Mesoporous and Encapsulated In₂O₃/Ti₃C₂T _x Schottky Heterojunctions for Rapid and ppb-Level NO₂ Detection at Room Temperature

Rapid and ultrasensitive detection of toxic gases at room temperature is highly desired in health protection but presents grand challenges in the sensing materials reported so far. Here, we present a gas sensor based on novel zero dimensional (0D)/two dimensional (2D) indium oxide (In2O3)/titanium carbide (Ti3C2Tx) Schottky heterostructures with a high surface area and rich oxygen vacancies for parts per billion (ppb) level nitrogen dioxide (NO2) detection at room temperature. The In2O3/Ti3C2Tx gas sensor exhibits a fast response time (4 s), good response (193.45% to 250 ppb NO2), high selectivity, and excellent cycling stability. The rich surface oxygen vacancies play the role of active sites for the adsorption of NO2 molecules, and the Schottky junctions effectively adjust the charge-transfer behavior through the conduction tunnel in the sensing material. Furthermore, In2O3 nanoparticles almost fully cover the Ti3C2Tx nanosheets which can avoid the oxidation of Ti3C2Tx, thus contributing to the good cycling stability of the sensing materials. This work sheds light on the sensing mechanism of heterojunction nanostructures and provides an efficient pathway to construct high-performance gas sensors through the rational design of active sites.