Understanding the electronic structure of Y2Ti2O5S2 for green hydrogen production: a hybrid-DFT and GW study

Katarina Brlec; Christopher N. Savory; David O. Scanlon

doi:10.1039/D3TA02801A

Understanding the electronic structure of Y₂Ti₂O₅S₂ for green hydrogen production: a hybrid-DFT and GW study

Katarina Brlec, Christopher N. Savory, David O. Scanlon^*

^*Corresponding author for this work

Chemistry

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Abstract

Utilising photocatalytic water splitting to produce green hydrogen is the key to reducing the carbon footprint of this crucial chemical feedstock. In this study, density functional theory (DFT) is employed to gain insights into the photocatalytic performance of an up-and-coming photocatalyst Y₂Ti₂O₅S₂ from first principles. Eleven non-polar clean surfaces are evaluated at the generalised gradient approximation level to obtain a plate-like Wulff shape that agrees well with the experimental data. The (001), (101) and (211) surfaces are considered further at hybrid-DFT level to determine their band alignments with respect to vacuum. The large band offset between the basal (001) and side (101) and (211) surfaces confirms experimentally observed spatial separation of hydrogen and oxygen evolution facets. Furthermore, relevant optoelectronic bulk properties were established using a combination of hybrid-DFT and many-body perturbation theory. The optical absorption of Y₂Ti₂O₅S₂ weakly onsets due to dipole–forbidden transitions, and hybrid Wannier–Mott/Frenkel excitonic behaviour is predicted to occur due to the two-dimensional electronic structure, with an exciton binding energy of 0.4 eV.

Original language	English
Pages (from-to)	16776-16787
Number of pages	12
Journal	Journal of Materials Chemistry A
Volume	11
Issue number	31
Early online date	20 Jul 2023
DOIs	https://doi.org/10.1039/D3TA02801A
Publication status	Published - 21 Aug 2023

Bibliographical note

Acknowledgements:
KB and DOS acknowledge support from the European Research Council, ERC (grant no. 758345). CNS is grateful to the Ramsay Memorial Fellowship Trust and the Department of Chemistry at UCL for the funding of a Ramsay Fellowship. We are grateful to the UK Materials and Molecular Modelling Hub for computational resources, which is partially funded by EPSRC (EP/P020194/1 and EP/T022213/1) and to UCL for the provision of the Kathleen (Kathleen@UCL) supercomputer. DOS acknowledges support from the EPSRC(EP/N01572X/1). DOS acknowledges membership of the Materials Design Network. Via our membership of the UK HEC Materials Chemistry Consortium, which is funded by the UK Engineering and Physical Sciences Research Council (EP/R029431), this work used the ARCHER2 UK National Supercomputing Service (http://www.archer2.ac.uk).

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Cite this

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title = "Understanding the electronic structure of Y2Ti2O5S2 for green hydrogen production: a hybrid-DFT and GW study",

abstract = "Utilising photocatalytic water splitting to produce green hydrogen is the key to reducing the carbon footprint of this crucial chemical feedstock. In this study, density functional theory (DFT) is employed to gain insights into the photocatalytic performance of an up-and-coming photocatalyst Y2Ti2O5S2 from first principles. Eleven non-polar clean surfaces are evaluated at the generalised gradient approximation level to obtain a plate-like Wulff shape that agrees well with the experimental data. The (001), (101) and (211) surfaces are considered further at hybrid-DFT level to determine their band alignments with respect to vacuum. The large band offset between the basal (001) and side (101) and (211) surfaces confirms experimentally observed spatial separation of hydrogen and oxygen evolution facets. Furthermore, relevant optoelectronic bulk properties were established using a combination of hybrid-DFT and many-body perturbation theory. The optical absorption of Y2Ti2O5S2 weakly onsets due to dipole–forbidden transitions, and hybrid Wannier–Mott/Frenkel excitonic behaviour is predicted to occur due to the two-dimensional electronic structure, with an exciton binding energy of 0.4 eV.",

author = "Katarina Brlec and Savory, {Christopher N.} and Scanlon, {David O.}",

note = "Acknowledgements: KB and DOS acknowledge support from the European Research Council, ERC (grant no. 758345). CNS is grateful to the Ramsay Memorial Fellowship Trust and the Department of Chemistry at UCL for the funding of a Ramsay Fellowship. We are grateful to the UK Materials and Molecular Modelling Hub for computational resources, which is partially funded by EPSRC (EP/P020194/1 and EP/T022213/1) and to UCL for the provision of the Kathleen (Kathleen@UCL) supercomputer. DOS acknowledges support from the EPSRC(EP/N01572X/1). DOS acknowledges membership of the Materials Design Network. Via our membership of the UK HEC Materials Chemistry Consortium, which is funded by the UK Engineering and Physical Sciences Research Council (EP/R029431), this work used the ARCHER2 UK National Supercomputing Service (http://www.archer2.ac.uk).",

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N1 - Acknowledgements: KB and DOS acknowledge support from the European Research Council, ERC (grant no. 758345). CNS is grateful to the Ramsay Memorial Fellowship Trust and the Department of Chemistry at UCL for the funding of a Ramsay Fellowship. We are grateful to the UK Materials and Molecular Modelling Hub for computational resources, which is partially funded by EPSRC (EP/P020194/1 and EP/T022213/1) and to UCL for the provision of the Kathleen (Kathleen@UCL) supercomputer. DOS acknowledges support from the EPSRC(EP/N01572X/1). DOS acknowledges membership of the Materials Design Network. Via our membership of the UK HEC Materials Chemistry Consortium, which is funded by the UK Engineering and Physical Sciences Research Council (EP/R029431), this work used the ARCHER2 UK National Supercomputing Service (http://www.archer2.ac.uk).

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N2 - Utilising photocatalytic water splitting to produce green hydrogen is the key to reducing the carbon footprint of this crucial chemical feedstock. In this study, density functional theory (DFT) is employed to gain insights into the photocatalytic performance of an up-and-coming photocatalyst Y2Ti2O5S2 from first principles. Eleven non-polar clean surfaces are evaluated at the generalised gradient approximation level to obtain a plate-like Wulff shape that agrees well with the experimental data. The (001), (101) and (211) surfaces are considered further at hybrid-DFT level to determine their band alignments with respect to vacuum. The large band offset between the basal (001) and side (101) and (211) surfaces confirms experimentally observed spatial separation of hydrogen and oxygen evolution facets. Furthermore, relevant optoelectronic bulk properties were established using a combination of hybrid-DFT and many-body perturbation theory. The optical absorption of Y2Ti2O5S2 weakly onsets due to dipole–forbidden transitions, and hybrid Wannier–Mott/Frenkel excitonic behaviour is predicted to occur due to the two-dimensional electronic structure, with an exciton binding energy of 0.4 eV.

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