Simultaneous enhancement in charge separation and onset potential for water oxidation in a BiVO4 photoanode by W – Ti codoping

Efficient charge separation of photo-generated electrons and holes is critical to achieve high solar to hydrogen conversion efficiency in photoelectrochemical (PEC) water splitting. N-type doping is generally used to improve the conductivity by increasing the majority carrier density and enhance the...

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Main Authors: Zhao, Xin, Hu, Jun, Wu, Bo, Banerjee, Amitava, Chakraborty, Sudip, Feng, Jianyong, Zhao, Zongyan, Chen, Shi, Ahuja, Rajeev, Sum, Tze Chien, Chen, Zhong
Other Authors: School of Materials Science & Engineering
Format: Article
Language:English
Published: 2019
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Online Access:https://hdl.handle.net/10356/81164
http://hdl.handle.net/10220/50066
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Institution: Nanyang Technological University
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spelling sg-ntu-dr.10356-811642023-07-14T15:45:19Z Simultaneous enhancement in charge separation and onset potential for water oxidation in a BiVO4 photoanode by W – Ti codoping Zhao, Xin Hu, Jun Wu, Bo Banerjee, Amitava Chakraborty, Sudip Feng, Jianyong Zhao, Zongyan Chen, Shi Ahuja, Rajeev Sum, Tze Chien Chen, Zhong School of Materials Science & Engineering School of Physical and Mathematical Sciences Charge Separation Water Oxidation Engineering::Materials Efficient charge separation of photo-generated electrons and holes is critical to achieve high solar to hydrogen conversion efficiency in photoelectrochemical (PEC) water splitting. N-type doping is generally used to improve the conductivity by increasing the majority carrier density and enhance the charge separation in the photoanode. However, minority carrier transport is also very important in the process of charge separation, especially in materials that possess inadequate minority carrier mobility. Herein, we take a BiVO4 PEC water splitting cell as an example to demonstrate how to analyze the limiting factor and to formulate the corresponding solutions to improve the hole mobility. The benefits and problems caused by n-type doping (W-doping here) of BiVO4 are analyzed. Codoping with Ti further enhances the charge separation by improving the hole transport and leads to a cathodic shift of the photocurrent onset potential. A high charge separation efficiency (79% at 1.23 VRHE) in a compact BiVO4 photoanode has been achieved without any nanostructure formation. Theoretical results show that W–Ti codoping has decreased the hole polaron hopping activation energy by 11.5% compared with mono-W doping, and this has resulted in a hole mobility increase by 29%. The calculated adsorption energy and reaction Gibbs free energies indicate that the Ti site is energetically more favorable for water splitting. Moreover, the Ti site possesses a lower overpotential in the W–Ti codoped sample compared with the mono-W doped sample. The current study indicates that in order to improve the solar energy conversion efficiency, there should be a balanced charge transport of both majority and minority charge carriers. This can be achieved by simply choosing appropriate codoping elements. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version 2019-10-01T07:28:51Z 2019-12-06T14:22:48Z 2019-10-01T07:28:51Z 2019-12-06T14:22:48Z 2018 Journal Article Zhao, X., Hu, J., Wu, B., Banerjee, A., Chakraborty, S., Feng, J., . . . Chen, Z. (2018). Simultaneous enhancement in charge separation and onset potential for water oxidation in a BiVO4 photoanode by W – Ti codoping. Journal of Materials Chemistry A, 6(35), 16965-16974. doi:10.1039/C8TA05491F 2050-7488 https://hdl.handle.net/10356/81164 http://hdl.handle.net/10220/50066 10.1039/C8TA05491F en Journal of Materials Chemistry A © 2018 The Author(s) . All rights reserved. This paper was published by Royal Society of Chemistry in Journal of Materials Chemistry A and is made available with permission of The Author(s) . 28 p. application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Charge Separation
Water Oxidation
Engineering::Materials
spellingShingle Charge Separation
Water Oxidation
Engineering::Materials
Zhao, Xin
Hu, Jun
Wu, Bo
Banerjee, Amitava
Chakraborty, Sudip
Feng, Jianyong
Zhao, Zongyan
Chen, Shi
Ahuja, Rajeev
Sum, Tze Chien
Chen, Zhong
Simultaneous enhancement in charge separation and onset potential for water oxidation in a BiVO4 photoanode by W – Ti codoping
description Efficient charge separation of photo-generated electrons and holes is critical to achieve high solar to hydrogen conversion efficiency in photoelectrochemical (PEC) water splitting. N-type doping is generally used to improve the conductivity by increasing the majority carrier density and enhance the charge separation in the photoanode. However, minority carrier transport is also very important in the process of charge separation, especially in materials that possess inadequate minority carrier mobility. Herein, we take a BiVO4 PEC water splitting cell as an example to demonstrate how to analyze the limiting factor and to formulate the corresponding solutions to improve the hole mobility. The benefits and problems caused by n-type doping (W-doping here) of BiVO4 are analyzed. Codoping with Ti further enhances the charge separation by improving the hole transport and leads to a cathodic shift of the photocurrent onset potential. A high charge separation efficiency (79% at 1.23 VRHE) in a compact BiVO4 photoanode has been achieved without any nanostructure formation. Theoretical results show that W–Ti codoping has decreased the hole polaron hopping activation energy by 11.5% compared with mono-W doping, and this has resulted in a hole mobility increase by 29%. The calculated adsorption energy and reaction Gibbs free energies indicate that the Ti site is energetically more favorable for water splitting. Moreover, the Ti site possesses a lower overpotential in the W–Ti codoped sample compared with the mono-W doped sample. The current study indicates that in order to improve the solar energy conversion efficiency, there should be a balanced charge transport of both majority and minority charge carriers. This can be achieved by simply choosing appropriate codoping elements.
author2 School of Materials Science & Engineering
author_facet School of Materials Science & Engineering
Zhao, Xin
Hu, Jun
Wu, Bo
Banerjee, Amitava
Chakraborty, Sudip
Feng, Jianyong
Zhao, Zongyan
Chen, Shi
Ahuja, Rajeev
Sum, Tze Chien
Chen, Zhong
format Article
author Zhao, Xin
Hu, Jun
Wu, Bo
Banerjee, Amitava
Chakraborty, Sudip
Feng, Jianyong
Zhao, Zongyan
Chen, Shi
Ahuja, Rajeev
Sum, Tze Chien
Chen, Zhong
author_sort Zhao, Xin
title Simultaneous enhancement in charge separation and onset potential for water oxidation in a BiVO4 photoanode by W – Ti codoping
title_short Simultaneous enhancement in charge separation and onset potential for water oxidation in a BiVO4 photoanode by W – Ti codoping
title_full Simultaneous enhancement in charge separation and onset potential for water oxidation in a BiVO4 photoanode by W – Ti codoping
title_fullStr Simultaneous enhancement in charge separation and onset potential for water oxidation in a BiVO4 photoanode by W – Ti codoping
title_full_unstemmed Simultaneous enhancement in charge separation and onset potential for water oxidation in a BiVO4 photoanode by W – Ti codoping
title_sort simultaneous enhancement in charge separation and onset potential for water oxidation in a bivo4 photoanode by w – ti codoping
publishDate 2019
url https://hdl.handle.net/10356/81164
http://hdl.handle.net/10220/50066
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