Enhanced acetone sensing properties of Co 3 O 4 nanosheets with highly exposed (111) planes

Co 3 O 4 nanosheets (NS-Co 3 O 4 ), nanorods (NR-Co 3 O 4 ), and nanofibers (NF-Co 3 O 4 ) were fabricated via hydrothermal and electrospinning methods, respectively. Single crystal sheet-like Co 3 O 4 was mainly exposed of (111) planes with a specific surface area of 39.2 m 2 /g, while NR-Co 3 O 4 and NF-Co 3 O 4 were polycrystalline with specific surface areas of 53.1 and 67.1 m 2 /g, respectively. Gas sensing response ( R g / R a ) of NS-Co 3 O 4 to 100 ppm acetone was ~6.1 at 160 °C, which was much higher than those of NR-Co 3 O 4 (~4.0), NF-Co 3 O 4 (~2.7) and other reported Co 3 O 4 nanostructures. The response and recovery time of NS-Co 3 O 4 to 100 ppm acetone were 98 and 7 s, respectively. NS-Co 3 O 4 had the smallest specific surface area, but exhibited the best acetone sensing properties, which was possibly due to their high exposure of (111) planes. There were only Co 2+ cations on (111) planes, which contained a lot of dangling bonds. Oxygen species in air could be adsorbed more easily on (111) planes than other randomly exposed planes. Thus, thicker holes accumulation layer formed and better gas sensing properties were obtained. This study has provided a basic understanding of the relationship between Co 3 O 4 nanocrystals with exposed certain planes and their gas sensing properties.