Gas sensing performance of Nb2CTx synthesized by hydrothermal assisted in-situ HF generation etching method

The Nb 2 CT x prepared by hydrothermal-assisted in-situ HF generation etching was investigated in terms of its gas sensor performance. The Nb 2 CT x was obtained by mixing Nb 2 AlC with pure water, hydrochloric acid, and fluoride (LiF or NH 4 F) and then hydrothermally treated at 180 °C for 24 h. This in-situ HF generation etching by hydrothermal treatment was more efficient and safer in the synthesis of the Nb 2 CT x than the direct HF etching. The Nb 2 CT x etched with LiF had relatively wide interlayer spacing because the hydration radius of Li + was larger than that of NH 4 + . The results also suggest that Nb 2 O 5 is formed during the synthesis process. These results suggest that interlayer spacing, surface termination, and secondary phases formation can be controlled by the etchant, and that hydrothermal treatment extended the applicability of insoluble etchants. The Nb 2 CT x synthesized with LiF was evaluated as a gas sensor at room temperature in air in the presence of designated concentrations of 6 different gases, which exhibited good sensitivity and repeatability and fast recovery time, except for NH 3 . Hydrothermal-assisted etching contributed to providing sufficient interlayer spacing for the gas response without an exfoliation process.