TY - JOUR
T1 - Competing Activation and Deactivation Mechanisms in Photodoped Bismuth Oxybromide Nanoplates Probed by Single-Molecule Fluorescence Imaging
AU - Shen, Meikun
AU - Ding, Tianben
AU - Luo, Jiang
AU - Tan, Che
AU - Mahmood, Khalid
AU - Wang, Zheyu
AU - Zhang, Dongyan
AU - Mishra, Rohan
AU - Lew, Matthew D.
AU - Sadtler, Bryce
N1 - Funding Information:
This material is based upon work supported by the National Science Foundation (NSF) under grant no. CHE-1753344 to B.S. and under grant no. ECCS-1653777 to M.D.L. R.M. acknowledges NSF for support through DMREF Grant 1729787. Acknowledgment is made to the donors of the American Chemical Society Petroleum Research Fund for partial support of this research (award # PRF58165-DNI10). Computational resources were provided by the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by NSF grant ACI-1548562. Electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy were performed at the Institute of Materials Science & Engineering at Washington University. X-ray diffraction was performed in the Department of Earth and Planetary Sciences at Washington University. The authors thank S. Singamaneni for use of his Raman spectrometer.
Publisher Copyright:
Copyright © 2020 American Chemical Society.
PY - 2020/7/2
Y1 - 2020/7/2
N2 - Oxygen vacancies in semiconductor photocatalysts play several competing roles, serving to both enhance light absorption and charge separation of photoexcited carriers as well as act as recombination centers for their deactivation. In this Letter, we show that single-molecule fluorescence imaging of a chemically activated fluorogenic probe can be used to monitor changes in the photocatalytic activity of bismuth oxybromide (BiOBr) nanoplates in situ during the light-induced formation of oxygen vacancies. We observe that the specific activities of individual nanoplates for the photocatalytic reduction of resazurin first increase and then progressively decrease under continuous laser irradiation. Ensemble structural characterization, supported by electronic-structure calculations, shows that irradiation increases the concentration of surface oxygen vacancies in the nanoplates, reduces Bi ions, and creates donor defect levels within the band gap of the semiconductor particles. These combined changes first enhance photocatalytic activity by increasing light absorption at visible wavelengths. However, high concentrations of oxygen vacancies lower the photocatalytic activity both by introducing new relaxation pathways that promote charge recombination before photoexcited electrons can be extracted and by weakening binding of resazurin to the surface of the nanoplates.
AB - Oxygen vacancies in semiconductor photocatalysts play several competing roles, serving to both enhance light absorption and charge separation of photoexcited carriers as well as act as recombination centers for their deactivation. In this Letter, we show that single-molecule fluorescence imaging of a chemically activated fluorogenic probe can be used to monitor changes in the photocatalytic activity of bismuth oxybromide (BiOBr) nanoplates in situ during the light-induced formation of oxygen vacancies. We observe that the specific activities of individual nanoplates for the photocatalytic reduction of resazurin first increase and then progressively decrease under continuous laser irradiation. Ensemble structural characterization, supported by electronic-structure calculations, shows that irradiation increases the concentration of surface oxygen vacancies in the nanoplates, reduces Bi ions, and creates donor defect levels within the band gap of the semiconductor particles. These combined changes first enhance photocatalytic activity by increasing light absorption at visible wavelengths. However, high concentrations of oxygen vacancies lower the photocatalytic activity both by introducing new relaxation pathways that promote charge recombination before photoexcited electrons can be extracted and by weakening binding of resazurin to the surface of the nanoplates.
UR - http://www.scopus.com/inward/record.url?scp=85087530389&partnerID=8YFLogxK
U2 - 10.1021/acs.jpclett.0c01237
DO - 10.1021/acs.jpclett.0c01237
M3 - Article
C2 - 32516535
AN - SCOPUS:85087530389
SN - 1948-7185
VL - 11
SP - 5219
EP - 5227
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
IS - 13
ER -