Hierarchical Assembly of α-Fe₂O₃ Nanorods on Multiwall Carbon Nanotubes as a High-Performance Sensing Material for Gas Sensors

Abstract

This paper presents a facile hydrolysis reaction and annealing for preparing a novel hierarchical nanoheterostructure via assembly of α-FeO nanorods onto multiwall carbon nanotubes (MWCNTs) backbones. The as-synthesized nanocomposites were characterized using XRD (X-ray diffraction), FESEM (Field emission scanning electron microscopy), TEM (Transmission electron microscopy), XPS (X-ray photoelectron spectroscopy) and BET (Surface Area and Porosity System). The observations showed uniform α-FeO nanorods approximately 100-200 nm in length and 50-100 nm in diameter that were hierarchically assembled onto the surface of the MWCNTs. The formation of the heterostructure was investigated by observing the evolution of the microstructure of the products at different reaction times. The X-ray photoelectron spectra (XPS) showed that the ability of the absorbing oxygen was enhanced by the formation of the heterostructure composites. Moreover, as a proof-of-concept presentation, the novel CNTs@α-FeO hierarchical heterostructure acted as a gas sensitive material. Significantly, the composites exhibited excellent sensing properties for acetone with high sensitivity, exceptional selectivity and good reproducibility. The response of the CNTs@α-FeO sensor to 100 ppm acetones at 225 °C was nearly 35, which was superior to the single α-FeO nanorods with a response of 16, and the detection limit of the sensor was 500 ppb. The enhanced properties were mainly attributed to the unique structure and p-n heterojunction between the CNTs and the α-FeO nanorods.

Grown Carbon Nanotubes on Electrospun Carbon Nanofibers as a 3D Carbon Nanomaterial for High Energy Storage Performance

“…concluded that short and small diameter CNTs perform better electrochemically, due to the insertion‐extraction speed of Li‐ions . The 3D CNTs‐CNFs nanomaterials displayed greater improvement in performance compared to their single compounds . Moreover, the production of the 3D CNTs grown‐CNFs also has many difficulties, such as in the control production parameters, the growth of carbon nanostructures, and the distribution of the CNTs on the CNFs, which can be the focus of future works.…”

“…The ratio I D /I G band is the main factor for evaluating the disorder and defect in the structure of carbon materials; the high ratio of I D /I G means high disorder degree and free defect. SWCNTs have low I D /I G ratio ,, . The ratio I D /I G band of the hierarchical 3D CNTs/CNFs (I D /I G =0.79) is lower than the ratio of pure CNFs and higher than CNTs (I D /I G =0.12) .…”

“…SWCNTs have low I D /I G ratio ,, . The ratio I D /I G band of the hierarchical 3D CNTs/CNFs (I D /I G =0.79) is lower than the ratio of pure CNFs and higher than CNTs (I D /I G =0.12) . This phenomenon explained by increasing the degree of graphitic crystallization of CNFs with growth the CNTs .…”

“…In fact, 3D‐carbon nanomaterials are a crucial frontier at research centers, and studies have sought to modify the morphology, nanostructure, and composition that control their potential applications . Construction of hybrid 3D‐carbon nanomaterials enhances the properties of their compounds, increases the specific area, and decreases the cost of purchasing expensive compounds .…”

“…Changing the structure of carbonaceous materials results in a large aspect ratio, surface defect sites, and radiative recombination paths, which positively affect their potential application . One advantage of using CNTs and CNFs is that they can be grown on the substrate in various morphologies under CVD conditions ,. In the last ten years, The number of published articles about producing 3D carbon nanomaterials and their hybrid materials has significantly increased in a variety of fields, as illustrated in Figure l.…”