As interest in triboelectric nanogenerators (TENGs) continues to increase, some studies have reported that certain limitations exist in TENG due to high potential difference, resulting in air ...breakdown and field emission. In addition, with known limitations such as extremely low voltage at low external resistance, a breakthrough is required to overcome the limitations of TENG. Here, a new TENG mechanism is reported, utilizing ion‐enhanced field emission (IEFE). Using a simple IEFE‐inducing layer, which consists of a charge accumulation layer and a metal‐to‐metal contact point, electrons can flow directly to a counter electrode while generating high‐output power. Under vertical contact–separation input, the generated root mean square (RMS) power of IEFE‐TENG is 635% higher compared to conventional TENG. As the fundamental mechanism of the IEFE‐TENG is based on installing this simple IEFE‐inducing layer, the power output of existing TENGs including sliding mode types can be boosted. This new TENG mechanism can be a new standard for metal–metal contact TENGs to effectively amplify the output power and to overcome potential limitations.
The ion‐enhanced field emission triboelectric nanogenerator (IEFE‐TENG) emission mechanism can be achieved by adding a simple layer. The IEFE‐TENG has a charge‐accumulating layer and a metal‐to‐metal contact point that allows electrons to flow directly to the counter electrode thereby minimizing the output loss. This new TENG mechanism can significantly increase root mean square (RMS) power of TENGs by up to 635%.
•Polyaniline is composited with MoS2 nanosheet-coated electrospun SnO2 nanotubes.•A highly selective NH3 sensing platform is developed at room temperature.•Good sensing performance of excellent ...selectivity, high response, favorable repeatability and acceptable flexibility.•The mechanism connected with the enhancing properties was also investigated and presented.
In this work, we developed a NH3 gas sensor based on polyaniline (PANI) composited with MoS2 nanosheet-coated SnO2 nanotubes (PMS) via electrostatic spinning, hydrothermal route and in-situ polymerization technique. The morphologies, nanostructures and compositions of the materials were obtained from X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field emission scanning electron microscopy (FESEM), Transmission electron microscope (TEM) and Brunauer-Emmett-Teller method (BET). Thanks to nanostructure and the synergistic properties of PANI and MoS2/SnO2, the designed PMS gas sensor exhibited response signal of 10.9 towards 100 ppm NH3 at room temperature and a low detection limit of 200 ppb with good response-recovery time, good repeatability, acceptable flexibility and excellent selectivity. This study offers a versatile platform to modify PANI for highly selective detection of NH3 gas sensor at room temperature.
Abstract
The stability of a field‐emission event, i.e., the stability of the emission current over a long period of time, against thermal effects, etc., is one of the key factors for its application ...in real devices. Although nanostructures have the advantages of high aspect ratios and faster device turn‐on times, the small masses and large surface areas make them vulnerable to both chemical and physical damages and they have a lower melting point compared to bulk materials of same compositions. SnO
2
, one of the most attractive oxide semiconductors, which has with a relatively low work function of 4.7 eV, has been a perspective candidate for field emitters. A highly stable field emitter based on thin and quasi‐aligned SnO
2
nanowire ensembles with uniform diameter is shown. Field‐emission measurements of these SnO
2
nanowire ensembles show low turn‐on and threshold voltages of 3.5 V μm
−1
and 4.63 V μm
−1
, respectively, at an anode–sample distance of 200 μm and very long term scale stability of more than 2400 min, acquired at the electric field of 4.65 V μm
−1
. Such values are not only better than those of the recently developed SnO
2
nanostructures with different morphologies and of randomly oriented SnO
2
nanowire ensembles with a similar diameter distribution, but also comparable with the most widely studied field‐emission materials, such as carbon nanotubes and ZnO nanostructures. The potential for using these thin SnO
2
nanowire ensembles with uniform diameter in field emitters is shown, with particular promise in those operated for long‐term real device applications.
