Quasi-2D Co3O4 nanoflakes as an efficient gas sensor versus alcohol VOCs

Abstract

Here, we study quasi-two-dimensional crystals of Co₃O₄ grown by electrochemical synthesis on Pt electrodes with a 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 the hexagonal nanoflakes α-Co(OH)₂. After heating up to 300 °C in 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 a mixture with air, over a wide range of temperatures up to 300 °C with a detection limit down to the ppb range with direct dependence on the molecule weight of the alcohol. We explain the observed features of the gas response of the Co₃O₄ nanoflakes by a shift in the electron density under the chemisorption of VOCs, verified by DFT calculations.