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 (WO
₃
) nanostructures using a carbon nanotube (CNT) sacrificial template and demonstrates its application to a highly sensitive NO
₂
sensor. All fabrication steps are scalable, and the C-doped WO
₃
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 WO
₃
nanostructures during a single annealing process. The synthesized C-doped WO
₃
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 WO
₃
is effective at lowering the optimal operating temperature. The developed sensor can sensitively detect various NO
₂
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.