Superior Supercapacitive Performance Research Articles

Reactant conversion-intercalation strategy toward interlayer-expanded MoS2 microflowers with superior supercapacitor performance.

In order to avoid the complicated control and fussy procedure associated with foreign species and templates in conventional synthesis strategies, a simple reactant conversion-intercalation strategy is developed to synthesize interlayer-expanded MoS2 (E-MoS2) by employing ammonium thiocyanate converted from a thiourea reactant as intercalator. In this strategy, the thiourea plays a bifunctionality role as reactant and intercalator precursor to ensure in situ embedding into the interlayers of MoS2 to expand the interlayer spacing. The optimal E-MoS2 obtained presents superior supercapacitor performance with a specific capacity of 246.8 F g-1 at 0.5 A g-1 in 1 M Na2SO4 electrolyte in a three-electrode system, outperforming pristine MoS2 prepared by a conventional hydrothermal method (42.5 F g-1 at 0.5 A g-1). Furthermore, a symmetric supercapacitor based on an E-MoS2 electrode delivers a high specific capacity of 261.3 F g-1 and energy density of 13.3 W h kg-1 at 0.5 A g-1, and excellent cycling life with 81.7% capacity retention after 3000 cycles at 2 A g-1. Density functional theory calculations reveal that the NH4+ and SCN- can be effectively adsorbed on the surface to be inserted into the interlayers during the growth of MoS2, resulting in an expanded interlayer spacing of 9.4 Å, and the favorable electrochemical performance stems from the large Na+ adsorption capacitance and low diffusion barrier of the E-MoS2. This work offers a novel intercalation strategy that may be generally applicable to other layer-structured materials, shedding some light on the development of high-performance electrode materials via interface engineering for energy applications.

Applications of Graphene: Supercapacitors and Gas Sensors

This paper provides a comprehensive overview of the unique physical and chemical properties and structures of graphene. It delves into the exceptional electronic and mechanical properties of graphene that make it a promising material for various applications. The paper particularly focuses on the use of graphene in supercapacitors and sensing techniques, specifically gas sensors. In the realm of energy storage, the paper elucidates how the high surface area and excellent conductivity of graphene contribute to the superior performance of graphene-based supercapacitors. It further explores the mechanism of charge storage in these devices, highlighting the role of pore sizes in graphene sheets on capacitance. In the context of gas sensors, the paper discusses how the sensitivity of graphene's electronic properties to its surrounding environment enables its use in detecting different gases. The paper concludes with a discussion of the challenges and future prospects in harnessing the potential of graphene in these applications.

Synthesis of Co9S8nanoflakes by a one-step solvent-free solid-state method for multiple electrocatalytic reactions

The one-step solvent-free solid-state method is adopted to synthesize Co8S9with a nanoflake structure and improved electronic conductivity. It yields superior electrochemical performance in acid HER, alkaline OER, and supercapacitors.

Synergistic coupling of NiVAl-layered double hydroxide with few-layered Ti3C2Tx–MXene nanosheets for superior asymmetric supercapacitor performance

In this study, we fabricate 3D Ti3C2Tx–MXene/NiVAl-LDH nanocomposites with enhanced structural stability, conductivity, and redox kinetics, preventing nanosheet aggregation and promoting full active site exposure.

Scalable multifunctional ultralight mesoporous micro yarn carbon for excellent durable supercapacitor and tremendous oils sorbent

