Low-temperature gas sensor with good long-term stability based on Co3O4/Ti3C2T 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 Co3O4 and alkalized Ti3C2Tx MXene to fabricate Co3O4/MX7.5 heterojunction. It can be found that Co3O4 nanoparticles (NPs) uniformly grow on the surface of alkalized Ti3C2Tx. Alkalized Ti3C2Tx with lower work function (lower than 3.9 eV) can transfer more electrons towards Co3O4 and promote the redox of Co2+. These increased Co2+ 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 Co3O4 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 Co3O4/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.