MXenes,
most commonly transition metal carbides, are a family of
two-dimensional (2D) materials with promising potential in, among
other applications, supercapacitors and batteries. MXenes are synthesized
by etching of aluminum or gallium layers in its parent MAX phase directly
by HF or by HF in situ formation using a fluoride
salt and strong acid. A commonly undesired byproduct of MXene synthesis
is AlF3·3H2O. To relieve MXenes from AlF3·3H2O impurity, it is important to elucidate
the factors that drive its formation. Here, we dually deduce the conditions
that lead to AlF3·3H2O formation while
exploring etching with cobalt fluorides (CoF2/CoF3). Previously uncharacterized, etching with cobalt fluorides offers
a forthright method to etch MXenes while intercalating cobalt cations.
The influence of this etching environment and AlF3·3H2O formation on MXene’s structure, morphology, and surface
bonding is investigated. Ionic strength of solution used for etching
is found to be a critical driving factor in the formation of AlF3·3H2O impurity formation. Specifically, when
the ionic strength falls between ∼8.5 and 10 M, AlF3 complexation is stable. As a result, Ti3C2T
x
MXene phase with AlF3·3H2O impurity is obtained. In contrast, near-pure MXene is the
only solid state product when I is smaller than 8.5
M or larger than 10 M. Hence, high purity MXene phase can be synthesized
by subtle compositional tuning to manipulate the ionic strength of
the etching environment.
Tailoring the graphene-covered Fe with Cs modifies the surface electronic properties of the catalysts such that selective C–O bond cleavage of phenol is achieved in liquid phase by inhibiting the facile tautomerization followed by ring saturation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.