis.
• This approach offers a new pathway for developing highly efficient catalysts for ammonia production under mild conditions.
• The catalyst demonstrates significant potential for industrial applications requiring sustainable ammonia synthesis.