Removing Fluoride-Terminations from Multilayered V₂CT_x MXene by Gas Hydrolyzation

Abstract

Two-dimensional MXenes have shown great promise for many different applications, but in order to fully utilize their potential, control of their termination groups is essential. Here we demonstrate hydrolyzation with a continuous gas flow as a method to remove F-terminations from multilayered V 2 C T x particles, in order to prepare nearly F-free and partly bare vanadium carbide MXene. Density functional theory calculations demonstrate that the substitution of F-terminations is thermodynamically feasible and presents partly nonterminated V 2 CO as the dominating hydrolyzation product. Hydrolyzation at elevated temperatures reduced the F content but only subtly changed the O content, as inferred from spectroscopic data. The ideal hydrolyzation temperature was found to be 300 °C, as a degradation of the V 2 C T x phase and a transition to vanadium oxycarbides and V 2 O 3 were observed at higher temperature. When tested as electrodes in Li-ion batteries, the hydrolyzed MXene demonstrated a reduced polarization compared with the pristine MXene, but no change in intercalation voltage was observed. Annealing in dry Ar did not result in the same F reduction, and the importance of water vapor was concluded, demonstrating hydrolyzation as a new and efficient method to control the surface terminations of multilayered V 2 C T x post etching. These results also provide new insights on the thermal stability of V 2 C T x MXene in hydrated atmospheres.

Scope, evaluation and current perspectives of MXene synthesis strategies for state of the art applications

“…8a) to be very effective to substantially reduce F terminations. 147 By employing gas hydrolyzation, oxygen (O) content remains relatively stable at ∼0.3 per unit formula of V 2 CT x . Some studies claim that, by doping MXenes with heteroatoms such as nitrogen (N) or sulfur (S), the electrical properties of supercapacitors are significantly enhanced.…”

Unveiling the Latest Advancements in Vanadium Carbide MXene based Supercapacitors and their Future Trends

“…It has been demonstrated that gas hydrolyzation can significantly reduce the number of fluoride terminations in multilayer V 2 CT x (ml-V 2 CT x ). [19] Naguib et al reported that F content was reduced while O content was found to increase after delamination. Energy dispersive spectroscopy (EDS) analy-sis also supported the results and showed that in delaminated V 2 CT x (d-V 2 CT x ), the V : O : F atomic ratio was 2.0 : 3.1 : 0.0, in comparison to the synthesized V 2 CT x powder, where this ratio was found to be 2.0 : 1.1 : 1.0.…”

“…However, synthesizing V 2 CT x with oxygen termination, that is, V 2 CO 2 , while maintaining the structure of MXene intact, is quite a difficult task. It has been demonstrated that gas hydrolyzation can significantly reduce the number of fluoride terminations in multilayer V 2 CT x (ml‐V 2 CT x ) [19] . Naguib et al reported that F content was reduced while O content was found to increase after delamination.…”