Abstract
Selective charge separation among different crystal facets of a semiconductor is an intriguing phenomenon for which there is no firm and full theoretical foundation currently. In this work, we report on a density functional theory + U characterization of band alignment and electron and hole polaron stabilities among the (010), (110), and (011) facets of bismuth vanadate BiVO4 (BVO). Computation-derived band alignment indicates that the conduction band minima are at nearly the same level among the three facets but that the valence band maxima exhibit a shift. We also modeled electron and hole polarons as localized electrons and holes on vanadium and oxygen, respectively, and determined their relative stabilities from a "bulk" region to a surface region. Calculated stabilities reveal similar stability profiles across the various facets, with electron polarons most stable when localized on subsurface V atoms and hole polarons most stable on surface O atoms. Calculations indicate a small stability preference for electron polarons toward the (011) facet and for hole polarons toward the (110) facet, whereas, experimentally, interfacial reduction is observed to take place selectively on the (010) facet and oxidation on the (110) and (011) facets. Facet selectivity could be occurring on the basis of thermodynamics (electron or holes showing a stronger affinity for some facets over others) or kinetics (electron or hole transport and/or redox processes being more efficient toward/on some facets over others) or a combination of both. This work establishes that thermodynamic stability alone is not responsible for the observed facet selectivity in BVO. Therefore, we surmise that polaron transport kinetics and interfacial redox kinetics are likely to have a role in facet selectivity in BVO. These issues will be the subject of future publications.
| Original language | English |
|---|---|
| Journal | Journal of Physical Chemistry C |
| DOIs | |
| Publication status | Accepted/In press - Jan 1 2019 |
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ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Energy(all)
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
Cite this
Photocatalytic Facet Selectivity in BiVO4 Nanoparticles : Polaron Electronic Structure and Thermodynamic Stability Considerations for Photocatalysis. / Liu, Taifeng; Zhao, Qianyu; Li, Can; Lyu, Yang; Dupuis, Michel.
In: Journal of Physical Chemistry C, 01.01.2019.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Photocatalytic Facet Selectivity in BiVO4 Nanoparticles
T2 - Polaron Electronic Structure and Thermodynamic Stability Considerations for Photocatalysis
AU - Liu, Taifeng
AU - Zhao, Qianyu
AU - Li, Can
AU - Lyu, Yang
AU - Dupuis, Michel
PY - 2019/1/1
Y1 - 2019/1/1
N2 - Selective charge separation among different crystal facets of a semiconductor is an intriguing phenomenon for which there is no firm and full theoretical foundation currently. In this work, we report on a density functional theory + U characterization of band alignment and electron and hole polaron stabilities among the (010), (110), and (011) facets of bismuth vanadate BiVO4 (BVO). Computation-derived band alignment indicates that the conduction band minima are at nearly the same level among the three facets but that the valence band maxima exhibit a shift. We also modeled electron and hole polarons as localized electrons and holes on vanadium and oxygen, respectively, and determined their relative stabilities from a "bulk" region to a surface region. Calculated stabilities reveal similar stability profiles across the various facets, with electron polarons most stable when localized on subsurface V atoms and hole polarons most stable on surface O atoms. Calculations indicate a small stability preference for electron polarons toward the (011) facet and for hole polarons toward the (110) facet, whereas, experimentally, interfacial reduction is observed to take place selectively on the (010) facet and oxidation on the (110) and (011) facets. Facet selectivity could be occurring on the basis of thermodynamics (electron or holes showing a stronger affinity for some facets over others) or kinetics (electron or hole transport and/or redox processes being more efficient toward/on some facets over others) or a combination of both. This work establishes that thermodynamic stability alone is not responsible for the observed facet selectivity in BVO. Therefore, we surmise that polaron transport kinetics and interfacial redox kinetics are likely to have a role in facet selectivity in BVO. These issues will be the subject of future publications.
AB - Selective charge separation among different crystal facets of a semiconductor is an intriguing phenomenon for which there is no firm and full theoretical foundation currently. In this work, we report on a density functional theory + U characterization of band alignment and electron and hole polaron stabilities among the (010), (110), and (011) facets of bismuth vanadate BiVO4 (BVO). Computation-derived band alignment indicates that the conduction band minima are at nearly the same level among the three facets but that the valence band maxima exhibit a shift. We also modeled electron and hole polarons as localized electrons and holes on vanadium and oxygen, respectively, and determined their relative stabilities from a "bulk" region to a surface region. Calculated stabilities reveal similar stability profiles across the various facets, with electron polarons most stable when localized on subsurface V atoms and hole polarons most stable on surface O atoms. Calculations indicate a small stability preference for electron polarons toward the (011) facet and for hole polarons toward the (110) facet, whereas, experimentally, interfacial reduction is observed to take place selectively on the (010) facet and oxidation on the (110) and (011) facets. Facet selectivity could be occurring on the basis of thermodynamics (electron or holes showing a stronger affinity for some facets over others) or kinetics (electron or hole transport and/or redox processes being more efficient toward/on some facets over others) or a combination of both. This work establishes that thermodynamic stability alone is not responsible for the observed facet selectivity in BVO. Therefore, we surmise that polaron transport kinetics and interfacial redox kinetics are likely to have a role in facet selectivity in BVO. These issues will be the subject of future publications.
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U2 - 10.1021/acs.jpcc.9b05929
DO - 10.1021/acs.jpcc.9b05929
M3 - Article
AN - SCOPUS:85070873902
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
ER -