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Title: Single-Nanoflake Photo-Electrochemistry Reveals Champion and Spectator Flakes in Exfoliated MoSe 2 Films

Semiconducting transition-metal dichalcogenide (TMD) nanoflake thin films are promising large-area electrodes for photo-electrochemical solar energy conversion applications. However, their energy conversion efficiencies are typically much lower than those of bulk electrodes. It is unclear to what extent this efficiency gap stems from differences among nanoflakes (e.g., area, thickness, and surface structural features). It is also unclear whether individual exfoliated nanoflakes can achieve energy conversion efficiencies similar to those of bulk crystals. Here, we use a single-nanoflake photo-electrochemical approach to show that there are both highly active and completely inactive nanoflakes within a film. For the exfoliated MoSe 2 samples studied herein, 7% of nanoflakes are highly active champions, whose photocurrent efficiency exceeds that of the bulk crystal. However, 66% of nanoflakes are inactive spectators, which are mostly responsible for the overall lower photocurrent efficiency compared to the bulk crystal. The photocurrent collection efficiency increases with nanoflake area and decreases more at perimeter edges than at interior step edges. These observations, which are hidden in ensemble-level measurements, reveal the underlying performance issues of exfoliated TMD electrodes for photo-electrochemical energy conversion applications.
Authors:
 [1] ;  [1] ;  [2] ; ORCiD logo [2] ; ORCiD logo [1]
  1. Colorado State Univ., Fort Collins, CO (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Report Number(s):
NREL/JA-5900-71132
Journal ID: ISSN 1932-7447
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 122; Journal Issue: 12; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; transition-metal dichalcogenide; nanoflake thin films; photovoltiacs; solar energy conversion
OSTI Identifier:
1435696

Todt, Michael A., Isenberg, Allan E., Nanayakkara, Sanjini U., Miller, Elisa M., and Sambur, Justin B.. Single-Nanoflake Photo-Electrochemistry Reveals Champion and Spectator Flakes in Exfoliated MoSe2 Films. United States: N. p., Web. doi:10.1021/acs.jpcc.7b12715.
Todt, Michael A., Isenberg, Allan E., Nanayakkara, Sanjini U., Miller, Elisa M., & Sambur, Justin B.. Single-Nanoflake Photo-Electrochemistry Reveals Champion and Spectator Flakes in Exfoliated MoSe2 Films. United States. doi:10.1021/acs.jpcc.7b12715.
Todt, Michael A., Isenberg, Allan E., Nanayakkara, Sanjini U., Miller, Elisa M., and Sambur, Justin B.. 2018. "Single-Nanoflake Photo-Electrochemistry Reveals Champion and Spectator Flakes in Exfoliated MoSe2 Films". United States. doi:10.1021/acs.jpcc.7b12715.
@article{osti_1435696,
title = {Single-Nanoflake Photo-Electrochemistry Reveals Champion and Spectator Flakes in Exfoliated MoSe2 Films},
author = {Todt, Michael A. and Isenberg, Allan E. and Nanayakkara, Sanjini U. and Miller, Elisa M. and Sambur, Justin B.},
abstractNote = {Semiconducting transition-metal dichalcogenide (TMD) nanoflake thin films are promising large-area electrodes for photo-electrochemical solar energy conversion applications. However, their energy conversion efficiencies are typically much lower than those of bulk electrodes. It is unclear to what extent this efficiency gap stems from differences among nanoflakes (e.g., area, thickness, and surface structural features). It is also unclear whether individual exfoliated nanoflakes can achieve energy conversion efficiencies similar to those of bulk crystals. Here, we use a single-nanoflake photo-electrochemical approach to show that there are both highly active and completely inactive nanoflakes within a film. For the exfoliated MoSe2 samples studied herein, 7% of nanoflakes are highly active champions, whose photocurrent efficiency exceeds that of the bulk crystal. However, 66% of nanoflakes are inactive spectators, which are mostly responsible for the overall lower photocurrent efficiency compared to the bulk crystal. The photocurrent collection efficiency increases with nanoflake area and decreases more at perimeter edges than at interior step edges. These observations, which are hidden in ensemble-level measurements, reveal the underlying performance issues of exfoliated TMD electrodes for photo-electrochemical energy conversion applications.},
doi = {10.1021/acs.jpcc.7b12715},
journal = {Journal of Physical Chemistry. C},
number = 12,
volume = 122,
place = {United States},
year = {2018},
month = {3}
}