Abstract
2D transition metal borides (MBenes) with abundant surface terminals hold great promise in molecular sensing applications. However, MBenes from etching with fluorine-containing reagents present inert -fluorine groups on the surface, which hinders their sensing capability. Herein, the multilayer fluorine-free MoBT(x) MBene (where T(x) represents O, OH, and Cl) with hydrophilic structure is prepared by a hydrothermal-assisted hydrochloric acid etching strategy based on guidance from the first-principle calculations. Significantly, the fluorine-free MoBT(x)-based humidity sensor is fabricated and demonstrates low resistance and excellent humidity performance, achieving a response of 90% to 98%RH and a high resolution of 1%RH at room temperature. By combining the experimental results with the first-principles calculations, the interactions between MoBT(x) and H(2)O, including the adsorption and intercalation of H(2)O, are understood first in depth. Finally, the portable humidity early warning system for real-time monitoring and early warning of infant enuresis and back sweating illustrates its potential for humidity sensing applications. This work not only provides guidance for preparation of fluorine-free MBenes, but also contributes to advancing their exploration in sensing applications.