Improved Electrocatalytic Water Splitting Reaction on CeO2(111) by Strain Engineering: A DFT+U Study

Tiantian Wu, Tejs Vegge, Heine Anton Hansen*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Ceria is a promising cathode material in solid oxide electrolysis cells (SOECs) because ceria can become a mixed electronic and ionic conductor through doping, which enables a high surface area for electrocatalysis. Here, we systemically investigate the effect of strain on the electrocatalytic water splitting reaction (WSR) for renewable hydrogen production on CeO2(111) by using density functional theory corrected for on-site Coulomb interactions (DFT+U). We find that tensile strain stabilizes the reduced states of ceria such as oxygen vacancies and surface hydroxyls, while compressive strain destabilizes the reduced states. These trends are explained by a downshift of the Ce 4f orbital energy under tensile strain and agree with the larger size of the Ce3+ ion in comparison to the Ce4+ ion. Our results show that hydroxyl decomposition into H2 has the highest activation energy along the WSR pathway (Ea) and that the free energy of hydroxyl formation (ΔGH) prior to hydroxyl decomposition can act as a thermodynamic barrier to the WSR. Compressive strain (<−3.0%) correlates strongly with increased WSR activity on CeO2(111) because it reduces the total barrier (ΔGH + Ea). Strain also effectively engineers the reaction pathway of the WSR at T > 1000 K. By a comparison of the total reaction barrier on different hydroxylated surfaces, the WSR is found to proceed readily via a Ce–H intermediate on excessively hydroxylated CeO2(111) under tensile strain because of the lower barrier, while the WSR proceeds preferentially and readily on the partially or fully hydroxylated CeO2(111) under compressive strain. In addition, a direct mapping between the most efficient WSR pathway and strain at different operating temperatures provides a better understanding of the efficient WSR on the CeO2(111) facet by strain engineering, which sheds light on electrocatalysis on oxide catalysts.
Original languageEnglish
JournalACS Catalysis
Volume9
Pages (from-to)4853-4861
ISSN2155-5435
DOIs
Publication statusPublished - 2019

Keywords

  • Sustainable hydrogen production
  • Ceria
  • Strain effect
  • DFT simulations
  • Descriptor analysis

Cite this

@article{21a676146a18475a8ccacfd660184180,
title = "Improved Electrocatalytic Water Splitting Reaction on CeO2(111) by Strain Engineering: A DFT+U Study",
abstract = "Ceria is a promising cathode material in solid oxide electrolysis cells (SOECs) because ceria can become a mixed electronic and ionic conductor through doping, which enables a high surface area for electrocatalysis. Here, we systemically investigate the effect of strain on the electrocatalytic water splitting reaction (WSR) for renewable hydrogen production on CeO2(111) by using density functional theory corrected for on-site Coulomb interactions (DFT+U). We find that tensile strain stabilizes the reduced states of ceria such as oxygen vacancies and surface hydroxyls, while compressive strain destabilizes the reduced states. These trends are explained by a downshift of the Ce 4f orbital energy under tensile strain and agree with the larger size of the Ce3+ ion in comparison to the Ce4+ ion. Our results show that hydroxyl decomposition into H2 has the highest activation energy along the WSR pathway (Ea) and that the free energy of hydroxyl formation (ΔGH) prior to hydroxyl decomposition can act as a thermodynamic barrier to the WSR. Compressive strain (<−3.0{\%}) correlates strongly with increased WSR activity on CeO2(111) because it reduces the total barrier (ΔGH + Ea). Strain also effectively engineers the reaction pathway of the WSR at T > 1000 K. By a comparison of the total reaction barrier on different hydroxylated surfaces, the WSR is found to proceed readily via a Ce–H intermediate on excessively hydroxylated CeO2(111) under tensile strain because of the lower barrier, while the WSR proceeds preferentially and readily on the partially or fully hydroxylated CeO2(111) under compressive strain. In addition, a direct mapping between the most efficient WSR pathway and strain at different operating temperatures provides a better understanding of the efficient WSR on the CeO2(111) facet by strain engineering, which sheds light on electrocatalysis on oxide catalysts.",
keywords = "Sustainable hydrogen production, Ceria, Strain effect, DFT simulations, Descriptor analysis",
author = "Tiantian Wu and Tejs Vegge and Hansen, {Heine Anton}",
year = "2019",
doi = "10.1021/acscatal.9b00203",
language = "English",
volume = "9",
pages = "4853--4861",
journal = "A C S Catalysis",
issn = "2155-5435",
publisher = "American Chemical Society",

}

Improved Electrocatalytic Water Splitting Reaction on CeO2(111) by Strain Engineering: A DFT+U Study. / Wu, Tiantian; Vegge, Tejs; Hansen, Heine Anton.

