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Simplifying the design of high-performance electrodes via efficient catalyst design is critical for alkaline water electrolysis and supercapacitor applications. Towards that end, we have developed the environmentally benign synthesis of ultrathin nanosheets of NiFe-layered double hydroxides (LDH) with inbuilt oxygen vacancies (V O) in this report. These NiFe-layered double hydroxide (GNiFe-LDH- V O) materials require low overpotentials for the oxygen evolution reaction (OER, η 50 = 200 and η 100 = 220 mV) with a small Tafel slope of 52.21 mV dec−1. The ex-situ characterizations and theoretical calculations suggest that oxygen vacancies configure to a more active state, resulting in the low binding energy of oxo intermediates, and thus much lower overpotential. Besides, it could operate stably for 100 h at current densities of 100 mA cm−2 for OER. It is significant that oxygen vacancies in GNiFe-LDH- V O aid in lowering the main obstacle of multistep OER, which will provide recommendations for the development of high-efficiency catalysts through in situ activation. In addition, GNiFe-LDH- V O exhibits a high areal capacitance of 1.6024 F cm−2 at a current density of 1 mA cm−2, with a capacitance retention ratio of 96.1% after 5000 galvanostatic charge-discharge (GCD) cycles when they are used as supercapacitor electrodes. [Display omitted] • Ultrathin NiFe-LDH nanosheets with oxygen vacancies via in situ green, dissolution-precipitation process. • The introduction of oxygen vacancies generates appropriate electronic conductivity and catalytic activity. • The outstanding performance, was demonstrated through both experimental and theoretical calculations. [ABSTRACT FROM AUTHOR]

In this study, bismuth telluride–based hybrids consisting of nanosheets were successfully prepared by disproportionation induced by microwave irradiation and applied on supercapacitor electrodes. Various analytical techniques were adopted to analyze the structure and composition of Bi 2 Te 3 /Bi 2 TeO 5. The unique disproportionation (Te0→Te2++Te4+) results in an interlocking nanosheet, in which the lamellar interspersed structure on the lamella can be visualized through high-magnification scanning electron microscopy. The large layer spacing with the interspersed structure provides more storage sites for electrolyte ion interactions and allows for better stabilization of the electrode structure. Result of electrochemical studies indicates that Bi 2 Te 3 /Bi 2 TeO 5 enables a capacity of 860 F g−1 (1 A g−1) and maintains 74.5% of the initial capacity through 2000 charge/discharge cycles. The Bi 2 Te 3 /Bi 2 TeO 5 anode is integrated into an ultracapacitor to attain a remarkable energy density of 89 Wh kg−1 in 6 M KOH. [Display omitted] [ABSTRACT FROM AUTHOR]

The primary goal for the development of energy-storage devices is to find affordable ways to increase their efficiency, activity, and stability. In this regard, transition metal oxide mainly MoO 3 enhances the electrochemical properties of the material due to various oxidation states. On the other hand, carbonaceous materials, such as reduced graphene oxide, provide a large surface area that increases the conductivity of nanomaterials. In this work, we have synthesized pristine and codoped MoO 3 material using the co-precipitation route. While the r-GO based composite was prepared by a simple sonication approach. The prepared composite material showed a higher specific capacitance of 987 F/g than the pristine and codoped material. The BAMO@r-GO discharges after 346 s which was the higher time of discharge than that of pure and codoped material. Moreover, the obtained results from EIS measurement confirmed that the composite material showed less resistance than all other synthesized materials. The synergistic effect between the r-GO and BAMO materials is the reason for the higher supercapacitor performances of BAMO@r-GO. Based on these results, the fabricated BAMO@r-GO material can be effectively utilized as an electrode material in electrochemically powered energy storage devices. [ABSTRACT FROM AUTHOR]

