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
N1 - Funding Information:
The work was supported in part by the National Natural Science Foundation of China (grant # 21703054). M.D. acknowledges also funds from the University at Buffalo and support from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award Number(s) DE-SC0019086 (interpretation of the data and writing of the manuscript).
PY - 2019/8/22
Y1 - 2019/8/22
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
VL - 123
SP - 20142
EP - 20151
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 33
ER -