Removing Fluoride-Terminations from Multilayered V2CTx MXene by Gas Hydrolyzation

• Published in: ACS omega 2022-06, Vol.7 (27), p.23790-23799
• Main Authors: Fagerli, Frode Håskjold, Wang, Zhaohui, Grande, Tor, Kaland, Henning, Selbach, Sverre M., Wagner, Nils Peter, Wiik, Kjell
• Format: Article
• Language: English
• ISSN: 2470-1343
• DOI: 10.1021/acsomega.2c02441

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.