As the precursor of 2D i -MXene, i -MAX phase appeals lots of exertions on the improvement of its chemical diversity, among which alloying is an effective strategy. Herein, we report on the synthesis of the M-alloyed i -MAX phase (Mo 0.75 M 0.25) 4/3 Er 2/3 GaC (M = Ti, V, Nb, Ta, W). Structure analysis identifies all of them as Cmcm orthorhombic. The corresponding M-alloyed i -MXene, (Mo 0.75 M 0.25) 1.33 CT z (M = Ti, V, Nb, Ta, W), was synthesized by HF etching and shows potential as an electrode for supercapacitors due to its improved charge storage performance and cyclic stability. A volumetric capacitance of 431.7 F g−1 was delivered at the scan rate of 2 mV s−1 for (Mo 0 · 75 V 0.25) 1.33 CT z , and a 94.8% capacitance was retained after 10,000 charge/discharge cycles for (Mo 0 · 75 W 0.25) 1.33 CT z. Modelling was performed to better understand the mechanism improving the electrochemical capacitance and to clarify the i-MXene alloying process. The alloying strategy shows a novel and simple way to control i-MXene's surface termination, which will make it facilitate to use in applications like high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

In this study, an electrospinning method was used to produce highly conductive freestanding carbon nanofibers (CNFs). The freestanding CNFs are compatible with hierarchical growth techniques, such as hydrothermal processes, for the nanostructure engineering of supercapacitor electrodes with enhanced electrochemically active sites. Therefore, the flower-like FeMoO 4 @CNF nanosheets were investigated to improve the electrochemical performance using aqueous and neutral electrolytes (Na 2 SO 4 and K 2 SO 4). The optimized FeMoO 4 @CNF electrode exhibits areal capacitances of 252 and 220 mF·cm−2 at a high current density of 2.5 mA·cm−2 with Na 2 SO 4 and K 2 SO 4 electrolytes, respectively. The wide potential window (1.6 V) of the symmetric supercapacitor delivered maximum energy densities of 22.4 and 19.6 μWh·cm−2 at a power density of 2 mW·cm−2 for Na 2 SO 4 and K 2 SO 4 electrolytes, respectively. [ABSTRACT FROM AUTHOR]

To improve the electrochemical performance and structural durability of supercapacitors, herein, well-ordered, porous Ni–Zn–Co ternary oxide nanostructures were synthesized by doping Ni to Zn–Co oxide using ultrasonic electrodeposition. Our investigations revealed that Ni–Zn–Co ternary oxide exhibited superior capacity and rate performance when compared to Zn–Co oxide. In particular, the incorporation of 1 mol/L of Ni markedly improved the electrochemical capabilities of the cathode materials. Remarkably, under the influence of ultrasonic power at 500 W, Ni–Zn–Co oxide exhibited a superior mass loading of 6.2 mg/cm2, coupled with exceptional electron transfer efficiency. The growth mechanism and valence composition of Ni–Zn–Co oxides were studied by SEM and XPS analysis. Moreover, electrodes fabricated from Ni–Zn–Co oxide, synthesized via ultrasonic electrodeposition, demonstrated remarkable area capacitance and rate capabilities, achieving an impressive 1.779 F/cm2 at a current density of 3 mA/cm2. Additionally, the supercapacitor incorporating the Ni–Zn–Co oxide electrode exhibited exceptional long-term stability, maintaining a capacity retention rate of 125.2 % over 24,000 cycles in a mild alkaline electrolyte. This study not only contributes to advancing high-performance cathode materials but also offers valuable perspectives on novel techniques for their fabrication. [ABSTRACT FROM AUTHOR]

Nanostructured material like FeSe 2 has been synthesized through a simple and cost-effective hydrothermal method. The effect of cationic, non-ionic, and anionic surfactants has been studied on the structural, morphological, and electrochemical properties of FeSe 2 electrode material. The FeSe 2 electrode material prepared with the assistance of CTAB surfactant displayed a superior specific capacitance value of 401 F g −1 at a scan rate of 10 mV s −1 and 337 F g −1 at a current density of 3.3 A g −1, respectively. The maximum energy density of the symmetric supercapacitor cell fabricated with the same material is evaluated to be 47 Wh kg−1 at a power density of 1667 W kg−1. The addition of the surfactant cetyltrimethylammonium bromide (CTAB) during the synthesis process is found to have a significant impact on the charge storage capability of the material, which is attributed to an increase in active surface area, porosity, reduced crystallite size, and reduced bulk resistance, etc. The real-time use of CTAB-based FeSe 2 symmetric cells has been verified via illuminating different voltage light-emitting diodes. Further, the electronic properties and the quantum capacitance of FeSe 2 material synthesized without the assistance of any surfactant have been analyzed theoretically using first-principles density functional theory calculations. Acquired results unveil the potential growth of FeSe 2 electrode material in energy storage applications. [ABSTRACT FROM AUTHOR]