Carbon-based materials have been widely employed for multipurpose applications such as superior energy storage and efficient oil–water separation. However, their commercial utilization has hindered by processing and engineering challenges. Herein, multifunctional ultralight mesoporous micro-yarn (MUMMY) carbon aerogel was derived from bio-waste. The fascinating structure, mesoporosity, high surface area and heteroatoms presence in the MUMMY carbon aerogel favors superior performance in supercapacitors and oil–water remediation. The binder-free and freestanding MUMMY carbon aerogel electrode exhibited an outstanding life span of 0.32 million cycles with 99 % capacitance retention at an ultrahigh scan rate of 10000 mV s−1 at 80 °C in an aqueous electrolyte. Further, the electric double layer capacitive behavior up to ultra-high scan rate 50000 mV s−1 was illustrated approving the high power device. In addition, a greater energy density of 64 Wh kg−1 at 80 °C was realized in an ionic liquid with a power density of 1500 W kg−1. Moreover, the MUMMY carbon aerogel determined a superior oil adsorption capacity of 215–348 times its weight. The adsorption capacity was conserved up to 87 %, 92 % and 99.8 % by combustion, squeezing, and distillation methods respectively after repeated nine cycles attributed to tremendous thermal stability and robustness. This MUMMY carbon aerogel has a great potential to use commercially as robust electrode materials for supercapacitors as well as super adsorbents for oil.

Design strategy for high-performance bifunctional electrode materials with heterogeneous structures formed by hydrothermal sulfur etching

The synthesis of efficient, stable, and green multifunctional electrode materials is a long-standing challenge for modern society in the field of energy storage and conversion. To this end, we successfully synthesized five bimetallic precursor materials with excellent performance by hydrothermal reaction with the assistance of a high concentration of polyvinylpyrrolidone (PVP), and then, sulfide etched the lamellar precursor materials among them to obtain the one-dimensional heterostructured samples. Benefiting from the synergistic effect of the bimetal and the continuous electron/ion transport structure, the samples displayed excellent bifunctional activity in supercapacitor and oxygen evolution reaction (OER). Regarding supercapacitors, the exceptional performance of 2817.2 F g−1 at 1 A g−1 was demonstrated, while the asymmetric supercapacitors made showed an extraordinary energy density of 150.2 Wh kg−1 at a power density of 618.5 W kg−1 and outstanding cycling performance (94.74% capacity retention after 20,000 cycles at 10 A g−1). Simultaneously, a wearable flexible electrode that can be wrapped around a finger was coated on a carbon cloth and was found to light up a 0.5-m-long strip of light. Moreover, it exhibited an ultralow oxygen reduction overpotential of 249 mV at 10 mA cm−2. Hence, our work provides a facile strategy to modulate the synthesis of heterogeneous structured sulfides with a continuous electron/ion transport pathway, which possesses excellent oxygen reduction electrocatalytic performance while meeting superior supercapacitor performance. Such work provides an effective approach for the construction of multifunctional electrochemical energy materials.

A highly stable solid-state supercapacitor device based on robust layer-by-layer electrodeposited poly-(3, 4-ethylenedioxythiophene)-reduced graphene oxide–molybdenum disulfide nanocomposite electrode

A ternary nanocomposite film of PEDOT-rGO-MoS2 for a symmetrical solid-state supercapacitor device has been fabricated via in-situ interconversions by employing efficient electrochemical approach. The higher porosity offered by popcorn like microstructures of PEDOT has enabled better stacking within PEDOT-rGO-MoS2 composite resulting in superior supercapacitive performance. The obtained electrode exhibits good volumetric capacitance (887.6 F cm−3) and high volumetric energy density (123 mWh cm−3) with high-power density (2930 mW cm−3). The efficiency in the supercapacitor performance originates from the synergy of the trio forming a well-integrated optimized energy storage system. Assembly of composite films into a solid-state symmetrical device with PVA-KCl gel-electrolyte has resulted in excellent cyclic stability, good capacitive retention of 98.3 % and coulombic efficiency of 100.2 % over 10,000 cycles. The obtained symmetrical device offered high areal energy density (1.1 μWh cm−2) has been successfully evaluated for its practical utility in the configuration of four devices connected in series with an output of 25 min to illuminate green LED. The findings pave a promising way for the development of energy efficient microelectronics by using the present device structure in future energy storage applications.

