Comparison of electrochemical response and electric field emission characteristics of pristine La2NiO4 and La2NiO4/CNT composites: Origin of multi-functionality with theoretical penetration by density functional theory

Karmakar, Subrata; Mistari, Chetan D.; Vaidyanathan, Antara; More, Mahendra A.; Chakraborty, Brahmananda; Behera, D.

doi:10.1016/j.electacta.2020.137676

Cited by 17 publications

(7 citation statements)

References 69 publications

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“…The work function can be defined as the difference of energy of an electron between the vacuum level and the Fermi level. Mathematically, the work function (φ w ) can be expressed as , φ normalw = e φ 0 − E normalF Here, φ 0 , e , and E F represent the electrostatic potential of the vacuum level, charge of an electron, and Fermi energy, respectively. We found that the work function of the Q-carbon electron field emitter is around 3.62 eV, which is in good agreement with the previous experimental outcomes .…”

Section: Simulation Results and Discussionmentioning

confidence: 99%

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Electric-Field Emission Mechanism in Q-Carbon Field Emitters

et al. 2023

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In this paper, we report the excellent field emission properties of Q-carbon and analyze its field emission characteristics through structural, morphological, and electronic property correlations, supported by density functional theory (DFT) simulation studies. The Q-carbon field emitters show impressive and stable field emission properties, such as a low turn-on electric field of ∼2.38 V/μm, a high emission current density of ∼33 μA/cm2, and a critical field of ∼2.44 V/μm for the transition from a linear region to the saturation region in the F–N plot. The outstanding field emission properties of Q-carbon are attributed to (i) a unique sp2/sp3 mixture in Q-carbon, (ii) sp2-bonded highly conductive amorphous carbon-rich channels inside the Q-carbon cluster, (iii) a large local field enhancement due to the local geometry and microstructure of Q-carbon, and (iv) the presence of sp2-bonded amorphous carbon regions in the composite film. The temperature-dependent field emission properties, such as extreme sensitivity and an enhancement in the emission current density with temperature, can be explained by the local density of states near the Fermi level and the excellent thermal stability of the Q-carbon field emitters. From DFT simulation studies, the computed work function and the field-enhancement factor were determined to be 3.62 eV and ∼2300, respectively, which explains the excellent field emission characteristics of Q-carbon. The obtained field emission properties, in most cases, were superior to those from other carbon/diamond-based field emitters, which will open new frontiers in field emission-based electronic applications.

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Section: Simulation Results and Discussionmentioning

confidence: 99%

“…Work Function Calculation.The work function can be defined as the difference of energy of an electron between the vacuum level and the Fermi level. Mathematically, the work function (φ w ) can be expressed as75,76…”

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Electric-Field Emission Mechanism in Q-Carbon Field Emitters

et al. 2023

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“…The high surface area of the tubular diamonds could be mainly attributed to the tubular structure and porous tube wall with nano and microstructures. The variation of specific electric double-layer capacitance with scan rates is shown in Figure f, and it was calculated by the equation − C sp = true∮ i ( V ) normald V 2 m s ( V f − V i ) where the closed integral part in the numerator is associated with the area under the curves, ( V f – V i ) is the working potential window, m is the gravimetric mass loaded, and s is the scan rate. The highest specific electric double-layer capacitance value was obtained at ∼18.1 mF cm –2 for 10 PLA-6 h HFCVD deposited tubular diamond structures.…”

Section: Resultsmentioning

confidence: 99%

Electrochemical Performance of Carbon-Nanotube-Supported Tubular Diamond

Haque,

Liu,

Karmakar

et al. 2023

ACS Appl. Eng. Mater.

