Low-temperature gas sensor with good long-term stability based on Co3O4/Ti3C2Tx heterojunction

As one of the two-dimensional (2D) nanomaterials , MXene exhibits great potential on gas-sensing owing to its high specific area, rich functional groups and great charge transfer mobility. Herein, electrostatic adsorption and calcination strategies were taken for ZIF-derived Co 3 O 4 and alkalized Ti 3 C 2 T x MXene to fabricate Co 3 O 4 /MX7.5 heterojunction . It can be found that Co 3 O 4 nanoparticles (NPs) uniformly grow on the surface of alkalized Ti 3 C 2 T x . Alkalized Ti 3 C 2 T x with lower work function (lower than 3.9 eV) can transfer more electrons towards Co 3 O 4 and promote the redox of Co 2+ . These increased Co 2+ ions can help to adsorb more adsorbed oxygen and produce more oxygen defects, which enhances contact interaction between ethanol molecules and adsorption sites. The formation of heterojunction between Co 3 O 4 and MXene is observed by UV–vis spectra, and this interface effect enhances the ability of gas sensors. Therefore, the sensors based on the obtained Co 3 O 4 /MX7.5 heterojunction can operate at a relatively low temperature (140 °C) with a response of 3500 % and a low detection limit of 1 ppm. And it also delivers long-term stability (about 30 days). This work demonstrates practical application for detecting ethanol at a relatively low working temperature and keeping their response in a long term.