Preparation of porous Co3O4 and its response to ethanol with low energy consumption.

Abstract

Co3O4 is a promising p-type semiconductor for ethanol detection. In this work, ethanol detection sensors were fabricated with nanostructured Co3O4, which exhibited higher selectivity and lower operating temperature. The Co3O4 was synthesised using ZIF-67 as a sacrificial precursor. The T400-Co3O4 that was obtained by calcining ZIF-67 at 400 °C showed the best sensing performance. Its response to 100 ppm ethanol vapor was 221.99 at a low optimal operating temperature (200 °C). Moreover, T400-Co3O4 achieved a low detection limit (1 ppm), remarkable repeatability, and higher selectivity compared to ammonia, carbon monoxide, acetone, hydrogen, methane, methanol, and nitrogen dioxide. The enhanced sensing performance was mainly attributed to three factors: (1) the adsorption/desorption of active adsorbed oxygen molecules (e.g. O− and O2−) and abundant oxygen vacancies, which increased the number of active sites; (2) the catalytic activity of Co3+, which greatly increased the reaction route and decreased the activation energy; and (3) the effective diffusion of gas molecules, which increased the effect of collisions between gas molecules and the material surface. This work provides an effective means to fabricate sensitive ethanol gas sensors with low energy consumption.