Superbases-templated carbons doped with electrochemically active oxygen as advanced supercapacitor electrodes

Templating techniques have been widely adopted for the synthesis of porous carbons, such as oxygen-doped porous carbon nanosheets (O-PCNs), but the effect of the surface characteristics of templates on the surface functionality and performance of a derived carbon has not been well studied. Herein, a series of laboratory-made superbases of K/Mg(OH)2 with different K/Mg ratios were employed as template to fabricate nanocarbon materials. The aim is to find out how the strength of template basicity could influence the surface functionalities and the supercapacitor performances of the derived O-PCNs. The resulting materials are rich in conjugated hydroxyl and carbonyl groups that are electrochemically active owing to the protection of the conjugated hydroxyl group by KOH and the dehydrogenation step catalyzed by magnesium oxide. Systematic investigations revealed that with the increase of basic strength, the content of the derived electrochemically active oxygen species in the forms of conjugated carbonyl (CO) and hydroxyl (COH) first increases from 8.4 atom% to 11.4 atom% then decreases to 9.25 atom%. Moreover, the microporosity of the O-PCNs stepwise increases with the rise of KOH loading, ascribable to the effect of KOH etching on the carbon skeleton. The O-PCN-20 templated by 20 % K/Mg(OH)2 is rich in porosity, large in surface area (930 m2/g) and high in active oxygen content (11.4 atom%). With high active surface area and extra Faradaic capacitance, O-PCN-20 exhibited superior supercapacitor performances including large specific capacitance of 375 F/g@1.0 A/g, high rate capability of 81.1 % (from 1.0 A/g to 20 A/g), energy density of 25.7 Wh/kg@900 W/kg and excellent cycling stability with near 100 % capacitance retentions after 10 000 cycles and more than 86.2 % capacitance retention over 20 000 cycles at large current density of 10 A/g, indicating O-PCN-20 has potential to be used as electrode material for energy storage devices.

Synchronized integration of iron/cobalt dual-metal in nitrogen-doped carbon hollow spheres for enriched supercapacitive and oxygen reduction reaction performances

The development of nonprecious metals in conjunction with heteroatoms doped carbon material as an effective electrocatalyst is critical for enhanced energy storage and conversion (ESC) properties. Nonprecious metals co-doping in a nitrogen-doped carbon matrix are considered potential candidates for this purpose, but their stability and activity remain insufficient to meet the demands of practical applications. In this work, the iron‑cobalt particles integrated nitrogen-doped carbon hollow spheres (FeCoNCHSs) as an efficient electrocatalyst for electrochemical supercapacitors and oxygen reduction reaction (ORR) towards alkaline fuel cells are reported. FeCoNCHSs were prepared by Fe+3/Co+2-mediated in-situ polymerization of dopamine on modified polystyrene and later pyrolysis under N2 atmosphere at 700 °C for 3 h. The as-synthesized materials were characterized and analyzed by various electrochemical and electroanalytical techniques. Importantly, the FeCoNCHSs show remarkable supercapacitive properties with the maximum capacitance value of 287.3 F g−1 at a scan rate of 2 m Vs−1. Moreover, the FeCoNCHSs exhibited an inspiring positive half-wave potential of ~0.83 V during ORR. Density functional theory (DFT) calculations further explain that the N-coordinated metal (Fe/Co) species are the main active sites to effectively improve the charge transfer and electrochemical activities. The efficient response of the electrode material can be attributed to their meso−/macroporous intact hollow spherical morphology, large porous surface area, and high N(pyridinic/pyrrolic/graphitic)-contents. Significantly, the synergistic effects of N-doping along with N-coordinated dual-metal (Fe/Co) species are also responsible for the superior supercapacitive and ORR performances.

A flower-like Co/Ni bimetallic metal-organic framework based electrode material with superior performance in supercapacitors

In this paper, a Co/Ni bimetallic metal-organic framework (ZIF-67 @Ni-salicylate) is successfully synthesized through a two-step method. By increasing the reaction time to 48 h, the effect of the hydrothermal treatment on structure changes and electrochemical properties of ZIF-67 @Ni-salicylate is demonstrated. Electrochemical measurements show that the ZIF-67 @Ni-salicylate hydrothermal-treated with 48 h possesses a high specific capacitance of 1493 F g−1 at 1 A g−1 and simultaneously excellent cycle stability. Impressively, the capacitance retention rate can reach 86.8% even under a high current density of 40 A g−1, which is much better than that in previous reports. Furthermore, an asymmetric supercapacitor (ASC) is assembled and two ASCs connected in series can light up a red LED for more than 30 min as demonstrated by the current-time curve. Our work will be useful for the preparation of high-performance supercapacitor electrode materials.

