Mesoporous and Encapsulated In₂O₃/Ti₃C₂T_<i>x</i> Schottky Heterojunctions for Rapid and ppb-Level NO₂ Detection at Room Temperature

Abstract

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 (Ti₃C₂T_<i>x</i>) 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/Ti₃C₂T_<i>x</i> 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 Ti₃C₂T_<i>x</i> nanosheets which can avoid the oxidation of Ti₃C₂T_<i>x</i>, 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.