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Title: Direct in Situ Measurement of Charge Transfer Processes During Photoelectrochemical Water Oxidation on Catalyzed Hematite

Electrocatalysts improve the efficiency of light-absorbing semiconductor photoanodes driving the oxygen evolution reaction, but the precise function(s) of the electrocatalysts remains unclear. We directly measure, for the first time, the interface carrier transport properties of a prototypical visible-light-absorbing semiconductor, α-Fe 2O 3, in contact with one of the fastest known water oxidation catalysts, Ni 0.8Fe 0.2O x, by directly measuring/controlling the current and/or voltage at the Ni 0.8Fe 0.2O x catalyst layer using a second working electrode. The measurements demonstrate that the majority of photogenerated holes in α-Fe 2O 3 directly transfer to the catalyst film over a wide range of conditions and that the Ni 0.8Fe 0.2O x is oxidized by photoholes to an operating potential sufficient to drive water oxidation at rates that match the photocurrent generated by the α-Fe 2O 3. The Ni 0.8Fe 0.2O x therefore acts as both a hole-collecting contact and a catalyst for the photoelectrochemical water oxidation process. Separate measurements show that the illuminated junction photovoltage across the α-Fe 2O 3|Ni 0.8Fe 0.2O x interface is significantly decreased by the oxidation of Ni 2+ to Ni 3+ and the associated increase in the Ni 0.8Fe 0.2O x electrical conductivity. Finally, in sum, themore » results illustrate the underlying operative charge-transfer and photovoltage generation mechanisms of catalyzed photoelectrodes, thus guiding their continued improvement.« less
Authors:
 [1] ;  [2] ;  [1] ;  [1] ; ORCiD logo [2] ; ORCiD logo [1]
  1. Univ. of Oregon, Eugene, OR (United States). Materials Science Inst., Dept. of Chemistry and Biochemistry
  2. Michigan State Univ., East Lansing, MI (United States). Dept. of Chemistry
Publication Date:
Grant/Contract Number:
SC0014279
Type:
Published Article
Journal Name:
ACS Central Science
Additional Journal Information:
Journal Volume: 3; Journal Issue: 9; Journal ID: ISSN 2374-7943
Publisher:
American Chemical Society (ACS)
Research Org:
Univ. of Oregon, Eugene, OR (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1375497
Alternate Identifier(s):
OSTI ID: 1421383

Qiu, Jingjing, Hajibabaei, Hamed, Nellist, Michael R., Laskowski, Forrest A. L., Hamann, Thomas W., and Boettcher, Shannon W.. Direct in Situ Measurement of Charge Transfer Processes During Photoelectrochemical Water Oxidation on Catalyzed Hematite. United States: N. p., Web. doi:10.1021/acscentsci.7b00310.
Qiu, Jingjing, Hajibabaei, Hamed, Nellist, Michael R., Laskowski, Forrest A. L., Hamann, Thomas W., & Boettcher, Shannon W.. Direct in Situ Measurement of Charge Transfer Processes During Photoelectrochemical Water Oxidation on Catalyzed Hematite. United States. doi:10.1021/acscentsci.7b00310.
Qiu, Jingjing, Hajibabaei, Hamed, Nellist, Michael R., Laskowski, Forrest A. L., Hamann, Thomas W., and Boettcher, Shannon W.. 2017. "Direct in Situ Measurement of Charge Transfer Processes During Photoelectrochemical Water Oxidation on Catalyzed Hematite". United States. doi:10.1021/acscentsci.7b00310.
@article{osti_1375497,
title = {Direct in Situ Measurement of Charge Transfer Processes During Photoelectrochemical Water Oxidation on Catalyzed Hematite},
author = {Qiu, Jingjing and Hajibabaei, Hamed and Nellist, Michael R. and Laskowski, Forrest A. L. and Hamann, Thomas W. and Boettcher, Shannon W.},
abstractNote = {Electrocatalysts improve the efficiency of light-absorbing semiconductor photoanodes driving the oxygen evolution reaction, but the precise function(s) of the electrocatalysts remains unclear. We directly measure, for the first time, the interface carrier transport properties of a prototypical visible-light-absorbing semiconductor, α-Fe2O3, in contact with one of the fastest known water oxidation catalysts, Ni0.8Fe0.2Ox, by directly measuring/controlling the current and/or voltage at the Ni0.8Fe0.2Ox catalyst layer using a second working electrode. The measurements demonstrate that the majority of photogenerated holes in α-Fe2O3 directly transfer to the catalyst film over a wide range of conditions and that the Ni0.8Fe0.2Ox is oxidized by photoholes to an operating potential sufficient to drive water oxidation at rates that match the photocurrent generated by the α-Fe2O3. The Ni0.8Fe0.2Ox therefore acts as both a hole-collecting contact and a catalyst for the photoelectrochemical water oxidation process. Separate measurements show that the illuminated junction photovoltage across the α-Fe2O3|Ni0.8Fe0.2Ox interface is significantly decreased by the oxidation of Ni2+ to Ni3+ and the associated increase in the Ni0.8Fe0.2Ox electrical conductivity. Finally, in sum, the results illustrate the underlying operative charge-transfer and photovoltage generation mechanisms of catalyzed photoelectrodes, thus guiding their continued improvement.},
doi = {10.1021/acscentsci.7b00310},
journal = {ACS Central Science},
number = 9,
volume = 3,
place = {United States},
year = {2017},
month = {8}
}