研究目的
To investigate the SO2-sensing properties of NiO nanowalls synthesized by the reaction of Ni foil in NH4OH solution.
研究成果
The synthesized NiO nanowalls exhibit high sensitivity and selectivity towards SO2 gas, with a linear response to concentration changes, good stability, and a limit of detection of 1 ppm. This method provides a simple and low-cost approach for developing effective SO2 sensors.
研究不足
The operating temperature is limited to a maximum of 300°C by the gas-testing system. The sensing performance may be influenced by factors such as electrode material, testing system setup, and chamber conditions. The presence of Ni3O2(OH)4 phase in the sample could affect properties but is not fully characterized.
1：Experimental Design and Method Selection:
A facile method was used to synthesize NiO nanowalls on a glass substrate through the chemical reaction of Ni foil with aqueous NH4OH, followed by dehydration at 500°C. The morphology and structure were characterized using FESEM and XRD, and gas-sensing properties were tested with a dynamic gas-testing system for H2S, NO2, NH3, and SO2 gases.
2：Sample Selection and Data Sources:
Commercial pure Ni foil (99.99% purity, thickness 0.1 mm) was used. Glass substrates (2 cm x 2 cm) were cleaned and positioned under the Ni plate in NH4OH solution.
3：99% purity, thickness 1 mm) was used. Glass substrates (2 cm x 2 cm) were cleaned and positioned under the Ni plate in NH4OH solution. List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Ni foil (Aldrich), NH4OH solution, glass substrates, acetic acid, acetone, ethanol, distilled water, Duran laboratory bottle, oven, hotplate, thermal evaporator for Au electrodes, FESEM (JEOL JSM-7610F), XRD (XPERT-PRO), TEM (Philips Telnai G2F20 S-TWIN), dynamic gas-testing system.
4：Experimental Procedures and Operational Workflow:
Ni foil was cleaned, folded, and immersed in NH4OH at 70°C for 48 hours. The glass substrate was covered with a green film, dried, annealed at 500°C for 1 hour, and Au electrodes were patterned. Morphology and structure were analyzed, and gas-sensing tests were conducted at temperatures from 50°C to 300°C with various gas concentrations.
5：Data Analysis Methods:
Gas response was defined as S = (Rg - Ra)/Ra * 100%, where Rg and Ra are resistances in gas and air. Response and recovery times were measured as time to reach 90% of steady-state values. XRD data were analyzed using Scherrer equation for crystallite size.
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Ni foil
thickness 0.1 mm, purity 99.99%
Aldrich
Used as the source material for synthesizing NiO nanowalls through reaction with NH4OH.
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FESEM
JEOL JSM-7610F
JEOL
Used to characterize the morphology of the NiO nanowalls.
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XRD
XPERT-PRO
Used to analyze the crystal structure of the samples.
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TEM
Philips Telnai G2F20 S-TWIN
Philips
Used for transmission electron microscopy observations of the NiO nanowalls.
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Duran laboratory bottle
100 ml
Duran
Used as a container for the reaction of Ni foil with NH4OH solution.
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Hotplate
Used for annealing the samples at 500°C.
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Thermal evaporator
Used to pattern Au electrodes on the annealed substrate.
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Dynamic gas-testing system
Used to measure the gas-sensing properties of the NiO nanowalls for H2S, NO2, NH3, and SO2 gases.
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