Crystal facet engineering strategy is an effective way to regulate the exposed facets, which affect the ability of the surface to adsorb and react with gas molecules, ultimately enhancing the gas-sensing properties. In this work, Co₃O₄ mesoporous nanosheets with dominant exposed {111} facets (Co₃O₄-60) or {112} facets (Co₃O₄-100) were synthesized by simply adjusting the condensation-reflux temperature. The sensing results toward toluene show that Co₃O₄-60 exhibited superior performance. According to the crystal structure analysis and work function calculations, the (111) facet composed of Co²⁺would adsorb more oxygen molecules, which have been proved by experimental characterization, facilitating the sensing efficiency. The results of X-ray photoelectron spectroscopy indicated that Co₃O₄-60 possesses a higher Co²⁺ content and chemisorbed oxygen ratio (52.9%). Furthermore, Co₃O₄-60 has a high electrical conductivity and a minor apparent activation energy for toluene (38.75 kJ/mol). The gas sensor based on Co₃O₄-60 exhibited a response of 20.6 for 100 ppm toluene with rapid recovery and a detection limit of 1 ppm. Besides, other properties such as selectivity, repeatability, and humidity resistance were evaluated. This work evidences that crystal facet engineering is a practical approach to improving the gas-sensing properties of pure-phase Co₃O₄.

原文链接：https://doi.org/10.1016/j.apsusc.2023.156714