Hierarchical Fe 2 O 3 @WO 3 nanostructures with ultrahigh specific surface areas: microwave-assisted synthesis and enhanced H 2 S-sensing performance

• Published in: RSC advances 2015, Vol.5 (1), p.328-337
• Main Authors: Yin, Li, Chen, Deliang, Feng, Mengjie, Ge, Lianfang, Yang, Dewei, Song, Zhanhong, Fan, Bingbing, Zhang, Rui, Shao, Guosheng
• Format: Article
• Language: English
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C4RA10500A

Hierarchical Fe 2 O 3 @WO 3 nanocomposites with ultrahigh specific areas, consisting of Fe 2 O 3 nanoparticles (NPs) and single-crystal WO 3 nanoplates, were synthesized via a microwave-heating (MH) in situ growth process. WO 3 nanoplates were derived by an intercalation and topochemical-conversion route, and the Fe 2 O 3 NPs were in situ grown on the WO 3 surfaces via a heterogamous nucleation. The water-bath-heating (WH) process was also developed to synthesize a Fe 2 O 3 @WO 3 nanocomposite for comparison purposes. The techniques of X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the samples obtained. The results show that α-Fe 2 O 3 NPs with a size range of 5–10 nm are uniformly, tightly anchored on the surfaces of WO 3 nanoplates in the Fe 2 O 3 @WO 3 samples obtained via the MH process, whereas the α-Fe 2 O 3 NPs are not uniform in particle-sizes and spatial distribution in the Fe 2 O 3 @WO 3 samples obtained via the WH process. The BET surface area of the 5wt%Fe 2 O 3 @WO 3 sample derived by the MH process is as high as 1207 m 2 g −1 , 5.9 times higher than that (203 m 2 g −1 ) of the corresponding WO 3 nanoplates. The dramatic enhancement in the specific surface area of the Fe 2 O 3 @WO 3 samples should be attributed to the hierarchical microstructure, which makes the internal surfaces or interfaces in aggregated polycrystals be fully outside surfaces via a house-of-cards configuration, where the single-layered and disconnected Fe 2 O 3 NPs are tightly anchored on the surfaces of the WO 3 nanoplates. The gas-sensing properties of the Fe 2 O 3 @WO 3 sensors were investigated. The gas-sensors based on the Fe 2 O 3 @WO 3 obtained via the MH process show a high response and selectivity to H 2 S at low operating temperatures. The 5%Fe 2 O 3 @WO 3 sample shows the highest H 2 S-sensing response at 150 °C. Its response to 10 ppm H 2 S is as high as 192, 4 times higher than that of the WO 3 -nanoplate sensor. The improvement in the gas-sensing performance of the Fe 2 O 3 @WO 3 nanocomposites can be attributed to the synergistic effect in compositions and the hierarchical microstructures with ultrahigh specific surface areas.