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Showing papers on "Quantum capacitance published in 2021"


Journal ArticleDOI
TL;DR: Carbon-based Quantum Dots (C-QDs) are carbon-based materials that experience the quantum confinement effect, which results in superior optoelectronic properties as discussed by the authors.
Abstract: Carbon-based Quantum dots (C-QDs) are carbon-based materials that experience the quantum confinement effect, which results in superior optoelectronic properties. In recent years, C-QDs have attracted attention significantly and have shown great application potential as a high-performance supercapacitor device. C-QDs (either as a bare electrode or composite) give a new way to boost supercapacitor performances in higher specific capacitance, high energy density, and good durability. This review comprehensively summarizes the up-to-date progress in C-QD applications either in a bare condition or as a composite with other materials for supercapacitors. The current state of the three distinct C-QD families used for supercapacitors including carbon quantum dots, carbon dots, and graphene quantum dots is highlighted. Two main properties of C-QDs (structural and electrical properties) are presented and analyzed, with a focus on the contribution to supercapacitor performances. Finally, we discuss and outline the remaining major challenges and future perspectives for this growing field with the hope of stimulating further research progress.

65 citations


Journal ArticleDOI
TL;DR: In this article, transition metal selenides MnSe2 and its hybrid with multiwalled carbon nanotubes (MWCNTs) are synthesized by a simplistic hydrothermal protocol.

27 citations


Journal ArticleDOI
TL;DR: In this paper, a defect-assisted defect-engineered Ni-Co-P/POx was investigated and the effect of defect engineering at the atomic level and the conversion of hydroxides to phosphides on conductivity and the overall electrochemical performance.

25 citations


Journal ArticleDOI
TL;DR: In this paper, the boundary between quantum capacitance and pseudocapacitance is blurred due to their similarity in electronic populations, and the authors proposed the rules to classify the contributions of QC and pseudo-CPA and their effects on the intrinsic ion transport kinetics based on the applied voltages and electronic structures.

24 citations


Journal ArticleDOI
TL;DR: In this paper, a few-layer graphene-based electrode is obtained by incorporating nitrogen-doped graphene (N-graphene), enabling a 3-fold enhancement in TENGs' power output.

24 citations


Journal ArticleDOI
TL;DR: In this article, the density functional theory of 56 kinds of 3D, 4d, 5d and 5d transition-metal and vacancy doped/co-doped graphene, named as TM@G and TM@VG, is used to evaluate the suitability of these materials for supercapacitors.

20 citations


Journal ArticleDOI
TL;DR: In this article, the stability, quantum capacitance, and surface charge storage of vacancy-defected, doped and co-doped germanene were studied based on first-principles method, and the results suggested that the enhancement of quantum capacity by introducing of transition-metal dopants (Ti, Cr, Mn, and Co) were more effective than that of B/N/Al-dopants.

19 citations


Journal ArticleDOI
12 Nov 2021-ACS Nano
TL;DR: In this article, the authors show that the incorporation of redox-active 7,7,8,8-tetracyanoquinodimethane (TCNQ) molecules into the pores of MOF@COF greatly improves the characteristics of the latter, thereby attaining high-performance energy storage devices.
Abstract: Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have been extensively investigated during the last two decades. More recently, a family of hybrid materials (i.e., MOF@COF) has emerged as particularly appealing for gas separation and storage, catalysis, sensing, and drug delivery. MOF@COF hybrids combine the unique characteristics of both MOF and COF components and exhibit peculiar properties including high porosity and large surface area. In this work, we show that the infiltration of redox-active 7,7,8,8-tetracyanoquinodimethane (TCNQ) molecules into the pores of MOF@COF greatly improves the characteristics of the latter, thereby attaining high-performance energy storage devices. Density functional theory (DFT) calculations were employed to guide the design of a MOF@COF-TCNQ hybrid with the TCNQ functional units incorporated in the pores of MOF@COF. To demonstrate potential application of our hybrids, the as-synthesized MOF@COF-TCNQ hybrid has been employed as an active material in supercapacitors. Electrochemical energy storage analysis revealed outstanding supercapacitor performance, as evidenced by a specific areal capacitance of 78.36 mF cm-2 and a high stack volumetric energy density of 4.46 F cm-3, with a capacitance retention of 86.4% after 2000 cycles completed at 0.2 A cm-2. DFT calculation results strongly indicate that the high capacitance of MOF@COF-TCNQ has a quantum capacitance origin. Our liquid-phase infiltration protocol of MOF@COF hybrids with redox-active molecules represents a efficacious approach to design functional porous hybrids.

