Tackling the Activity Trend of Metal-Loaded Metal Nitride Catalysts for NH₃ Synthesis by a First-Principles...

Area of Science:

• Catalysis
• Materials Science
• Chemical Engineering

Background:

• Ammonia (NH3) is a key industrial chemical, predominantly synthesized via the energy-intensive Haber-Bosch process.
• Dual-site catalysts offer a promising alternative for NH3 synthesis under milder conditions by spatially separating N2 and H2 activation.
• Current experimental advancements in dual-site catalysts face challenges in design and feasibility.

Purpose of the Study:

• To investigate the activity map of metal-loaded metal nitride catalysts for ammonia synthesis.
• To identify the key descriptors for optimizing dual-site catalyst performance.
• To provide a theoretical framework for the rational design of novel ammonia synthesis catalysts.

Main Methods:

• First-principles microkinetic simulations were employed to model various metal-loaded metal nitride catalyst systems.
• The study systematically explored the relationship between catalyst structure and activity for ammonia synthesis.
• Key parameters such as nitrogen vacancy formation energy (Ev) and hydrogen adsorption energy (EH) were analyzed.

Main Results:

• The optimal active region for dual-site catalysts was identified, requiring a nitrogen vacancy formation energy (Ev) of approximately 1.50 eV and a hydrogen adsorption energy (EH) of approximately -0.30 eV.
• A clear trend was established, aligning with and rationalizing existing experimental observations for metal-loaded metal nitrides.
• The study provides quantitative guidelines for catalyst design.

Conclusions:

• The findings offer a robust framework for designing highly effective metal-loaded metal nitride catalysts for ammonia synthesis.
• This theoretical work elucidates the dual-site mechanism, guiding future experimental efforts.
• The identified optimal energy ranges pave the way for more sustainable and efficient ammonia production.