In this study, in-situ cerium-assembled tungsten oxide carbon nanofibers were successfully prepared via simple electrospinning and calcination technology and were used as flexible electrodes without conductive agent and adhesive. It was confirmed that the introduction of Ce has better maintained the continuous morphology of one-dimensional fibers to provide a continuous uninterrupted reaction position by the SEM TEM and XPS results. The addition of cerium improved the wettability of the material, which was propitious to the penetration of the electrolyte, made the electrolyte more fully contact with the active site, and enhanced the interface transmission effectiveness by the liquid contact angle test. Otherwise, the XRD and XPS results exhibited that the addition of cerium has caused the lattice expansion of the tungsten oxide, which generated the self-adjustable strain relaxation ability of electrode material in the process of continuous constant voltage charge and discharge. It proved that the introduction of cerium has promoted electron transfer, which improved the electrochemical performance of electrode material. In this paper, compared with WO 3 -CNFs without Ce, the Ce/WO 3 -CNFs have wide lattice spacing and hydrophilicity, fully contact with the electrolyte in the electrochemical reaction, and provide high electron transfer ability. The Ce/WO 3 -CNFs shows the maximum specific capacitance (407 F g−1) and excellent cycling stability (10,000 cycles at 5 A g−1 with a retention rate of 80 %). Otherwise, the flexible asymmetric supercapacitor device was prepared using the Ce/WO 3 -CNFs as cathode, and the CNFs as the anode, which exhibited the maximum energy density was 35.75 Wh kg−1 and a power density was 362.54 W kg−1 at 0.5A g−1. The results show that rare earth doping is an effective way and that the Ce/WO 3 -CNFs are promising electrode materials for supercapacitors. For the first time, in-situ cerium-assembled tungsten oxide carbon nanofibers were successfully prepared via simple electrospinning and calcination technology, which could directly serve as a flexible electrode without conductive agent and adhesive. And then, the flexible solid-state asymmetric supercapacitor was prepared using the Ce/WO 3 -CNFs as the cathode, the CNFs as the anode, and a PVA/KOH gel as electrolytes. [Display omitted] • The Ce/WO 3 -CNFs is used as binder-free electrode for supercapacitor. • Cerium improves the electrochemical performance of WO 3. • The improvement of electrode material wettability promotes the transportation of ions and electron between electrode and electrolyte. [ABSTRACT FROM AUTHOR]

Rational design and structural regulation of nanomaterials play a vital role in advancing clean energy and energy storage technologies. Metal-organic frameworks (MOFs) are highly regarded as ideal bi-functional electrocatalytic materials for overall water splitting and supercapacitors applications. However, the utilization of MOF materials in practical applications still presents significant challenges due to their inherent limitations in electrical conductivity and morphology control. In this study, we successfully synthesized FeCo-MOF material and effectively regulated its morphology and electronic structure by varying the amount of RuCl 3. and its active surface area was increased. The results show that the addition of Ru can not only introduce new metal active sites, but also shorten the path of ion diffusion. Furthermore, it can establish electronic coupling with the Fe and Co active sites interface, thereby tuning their electronic structures. The optimized 0.04 Ru/FeCo-MOF catalyst displayed remarkably low overpotential and high activity in both oxygen evolution reaction (OER) (η 50 = 309 mV) and hydrogen evolution reaction (HER) (η 10 = 180 mV). In a two-electrode system, the 0.04 Ru/FeCo-MOF||0.04 Ru/FeCo-MOF drived 10 mA cm−2 current density only need low voltage of 1.498 V. Moreover, this material also exhibits a high specific capacitance of 8600 mF cm−2 and excellent cycle stability in supercapacitor applications (88.9%). This synthesis strategy encompassing the regulation of both morphology and electronic structure presents a distinctive perspective for MOF design. Ru/FeCo-MOF were successfully synthesized through solvothermal method with ion-exchange strategy show efficient overall water splitting and excellent supercapacitor performance. [Display omitted] • Ru/FeCo-MOF was fabricated through simple solvothermal method with ion-exchange strategy. • Rational doping amount of Ru can modulate the morphological and electronic structure of Ru/FeCo-MOF. • The fabricated Ru/FeCo-MOF present efficient overall water splitting and supercapacitor performance. [ABSTRACT FROM AUTHOR]

