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

Abstract

The Nb2CTx prepared by hydrothermal-assisted in-situ HF generation etching was investigated in terms of its gas sensor performance. The Nb2CTx was obtained by mixing Nb2AlC with pure water, hydrochloric acid, and fluoride (LiF or NH4F) 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 Nb2CTx than the direct HF etching. The Nb2CTx etched with LiF had relatively wide interlayer spacing because the hydration radius of Li+ was larger than that of NH4+. The results also suggest that Nb2O5 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 Nb2CTx 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 NH3. Hydrothermal-assisted etching contributed to providing sufficient interlayer spacing for the gas response without an exfoliation process.