HCl-Based Hydrothermal Etching Strategy toward Fluoride-Free MXenes

Due to their ultrathin layered structure and rich elemental variety, MXenes are emerging as a promising electrode candidate in energy generation and storage. MXenes are generally synthesized via hazardous fluoride-containing reagents from robust MAX materials, unfortunately resulting in plenty of inert fluoride functional groups on the surface that noticeably decline their performance. Density functional theory calculations are used to show the etching feasibility of hydrochloric acid (HCl) on various MAX phases. Based on this theoretical guidance, fluoride-free Mo2C MXenes with high efficiency about 98% are experimentally demonstrated. The Mo2C electrodes produced by this process exhibit high electrochemical performance in supercapacitors and sodium-ion batteries owing to the chosen surface functional groups created via the HCl etch process. This strategy enables the development of fluoride-free MXenes and opens a new window to explore their potential in energy-storage applications.

Automated summary

MXenes are promising electrode materials in energy generation and storage due to their ultrathin layered structure and rich elemental variety, but the presence of fluoride in traditional synthesis methods leads to performance decline. Density functional theory calculations demonstrate the etching feasibility of hydrochloric acid on MAX phases, and the successful preparation of high-efficiency fluoride-free Mo2C MXenes with excellent electrochemical performance is achieved.