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Updated: Sep 27, 2025

Ammonia Synthesis at Low Pressure
Published on: August 23, 2017
Reaction Mechanisms, Kinetics, and Improved Catalysts for Ammonia Synthesis from Hierarchical High Throughput
Jon Fuller1, Qi An1, Alessandro Fortunelli2,3
1Department of Chemical and Materials Engineering, University of Nevada, Reno, Nevada 89577, United States.
Researchers optimized the Haber-Bosch process for ammonia synthesis by identifying atomic-level mechanisms and using hierarchical high-throughput catalysis screening to discover highly effective iron (Fe) catalyst dopants, significantly improving ammonia production efficiency.
Area of Science:
- Catalysis
- Materials Science
- Chemical Engineering
Background:
- The Haber-Bosch (HB) process is critical for ammonia (NH3) production, essential for fertilizers and hydrogen storage.
- Current HB process demands high energy (2% of global usage) due to inefficient iron (Fe) catalysts requiring high temperatures and pressures.
- Previous research on improving HB process catalysts has yielded slow progress.
Purpose of the Study:
- To elucidate the atomic-level reaction mechanism of ammonia synthesis on industrial Fe catalysts.
- To leverage mechanistic understanding for the rational design of significantly improved HB catalysts.
- To develop and apply a novel hierarchical high-throughput catalysis screening (HHTCS) approach for catalyst discovery.
Main Methods:
- Density Functional Theory (DFT) was used to determine reaction mechanisms and free-energy barriers on Fe(111) and Fe(211) surfaces.
- Kinetic Monte Carlo (kMC) simulations integrated DFT data to predict catalyst turnover frequencies (TOFs) with high accuracy.
- The HHTCS approach was developed to efficiently screen over 50 dopant candidates by focusing on critical reaction steps.
Main Results:
- Accurate DFT/kMC predictions validated against experimental data, with predicted barriers within 0.04 eV of experimental values.
- HHTCS significantly reduced computational cost, enabling rapid screening of numerous dopant-Fe catalyst combinations.
- Identified high-performance dopants for Fe(111): Si (43x rate increase), Ni (16x), Co (8x), Pt/Rh (3x), Pd/Cu (2x). For Fe(211), Co showed a 3x rate increase.
Conclusions:
- The study successfully determined the HB reaction mechanism on Fe surfaces and established a new paradigm for rational catalyst design.
- The HHTCS method provides an efficient pathway for discovering novel, high-performance catalysts for ammonia synthesis.
- Specific dopants like Si, Ni, and Co show potential for dramatically enhancing the efficiency of the Haber-Bosch process.
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