The Influence of Nb on the Synthesis of WO3 Nanowires and the Effects on Hydrogen Sensing Performance

Abstract

Hydrogen sensing is becoming one of the hottest topics in the chemical sensing field, due to its wide number of applications and the dangerousness of hydrogen leakages. For this reason, research activities are focusing on the development of high-performance materials that can be easily integrated in sensing devices. In this work, we investigated the influence of Nb on the sensing performances of WO3 nanowires (NWs) synthetized by a low-cost thermal oxidation method. The morphology and the structure of these Nb-WO3 nanowires were investigated by field emission scanning electron microscope (FE-SEM), high-resolution transmission electron microscope (HR-TEM), X-ray diffraction (XRD), Raman and X-ray photoelectron (XPS) spectroscopies, confirming that the addition of Nb does not modify significantly the monoclinic crystal structure of WO3. Moreover, we integrated these NWs into chemical sensors, and we assessed their performances toward hydrogen and some common interfering compounds. Although the hydrogen sensing performances of WO3 nanowires were already excellent, thanks to the presence of Nb they have been further enhanced, reaching the outstanding value of more than 80,000 towards 500 ppm @ 200 °C. This opens the possibility of their integration in commercial equipment, like electronic noses and portable devices.

One-Dimensional Nanostructured Oxide Chemoresistive Sensors

“…In a recent article, a successful attempt to grow Nb-doped tungsten oxide nanowires by thermal oxidation has been reported. 107 To achieve Nb-WO 3 nanostructures, the metal layer deposition was performed with magnetron sputtering using a target of W with a variable number of niobium insets. An alloy of metallic tungsten–niobium was deposited on an alumina substrate, with a composition that varies with the number of Nb insets.…”

“…For instance, as previously discussed, Nb doping in WO 3 nanowires enhances the sensing performance with respect to H 2 . 107 In a similar framework, surface functionalization with metal clusters and 2D materials can also be used to further improve the sensing performance. In a recent report, SnO 2 nanowires were functionalized with a graphene oxide layer for low-temperature NO 2 sensing in the presence of UV light.…”

Chemical Gas Sensors Studied at SENSOR Lab, Brescia (Italy): From Conventional to Energy-Efficient and Biocompatible Composite Structures

“…In the meanwhile, the sensing performance of metal oxide nanomaterials can be improved by either doping or preparing solid solutions [6,[72][73][74][75]. The effect of Zn-doping on the sensitivity of In 2 O 3 nanowires was investigated towards different gases, such as carbon monoxide (CO), NO 2 , ethanol, and H 2 [73].…”

“…In addition, the Zn incorporation into the In2O3 lattice creates more oxygen vacancies and increases the surface defects, which enhance the receptor function for reducing gases. The doping of Co3O4 nanomaterials with fluorine (F) resulted in higher responses towards volatile organic compounds (VOCs) and lowered the working temperature (200 °C) compared to the fluorine-free systems [74]. This behavior was attributed to the high fluorine electronegativity.…”

“…The manufacturing of gas sensors based on composite nanomaterials and heterojunctions provides novel opportunities to improve the sensing properties of metal oxides [7,43,78,79]. The The doping of Co 3 O 4 nanomaterials with fluorine (F) resulted in higher responses towards volatile organic compounds (VOCs) and lowered the working temperature (200 • C) compared to the fluorine-free systems [74]. This behavior was attributed to the high fluorine electronegativity.…”