MOF-derived synthesis of Co<inf>3</inf>O<inf>4</inf> nanospheres with rich oxygen vacancies for long-term stable and highly selective n-butanol sensing performance.

Abstract

Long-term stability and selectivity are crucial for the practical application of gas sensors, which are closely related to the microstructure and composition of sensor materials. In this work, Co-based metal organic framework (MOF) is used as a precursor and prepared by a simple hydrothermal method. After calcination, a series of Co3O4 nanospheres with various microstructures are derived. When the calcination temperature increases from 300 °C to 500 °C, the microstructure of Co3O4 nanospheres changed from rough solid to porous, and then transformed into porous core-shell. When assembled into the gas sensors, the Co3O4 nanospheres with porous structure calcined at 400 °C (Co3O4-400) show the highly selective response of 53.78 for 100 ppm n-butanol at the operating temperature of 140 °C. Moreover, the theoretical limit of detection was calculated to be 150 ppb. The reproducibility, selectivity and stability of the gas sensor were further verified to be excellent. After 45 days, the response value of Co3O4-400 is at 86.74%, even after 75 days, the response value remains at 74.93%. The main reason can be attributed to the large specific surface area, abundant pore structure and a large number of oxygen vacancies on its surface. These findings provide reference for the development of p-type metal oxide semiconductor (MOS) sensors with long-term stability and high performance.