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Title: Understanding the MXene Pseudocapacitance

Abstract

MXenes have attracted great attention as next-generation capacitive energy-storage materials, but the mechanisms underlying their pseudocapacitive behavior are not well understood. Here we provide a theoretical description of the surface redox process of Ti 3C 2T x (T = O, OH), a prototypical MXene, in 1 M H 2SO 4 electrolyte, based on joint density functional theory with an implicit solvation model and the analysis of Gibbs free energy under a constant-electrode potential. From the dependence of the O/OH ratio (or the surface H coverage) and the surface charge on the applied potential, we obtain a clear picture of the capacitive energy-storage mechanism of Ti 3C 2T x that shows good agreement with previous experimental findings in terms of the integral capacitance and Ti valence change. We find a voltage-dependent redox/double-layer co-charging behavior: the capacitive mechanism is dominated by the redox process, but the electric double-layer charge works against the redox process. This new insight may be useful in improving the capacitance of MXenes.

Authors:
 [1]; ORCiD logo [2];  [3]; ORCiD logo [4]; ORCiD logo [3]; ORCiD logo [1]
  1. Univ. of California, Riverside, CA (United States)
  2. Tulane Univ., New Orleans, LA (United States)
  3. Drexel Univ., Philadelphia, PA (United States)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lawrence Berkeley National Laboratory-National Energy Research Scientific Computing Center
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1493989
Alternate Identifier(s):
OSTI ID: 1484259
Grant/Contract Number:  
AC05-00OR22725; AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physical Chemistry Letters
Additional Journal Information:
Journal Volume: 9; Journal Issue: 6; Journal ID: ISSN 1948-7185
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Zhan, Cheng, Naguib, Michael, Lukatskaya, Maria, Kent, Paul R. C., Gogotsi, Yury, and Jiang, De-en. Understanding the MXene Pseudocapacitance. United States: N. p., 2018. Web. doi:10.1021/acs.jpclett.8b00200.
Zhan, Cheng, Naguib, Michael, Lukatskaya, Maria, Kent, Paul R. C., Gogotsi, Yury, & Jiang, De-en. Understanding the MXene Pseudocapacitance. United States. doi:10.1021/acs.jpclett.8b00200.
Zhan, Cheng, Naguib, Michael, Lukatskaya, Maria, Kent, Paul R. C., Gogotsi, Yury, and Jiang, De-en. Tue . "Understanding the MXene Pseudocapacitance". United States. doi:10.1021/acs.jpclett.8b00200. https://www.osti.gov/servlets/purl/1493989.
@article{osti_1493989,
title = {Understanding the MXene Pseudocapacitance},
author = {Zhan, Cheng and Naguib, Michael and Lukatskaya, Maria and Kent, Paul R. C. and Gogotsi, Yury and Jiang, De-en},
abstractNote = {MXenes have attracted great attention as next-generation capacitive energy-storage materials, but the mechanisms underlying their pseudocapacitive behavior are not well understood. Here we provide a theoretical description of the surface redox process of Ti3C2Tx (T = O, OH), a prototypical MXene, in 1 M H2SO4 electrolyte, based on joint density functional theory with an implicit solvation model and the analysis of Gibbs free energy under a constant-electrode potential. From the dependence of the O/OH ratio (or the surface H coverage) and the surface charge on the applied potential, we obtain a clear picture of the capacitive energy-storage mechanism of Ti3C2Tx that shows good agreement with previous experimental findings in terms of the integral capacitance and Ti valence change. We find a voltage-dependent redox/double-layer co-charging behavior: the capacitive mechanism is dominated by the redox process, but the electric double-layer charge works against the redox process. This new insight may be useful in improving the capacitance of MXenes.},
doi = {10.1021/acs.jpclett.8b00200},
journal = {Journal of Physical Chemistry Letters},
issn = {1948-7185},
number = 6,
volume = 9,
place = {United States},
year = {2018},
month = {2}
}

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Figures / Tables:

Figure 1 Figure 1: Partially protonated Ti3C2O2 as a prototypical MXene electrode in an acidic electrolyte: side view (left) and top view (right). The 2D material has an ideal surface area (counting two sides) of ∼479 m2/g.

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Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.