posted on 2020-03-23, 18:11authored byZixing Wang, Zhong Xu, Haichao Huang, Xiang Chu, Yanting Xie, Da Xiong, Cheng Yan, Haibo Zhao, Haitao Zhang, Weiqing Yang
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chemistry and surface functionalization provide MXenes enhanced
electrochemical activity yet severely exacerbate their self-discharge
behavior in supercapacitors. However, this self-discharge behavior
and its related mechanism are still remaining issues. Herein, we propose
a chemically interface-tailored regulation strategy to successfully
unravel and efficiently alleviate the self-discharge behavior of Ti3C2Tx MXene-based supercapacitors.
As a result, Ti3C2Tx MXenes with fewer F elements (∼0.65 atom %) show a positive
self-discharge rate decline of ∼20% in comparison with MXenes
with higher F elements (∼8.09 atom %). Such decline of the
F elements can highly increase tight-bonding ions corresponding to
an individual self-discharge process, naturally resulting in a dramatic
50% increase of the transition potential (VT). Therefore, the mixed self-discharge rate from both tight-bonding
(contain fewer F elements) and loose-bonding ions (contain more F
elements) is accordingly lowered. Through chemically interface-tailored
engineering, the significantly changed average oxidation state and
local coordination information on MXene affected the interaction of
ion counterparts, which was evidently revealed by X-ray absorption
fine structures. Theoretically, this greatly improved self-discharge
performance was proven to be from higher adsorption energy between
the interface of the electrode and the electrolyte by density functional
theory. Therefore, this chemically interface-tailored regulation strategy
can guide the design of high-performance MXene-based supercapacitors
with low self-discharge behavior and will promote its wider commercial
applications.