Facile preparation of TiCT sheets by selectively etching in a HSO/HO mixture.

MXenes and MXene-based composite materials have potential applications in a wide range of areas due to their unique physical and chemical characteristics. At present, it is still a major challenge to develop a simple, safe, and efficient route to prepare MXenes without using fluorinated etchants. Herein, we design a facile method to prepare TiCT MXene sheets by selectively etching TiAlC powders in an aqueous diluted HSO solution with HO as an oxidant. In a system of HSO and HO, an aqueous HSO solution with a concentration of 6 mol/L is a strongly acidic medium with no volatility, and 30% HO acts as a strong green oxidizer without harmful by-products. The experimental process is safe and convenient to conduct in a beaker under a water bath of 40°C. The etching process can be completed in 1 h under the air atmosphere conditions. The experimental results confirmed that the etched TiAlC powders can be successfully separated into TiCT nanosheets under ultrasound treatment without using any intercalation agent. The relevant etching mechanism is may be attributed to the synergy effect of HSO and HO, which triggers sequential selective etching of Al layers from the TiAlC phase. It may provide a new green way to prepare MXene-based materials without using toxic HF or HF-containing etchants.