The realization of
the broad range of application of MXenes relies
on the successful and reproducible synthesis of quality materials
of tailored properties. To date, most MXenes have been produced making
use of acid-based etching methods, yet an in-depth understanding of
etching processes is lacking. Herein, we have engaged in a comprehensive
study of the multiple variables involved in the synthesis of V2CTxwith focus on the properties
of etched materials. Two main sets of experiments were considered,
each using a different V2AlC precursor and a range of synthesis
variables including reaction time and temperature, mixing rate, and
type of acid. Correlations of synthesis conditions–materials
properties were investigated using a broad range of characterization
techniques including analytical methods, scanning and transmission
electron microscopy, X-ray diffraction (XRD), and X-ray photoelectron
spectroscopy (XPS). Findings indicated the crucial relevance of properties
of the MAX precursor such as elemental composition, particle size,
and crystal structure on etching processes and properties of etched
materials. Particularly, depending on the MAX precursor, two etching
patterns were identified, core–shell and plate-by-plate, the
latter describing a more efficient etching. Combined studies of elemental
composition, crystal structure, and yield quantification allowed us
to evaluate the effectiveness of etching processes. XRD studies revealed
key crystal-structure-type of acid correlations showing advantages
of using a HF/HCl mix over only HF. Analytical methods XRD and XPS
delivered insights into undergoing chemical processes and their influence
on bulk and surface chemistry of etched materials. The relevance for
reaction kinetics of highly correlated variables such as reaction
vessel dimensions, mixing efficiency, and reaction temperature was
recognized. For the first time, a MXene synthesis has been investigated
comprehensively highlighting its multivariable nature and the high
variable intercorrelation, opening up venues for further investigation
on MAX and MXene synthesis.