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Title: Operando Phonon Studies of the Protonation Mechanism in Highly Active Hydrogen Evolution Reaction Pentlandite Catalysts

Synthetic pentlandite (Fe 4.5Ni 4.5S 8) is a promising electrocatalyst for hydrogen evolution, demonstrating high current densities, low overpotential, and remarkable stability in bulk form. The depletion of sulfur from the surface of this catalyst during the electrochemical reaction has been proposed to be beneficial for its catalytic performance, but the role of sulfur vacancies and the mechanism determining the reaction kinetics are still unknown. In this paper, we have performed electrochemical operando studies of the vibrational dynamics of pentlandite under hydrogen evolution reaction conditions using 57Fe nuclear resonant inelastic X-ray scattering. Comparing the measured Fe partial vibrational density of states with density functional theory calculations, we have demonstrated that hydrogen atoms preferentially occupy substitutional positions replacing pre-existing sulfur vacancies. Once all vacancies are filled, the protonation proceeds interstitially, which slows down the reaction. Finally, our results highlight the beneficial role of sulfur vacancies in the electrocatalytic performance of pentlandite and give insights into the hydrogen adsorption mechanism during the reaction.
Authors:
 [1] ;  [2] ;  [1] ;  [1] ; ORCiD logo [3] ;  [1] ;  [4] ;  [4] ;  [4] ;  [5] ;  [5] ;  [5] ;  [2] ;  [2] ;  [2] ; ORCiD logo [6]
  1. Ruhr Univ., Bochum (Germany). Dept. of Physics
  2. Max Planck Inst. for Iron Research, Düsseldorf (Germany)
  3. Ruhr Univ., Bochum (Germany). Dept. of Physics; Univ. of Central Florida, Orlando, FL (United States). Dept. of Physics
  4. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source
  5. Ruhr Univ., Bochum (Germany). Inorganic Chemistry
  6. Ruhr Univ., Bochum (Germany). Dept. of Physics; Fritz Haber Inst. of the Max Planck Society, Berlin (Germany). Dept. of Interface Science
Publication Date:
Grant/Contract Number:
AC02-06CH11357; 1213182; DMR 1207065; AP242/2-1
Type:
Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 139; Journal Issue: 41; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States); Ruhr Univ., Bochum (Germany); Max Planck Inst. for Iron Research, Düsseldorf (Germany)
Sponsoring Org:
USDOE Office of Science (SC); National Science Foundation (NSF); German Research Foundation (DFG); Fonds der Chemischen Industrie (FCI) (Germany)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1461408

Zegkinoglou, Ioannis, Zendegani, Ali, Sinev, Ilya, Kunze, Sebastian, Mistry, Hemma, Jeon, Hyo Sang, Zhao, Jiyong, Hu, Michael Y., Alp, E. Ercan, Piontek, Stefan, Smialkowski, Mathias, Apfel, Ulf-Peter, Kormann, Fritz, Neugebauer, Jorg, Hickel, Tilmann, and Roldan Cuenya, Beatriz. Operando Phonon Studies of the Protonation Mechanism in Highly Active Hydrogen Evolution Reaction Pentlandite Catalysts. United States: N. p., Web. doi:10.1021/jacs.7b07902.
Zegkinoglou, Ioannis, Zendegani, Ali, Sinev, Ilya, Kunze, Sebastian, Mistry, Hemma, Jeon, Hyo Sang, Zhao, Jiyong, Hu, Michael Y., Alp, E. Ercan, Piontek, Stefan, Smialkowski, Mathias, Apfel, Ulf-Peter, Kormann, Fritz, Neugebauer, Jorg, Hickel, Tilmann, & Roldan Cuenya, Beatriz. Operando Phonon Studies of the Protonation Mechanism in Highly Active Hydrogen Evolution Reaction Pentlandite Catalysts. United States. doi:10.1021/jacs.7b07902.
Zegkinoglou, Ioannis, Zendegani, Ali, Sinev, Ilya, Kunze, Sebastian, Mistry, Hemma, Jeon, Hyo Sang, Zhao, Jiyong, Hu, Michael Y., Alp, E. Ercan, Piontek, Stefan, Smialkowski, Mathias, Apfel, Ulf-Peter, Kormann, Fritz, Neugebauer, Jorg, Hickel, Tilmann, and Roldan Cuenya, Beatriz. 2017. "Operando Phonon Studies of the Protonation Mechanism in Highly Active Hydrogen Evolution Reaction Pentlandite Catalysts". United States. doi:10.1021/jacs.7b07902. https://www.osti.gov/servlets/purl/1461408.
@article{osti_1461408,
title = {Operando Phonon Studies of the Protonation Mechanism in Highly Active Hydrogen Evolution Reaction Pentlandite Catalysts},
author = {Zegkinoglou, Ioannis and Zendegani, Ali and Sinev, Ilya and Kunze, Sebastian and Mistry, Hemma and Jeon, Hyo Sang and Zhao, Jiyong and Hu, Michael Y. and Alp, E. Ercan and Piontek, Stefan and Smialkowski, Mathias and Apfel, Ulf-Peter and Kormann, Fritz and Neugebauer, Jorg and Hickel, Tilmann and Roldan Cuenya, Beatriz},
abstractNote = {Synthetic pentlandite (Fe4.5Ni4.5S8) is a promising electrocatalyst for hydrogen evolution, demonstrating high current densities, low overpotential, and remarkable stability in bulk form. The depletion of sulfur from the surface of this catalyst during the electrochemical reaction has been proposed to be beneficial for its catalytic performance, but the role of sulfur vacancies and the mechanism determining the reaction kinetics are still unknown. In this paper, we have performed electrochemical operando studies of the vibrational dynamics of pentlandite under hydrogen evolution reaction conditions using 57Fe nuclear resonant inelastic X-ray scattering. Comparing the measured Fe partial vibrational density of states with density functional theory calculations, we have demonstrated that hydrogen atoms preferentially occupy substitutional positions replacing pre-existing sulfur vacancies. Once all vacancies are filled, the protonation proceeds interstitially, which slows down the reaction. Finally, our results highlight the beneficial role of sulfur vacancies in the electrocatalytic performance of pentlandite and give insights into the hydrogen adsorption mechanism during the reaction.},
doi = {10.1021/jacs.7b07902},
journal = {Journal of the American Chemical Society},
number = 41,
volume = 139,
place = {United States},
year = {2017},
month = {9}
}