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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