In: ACS Catalysis, Vol. 9, 2019, p. 4853-4861.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Improved Electrocatalytic Water Splitting Reaction on CeO2(111) by Strain Engineering: A DFT+U Study

AU - Wu, Tiantian

AU - Vegge, Tejs

AU - Hansen, Heine Anton

PY - 2019

Y1 - 2019

N2 - Ceria is a promising cathode material in solid oxide electrolysis cells (SOECs) because ceria can become a mixed electronic and ionic conductor through doping, which enables a high surface area for electrocatalysis. Here, we systemically investigate the effect of strain on the electrocatalytic water splitting reaction (WSR) for renewable hydrogen production on CeO2(111) by using density functional theory corrected for on-site Coulomb interactions (DFT+U). We find that tensile strain stabilizes the reduced states of ceria such as oxygen vacancies and surface hydroxyls, while compressive strain destabilizes the reduced states. These trends are explained by a downshift of the Ce 4f orbital energy under tensile strain and agree with the larger size of the Ce3+ ion in comparison to the Ce4+ ion. Our results show that hydroxyl decomposition into H2 has the highest activation energy along the WSR pathway (Ea) and that the free energy of hydroxyl formation (ΔGH) prior to hydroxyl decomposition can act as a thermodynamic barrier to the WSR. Compressive strain (<−3.0%) correlates strongly with increased WSR activity on CeO2(111) because it reduces the total barrier (ΔGH + Ea). Strain also effectively engineers the reaction pathway of the WSR at T > 1000 K. By a comparison of the total reaction barrier on different hydroxylated surfaces, the WSR is found to proceed readily via a Ce–H intermediate on excessively hydroxylated CeO2(111) under tensile strain because of the lower barrier, while the WSR proceeds preferentially and readily on the partially or fully hydroxylated CeO2(111) under compressive strain. In addition, a direct mapping between the most efficient WSR pathway and strain at different operating temperatures provides a better understanding of the efficient WSR on the CeO2(111) facet by strain engineering, which sheds light on electrocatalysis on oxide catalysts.

AB - Ceria is a promising cathode material in solid oxide electrolysis cells (SOECs) because ceria can become a mixed electronic and ionic conductor through doping, which enables a high surface area for electrocatalysis. Here, we systemically investigate the effect of strain on the electrocatalytic water splitting reaction (WSR) for renewable hydrogen production on CeO2(111) by using density functional theory corrected for on-site Coulomb interactions (DFT+U). We find that tensile strain stabilizes the reduced states of ceria such as oxygen vacancies and surface hydroxyls, while compressive strain destabilizes the reduced states. These trends are explained by a downshift of the Ce 4f orbital energy under tensile strain and agree with the larger size of the Ce3+ ion in comparison to the Ce4+ ion. Our results show that hydroxyl decomposition into H2 has the highest activation energy along the WSR pathway (Ea) and that the free energy of hydroxyl formation (ΔGH) prior to hydroxyl decomposition can act as a thermodynamic barrier to the WSR. Compressive strain (<−3.0%) correlates strongly with increased WSR activity on CeO2(111) because it reduces the total barrier (ΔGH + Ea). Strain also effectively engineers the reaction pathway of the WSR at T > 1000 K. By a comparison of the total reaction barrier on different hydroxylated surfaces, the WSR is found to proceed readily via a Ce–H intermediate on excessively hydroxylated CeO2(111) under tensile strain because of the lower barrier, while the WSR proceeds preferentially and readily on the partially or fully hydroxylated CeO2(111) under compressive strain. In addition, a direct mapping between the most efficient WSR pathway and strain at different operating temperatures provides a better understanding of the efficient WSR on the CeO2(111) facet by strain engineering, which sheds light on electrocatalysis on oxide catalysts.

KW - Sustainable hydrogen production

KW - Ceria

KW - Strain effect

KW - DFT simulations

KW - Descriptor analysis

U2 - 10.1021/acscatal.9b00203

DO - 10.1021/acscatal.9b00203

M3 - Journal article

VL - 9

SP - 4853

EP - 4861

JO - A C S Catalysis

JF - A C S Catalysis

SN - 2155-5435

ER -