Aerosol-Assisted CVD-Grown PdO Nanoparticle-Decorated Tungsten Oxide Nanoneedles Extremely Sensitive and Selective to Hydrogen

Abstract

We report for the first time the successful synthesis of palladium (Pd) nanoparticle (NP)-decorated tungsten trioxide (WO3) nanoneedles (NNs) via a two-step aerosol-assisted chemical vapor deposition approach. Morphological, structural, and elemental composition analysis revealed that a Pd(acac)2 precursor was very suitable to decorate WO3 NNs with uniform and well-dispersed PdO NPs. Gas-sensing results revealed that decoration with PdO NPs led to an ultrasensitive and selective hydrogen (H2) gas sensor (sensor response peaks at 1670 at 500 ppm of H2) with low operating temperature (150 °C). The response of decorated NNs is 755 times higher than that of bare WO3 NNs. Additionally, at a temperature near that of the ambient temperature (50 °C), the response of this sensor toward the same concentration of H2 was 23, which is higher than that of some promising sensors reported in the literature. Finally, humidity measurements showed that PdO/WO3 sensors displayed low-cross-sensitivity toward water vapor, compared to bare WO3 sensors. The addition of PdO NPs helps to minimize the effect of ambient humidity on the sensor response.

Facile synthesis of mesoporous hierarchical Co3O4–TiO2 p–n heterojunctions with greatly enhanced gas sensing performance

“…5,27,[33][34][35] It is worth noting that the formation of p-n heterojunctions is an efficient and cost-effective technique to improve the activity and sensitivity of gas sensors 3,34,35 , and hierarchical structures offer abundant pores and large surface area which benefit the diffusion and adsorption of testing gases. 26 For example, Deng et al 16 prepared CuO-TiO2 heterostructure nanofibers and found that the formation of p-n heterojunctions considerably improved the sensitivity of TiO2 nanofibers to formaldehyde at 200 ºC.…”

Flexible Gas Sensors Employing Octahedral Indium Oxide Films

“…The nature of oxygen species depends on the temperature of the metal oxide [19,22,23]. O 2(g) ↔ O 2(ads) O 2(ads) + e − ↔ O 2 − (ads)    (<150 °C) O 2 − (ads) + e − ↔ 2O − (ads)    (150–400 °C) O − (ads) + e − ↔ O 2− (ads)    (>400 °C)…”

“…Pt or Pd nanoparticles supported onto n-type metal oxides have been reported to enhance response towards hydrogen via a combination of chemical and electronic sensitization effects [19,22,23]. …”

Gas Sensing Approaches Based on WO3 Nanowire-Back Gated Devices

“…Pt-nanoparticle decorated WO3 nanowires were co-deposited directly onto the electrode area in a single step aerosol assisted-CVD (AA-CVD). Prior to the deposition of the nanowires, the substrate was heated to a temperature of 380 °C, and followed by the transfer of ultrafine aerosols to the heated substrate by N2 carrier gas at a flow rate of 0.5 L/min [5,7]. Surface morphology images were taken using Scanning Electron Microscopy (ESEM) with FEI Quanta 60 and Tunneling Electron Microscopy with JOEL model 1011 equipment.…”

“…To this end, there has been much progress in the fabrication, and integration of different single crystalline SMOx nanostructures decorated with metal nanoparticles for gas sensing at low temperature; as well as optimizing the minimum power consumption of such devices while maintaining high sensor performance and stability [4]. Recently, highly sensitive gas sensors based on nanoparticle decorated WO3 nanowires for the detection of various gases at low temperature have been explored [5,6].…”