Dynamics of photogenerated holes in undoped BiVO4 photoanodes for solar water oxidation

Hdl Handle:
http://hdl.handle.net/10149/596337
Title:
Dynamics of photogenerated holes in undoped BiVO4 photoanodes for solar water oxidation
Authors:
Ma, Y. (Yimeng); Pendlebury, S. R. (Stephanie); Reynal, A. (Anna); Le Formal, F. (Florian); Durrant, J. R. (James)
Affiliation:
Teesside University, School of Science & Engineering.
Citation:
Ma, Y.; Pendlebury, S. R.; Reynal, A.; LeFormal, F.; Durrant, J. R. (2014) Dynamics of photogenerated holes in undoped BiVO4 photoanodes for solar water oxidation' Chemical Science; 5 (8): 2964-2973
Publisher:
R S C Publications
Journal:
Chemical Science
Issue Date:
1-Aug-2014
URI:
http://hdl.handle.net/10149/596337
DOI:
10.1039/c4sc00469h
Additional Links:
http://xlink.rsc.org/?DOI=c4sc00469h
Abstract:
The dynamics of photogenerated holes in undoped BiVO 4 photoanodes for water splitting were studied using transient absorption spectroscopy, correlated with photoelectrochemical and transient photocurrent data. Transient absorption signals of photogenerated holes were identi fi ed using electron/ hole scavengers and applied electrical bias in a complete photoelectrochemical cell. The yield of long- lived (0.1 – 1 s) photogenerated holes is observed to correlate as a function of applied electrical bias with the width of the space charge layer, as determined by electrochemical impedance spectroscopy. The transient absorption decay time constant of these long-lived holes is also observed to be dependent upon the applied bias, assigned to kinetic competition between water oxidation and recombination of these surface accumulated holes with bulk electrons across the space charge layer. The time constant for this slow recombination measured with transient absorption spectroscopy is shown to match the time constant of back electron transfer from the external circuit determined from chopped light transient photocurrent measurements, thus providing strong evidence for these assignments. The yield of water oxidation determined from these measurements, including consideration of both the yield of long-lived holes, and the fraction of these holes which are lost due to back electron/hole recombination, is observed to be in good agreement with the photocurrent density measured for BiVO 4 photoanodes as a function of bias under continuous irradiation. Overall these results indicate two distinct recombination processes which limit photocurrent generation in BiVO 4 photoanodes: fi rstly rapid ( # microseconds) electron/hole recombination, and secondly recombination of surface-accumulated holes with bulk BiVO 4 electrons. This second ‘ back electron transfer ’ recombination occurs on the milliseconds – seconds timescale, and is only avoided at strong anodic biases where the potential drop across the space charge layer provides a su ffi ciently large energetic barrier to prevent this recombination process.
Type:
Article
ISSN:
2041-6520; 2041-6539
Rights:
Author can archive post-print (ie final draft post-refereeing) after 12 month embargo from acceptance. For full details see http://www.sherpa.ac.uk/romeo [Accessed 16/02/2016]

Full metadata record

DC FieldValue Language
dc.contributor.authorMa, Y. (Yimeng)en
dc.contributor.authorPendlebury, S. R. (Stephanie)en
dc.contributor.authorReynal, A. (Anna)en
dc.contributor.authorLe Formal, F. (Florian)en
dc.contributor.authorDurrant, J. R. (James)en
dc.date.accessioned2016-02-16T11:15:59Zen
dc.date.available2016-02-16T11:15:59Zen
dc.date.issued2014-08-01en
dc.identifier.citationChemical Science; 5 (8): 2964-2973en
dc.identifier.issn2041-6520en
dc.identifier.issn2041-6539en
dc.identifier.doi10.1039/c4sc00469hen
dc.identifier.urihttp://hdl.handle.net/10149/596337en
dc.description.abstractThe dynamics of photogenerated holes in undoped BiVO 4 photoanodes for water splitting were studied using transient absorption spectroscopy, correlated with photoelectrochemical and transient photocurrent data. Transient absorption signals of photogenerated holes were identi fi ed using electron/ hole scavengers and applied electrical bias in a complete photoelectrochemical cell. The yield of long- lived (0.1 – 1 s) photogenerated holes is observed to correlate as a function of applied electrical bias with the width of the space charge layer, as determined by electrochemical impedance spectroscopy. The transient absorption decay time constant of these long-lived holes is also observed to be dependent upon the applied bias, assigned to kinetic competition between water oxidation and recombination of these surface accumulated holes with bulk electrons across the space charge layer. The time constant for this slow recombination measured with transient absorption spectroscopy is shown to match the time constant of back electron transfer from the external circuit determined from chopped light transient photocurrent measurements, thus providing strong evidence for these assignments. The yield of water oxidation determined from these measurements, including consideration of both the yield of long-lived holes, and the fraction of these holes which are lost due to back electron/hole recombination, is observed to be in good agreement with the photocurrent density measured for BiVO 4 photoanodes as a function of bias under continuous irradiation. Overall these results indicate two distinct recombination processes which limit photocurrent generation in BiVO 4 photoanodes: fi rstly rapid ( # microseconds) electron/hole recombination, and secondly recombination of surface-accumulated holes with bulk BiVO 4 electrons. This second ‘ back electron transfer ’ recombination occurs on the milliseconds – seconds timescale, and is only avoided at strong anodic biases where the potential drop across the space charge layer provides a su ffi ciently large energetic barrier to prevent this recombination process.en
dc.publisherR S C Publicationsen
dc.relation.urlhttp://xlink.rsc.org/?DOI=c4sc00469hen
dc.rightsAuthor can archive post-print (ie final draft post-refereeing) after 12 month embargo from acceptance. For full details see http://www.sherpa.ac.uk/romeo [Accessed 16/02/2016]en
dc.titleDynamics of photogenerated holes in undoped BiVO4 photoanodes for solar water oxidationen
dc.typeArticleen
dc.contributor.departmentTeesside University, School of Science & Engineering.en
dc.identifier.journalChemical Scienceen
or.citation.harvardMa, Y.; Pendlebury, S. R.; Reynal, A.; LeFormal, F.; Durrant, J. R. (2014) Dynamics of photogenerated holes in undoped BiVO4 photoanodes for solar water oxidation' Chemical Science; 5 (8): 2964-2973en
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