Promotional Effect of Mn On NH₃ Synthesis Over Inverse Iron Catalyst.

Area of Science:

• Catalysis
• Materials Science
• Chemical Engineering

Background:

• The Haber-Bosch process, established over a century ago, remains critical for global ammonia production.
• Current industrial ammonia synthesis relies on early 20th-century iron catalysts, highlighting the need for improved alternatives.
• Developing catalysts with superior activity under mild conditions presents an ongoing challenge.

Purpose of the Study:

• To develop and characterize a novel manganese-incorporated iron (FeMn) catalyst for ammonia synthesis.
• To evaluate the catalytic activity of the FeMn catalyst under mild conditions compared to conventional catalysts.
• To elucidate the mechanism behind the enhanced activity observed with the FeMn catalyst.

Main Methods:

• A facile sol-gel method was employed to prepare the manganese-incorporated iron (FeMn) catalyst.
• Ammonia synthesis rates were measured under mild conditions.
• Kinetic analysis, structural, and surface analyses were performed to understand the catalyst's performance.

Main Results:

• The FeMn catalyst demonstrated an approximately twofold higher ammonia formation rate compared to the conventional commercial iron catalyst.
• Kinetic analysis indicated a lower apparent activation energy for ammonia synthesis with the FeMn catalyst, suggesting enhanced N2 activation.
• Surface analysis revealed Mn enrichment, which favors N2 activation and facilitates N≡N bond cleavage.

Conclusions:

• Manganese incorporation into iron catalysts is an effective strategy to enhance ammonia synthesis activity under mild conditions.
• The FeMn catalyst offers a significant improvement over traditional catalysts, potentially impacting industrial ammonia production.
• This work provides a simple and effective approach to boost the performance of Fe-based catalysts for sustainable ammonia synthesis.