Facile synthesis of hierarchical Co3O4/MWCNT composites with enhanced acetone sensing property

A facile hydrothermal approach is reported for the preparation of a series of hierarchical cobalt tetraoxide (Co3O4)/multi-walled carbon nanotube (MWCNT) composites with different MWCNT amount. The material characterization reveals that the broccoli-like nano-agglomerates of Co3O4 nanoparticles are anchored to the surface of the intertwined MWCNT network structure in all the Co3O4/MWCNT composites. The optimized Co3O4/MWCNT based chemiresistive sensor has ultralow limit of detection of 0.41 ppm, and up to 5 times greater sensing response than the pristine Co3O4 based sensor while exposed to 100 ppm of acetone gas at 140 degrees C. The Co3O4/MWCNT based sensor has a short response time of 15 s and a short recovery time of 18 s, respectively. In addition, the Co3O4/MWCNT based sensor presents long-term stability, good reproducibility and high selec-tivity. The possible mechanisms of the enhanced chemiresistive response of the composite include the formation of the p-p hetero-junctions at the interface between Co3O4 and MWCNT, the increased amount of adsorbed oxygen species on the composite surface, and the mesoporous structure of the composite.