Facile fabrication of hexagonal Ni(OH)2 nanoparticles anchored g-C3N4 layered nanocomposite electrode material for energy storage applications

Nickel hydroxide (NiOH)2 has been recognized as an efficient electrode material for energy storage applications because of its attractive characteristics and high theoretical capacitance. However, the reduced cyclic stability of (NiOH)2 prevents it from being used in practical applications. To overcome this problem, we present a combination of nanocomposite (Ni(OH)2 with g-C3N4) prepared in an easy way of synthesis method. In the present study, the g-C3N4 was found to have great chemical stability and to enable a perpendicular charge-transportation in the charge-discharge processing that allows for easier electron transport. The structural and morphological properties confirm the formation of Ni(OH)2/g-C3N4 nanocomposite, in addition, Rietveld refinement was also performed on the XRD patterns. The nanocomposite Ni(OH)2/g-C3N4 shows high specific capacitances (463 F/g), good rate capability (94 %), and cycle stabilities as compared to Ni(OH)2. These attractive findings of the nanocomposite Ni(OH)2/g-C3N4 reveal that this could find a capable electrode material for superior performance supercapacitors.

Hydroxyl-Functionalized Covalent Organic Frameworks as High-Performance Supercapacitors.

Covalent organic frameworks (COFs) have attracted significant interest because of their heteroatom-containing architectures, high porous networks, large surface areas, and capacity to include redox-active units, which can provide good electrochemical efficiency in energy applications. In this research, we synthesized two novel hydroxy-functionalized COFs—TAPT-2,3-NA(OH)2, TAPT-2,6-NA(OH)2 COFs—through Schiff-base [3 + 2] polycondensations of 1,3,5-tris-(4-aminophenyl)triazine (TAPT-3NH2) with 2,3-dihydroxynaphthalene-1,4-dicarbaldehyde (2,3-NADC) and 2,6-dihydroxynaphthalene-1,5-dicarbaldehyde (2,6-NADC), respectively. The resultant hydroxy-functionalized COFs featured high BET-specific surface areas up to 1089 m2 g–1, excellent crystallinity, and superior thermal stability up to 60.44% char yield. When used as supercapacitor electrodes, the hydroxy-functionalized COFs exhibited electrochemical redox activity due to the presence of redox-active 2,3-dihydroxynaphthalene and 2,6-dihydroxynaphthalene in their COF skeletons. The hydroxy-functionalized COFs showed specific capacitance of 271 F g−1 at a current density of 0.5 A g−1 with excellent stability after 2000 cycles of 86.5% capacitance retention. Well-known pore features and high surface areas of such COFs, together with their superior supercapacitor performance, make them suitable electrode materials for use in practical applications.

Fabrication of ionic liquid based D-Ti3C2/MoO3 hybrid electrode system for efficient energy storage applications

Recently, Ti3C2 MXene with facile physicochemical properties is a fascinating candidate material for energy storage applications. Herein, solvothermal method was employed to fabricate the novel d-Ti3C2/MoO3@IL by incorporation of imidazolium based ionic liquid to MoO3 nanorods (MoO3@IL); which was intimately anchored onto the surface of d-Ti3C2 MXene. Additionally, this d-Ti3C2 MXene acts as a promising conductive substrate not only to maintain structural stability, but maintains the electrophilicity of electroactive centers as well. Similarly, MoO3@IL improves electrical conductivity due to ionic liquid, and improves reaction kinetics by supplying effective channel for charge transport system with improved pseudocapacitance. Owing to the intimate interaction, the d-Ti3C2/MoO3@IL electrode exhibited exceptional electrochemical performances with specific capacitance of 1680 F g–1 at 1 A g–1, outstanding rate performance, and excellent cyclic stability. Moreover, the symmetric supercapacitor (SSC) device from d-Ti3C2/MoO3@IL demonstrated excellent energy densities of 41 Wh kg–1 and 9.6 Wh kg–1 at power densities of 990 W kg–1 and 3456 W kg–1 respectively. We have employed this novel hybrid electrode material for SSC device application for the first time. The results proved that d-Ti3C2/MoO3@IL is an advanced electrode material, and this scheme provides the valuable method to fabricate MXene and ionic liquid based electrodes with superior electrochemical performance for supercapacitors.

