Abstract
In this work, we present a strategy to improve the gas-sensing performance of NiFe2O4 via a controllable annealing Ni/Fe precursor to fluffy NiFe2O4 nanosheet flowers. X-ray diffraction (XRD), a scanning electron microscope (SEM), nitrogen adsorption–desorption measurements and X-ray photoelectron spectroscopy (XPS) were used to characterize the crystal structure, morphology, specific surface area and surface structure. The gas-sensing performance was tested and the results demonstrate that the response was strongly influenced by the specific surface area and surface structure. The resultant NiFe2O4 nanosheet flowers with a heating rate of 8 °C min−1, which have a fluffier morphology and more oxygen vacancies in the surface, exhibited enhanced response and shortened response time toward ethanol. The easy approach facilitates the mass production of gas sensors based on bimetallic ferrites with high sensing performance via controlling the morphology and surface structure.
Highlights
Resistive gas sensors based on metal oxides, most of which are semiconductors, have been widely used in a range of commercial gas detection systems [1]
After being washed with deionized water and ethanol for three times and dried, the yellow sediment was annealed at 500 ◦ C for 3 h to obtain NiFe2 O4 nanosheet-assembled flowers (NSFs) with a heating rate of 2, 5 and 8 ◦ C min−1, respectively, denoted as NFO-2, NFO-5 and NFO-8 NSFs
The crystal structure, morphology and surface property of NiFe2 O4 were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), nitrogen adsorption–desorption measurement and X-ray photoelectron spectroscopy (XPS)
Summary
Resistive gas sensors based on metal oxides, most of which are semiconductors (containing n-type and p-type semiconductors), have been widely used in a range of commercial gas detection systems [1]. NiFe2 O4 having an inverse spinel ferrite structure is characterized to be an n-type or p-type semiconductor which can be altered by controlling the stoichiometric and cation distribution [8,9,10,11]. Many efforts have been made to apply NiFe2 O4 with various microstructures to the energy storage [12], catalysis [13] and effective detection of hazardous gases [14]. The gas-sensing properties of the NiFe2 O4 -based sensor are expected to be further enhanced. Regulating the surface active sites and microstructures of NiFe2 O4 is considered to be an effective method as the gas-sensing process involves the surface reaction
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