Abstract
Hierarchical WO3 nanomesh, assembled from single-crystalline WO3 nanowires, is prepared via a hydrothermal method using thiourea (Tu) as the morphology-controlling agent. Formation of the hierarchical architecture comprising of WO3 nanowires takes place via Ostwald ripening mechanism with the growth orientation. The sensor based on WO3 nanomesh has good electrical conductivity and is therefore suitable as NO2 sensing material. The WO3 nanomesh sensor exhibited high response, short response and recovery time, and excellent selectivity towards ppb-level NO2 at low temperature of 160 ℃. The superior gas performance of the sensor was attributed to the high-purity hexagonal WO3 with high specific surface area, which gives rise to enhanced surface adsorption sites for gas adsorption. The electron depletion theory was used for explaining the NO2-sensing mechanism by the gas adsorption/desorption and charge transfer happened on the surface of WO3 nanomesh.
Highlights
NO2, as one of the most toxic and harmful gases in the atmosphere, is the precursor of acid rain and photochemical smog
The main diffraction peaks of the sample synthesized without adding Tu can be well synthesized in precursor without Tu consists of micronlevel flowers assembled with rectangular blocks
As the operating temperature increases, the response and recovery time of the sensor becomes shorter. These results indicate that the increase in temperature increases the adsorption and desorption rate of NO2 gas on the surface of WO3 namomesh
Summary
NO2, as one of the most toxic and harmful gases in the atmosphere, is the precursor of acid rain and photochemical smog. The method is not always effective, because the noble metal particles tend to catalytic poisoning and noble metal modification increases the fabricating cost [21] Another way to achieve this is to increase their surfaceto-volume ratio by preparing hierarchical nanostructures. The as-prepared WO3 nanomesh exhibited high sensibility, short response and recovery time, and good sensing selectivity to NO2 at a relatively low working temperature of 160 °C. Such excellent performance can be attributed to the highly exposed surface area, which propels the interaction between NO2 gas and sensing element. The sensing mechanism is explained in terms of the gas adsorption/desorption and electron transport between gas molecules and WO3 nanomesh
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