Sensing performance of palladium-functionalized WO ₃ nanowires by a drop-casting method

In this work, we show a simple way to functionalize tungsten oxide nanowires (WO ₃ -NWs) using a saturated palladium chloride (PdCl ₂ ) solution deposited by a drop-casting method. WO ₃ -NWs were synthesized by close-spaced chemical vapor deposition (CSVT). The morphological and structural characterizations showed that the diameters of WO ₃ -NWs are in the range from 50 to 200 nm with lengths above 10 μm, and correspond to the orthorhombic phase of WO ₃ , respectively. The sensor was fabricated using the WO ₃ -NWs and tested with hydrogen and volatile organic compounds (VCO's). A comparative study was done on the sensing performance, before and after the Palladium functionalization of the WO ₃ -NWs, considering a wide range of gas concentrations and moderate operating temperatures (100-400 °C). The results show that this simple functionalization process significantly increases the sensor sensitivity and reduces the time constants. In addition, it has been shown that at 300 °C the decorated sensor becomes more selective to hydrogen and xylene for all concentrations considered in this research. Finally, the mechanisms involved in improving the gas sensing properties of WO ₃ -NWs functionalized with Palladium are discussed.