16 citations


Journal ArticleDOI
TL;DR: In this paper, the authors presented the electronic structures and quantum capacitance for pristine δ-MnO2 with O vacancy employing density functional theory (DFT) simulations and showed that the defect structural design exhibited excellent electrocatalytic OER activity with lowest overpotential (η20, 300mV) and Tafel slope (71 mV/dec).

15 citations


Journal ArticleDOI
02 Aug 2021
TL;DR: In this article, the authors demonstrate the extraordinary capacitance performance of Rb-ion intercalation in the inter-layer of the 1T, 2H, and 3R MoS2 polymorphs.
Abstract: Intercalation of alkali metals has proved to be an effective approach for the enhancement of the energy storage performance in layered-2D MoS2. However, the research so far has been limited to the Li and Na ion intercalation with K ions being recently investigated. Herein, we demonstrate, for the first time, the extraordinary capacitance performance of Rb-ion intercalation in the inter-layer of the 1T, 2H, and 3R MoS2 polymorphs. This work elucidates the capacitance performance in terms of quantum capacitance and intercalation strength. Rb-Intercalation into MoS2 layers stabilizes the 1T phase more than Li ions and imparts metallic behavior to the semiconducting 2H and 3R phases. Concurrently, the quantum capacitance of the three phases dramatically increases, surpassing that of graphene and doped graphene. The calculated quantum capacitance can reach as high as 2700, 3250, and 3300 F g−1 for the 1T, 2H, and 3R phases, respectively, rendering the Rb ion a superior choice for boosting the energy storage performance of the MoS2-based supercapacitor electrodes.

14 citations


Journal ArticleDOI
01 Aug 2021-Vacuum
TL;DR: In this article, the effect of atomic vacancy on stability, electronic and optical properties, quantum capacitance and surface charge storage of pristine and vacancy-defected Zr2CO2 MXenes were investigated.


Journal ArticleDOI
TL;DR: In this paper, the performance of 2H, 1T, and 1T′ phases of MoS2 in its pristine form and heterostructures with carbon-based structures as an electrode in the supercapacitors using density functional theory was investigated.
Abstract: 1T Molybdenum disulfide (1T-MoS2) has been widely studied experimentally as an electrode for supercapacitors due to its excellent electrical and electrochemical properties. Whereas the capacitance value in MoS2 is limited due to the lower density of electrons near the Fermi level, and unable to fulfill the demand of industry i.e. quantum capacitance preferably higher than 300 μF/cm2. Here, we investigated the performance of 2H, 1T, and 1T′ phases of MoS2 in its pristine form and heterostructures with carbon-based structures as an electrode in the supercapacitors using density functional theory. Specifically, we reported that the underneath carbon nanotube (CNT) is responsible for the structural phase transition from 1T to 1T′ phase of MoS2 monolayer in 1T′-MoS2/CNT heterostructure. This is the main reason for a large density of states near Fermi level of 1T′-MoS2/CNT that exhibits high quantum capacitance (CQ) of 500 μF/cm2 at a potential of 0.6 V. Also, we observed that the nitrogen doping and defects in the underneath carbon surface amplify the CQ of heterostructure for a wider range of electrode potential. Therefore, the 1T′-MoS2/N doped CNT can be explored as an electrode for next-generation supercapacitors.

Journal ArticleDOI
TL;DR: In this article, a 441-pixel array of quantum capacitance detectors (QCDs) with readout frequencies between 700 and 850 MHz is presented. But their performance is limited to single-photon detection and counting at that frequency.
Abstract: Quantum capacitance detectors (QCDs) are photon shot noise-limited terahertz detectors based on a single Cooper-pair box superconducting qubit. The QCD has demonstrated photon shot noise-limited performance for 1.5 THz radiation under loading conditions between 10 − 20 and 10 − 18 W and single-photon detection and counting at that frequency. We report here fabrication and preliminary characterization of a 441 pixel array of QCDs with readout frequencies between 700 and 850 MHz.

Journal ArticleDOI
TL;DR: A two-dimensional rectangular carbon formed by four-, eight-and ten-membered carbon rings, named R10-graphene, was found by the particle swarm optimization method as mentioned in this paper.


Journal ArticleDOI
15 Aug 2021-Carbon
TL;DR: In this article, a carbon nanotube (CNT) based TFET with abrupt p-i-n tunneling junctions controlled by electrostatic doping is reported, achieving a minimum subthreshold swing (SSmin) of ∼41 mV/dec with nearly no temperature dependence.

