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Effect of Co doping on mechanism and kinetics of ammonia synthesis on Fe(1 1 1) surface

Qian, Jin and Fortunelli, Alessandro and Goddard, William A., III (2019) Effect of Co doping on mechanism and kinetics of ammonia synthesis on Fe(1 1 1) surface. Journal of Catalysis, 370 . pp. 364-371. ISSN 0021-9517. doi:10.1016/j.jcat.2019.01.001.

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With the aim of improving the efficiency of the Haber-Bosch industrial process for the synthesis of ammonia, here we explore doping the traditional Fe-based Haber-Bosch catalyst with an impurity element. Starting from a previous experimentally-validated theoretical investigation of the reaction mechanism for Haber-Bosch synthesis of ammonia on the Fe bcc(1 1 1) surface, we focus on changes in mechanism and kinetics brought about by substitutional doping of 25% top layer iron with cobalt. The choice of Co is justified by the analysis of the wave functions of the critical reaction steps on the Fe(1 1 1) surface which showed that large changes in the net spin (magnetization) of the Fe atoms are thereby involved, and suggested that dopants with modified spins might accelerate rates. Quantum Mechanics values of free energies and reaction barriers are calculated for the Co-doped system for a set of 20 important surface configurations of adsorbates, and used as input to kinetic Monte Carlo (kMC) simulations to obtain final ammonia production. We find that at T = 673 K, P(H_2) = 15 atm, P(N_2) = 5 atm, and P(NH_3) = 1 atm, target conditions to drastically reduce the extreme energy cost of industrial ammonia synthesis process, top-layer Co doping leads to an acceleration by a factor of 2.3 in reaction rates of ammonia synthesis, and therefore an expected corresponding decrease in production costs.

Item Type:Article
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URLURL TypeDescription
Qian, Jin0000-0002-0162-0477
Fortunelli, Alessandro0000-0001-5337-4450
Goddard, William A., III0000-0003-0097-5716
Additional Information:© 2019 Elsevier Inc. Received 14 October 2018, Revised 30 December 2018, Accepted 1 January 2019, Available online 22 January 2019. This work was supported by the U.S. Department of Energy (USDOE), Office of Energy Efficiency and Renewable Energy (EERE), Advanced Manufacturing Office Next Generation R&D Projects under contract no. DE-AC07-05ID14517 (program manager Dickson Ozokwelu, in collaboration with Idaho National Labs, Rebecca Fushimi). This project was completed with funding from NSF (CBET 1512759). A.F. gratefully acknowledges financial support from a Short-Term Mission (STM) funded by Italian Consiglio Nazionale delle Ricerche (CNR). Many of the calculations were carried out on a GPU-cluster provided by DURIP (Cliff Bedford, program manager). This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number ACI-1548562. We have no conflict of interest to declare.
Funding AgencyGrant Number
Department of Energy (DOE)DE-AC07-05ID14517
Consiglio Nazionale delle Ricerche (CNR)UNSPECIFIED
Subject Keywords:Haber-Bosch; Density functional theory; PBE-D3 exchange-correlation functional; Reaction barriers; Kinetic Monte Carlo; Heterogeneous catalysis
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Record Number:CaltechAUTHORS:20190123-073842312
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Official Citation:Jin Qian, Alessandro Fortunelli, William A. Goddard, Effect of Co doping on mechanism and kinetics of ammonia synthesis on Fe(1 1 1) surface, Journal of Catalysis, Volume 370, 2019, Pages 364-371, ISSN 0021-9517, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92407
Deposited By: Tony Diaz
Deposited On:23 Jan 2019 17:46
Last Modified:16 Nov 2021 03:50

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