Closed loop acquisition of multi-levels humidity sensors by spontaneous optimization TiO2/Ti3C2Tx heterojunction without artificial intervention

Finding a simple way to improve the performance of Ti3C2Tx humidity sensors is a huge challenge. Unlike the complex preparation process in the past, we reported on different levels of humidity sensors that can be obtained during the oxidation process of few-layer Ti3C2Tx without artificial intervention. The Ti3C2Tx content m in the oxidation products of anatase TiO2/mTi3C2Tx could be readily optimized by monitoring the storage time. A small portion of the surface of Ti3C2Tx was transformed into rutile TiO2 by ultraviolet ozone (UV) irradiation, and a rutile-anatase TiO2/mTi3C2Tx triple junction material is obtained. The corresponding sensor exhibits different levels of sensing performance. In addition, a new sensing mechanism that gradually degrades from inductance characteristics to capacitive characteristics has been revealed. The closed-loop recycling mode without material loss designed in this work is also expected to solve the reuse problem of Mxene waste after oxidation.