Understanding the MXene Pseudocapacitance
- Univ. of California, Riverside, CA (United States)
- Tulane Univ., New Orleans, LA (United States)
- Drexel Univ., Philadelphia, PA (United States)
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
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.
- Research Organization:
- Energy Frontier Research Centers (EFRC) (United States). Fluid Interface Reactions, Structures and Transport Center (FIRST); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- AC05-00OR22725; AC02-05CH11231
- OSTI ID:
- 1493989
- Alternate ID(s):
- OSTI ID: 1484259
- Journal Information:
- Journal of Physical Chemistry Letters, Vol. 9, Issue 6; ISSN 1948-7185
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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