AUTHOR=Tian Zhengshan , Tian Hao , Cao Kesheng , Bai Suzhen , Peng Qinlong , Wang Yabo , Zhu Qiuxiang 

TITLE=Facile preparation of Ti3C2Tx sheets by selectively etching in a H2SO4/H2O2 mixture

JOURNAL=Frontiers in Chemistry

VOLUME=10

YEAR=2022

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2022.962528

DOI=10.3389/fchem.2022.962528

ISSN=2296-2646

ABSTRACT=<p>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 Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub> MXene sheets by selectively etching Ti<sub>3</sub>AlC<sub>2</sub> powders in an aqueous diluted H<sub>2</sub>SO<sub>4</sub> solution with H<sub>2</sub>O<sub>2</sub> as an oxidant. In a system of H<sub>2</sub>SO<sub>4</sub> and H<sub>2</sub>O<sub>2</sub>, an aqueous H<sub>2</sub>SO<sub>4</sub> solution with a concentration of 6 mol/L is a strongly acidic medium with no volatility, and 30% H<sub>2</sub>O<sub>2</sub> 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 Ti<sub>3</sub>AlC<sub>2</sub> powders can be successfully separated into Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub> nanosheets under ultrasound treatment without using any intercalation agent. The relevant etching mechanism is may be attributed to the synergy effect of H<sub>2</sub>SO<sub>4</sub> and H<sub>2</sub>O<sub>2</sub>, which triggers sequential selective etching of Al layers from the Ti<sub>3</sub>AlC<sub>2</sub> phase. It may provide a new green way to prepare MXene-based materials without using toxic HF or HF-containing etchants.</p>