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Title: On the mechanism of the electrochemical conversion of ammonia to dinitrogen on Pt(1 0 0) in alkaline environment

Abstract

The electrochemical oxidation of ammonia to dinitrogen is a model reaction for the electrocatalysis of the nitrogen cycle, as it can contribute to the understanding of the making/breaking of N—N, N—O, or N—H bonds. Moreover, it can be used as the anode reaction in ammonia electrolyzers for H2 production or in ammonia fuel cells. Here, we study the reaction on the N2-forming Pt(1 0 0) electrode using a combination of electrochemical methods, product characterization and computational methods, and suggest a mechanism that is compatible with the experimental and theoretical findings. We propose that N2 is formed via an *NH + *NH coupling step, in accordance with the Gerischer-Mauerer mechanism. Other N—N bond forming steps are considered less likely based on either their unfavourable energetics or the low coverage of the necessary monomers. The N—N coupling is inhibited by strongly adsorbed *N and *NO species, which are formed by further oxidation of *NH.

Authors:
 [1];  [2];  [3];  [2];  [4];  [5];  [2]
  1. Univ. of Illinois, Urbana-Champaign, IL (United States). Dept. of Chemistry; Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division; Leiden Univ. (Netherlands). Leiden Inst. of Chemistry
  2. Leiden Univ. (Netherlands). Leiden Inst. of Chemistry
  3. Leiden Univ. (Netherlands). Leiden Inst. of Chemistry; Univ. of Barcelona (Spain). Inst. of Theoretical and Computational Chemistry of the Univ. of Barcelona (IQTCUB) and Dept. of Materials Science and Physical Chemistry
  4. Univ. of Illinois, Urbana-Champaign, IL (United States). Dept. of Chemistry
  5. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; European Commission (EC); China Scholarship Council (CSC); Netherlands Organization for Scientific Research (NWO); Ministry of Education, Culture and Sport (MEC); USDOE
OSTI Identifier:
1461283
Alternate Identifier(s):
OSTI ID: 1548775
Grant/Contract Number:  
AC02-06CH11357; IOF-327650; 722.014.009; RYC-2015-18996
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Catalysis
Additional Journal Information:
Journal Volume: 359; Journal Issue: C; Journal ID: ISSN 0021-9517
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Ammonia oxidation; Electrocatalysis; Nitrogen cycle; Physical electrochemistry; Single-crystal electrochemistry

Citation Formats

Katsounaros, Ioannis, Figueiredo, Marta C., Calle-Vallejo, Federico, Li, Hongjiao, Gewirth, Andrew A., Markovic, Nenad M., and Koper, Marc T. M. On the mechanism of the electrochemical conversion of ammonia to dinitrogen on Pt(1 0 0) in alkaline environment. United States: N. p., 2018. Web. doi:10.1016/j.jcat.2017.12.028.
Katsounaros, Ioannis, Figueiredo, Marta C., Calle-Vallejo, Federico, Li, Hongjiao, Gewirth, Andrew A., Markovic, Nenad M., & Koper, Marc T. M. On the mechanism of the electrochemical conversion of ammonia to dinitrogen on Pt(1 0 0) in alkaline environment. United States. doi:10.1016/j.jcat.2017.12.028.
Katsounaros, Ioannis, Figueiredo, Marta C., Calle-Vallejo, Federico, Li, Hongjiao, Gewirth, Andrew A., Markovic, Nenad M., and Koper, Marc T. M. Sat . "On the mechanism of the electrochemical conversion of ammonia to dinitrogen on Pt(1 0 0) in alkaline environment". United States. doi:10.1016/j.jcat.2017.12.028. https://www.osti.gov/servlets/purl/1461283.
@article{osti_1461283,
title = {On the mechanism of the electrochemical conversion of ammonia to dinitrogen on Pt(1 0 0) in alkaline environment},
author = {Katsounaros, Ioannis and Figueiredo, Marta C. and Calle-Vallejo, Federico and Li, Hongjiao and Gewirth, Andrew A. and Markovic, Nenad M. and Koper, Marc T. M.},
abstractNote = {The electrochemical oxidation of ammonia to dinitrogen is a model reaction for the electrocatalysis of the nitrogen cycle, as it can contribute to the understanding of the making/breaking of N—N, N—O, or N—H bonds. Moreover, it can be used as the anode reaction in ammonia electrolyzers for H2 production or in ammonia fuel cells. Here, we study the reaction on the N2-forming Pt(1 0 0) electrode using a combination of electrochemical methods, product characterization and computational methods, and suggest a mechanism that is compatible with the experimental and theoretical findings. We propose that N2 is formed via an *NH + *NH coupling step, in accordance with the Gerischer-Mauerer mechanism. Other N—N bond forming steps are considered less likely based on either their unfavourable energetics or the low coverage of the necessary monomers. The N—N coupling is inhibited by strongly adsorbed *N and *NO species, which are formed by further oxidation of *NH.},
doi = {10.1016/j.jcat.2017.12.028},
journal = {Journal of Catalysis},
number = C,
volume = 359,
place = {United States},
year = {2018},
month = {2}
}

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Figures / Tables:

Figure 1 Figure 1: Cyclic voltammetry in a stagnant solution on Pt(100) in 0.1 M KOH with (black curves) or without (grey curves) the addition of 1 mM NH4ClO4. The solid vs dashed curves represent the corresponding voltammograms for different upper potential limits. The red curve corresponds to the hydrodynamic voltammogram inmore » 1 mM NH3 with 400 rpm. The scan rate was 0.05 V s -1 in all measurements. « less

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