Journal ArticleDOI
TL;DR: In this article, a gate-defined few-electron quantum dot in bilayer graphene is used to read out individual charge states in a gate defined few electron quantum dot, where an LC resonator with a resonance frequency close to 280 MHz is directly coupled to an Ohmic contact of the quantum dot device.
Abstract: We demonstrate dispersive readout of individual charge states in a gate-defined few-electron quantum dot in bilayer graphene. We employ a radio frequency reflectometry circuit, where an LC resonator with a resonance frequency close to 280 MHz is directly coupled to an Ohmic contact of the quantum dot device. The detection scheme based on changes in the quantum capacitance operates over a wide gate-voltage range and allows us to probe excited states down to the single-electron regime. Crucially, the presented sensing technique avoids the use of an additional, capacitively coupled quantum device such as a quantum point contact or single electron transistor, making dispersive sensing particularly interesting for gate-defined graphene quantum dots.

Journal ArticleDOI
Xiaojie Chen1, Wenxian Xu1, Jiaming Jin1, Peixian Wang1, Bin Song1, Pimo He1 
TL;DR: In this paper, the structural, electronic, and capacitance properties of B- or O-doped carbon nitride monolayers were systematically investigated using first-principles calculations.
Abstract: The structural, electronic, and capacitance properties of B- or O-doped carbon nitride monolayers were systematically investigated using first-principles calculations. Different single-atom substitutions (i.e., B or O dopant on a Cx or Ny substitution site) were considered for this work. The substitution site plays an important role in regulating the stability and electronic structure of carbon nitride monolayers. B or O doping could make carbon nitride monolayers produce large local density of states near Fermi level contributed mainly from the hybridization of the 2p states of C, N, and the doped atom (B or O), thus significantly improving conductivity, quantum capacitance, and surface charge density of the structures. The results show that the quantum capacitances of the B-doped carbon nitride monolayers are much greater than those of the B-doped graphene monolayers. Furthermore, B-doped C3N at the C1 site, B-doped tg-C3N4 at the N2 site, and O-doped tg-C3N4 at the N1 site are strongly recommended as the electrodes in symmetrical supercapacitors, while the other doped components could also be used as cathode or anode materials in asymmetrical supercapacitors. The findings of this study suggest that doped carbon nitride structures could be considered as promising electrode materials for supercapacitors.

Journal ArticleDOI
14 Sep 2021-Energies
TL;DR: In this article, the principles of capacitance and ion transport are described from a theoretical and practical point of view, and various applications of these concepts can be found in biological sensors and microsupercapacitors.
Abstract: Ion transport is a significant concept that underlies a variety of technologies including membrane technology, energy storages, optical, chemical, and biological sensors and ion-mobility exploration techniques. These applications are based on the concepts of capacitance and ion transport, so a prior understanding of capacitance and ion transport phenomena is crucial. In this review, the principles of capacitance and ion transport are described from a theoretical and practical point of view. The review covers the concepts of Helmholtz capacitance, diffuse layer capacitance and space charge capacitance, which is also referred to as quantum capacitance in low-dimensional materials. These concepts are attributed to applications in the electrochemical technologies such as energy storage and excitable ion sieving in membranes. This review also focuses on the characteristic role of channel heights (from micrometer to angstrom scales) in ion transport. Ion transport technologies can also be used in newer applications including biological sensors and multifunctional microsupercapacitors. This review improves our understanding of ion transport phenomena and demonstrates various applications that is applicable of the continued development in the technologies described.

Journal ArticleDOI
TL;DR: In this paper, a three-component vertically designed (TCVD) device composed of ferrocene adsorbed on monolayer graphene supported on lithographically designed gold subsurface on silicon wafer was introduced to detect double-stranded DNA and DNA hybridization.

Journal ArticleDOI
22 Oct 2021-Small
TL;DR: In this paper, the authors investigated the effect of ion intercalation behavior in 2D materials with different spacings (Ti3 C2 Tx, δ-MnO2, and reduced graphene oxide) on energy storage performance.
Abstract: The ion intercalation behavior in 2D materials is widely applied in energy storage, electrocatalysis, and desalination. However, the detailed effect of ions on the performance, combining the influence of interlayer force and the change of solvent shell, is far less well understood. Here the solvated alkali metal ions with different sizes are intercalated into the lattice of 2D materials with different spacings (Ti3 C2 Tx , δ-MnO2 , and reduced graphene oxide) to construct the intercalation model related with sub-nanometer confined ions and solvent molecules to further understand the intercalation capacitance. Based on electrochemical methods and density functional theory calculation, the ions lose the electrostatic shielding solvent shell or shorten the distance between the layers, resulting in a significant increase in capacitance. It is found that the intercalation capacitance arises from the diffusion of solvated ions and is controlled by quantum and electrochemical capacitance for desolvated ions. This effect of solvation structure on performance can be applied in a variety of electrochemical interface studies and provides a new research view for energy storage mechanisms.

