Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published February 2019 | Supplemental Material
Journal Article Open

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

Abstract

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.

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.

Attached Files

Supplemental Material - 1-s2.0-S002195171930003X-mmc1.pdf

Supplemental Material - 1-s2.0-S002195171930003X-mmc2.xlsx

Files

1-s2.0-S002195171930003X-mmc1.pdf
Files (990.1 kB)
Name Size Download all
md5:5ed460aafa00db00f540b04b75ad935b
947.6 kB Preview Download
md5:3b23263578171a0f0cc6a214e168ed82
42.5 kB Download

Additional details

Created:
August 22, 2023
Modified:
October 20, 2023