Electrode materials with high electrochemical activity and outstanding stability is of great significance to improve the performance of supercapacitors. A composite material comprised of core-shell FeCo 2 O 4 @FeCo 2 S 4 nanospheres and MXene nanosheets was synthesized through solvothermal combined with self-assembly. The FeCo 2 O 4 @FeCo 2 S 4 -MXene hybrids as electrode materials exhibit a high specific capacitance of 1090.6 F g−1 at 1 A g−1. All-solid-state supercapacitor using FeCo 2 O 4 @FeCo 2 S 4 -MXene as the positive electrode possesses a high energy density of 49.8 Wh kg−1 at 800 W kg−1and great cycle life with 87.85 % retention over 20,000 cycles at 1 A g−1. The synergistic effect of FeCo 2 O 4 @FeCo 2 S 4 and MXene is the main reason for the exceptional electrochemical performance. FeCo 2 O 4 @FeCo 2 S 4 anchored to MXene prevents the restacking of MXene, while MXene provides a conductive network for accelerating carrier transfer and a skeleton for preventing FeCo 2 O 4 @FeCo 2 S 4 from collapsing during long-term cycling. In view of the above excellent performance, this study provides a feasible idea for future research on high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Metal phosphates are an emerging class of materials with large porosity that endows them with high specific capacity and ionic conductivity. However, the binder and carbon additive are required to fabricate the electrodes which adds extra expenditure to the supercapacitor's overall fabrication cost. The binder-free electrode fabrication provides a hope to eliminate the need for binders and hence the carbon additive for supercapacitor applications. In this work, a binder-free zinc phosphate hydrate (ZPOH) based electrode is fabricated using a cost-effective hydrothermal method. Two additional electrodes were also fabricated – one without carbon additive (ZPOWCB) and another with the addition of carbon additive (ZPOCB) using the conventional slurry preparation method. ZPOH electrode showed remarkable enhancement in the specific capacity compared to the other two electrodes as it achieved a specific capacity of 433 C/g at a current density of 2 A/g. Moreover, ZPOH also showed negligible charge transfer resistance (R ct), depicting good electrolyte ions interaction with the active material. Hence, the easy and simple binder-free hydrothermal approach is more suitable for preparing electrode materials for energy storage applications. [ABSTRACT FROM AUTHOR]

Innovatively regulating the crystalline-amorphous (c-a) interface of electrode materials is critical for enhancing supercapacitor and electrochemical water splitting performance. In this research, an oxygen defect-rich Fe 3 O 4 @Fe electrode material with a unique and tunable c-a interface was synthesized using prussian blue (PB) as a template. The resulting interface facilitates electron transport and ion diffusion, increases the charge storage active sites, and enhances energy storage capacity. Density functional theory (DFT) simulations demonstrated that oxygen defects can effectively enhance ionic conductivity and facilitate electrochemical water splitting. The optimal Fe 3 O 4 @Fe electrode exhibits remarkable specific capacitance (1526.766 mF cm−2 at 1 mA cm−2) and exceptional oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance, with overpotential values of 231 and 359 mV at 10 mA cm−2, respectively. Furthermore, as an overall water splitting electrocatalyst, the optimal Fe 3 O 4 @Fe can reach 10 mA cm−2 at a battery voltage of 1.645 V, demonstrating its tremendous potential as a highly efficient electrocatalyst. The oxygen defect-rich Fe 3 O 4 @Fe electrode materials with unique c-a interface are a kind of highly efficient multifunctional electrode material for supercapacitors and overall water splitting. [Display omitted] • The tunable c-a interface enhances electron transport, ion diffusion, and energy storage capability. • Introduction of oxygen vacancies improves electron transfer kinetics and electrochemically active area. • The unique synergistic interaction between the c-a interface and oxygen vacancies enhances rate performance. [ABSTRACT FROM AUTHOR]