3D printed solid-state composite electrodes and electrolytes for high-energy-density flexible microsupercapacitors

Although flexible microsupercapacitors (MSCs) have attracted significant attention for wearable electronics, their energy storage performance and energy density need to be improved for widespread applications. In this study, flexible MSCs displaying enhanced areal capacitance and energy density with high active material loading were fabricated; to realize this, three-dimensional (3D) printing was utilized to deposit an electrochemically stable ionic liquid (IL)-based solid-state ionogel electrolyte and a 3D interconnected large mesoporous carbon (3DMC)-based composite electrode. The ionogel consisting of 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide ([EMI][TFSI]) and polyvinylidene fluoride-co-hexafluoropropylene (P(VDF-HFP)) was employed to increase an operating potential range of the MSCs. The 3DMC composite electrode, which consists of 3DMC, single-walled carbon nanotubes (SWCNTs), P(VDF-HFP), and [EMI][TFSI], was successfully printed to facilitate ion transport of the ionogel and to customize 3D structures. 3D printed MSCs exhibited outstanding supercapacitive energy storage performance, including very high specific capacitance of 110.4 mF cm−2, energy density of 60.6 μWh cm−2, power density of 0.89 mW cm−2, and outstanding mechanical durability of 97% capacitance retention after 1000 successive 90° bending/releasing cycles. These results provide a promising strategy for fabricating flexible MSCs based on composite electrolytes and electrodes for superior supercapacitive energy storage performance.

N-doped hollow carbon nanoplates with mesoporous thin shells towards high-performance supercapacitors

Integrating hollow structures and ordered mesopores in carbon materials is critical for electrochemical devices to facilitate fast ion-transport pathways and large ion-accessible surface areas. In this work, a self-templating method is used to prepare hollow ordered mesoporous carbon (HOMC) materials by self-assembling resol-F127 composite micelles on the surface of two-dimensional (2D) metal-organic-framework (MOF) nanoplates, followed by polymerization and carbonization. During the hydrothermal reaction, MOF nanoplates act as a 2D template to assemble resol-F127 composite micelles, leading to hollow ordered mesostructured polymer (HOMP). At the same time, N-containing species are released from the dissolved MOF nanoplates, resulting in N-doped HOMC after carbonization. Benefiting from the structural advantages (e.g., high surface area, hierarchical porous architecture composed of hollow interiors and thin mesoporous shells) and the high amount of N-doping, the as-prepared HOMC exhibits superior electrochemical performance for supercapacitors, demonstrated by a high specific capacitance of 271 F g−1 at a current density of 0.5 A g−1, excellent rate capability, and high capacitance retention of 98.1% after 20,000 cycles. The strategy can provide a new avenue for designing and constructing hollow carbon materials for various applications in electrochemical energy storage devices.

