Carbon-Doped WO3 Nanostructure Based on CNT Sacrificial Template and its Application to Highly Sensitive NO2 Sensor

This paper first reports a technique for the fabrication of carbon (C)-doped tungsten oxide (WO3) nanostructures using a carbon nanotube (CNT) sacrificial template and demonstrates its application to a highly sensitive NO2 sensor. All fabrication steps are scalable, and the C-doped WO3 synthesis and CNT removal are conducted simultaneously using a single annealing procedure. The prepared nanostructures are analyzed based on scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and energy-dispersive X-ray spectroscopy. These analysis methods confirm that the CNT template is completely removed and that the carbon is doped into the synthesized WO3 nanostructures during a single annealing process. The synthesized C-doped WO3 nanostructures exhibit high porosity and a large surface area of which CNT template originally have, which is a highly advantageous aspect to sensitive gas detection. In addition, carbon doping into WO3 is effective at lowering the optimal operating temperature. The developed sensor can sensitively detect various NO2 concentrations from 8 down to 0.5 ppm at room temperature, which is attributed to the carbon-doping effect and large surface area of the synthesized nanostructures.