The study presents a new two-step KOH activation strategy for the facile preparation of three-dimensionally (3D) O-doped interconnected hierarchical porous carbons with ultrahigh surface area (up to 4048.2 m2/g) derived from cost-effective biomass. The resulting porous carbon electrodes exhibited excellent electrochemical performances, with specific capacitances reaching up to 419 F/g at 0.5 A/g and energy densities up to 30.3 W h/kg at 250 W/kg. Meanwhile, the electrodes showed outstanding cycling stability (up to 91.2%) after 20,000 cycles. Compared to the conventional KOH activation method, the new strategy was found to be more effective in improving the porous structure, increasing the specific surface area, and enhancing O-doping of the obtained porous carbons. As a result, the electrochemical performances of the obtained carbon electrode materials were significantly enhanced. The positive effects of this new strategy were confirmed for four types of biomass, including lotus seedpods, rice husk, reed straw and corn cob. Overall, this work provides a simple and effective way to produce superb porous biomass-derived carbon materials for supercapacitor with high performance. [Display omitted] • A new and simple KOH activation strategy was proposed. • The new strategy can effectively increase the specific surface area and enhance O-doping. • 3D hierarchical porous carbon with an ultrahigh surface area of 4048 m2/g was obtained. • High specific capacitance of 419 F/g at 0.5 A/g was achieved. • Remarkable energy density of 30.3 W h/kg at 250 W/kg was achieved. [ABSTRACT FROM AUTHOR]

Bi nanoflakes on Ni foam (NF) for supercapacitors (SCs) are prepared by simple one-step microwave irradiation without further calcination. XRD and XPS results reveal the successful synthesis of Bi crystal. SEM and EDS results uncover the growth of Bi and the constituent elements of the complexes. The Bi anode on NF (Bi/NF) not only enables an ultra-large specific capacity of 4651 F g−1 (1 A g−1) and a capacity maintenance rate of 75% (after 1000 cycles), but it also exhibits outstanding catalytic hydrogen precipitation reaction, reaching an overpotential of −136 mV versus the reversible hydrogen electrode at −10 mA cm−2 and Tafel slope of 114.4 mV dec−1. The Bi anode is gathered into the asymmetric SC, which demonstrates an ultra-high energy density of 125 Wh kg−1 (power density of 640 W kg−1) in an alkaline electrolyte. [Display omitted] • In situ growth of Bi nanosheet on nickel foam via microwave method. • Bi/NF with a high capacity of 4651 F g−1 and maintenance of 75% (1000 cycles). • CoSe 2 @NiSe 2 //Bi/NF with 125 Wh kg−1 and cycle stability of 88% (3000 cycles). • Bi/NF catalyst with −136 mV at −10 mA cm−2 and a low Tafel slope of 114.4 mV dec−1. [ABSTRACT FROM AUTHOR]

The demand for high-energy storage supercapacitors with appropriate designs has been emerging in recent times. Aimed at enhancing the electrochemical storage performance of supercapacitors, g-C 3 N 4 /WO 3 (H 2 O) 0.33 (GCN/WO) nanostructures have been prepared in a simple wet impregnation process by mixing the synthesized g-C 3 N 4 , and WO 3 (H 2 O) 0.33 materials and their performances were compared systematically with their individual components. The successful formation of C 3 N 4 /WO 3 (H 2 O) 0.33 nanostructure has been confirmed by the XRD, SEM, EDS, HR-TEM, HAADF and XPS spectroscopy analyses. The prepared GCN/WO nanostructures showed greater specific capacitance of 466.88C g−1 at 1.5 A g−1 than their counterparts (GCN 87.87C g−1 and WO 140.64C g−1) with remarkable cyclic stability of 98.6% over 10000 cycles. Notably, the fabricated hybrid asymmetric supercapacitor devices (HASDs) exhibited ultrahigh power density of 255.23 W kg−1 at energy density of 10.07 Wh kg−1. The enhanced electrochemical capacitor characteristics of GCN/WO nanostructures could be attributed to the positive synergistic effect of GCN and WO. Thus, the strategy utilizing this synergistic effect between GCN and WO in a simple impregnation process is a viable alternative to fabricate the high capacitance electrodes for application in supercapacitors. [Display omitted] [ABSTRACT FROM AUTHOR]