ZnCo2O4 (ZC-UAH) nanomaterials fabricated using an essential-route hydrothermal technique followed by a post-annealing procedure and used as the materials for high performance supercapacitors (SCs) ...by varying three reagents: urea (UA), ammonium fluoride (AF), and hexamethylenetetramine (HT). A reagent composite (ZC-UAH) served as a large surface area, high electrical conductivity, growth modifier during fabrication, and provide active abundant active sites for Faradaic redox reactions. The resulting products of the crystalline structural, composition, morphological, surface analysis behaviors were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and Brunauer-Emmett-Teller analysis. The electrochemical properties of the as-prepared materials were tested using a three-electrode system. As a result, the reagent-assisted composite of the ZC-UAH electrode material showed a higher specific capacity of 462.5C g−1 at a current density of 1 A g−1 within the potential range of 0.0–0.4 V in the 2 M KOH electrolyte solution. In addition, the ZC-UAH composite delivered excellent cycling stability, retaining 97.4% of its initial capacitance after 5000 cycles. These outcomes show that the reagent-assisted composite of the ZC-UAH electrode material has remarkable application potential and can achieve better characteristics for high-performance supercapacitors in energy storage applications.
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•ZnCo2O4 (ZC-UAH) composite has been designed by various active precursors.•ZC-UAH-based supercapacitor can afforded rich active sites for redox reactions.•ZC-UAH-based supercapacitor showed excellent electrochemical activities.•ZC-UAH-based supercapacitor showed excellent cyclability.
The stability of a field‐emission event, i.e., the stability of the emission current over a long period of time, against thermal effects, etc., is one of the key factors for its application in real ...devices. Although nanostructures have the advantages of high aspect ratios and faster device turn‐on times, the small masses and large surface areas make them vulnerable to both chemical and physical damages and they have a lower melting point compared to bulk materials of same compositions. SnO2, one of the most attractive oxide semiconductors, which has with a relatively low work function of 4.7 eV, has been a perspective candidate for field emitters. A highly stable field emitter based on thin and quasi‐aligned SnO2 nanowire ensembles with uniform diameter is shown. Field‐emission measurements of these SnO2 nanowire ensembles show low turn‐on and threshold voltages of 3.5 V μm−1 and 4.63 V μm−1, respectively, at an anode–sample distance of 200 μm and very long term scale stability of more than 2400 min, acquired at the electric field of 4.65 V μm−1. Such values are not only better than those of the recently developed SnO2 nanostructures with different morphologies and of randomly oriented SnO2 nanowire ensembles with a similar diameter distribution, but also comparable with the most widely studied field‐emission materials, such as carbon nanotubes and ZnO nanostructures. The potential for using these thin SnO2 nanowire ensembles with uniform diameter in field emitters is shown, with particular promise in those operated for long‐term real device applications.
A highly stable field emitter based on thin, quasi‐aligned SnO2 nanowire ensembles with uniform diameter is reported. Field‐emission measurements of these SnO2 nanowire ensembles showed low turn‐on and threshold voltages and very long‐term stability of more than 2400 min. The excellent field emission characteristics are mainly attributed to their high crystallinity, high aspect ratio, uniform 1D geometry and diameter distribution, and quasi‐aligned growth.
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•ZnO, WO3, binary composite WO3-ZnO and ternary WO3-ZnO@rGO nanocomposites were prepared.•The minimum bandgap was 2.62 eV for WO3.•Maximum photocatalytic activity (i.e. > 90 %) was ...observed by rGO based composite.
Novel graphene supported ternary nanocomposites (WO3-ZnO@rGO) were prepared via simple ultrasound assisted fabrication of WO3-ZnO binary nanostructures over 2D rGO nanosheets. Structural, morphological and elemental characterization of as-synthesized samples were carried out through X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FE-SEM) and Energy dispersive X-ray spectroscopy (EDX). Optical band gap analysis under UV–vis spectroscopy (UV–vis) revealed a decrement in the band gap energy value of WO3-ZnO@rGO ternary nanocomposites. Current-voltage (I–V) measurements evidenced the ohmic response of rGO supported WO3-ZnO nanocomposites as compared to bare samples. To evaluate the photocatalytic efficiency of WO3-ZnO@rGO nanocomposites in comparison to bare nanostructures, wastewater organic pollutant methylene blue (MB) dye was chosen as benchmark reaction. Results suggested that impregnation of WO3-ZnO over rGO sheets significantly improved the photocatalytic efficiency of WO3-ZnO@rGO with 94 % dye removal within 90 min under visible light irradiation. The enhanced photocatalytic efficiency is ascribed to synergistic effects originating at WO3-ZnO@rGO interfaces subsidizing high quantum yield and effective separation and transfer of photo induced electron-hole pairs. Moreover, WO3-ZnO@rGO also retained its remarkable dye degradation efficiency even after four recycling tests.
