Quasi-2D Co3O4 Nanoflakes as Efficient Gas Sensor versus Alcohol VOCs

We study quasi-two-dimensional crystals of Co3O4 grown by electrochemical synthesis on Pt electrodes in nanoflake morphology to serve as a gas sensor. When synthesizing in aqueous electrolytes under applied electrical bias the material follows a self-hierarchical architecture to primarily appear as hexagonal nanoflakes, α-Co(OH)2. Following heating up to 300 oC in the air, the as-synthesized material transforms to Co3O4 preserving the original hierarchical morphology. The Co3O4 nanoflakes have been found to have remarkable chemiresistive response when exposed to various kinds of alcohol vapors, at low ppm concentrations in mixture with air, over a wide range of temperatures, up to 300 oC with a detection limit down to ppb range in the direct dependence on the alcohol molecule weight. We explain observed features of the gas response of Co3O4 nanoflakes by a shift of electron density under VOCs chemisorption verified by DFT calculations.