The vast majority of Earth-orbiting satellites carry an electrical power subsystem (EPS) which main components are solar panels and secondary batteries. During eclipse periods, satellites are powered only by rechargeable batteries which have a large energy density but a limited power density. This fact limits the power capabilities of small satellites during eclipse periods. Due to the large power density of Supercapacitors (SCs), ground and on-orbit tests have been conducted to verify their applicability on satellite EPSs. At the moment, no studies are underway on the issue of sizing SCs for eclipse operations. Hybrid configuration could reduce the mass and volume of EPS or maintain those reference values but increasing peak power capabilities. This paper deals with this issue. On the one hand, novel analytical expressions of a variable capacitance SCs are derived, including time–voltage dependence in constant power applications. Also an equivalent formulation for a SCs bank (SCsB) is derived. On the other hand, a SCsB sizing procedure is presented, considering the energy and power requirements of a particular space mission as an input. Finally, a simple mission is analysed, the results showing an improvement on the hybrid EPS design with respect to the traditional, being the mass reduction of 36%. • Implementation of a simple but accurate supercapacitor (SC) model for spacecraft applications. • Innovative analytical expressions of the performance of a SC in constant power applications. • Novel determination of the electrical parameters of a SCs bank, treated as an equivalent SC model. • Estimation of key variables in the operation of hybrid storage systems for space applications. • Preliminary design of a SCs bank devoted to supply high power during eclipse times. [ABSTRACT FROM AUTHOR]

One of the most promising topics in the study of advanced energy applications is the creation of extraordinarily effective electrodes substances for higher-power devices. Scientific community has recently become interested in MXene because of its exceptional electrochemical characteristics, especially in comparison with two-dimensional (layered materials) like graphene/MY (M = Metal and Y S, O, Se, N, P etc). Layer restacking of MXene, however, reduces its supercapacitive performance as an electrode material because of functional group interactions. This work examines MXene and its composites with manganese ferrite MnFe 2 O 4 nanostructure (MnF) for use as a battery-like hybrid supercapacitor in an effort to resolve this problem. In this work, MnF were used as interlayer spacers between layers of MXene nanosheet. When compared to either MnF or MXene alone, the electrochemical investigations demonstrate that the composite (MnF/MXene) has improved electrochemical characteristics. For MnF, MXene, and MnF/MXene composites, maximum (specific capacitance, C s) around 1A g−1 was calculated to be around of 594, 1046.25, and 1268.75 F g−1, respectively. The MnF/MXene composites exhibited the high surface area of 975.3 cm2 resultant decreased the lesser charge transfer resistance (R ct) around 0.25 Ω, and shows a stable behavior for 50 h over 5000 cycles. In this study, 2D MXene was found to be the most effective capacitive electrode, outperforming carbon-based electrodes in an asymmetric assembly. As a result, the hierarchical MnF structure produced on different substrates in conjunction with MXene is a promising material for storage of energy. [ABSTRACT FROM AUTHOR]

In this study, we utilized a successive ionic layer adsorption and reaction (SILAR) route to attach bismuth selenide (Bi 2 Se 3) nanoparticles on one dimensional (1D) cadmium sulfide nanowires (CdS NWs) at ambient temperature (27 °C) to design CdS@Bi 2 Se 3 core-shell nanostructure towards active electrode for supercapacitor application. To verify and explore the retrieved surface configuration, structural, elemental, compositional, and surface morphological investigations were performed. The designed CdS@Bi 2 Se 3 core-shell nanostructure not only offers the tremendous number of active areas, but also a continuous and quick one directional electron transport channels, demonstrating noticeable electrochemical performance with specific capacitance of 198 F g−1 (aerial capacitance 59.5 mF/cm2) with 80% cyclic retention @ 2000 cycles. Superior electrochemical activity was enhanced through the mutualistic involvement of Na+ ion insertion/extraction via non-stoichiometric bismuth selenide, which was well supported through electrochemical impedance (EIS) studies. [ABSTRACT FROM AUTHOR]

