3 research outputs found
X‑ray Insights into Formation of −O Functional Groups on MXenes: Two-Step Dehydrogenation of Adsorbed Water
Engineered MXene surfaces with more −O functional
groups
are feasible for realizing higher energy density due to their higher
theoretical capacitance. However, there have been only a few explorations
of this regulation mechanism. Investigating the formation source and
mechanism is conducive to expanding the adjustment method from the
top-down perspective. Herein, for the first time, the formation dynamics
of −O functional groups on Mo2CTx are discovered as a two-step dehydrogenation of adsorbed water
through in situ near-ambient-pressure X-ray photoelectron spectroscopy,
further confirmed by ab initio molecular dynamics simulations. From
this, the controllable substitution of −F functional groups
with −O functional groups is achieved on Mo2CTx during electrochemical cycling in an aqueous
electrolyte. The obtained Mo2CTx with rich −O groups exhibits a high capacitance of 163.2
F g –1 at 50 mV s –1, together
with excellent stability. These results offer new insights toward
engineering surface functional groups of MXenes for many specific
applications
X‑ray Insights into Formation of −O Functional Groups on MXenes: Two-Step Dehydrogenation of Adsorbed Water
Engineered MXene surfaces with more −O functional
groups
are feasible for realizing higher energy density due to their higher
theoretical capacitance. However, there have been only a few explorations
of this regulation mechanism. Investigating the formation source and
mechanism is conducive to expanding the adjustment method from the
top-down perspective. Herein, for the first time, the formation dynamics
of −O functional groups on Mo2CTx are discovered as a two-step dehydrogenation of adsorbed water
through in situ near-ambient-pressure X-ray photoelectron spectroscopy,
further confirmed by ab initio molecular dynamics simulations. From
this, the controllable substitution of −F functional groups
with −O functional groups is achieved on Mo2CTx during electrochemical cycling in an aqueous
electrolyte. The obtained Mo2CTx with rich −O groups exhibits a high capacitance of 163.2
F g –1 at 50 mV s –1, together
with excellent stability. These results offer new insights toward
engineering surface functional groups of MXenes for many specific
applications
Monolayer Thiol Engineered Covalent Interface toward Stable Zinc Metal Anode
Interface engineering of zinc metal anodes is a promising
remedy
to relieve their inferior stability caused by dendrite growth and
side reactions. Nevertheless, the low affinity and additional weight
of the protective coating remain obstacles to their further implementation.
Here, aroused by DFT simulation, self-assembled monolayers (SAMs)
are selectively constructed to enhance the stability of zinc metal
anodes in dilute aqueous electrolytes. It is found that the monolayer
thiol molecules relatively prefer to selectively graft onto the unstable
zinc crystal facets through strong Zn–S chemical interactions
to engineer a covalent interface, enabling the uniform deposition
of Zn2+ onto (002) crystal facets. Therefore, dendrite-free
anodes with suppressed side reactions can be achieved, proven by in
situ optical visualization and differential electrochemical mass spectrometry
(DEMS). In particular, the thiol endows the symmetric cells with a
4000 h ultrastable plating/stripping at a specific current density
of 1.0 mA cm–2, much superior to those of bare zinc
anodes. Additionally, the full battery of modified anodes enables
stable cycling of 87.2% capacity retention after 3300 cycles. By selectively
capping unstable crystal facets with inert molecules, this work provides
a promising design strategy at the molecular level for stable metal
anodes