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Tubular diamond structures with high surface areas are very desirable for various potential electrochemical applications. Here, we report a simple and cost-effective two-step method for the synthesis of a diamond tube with a porous tube wall from carbon nanotube (CNT) hollow fibers via pulsed laser annealing (PLA) and hot filament chemical vapor deposition (HFCVD). These diamond tubes exhibit high double-layer capacitances of 11.65−18.07 mF cm −2 , three orders of magnitudes higher than the equivalent flat diamond films. Scanning electron microscopy (SEM) shows the presence of diamond microspheres composed of both micro-and nanocrystallites on the entire tube after 3−6 h HFCVD. The number density of the diamond, the average size of diamond microspheres, and the nanocrystallite content on the microspheres can be controlled by HFCVD time and laser annealing parameters of CNT hollow fibers. The electron back-scattered diffraction analysis shows the crystallographic orientation of the prepared diamond along the ⟨101⟩ plane. Raman spectra show a sharp characteristic/signature diamond peak at ∼1332 cm −1 , corresponding to an unstrained high-quality diamond. The magnificent electrochemical performances of these CNT-supported diamond tubes are explained by their significantly enhanced electroactive surface area and the presence of a very small fraction (0.73−1.03%) of sp 2 carbon in diamond tubes for electron conduction. The density of states, band gaps, and outmost quantum capacitance (∼200 μF/cm 2 at −2.2 V electrode potential) of the tubular diamond are calculated by the density functional theory calculations, which support our experimental findings and suggest its future potentiality as an efficient supercapacitor electrode material.

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“…The electric field emission process is described by the well-known Fowler− Nordheim (F−N) theory which is based on a simplified onedimensional (1D) free electron model associated with Wentzel− Kramers−Brillouin (WKB) approximation. 49,50 According to this model, the tunneling probability is determined for a flat conducting planar surface through a triangular potential energy barrier, and field emission current density (J) strongly depends on the local electric field (E local ) by 51 = i k j j j j j y…”

Section: ■ Experimental Results and Discussionmentioning

confidence: 99%

“…The electron emission starts from the surface through a quantum mechanical tunneling process and the experimental setup for electric field emission is also shown inset of Figure a. The electric field emission process is described by the well-known Fowler–Nordheim (F–N) theory which is based on a simplified one-dimensional (1D) free electron model associated with Wentzel–Kramers–Brillouin (WKB) approximation. , According to this model, the tunneling probability is determined for a flat conducting planar surface through a triangular potential energy barrier, and field emission current density ( J ) strongly depends on the local electric field ( E local ) by J = a E normall normalo normalc normala normall 2 φ .25em exp ( − b φ 3 / 2 E l o c a l ) where a and b are the 1st and 2nd F–N constants having values 1.54 × 10 –6 A eV/V 2 and 6.83 × 10 7 cm –1 V eV –3/2 , respectively. The parameter φ is called the local work function and its value was calculated at 4.84 eV by DFT calculation .…”

Section: Resultsmentioning

confidence: 99%

Tubular Diamond as an Efficient Electron Field Emitter

Karmakar

Sarkar

Mistari

et al. 2023

ACS Appl. Electron. Mater.

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Herein, we present a straightforward and cost-effective procedure for producing conductive diamond tubes on the surface of porous carbon nanotube hollow fibers using successive 10-pulsed laser annealing shots and 6 h of hot filament chemical vapor deposition techniques. Room-temperature Raman and X-ray diffraction spectra reveal the signature T2g peaks near 1332.4 cm–1 and 111 planes of diamonds near 43.9°, respectively. A low turn-on field (E TO) ∼1.85 V/μm@1 μA/cm2 and a threshold field (E TH) ∼2.54 V/μm@10 μA/cm2 were observed for the tubular diamond structures. The field enhancement factor (β) was calculated at 3594 and highly stable field emission current stability was observed over a long period of 4 h. For the first time, a good insight into the field emission results of the diamond is established with the structural, electronic properties, and the work function (φ) ∼4.84 eV analysis conducted by the density functional theory simulation. Finite electronic states at the Fermi level are observed beyond a band gap, and it demonstrates the wide-band gap (4.4 eV) semiconducting nature of the diamond. The Bader charge analysis and maximum entropy method pattern revealed the negative electron affinity of the diamond, and it is responsible for the emission of electrons from the conduction band of the diamond. Besides, the accumulation of charge carriers, which contributes to the electric field emission, takes place due to the weak π bonds of carbon atoms. The low turn-on field, the high field enhancement factor, and the good field emission current stability of tubular diamond offer great prospects for future efficient and low-cost field emission devices.

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Comparison of electrochemical response and electric field emission characteristics of pristine La2NiO4 and La2NiO4/CNT composites: Origin of multi-functionality with theoretical penetration by density functional theory

Cited by 17 publications

References 69 publications

Electric-Field Emission Mechanism in Q-Carbon Field Emitters

Electric-Field Emission Mechanism in Q-Carbon Field Emitters

Electrochemical Performance of Carbon-Nanotube-Supported Tubular Diamond

Tubular Diamond as an Efficient Electron Field Emitter

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