The electrochemical performance of flexible carbon-nanotube (CN) based supercapacitors (SCs) is reported in this research. A mixture of Boron nitride (BN), graphene (G) and lithium titanate (Li 2 TiO 3 , LiTi) was added on the SC electrodes to enhance their capacitance/energy-density. SC devices were fabricated with the names of CN-SC, CN/BNG-SC and CN/BNG + LiTi-SC and generated a capacitance/energy density of 329.7 F g−1/7.3 Wh kg−1, 890.2 F g−1/35.2 Wh kg−1 and 1662.6 F g−1/124.2 Wh kg−1, respectively. From those last values, we realize that adding BN, G and LiTi (CN/BNG + LiTi-SC), enhanced the capacitance and the energy density by ~ 4 and ≈ 16 times, respectively. Interestingly, the output voltage of the SCs also increased from 0.1 to 0.4 V after adding these three compounds to their electrodes. The SC electrodes were analyzed by UV–vis absorbance, Raman and XPS and found the presence of defects (oxygen vacancies) and Ti3+/Ti4+ species, which worked as redox centers for the charge storage. Moreover, the best CN/BNG + LiTi-SC device was subjected to 500 bending/charging-discharging cycles and maintained a capacitance of 86–97% despite the mechanical deformations. Finally, we demonstrated that the incorporation of the BN and LiTi materials on the SC electrodes produced a widening of the operating voltage window from 1.2 to 2.2 V, which is of particular interest to increase the lifetime of portable energy sources. [ABSTRACT FROM AUTHOR]

With the development of the energy industry, electrochemical energy storage technology is increasingly involved in developing innovations in the field. The materials of the electrode have a significant influence on the performance of energy storage devices. For this purpose, two-dimensional MXene with excellent electrical conductivity, mechanical strength, and a variety of possible surface-active terminations are attracting much attention. In the present work, S-decorated d-Mo 2 CT x (d-Mo 2 CT x- -S) is designed. The first-principles calculations reveal that it may possess good energy storage characteristics. Due to the decoration with S, unique morphology and structure are obtained, conferring stability, optimized Li+ storage, improved charge transport, and lithium-ion adsorption capabilities. Compared with d-Mo 2 CT x , d-Mo 2 CT x- -S exhibits higher discharge capacity (623 mAh g−1 at 1 A g−1) as lithium-ion electrode material and higher specific capacitance (561 F g−1 at 1 A g−1). As a supercapacitor, the material also shows excellent cyclic stability (20,000 charge-discharge cycles). This work may inspire the exploration of other MXene and new surface functionalization methods to improve the performance of MXene as electrode materials for new energy devices. [ABSTRACT FROM AUTHOR]

Recent research has focused on the search for new electrode materials to improve the specific capacitance of supercapacitors. Conductive polymers and metal oxides have been extensively tested as electrode materials for supercapacitors. Incorporating both conductive polymers and metal oxides into a composite provides excellent results for the electrochemical performance of supercapacitors. In this present work, we have fabricated the nanoscale α-NiMoO 4 particles that enwrapped on electronically conducting polymer nanocomposites (PNCs) based on Polyvinyl alcohol (PVA)/Poly(vinyl) pyrrolidone (PVP) for supercapacitor applications. The different concentrations of PVA/PVP with α-NiMoO 4 loaded polymer nanocomposites were developed by using a solution casting method. All the polymer nanocomposites have been subjected to Scanning Electron Microscopy (SEM), Fourier Transforms Infrared (FTIR), X-ray diffraction (XRD), and electrochemical studies. The prepared PNCs surface morphology has been acquired as a non-uniform rod-like structure. The electrochemical performances of the prepared PNCs have been investigated and the resultant value of the maximum specific capacitance is 15.56 F g−1 for 1 wt % of α-NiMoO 4 nanoparticles(NPs) loaded polymer blended electrode at a scan rate of 5 mVs−1. The prepared PNCs exhibit 97.12% of columbic efficiency studied by using two electrode systems at room temperature in an aqueous electrolyte solution of 3 M KOH. From these investigation, it has been revealed that the PVA/PVP/α-NiMoO 4 composites could be portable and flexible electrodes for energy storage applications. [Display omitted] • α-NiMoO 4 NPs decorated polymers nanocomposites have been prepared by solution casting technique. • Structural studies of polymer composites have been investigated by XRD, SEM and FTIR spectral analyses. • 1 wt % of α-NiMoO 4 nanoparticles loaded polymer nanocomposite has exhibits 97.12% of columbic efficiency. • Prepared nanocomposites could be portable and flexible electrodes for energy storage applications. [ABSTRACT FROM AUTHOR]