This paper proposes a six-plate capacitive coupler for large air-gap capacitive power transfer to reduce electric field emissions to the surrounding environment. Compared to the conventional ...four-plate horizontal structure, the six-plate coupler contains two additional plates above and below the inner four-plate coupler to provide a shielding effect. Since there is a capacitive coupling between every two plates, the six-plate coupler results in a circuit model consisting of 15 coupling capacitors. This complex model is first simplified to an equivalent three-port circuit model, and then to a two-port circuit model which is used in circuit analysis and parameter design. This six-plate coupler can eliminate the external parallel capacitor in the previous LCLC topology, which results in the LCL compensation and reduces the system cost. Due to the symmetry of the coupler structure, the voltage between shielding plates is limited, which reduces electric field emissions. Finite element analysis by Maxwell is used to simulate the coupling capacitors and electric field distribution. Compared to the four-plate horizontal and vertical structures, the six-plate coupler can significantly reduce electric field emissions and expand the safety area from 0.9 to 0.1 m away from the coupler in the well-aligned case. A 1.97 kW prototype is implemented to validate the six-plate coupler, which achieves a power density of 1.95 kW/m 2 and a dc-dc efficiency of 91.6% at an air-gap of 150 mm. Experiments also show that the output power maintains 65% of the well-aligned value at 300 mm X misalignment, and 49% at 300 mm Y misalignment.
We report the synthesis of klockmannite (CuSe) via a three-probe electrochemical set-up (chronoampereometry). The structural properties are examined by X-ray diffraction and Raman spectroscopy. Field ...emission scanning electron microscopy (FESEM) analysis revealed the formation of vertically aligned CuSe nanosheets with an average thickness of 34 nm and an average lateral size of 700 nm. The CuSe nanosheets exhibit impressive field electron emission characteristics with a turn-on field of 1.4 V/µm for 10 µA/cm2 emission current density. Also, a high current density of 5.8 mA/cm2 is observed at a relatively low applied field of 3.1 V/µm. Complementary first-principles DFT calculations show that CuSe displays metallic conductivity, and the (001) surface has a low work function of 5.12 eV, which is believed to be responsible for the impressive field emission characteristics.
Here in this article, we report the synthesis of klockmannite (CuSe) via a three-probe electrochemical set-up (chronoampereometry). The structural properties are examined by X-ray diffraction and Raman spectroscopy. Field Emission Scanning Electron Microscope (FESEM) analysis revealed the formation of vertically aligned CuSe nanosheets with average thickness of 34 nm and average lateral size of 700 nm. The CuSe nanosheets exhibit impressive field electron emission characteristics with a turn-on field of 1.4 V/µm for 10 µA/cm2 emission current density. Also, a high current density of 5.8 mA/cm2 is observed at a relatively low applied field of 3.1 V/µm. Complementary first-principles DFT calculations show that CuSe display metallic conductivity, and the (001) surface has a low work function of 5.12 eV, which is believe to be responsible for the impressive field emission characteristics. Display omitted
•Synthesis of 2D vertically aligned CuSe nanosheets are carried by three-probe electrochemical set-up (chronoampereometry).•Low turn-on of 1.4 V/µm is observed.•High current density 1.46 mA/cm2 is achieved.•Complementary first-principles DFT calculations are carried out.
In this work, we demonstrate suspended two- and four-terminal field emission devices for high-temperature operation. The planar structures were fabricated with tungsten on a 200-nm silicon nitride ...membrane. The insulator in the vicinity of the terminals was removed to minimize undesirable Frenkel-Poole emission and increase the resistance of leakage current pathways. The effects of temperatures up to 450 °C on Fowler-Nordheim emission characteristics and parasitic leakage resistance were studied. Turn-on voltages with magnitudes under 15 V that further decreased as a function of increasing temperature for the two-terminal device were reported. Gating at temperatures of 150 °C and 300 °C was shown for the four-terminal device, and corresponding transconductance and cutoff frequency values were computed.
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