ABSTRACT
Because of the outbreak of COVID-19 pandemic, the disinfectants have become a daily necessity. The chlorine gas is an important industrial raw material for disinfectants. And the demand of chlorine gas is increasing. As is known to all, chlorine gas is a toxic gas and harmful to health. However, the gas sensors based on common metal oxide semiconductor are not sensitive to low concentrations of chlorine gas. Therefore, it is of great significance to develop the gas sensing materials based on metal oxide semiconductor that are high sensitivity to trace leakage of chlorine gas. In this work, In2O3 microtubules were synthesized by bio-template method with degreasing cotton. In2O3 microtubules was simply treated with NaBH4 reduction and In2O3 microtubules with abundant oxygen vacancies were successfully prepared at room temperature. The effects of the method on the crystal structure, morphology and oxygen vacancies were investigated by means of XRD, SEM, XPS and EPR. The results showed that this method could effectively enhance the concentration of oxygen vacancies in In2O3 materials without the destruction on crystal structure and morphology. In the gas sensing tests, the gas response of In2O3 microtubules with NaBH4 treatment was about 13 times higher than In2O3 microtubules to the same low concentration of chlorine gas. In another word, the In2O3 microtubules were more sensitive to low concentration of chlorine gas after NaBH4 treatment. According to the analysis of gas sensing mechanism, chlorine gas molecule was not only directly adsorbed on the material surface but also oxygen vacancies of material surface. Thus it can be seen that the oxygen vacancies on material surface played an important role in chlorine gas-sensing performance. Because there are more oxygen vacancies in the In2O3 microtubules treated by NaBH4 than the untreated, the In2O3 microtubules with abundant oxygen vacancies exhibited excellent sensitivity to low concentration chlorine gas. © 2022, Editorial Board of Journal of Functional Materials. All right reserved.
ABSTRACT
Continuous exposure to high concentration of nitrogen dioxide (NO2) severely affects the human respiratory system. Besides, NO2 has been recently observed to foster COVID-19, resulting in increased fatality rate;thus highly selective gas sensors are required for detecting NO2 at sub-ppb level. In this direction, we have synthesized two-dimensional MXene-based tin oxide (SnO2) heterostructures with varying MXene wt% (10–40wt%) using a facile hydrothermal method for room-temperature NO2 detection. The synthesized heterostructures have been structurally, optically, and electrically characterized using a suite of characterization techniques, namely, X-ray diffraction, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and Brunauer–Emmett–Teller techniques. The optimal incorporation of MXene in SnO2 nanoparticles effectively decumulates them, increasing the specific surface area of heterostructures and thereby exposing large number of adsorption sites. 20-wt% SnO2/MXene heterostructures-based sensor exhibits nearly five times higher response (231%) toward 30-ppb NO2 at room temperature with shorter response time (146s) and recovery time (102s) than pristine SnO2. Moreover, the sensor showed high selectivity, sensitivity, repeatability, reproducibility, and stable sensing response under humid conditions. The assembly of these results suggests that SnO2/MXene platform provides a pathway for realizing highly responsive NO2 sensors. Herein, possible gas sensing mechanism based on the formation of SnO2/MXene heterostructures has been discussed.