Synthesis of mesoporous Bi2WO6 architectures and their gas sensitivity to ethanol

Abstract

Uniform hierarchical multilayered Bi₂WO₆ architectures were synthesized by a facile template-free hydrothermal process, and their synthesis conditions and formation mechanism were carefully investigated. XRD, XPS, FE-SEM, and HR-TEM techniques were employed to determine their phase composition, morphology and microstructure. Nitrogen adsorption and desorption isotherms were conducted to examine the specific surface area and the pore nature of the as-prepared sample. The results show that the as-prepared Bi₂WO₆ architectures consist of secondary nanoplates and have a mesoporous nest-like morphology with a diameter of 3–4 μm, and have very large specific surface areas. The largest surface area of 47.72 m² g⁻¹ is achieved when synthesized at 190 °C for 2.0 h. Furthermore, the Bi₂WO₆ samples were fabricated into a gas sensor, and the experimental results showed that the samples exhibited high sensitivity and a fast response–recovery to ethanol gas at lower temperatures (300 °C). For 100 ppm ethanol, the sensitivity of the best sensor (GS2) was 34.6, which is about 3-fold higher than the reported mesoporous ZnO based gas sensor because its mesoporous structure provided a high surface-to-volume ratio and surface accessibility for the ethanol. A plausible enhancement gas responding mechanism of the nest-like Bi₂WO₆ sensors was also proposed based on the structure and response–recovery properties.