Abstract
A novel hierarchical heterostructures based on α-Fe2O3/NiO nanosheet-covered fibers were synthesized using a simple two-step process named the electrospinning and hydrothermal techniques. A high density of α-Fe2O3 nanosheets were uniformly and epitaxially deposited on a NiO nanofibers. The crystallinity, morphological structure and surface composition of nanostructured based on α-Fe2O3/NiO composites were investigated by XRD, SEM, TEM, EDX, XPS and BET analysis. The extremely branched α-Fe2O3/NiO nanosheet-covered fibers delivered an extremely porous atmosphere with huge specific surface area essential for superior gas sensors. Different nanostructured based on α-Fe2O3/NiO composites were also explored by adjusting the volume ratio of the precursors. The as-prepared samples based on α-Fe2O3/NiO nanocomposite sensors display apparently enhanced sensing characteristics, including higher sensing response, quick response with recovery speed and better selectivity towards acetone gas at lower operating temperature as compared to bare NiO nanofibers. The sensing response of S-2 based α-Fe2O3/NiO nanosheet-covered fibers were 18.24 to 100 ppm acetone gas at 169 °C, which was about 6.9 times higher than that of bare NiO nanofibers. The upgraded gas sensing performance of composites based on α-Fe2O3/NiO nanosheet-covered fibers might be ascribed to the exclusive morphologies with large surface area, p-n heterojunctions and the synergetic performance of α-Fe2O3 and NiO.
Highlights
A novel hierarchical heterostructures based on α-Fe2O3/nickel oxide (NiO) nanosheet-covered fibers were synthesized using a simple two-step process named the electrospinning and hydrothermal techniques
Morphological structure and compositional features of the as-prepared bare NiO and the nanocomposites based on α-Fe2O3/NiO samples were described by using X-ray diffraction patterns (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), EDS, X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller method (BET) examination
All the XRD peaks present in the composites based on α-Fe2O3/NiO corresponds well with the standard crystallographic patterns of the face-centered cubic phase of NiO (JCPDS Card No 47-1049) and the rhombohedral phase of α-Fe2O3 (JCPDS Card No 33-0664) without any extra peaks, which indicates the high purity of α-Fe2O3/NiO heterostructures
Summary
A novel hierarchical heterostructures based on α-Fe2O3/NiO nanosheet-covered fibers were synthesized using a simple two-step process named the electrospinning and hydrothermal techniques. The sensing response of S-2 based α-Fe2O3/NiO nanosheet-covered fibers were 18.24 to 100 ppm acetone gas at 169 °C, which was about 6.9 times higher than that of bare NiO nanofibers. P-type nickel oxide (NiO) with 3.4 eV energy gap and n-type hematite (α-Fe2O3) with 2.0 eV energy gap are dissimilar imperative functional materials existing as various morphological structures[17,18,19,20], which have received general attention because of their unique physical and chemical features leading to their great performance in wide range of applications including dye-sensitized solar cells[21,22], catalysis[23,24], gas sensors[25,26], electrodes[27,28], magnetic materials[29,30] and electrochemical supercapacitors[31,32] etc. A number of approaches had been established to prepare NiO and α-Fe2O3 based nanomaterials including the hydrothermal method[39,40], the pulsed laser deposition method[41], the solution plasma method[42], the micro emulsion method[43], chemical vapor deposition, the template-assisted approach[44] and electrospinning[45]
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