Journal ArticleDOI
20 Mar 2021
TL;DR: In this paper, the density of states and quantum capacitance of pure and doped Nb2N and Nb4N3 single-layer and multi-layer bulk structures were investigated using density functional theory calculations.
Abstract: The density of states and quantum capacitance of pure and doped Nb2N and Nb4N3 single-layer and multi-layer bulk structures are investigated using density functional theory calculations. The calculated value of quantum capacitance is quite high for pristine Nb2N and decent for Nb4N3 structures. However for cobalt-doped unpolarized structures, significant increase in quantum capacitance at Fermi level is observed in the case of Nb4N3 as compared to minor increase in case of Nb2N. These results show that pristine and doped Nb2N and Nb4N3 can be preferred over graphene as the electrode material for supercapacitors. The spin and temperature dependences of quantum capacitance for these structures are also investigated.

Journal ArticleDOI
25 Feb 2021
TL;DR: In this paper, the quantum capacitance, stability, and electronic properties of single-walled carbon nanotubes decorated with B12 icosahedral boron clusters were investigated.
Abstract: We explore the quantum capacitance, stability, and electronic properties of single-walled carbon nanotubes decorated with B12 icosahedral boron clusters by first-principle calculation methods implemented in the SIESTA code. After the optimization of the built supercells, the B12 clusters formed bonds with the walls of the carbon nanotubes and demonstrated metallic properties in all cases. The network of carbon nanotubes with its large area and branched surface is able to increase the capacity of the electric double-layer capacity, but the low quantum capacity of each nanotube in this network limits its application in supercapacitors. We found that the addition of boron clusters to both the outer and inner walls increased the quantum capacitance of carbon nanotubes. The calculation of the transmission function near the Fermi energy showed an increase in the conductivity of supercells. It was also found that an increase in the concentration of boron clusters in the structure led to a decrease in the heat of formation that positively affects the stability of supercells. The calculation of the specific charge density showed that with an increase in the boron concentration, the considered material demonstrated the properties of an asymmetric electrode.

Journal ArticleDOI
TL;DR: In this article, the band structures and capacitive properties of eight borophene related sheets, in which seven have Dirac cone at their Fermi levels as graphene, were studied.

Journal ArticleDOI
TL;DR: In this paper, the supercapacitance properties of V10O14(OH)2 and its hybrid with reduced graphene oxide (rGO/V10O 14(OH)-2 have been synthesized by a simple hydrothermal process, and the capacitance property has been explored.


Journal ArticleDOI
TL;DR: In this paper, the electrochemical properties of different phases of two-dimensional (2D) phosphorus using Joint Density Functional Theory (JDFT) have been investigated, and the 2D counterpart of black, blue and green phosphorus are studied as promising candidates for being electrodes of supercapacitor.
Abstract: In this paper we investigate the electrochemical properties of different phases of two-dimensional (2D) phosphorus using Joint Density Functional Theory (JDFT). The 2D counterpart of black, blue and green phosphorus are studied here as promising candidates for being electrodes of supercapacitor. Band structure, quantum capacitance, charge density and energy density of black, blue and green 2D phosphorous are obtained here by utilizing JDFT. Using JDFT, we examine how the different phases of 2D phosphorous charge up against applied voltage and the results are compared with each other. Our results show that the area-normalized capacitances of these 2D phosphorous structures are higher than that of graphene. Also the 2D phosphorous structures have higher mass-normalized capacitance than graphene at the higher voltages.

Journal ArticleDOI
TL;DR: In this paper, the impact of the graphene electrodes on the miniaturization of organic devices has been assessed, with particular attention to the influence of the contact resistances as well as the parasitic overlap gate capacitance on the device bandwidth.

Journal ArticleDOI
14 Nov 2021-Vacuum
TL;DR: In this paper, the structural, electronic properties and quantum capacitance of Ti2CO2 monolayer with different oxygen vacancy concentration (OVC) were investigated, and the band unfolding technique was performed to obtain the effective band structure in the primitive cell.