Enhanced Electrodes for Supercapacitor Applications Prepared by Hydrothermal-Assisted Nano Sheet-Shaped MgCo2O4@ZnS

In this paper, we report on nanodisc-shaped MgCo2O4 wrapped with ZnS, achieved using the sol–gel-assisted hydrothermal method. This enhances the electrochemical performance, with the electrode delivering superior supercapacitive performance compared to MgCo2O4. Moreover, the nanodisc provides more active sites and allows smooth charge transfer during faradaic reactions. The nanodisc-shaped MgCo2O4 with ZnS delivers a capacitance of approximately 910 F/g at 1 A/g. The fabricated asymmetric capacitor is composed of MgCo2O4@ZnS and activated carbon (AC). The nanodisc-shaped MgCo2O4@ZnS provides more active sites and allows the smooth transport of electrons during long-term cycling. In addition, the electrode side reactions and electrolyte decomposition are significantly reduced due to the ZnS coating on the surface of the MgCo2O4, allowing this asymmetric capacitor to deliver an energy density of 43 Wh·kg−1 at 1454 W·kg−1. The performance of the asymmetric capacitor exhibits enhanced supercapacitive performance and opens a new way to investigate asymmetric supercapacitor devices.

High-temperature deoxygenation-created highly porous graphitic carbon nanosheets for ultrahigh-rate supercapacitive energy storage

Developing carbon-based supercapacitors with high rate capability is of great importance to meet the emerging demands for devices that requires high energy density as well as high power density. However, it is hard to fabricate a nanocarbon with high electro-active surface area meanwhile maintaining superior conductivity to ensure the high rate capability since excellent conductivity is usually realized by high temperature graphitization, which would lead to the structural collapse and sintering resulting in low surface area. Herein, we reported a highly porous graphitic carbon nanosheet with an unprecedented rate capability of 98% of its initial capacitance from 0.5 to 50 A/g for ultrahigh-rate supercapacitive energy storage. These hierarchical mesoporous carbon nanosheets (HMCN) were fabricated by a template induced catalytic graphitization approach, in which sheet-like Mg(OH)2 was employed as catalytic template in situ catalytically polymerizing of catechol and formaldehyde and catalytically graphitizing of the formed carbon skeleton. Upon the co-effect of template (avoiding the sintering) and the deoxygenation (creating the pores) during the high temperature graphitization process, the obtained HMCN material possesses nanosheet morphology with highly porous graphitic microstructure rich in mesoporosity, large in surface area (2316 m2/g), large in pore volume (3.58 cm3/g) and excellent in conductivity (109.8 S/cm). In 1.0 M TEABF4/AN, HMCN exhibits superior supercapacitive performance including large energy density of 52.2 Wh/kg at high power density of 118 kW/kg, long-cycling stability and excellent rate capability, making HMCN a promising electrode material for supercapacitor devices.

Controlling Morphologies and Structures of PANI@Carbon with Superior Rate Performance for Supercapacitors

Controlling Morphologies and Structures of PANI@Carbon with Superior Rate Performance for Supercapacitors

Novel cobalt doped hafnium oxide/reduced graphene oxide nanosphere composite materials exhibit superior supercapacitor performance and long cyclic stability

This paper describes a unique synthesized nanosphere using6% Cobalt doped hafnium oxide/reduced graphene oxide nanocomposite (6% Co doped HfO2/rGO) for its feasibility as electrode materialin supercapacitor applications utilizing a simple one-step hydrothermal technique. The structural behavior, binding energies, and quality of the synthesized 6% Co doped HfO2/rGO nanocomposite were exhibited by XRD, FTIR, XPS, and Raman analyses. The 6% Co doped HfO2 nanospheres in the 6% Co doped HfO2/rGO nanocomposite were coated across the exterior of the rGO sheet, according to HR-SEM and HR-TEM imaging. The 6% Co doped HfO2/rGO nanocomposite revealed enhanced specific capacitance (1015 F/g at 1A/g), which was compared to 6% Co doped HfO2 (396 F/g at 1A/g) electrode in the redox active 1 M H2SO4 electrolyte (0.0 to 0.7 V). After 4000 continuous cycles, the electrode material maintained 97 % of its capability and exceptional long-term cyclic stability. The superior super-capacitive performance established the 6% Co doped HfO2/rGO nanocomposite as a promising electrode for supercapacitor applications.

Vaporized Hydrothermal Functionalization of Carbon Fiber and Its Superior Supercapacitor Performance

Vaporized Hydrothermal Functionalization of Carbon Fiber and Its Superior Supercapacitor Performance