Single-Nanoflake Photo-Electrochemistry Reveals Champion and Spectator Flakes in Exfoliated MoSe 2 Films
Abstract
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:
-
[2];
[1]
- Colorado State Univ., Fort Collins, CO (United States)
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Publication Date:
- Research Org.:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
- OSTI Identifier:
- 1435696
- Report Number(s):
- NREL/JA-5900-71132
Journal ID: ISSN 1932-7447; TRN: US1900084
- Grant/Contract Number:
- AC36-08GO28308
- Resource 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
- 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
Citation Formats
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., 2018.
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. Tue .
"Single-Nanoflake Photo-Electrochemistry Reveals Champion and Spectator Flakes in Exfoliated MoSe2 Films". United States. doi:10.1021/acs.jpcc.7b12715. https://www.osti.gov/servlets/purl/1435696.
@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}
}
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Figure 1: Photo-electrochemical characterization and microscopy of nanoflake and bulk MoSe2 electrodes. (a) Experimental setup for single-nanoflake photocurrent mapping in a three-electrode electro-chemical flow cell. The same cell was used for bulk crystal mapping. ctr = Pt wire counter electrode and ref = Ag/AgI wire reference electrode. (b) Current−potential curvesmore »
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