Rational composition and structural design of electrode substances are critical for lithium-ion batteries (LIBs) and supercapacitors (SCs) with good cycling steadiness and superb rate capability. Therefore, we report a novel electrode material consisting of V 2 O 3 quantum dots (QDs, about 6.64 nm) well-distributed on mesoporous carbon (MC) nanosheets. V 2 O 3 has high intrinsic conductivity and an open tunnel-like lattice structure, facilitating electron transfer and ion intercalation. The composite architectures can offer more electrochemical active sites, shorten ion/electron diffusion paths, and reduce volume swings during the charging/discharging process. The synergic effect of these merits significantly improves the reaction kinetics and prevents structural damage to the entire electrode. As a result, V 2 O 3 -QDs/MC nanosheets exhibit a large capacity/capacitance, excellent cycling steadiness, and high rate performance. For LIBs, V 2 O 3 -QDs/MC displays a great reversible capacity of 931 mAh g−1 at 0.2 A g−1 over 500 cycles and fast and stable lithium storage behaviors with 822 mAh g−1 at 2 A g−1 after 1000 cycles. For SCs, V 2 O 3 -QDs/MC manifests a considerable specific capacitance of 270 F g−1 at 1 A g−1 and satisfactory durability for at least 5000 cycles at 10 A g−1. This work informs a good structure design for constructing advanced metal oxide-based nanostructured electrode materials. [Display omitted] [ABSTRACT FROM AUTHOR]

The development of new carbon materials for high-energy-density supercapacitors and efficient filter membranes is still challenging. In this work, a novel biomass carbon material with large specific surface area and high oxygen content was fabricated for high-energy and environmental applications. The as-obtained carbon material exhibited high specific capacitance of 437 F g-1 at 1 A g-1 with superior capacitance retention of 90.9% after 100,000 cycles even at 100 A g-1 in H 2 SO 4 electrolyte when tested in a three-electrode setup. The material also showed elevated specific capacitance in metal ion electrolyte, conducive to expanding its applications in aqueous metal ion supercapacitors. After assembly into a symmetric supercapacitor, the material showed an excellent energy density of 39.33 Wh kg-1 with outstanding capacitance retention of 125% after 100,000 GCD charge/discharge cycles at 20 A g-1. A new membrane was also prepared using the fabricated carbon material for the removal of different pollutants, such as heavy metal ions, antibiotics, and dyes. The tests revealed the new carbon-based membrane to exhibit an ultra-high flux of 1200 L m-2 h-1 bar-1 toward different pollutants with substantial rejection of ciprofloxacin (93.1%). Overall, this work provided a new research paradigm for the multifunctional application and theoretical exploration of novel carbon-based materials. [ABSTRACT FROM AUTHOR]

Nitrogen-doped Bernal graphene has several advantages, including improved electrical conductivity, enhanced stability and better compatibility with electrolytes. This article presents the synthesis of few-layer pristine graphene and nitrogen-doped Bernal graphene (CVDNG) through the Low-pressure chemical vapor deposition approach and its application for flexible supercapacitors. A novel hot lamination-assisted approach is employed to transfer the graphene on the desired substrates, enabling the reusability of copper. Raman mapping is utilized to analyze the characteristic bands and statistical distribution of Bernal stacking in CVDNG. The doping in graphene is confirmed through the X-ray photoelectron spectroscopy suggesting the content of pyrrolic-N (73.38%), pyridinic-N (20.28%) and graphitic-N (6.38%) in the CVDNG. Cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy are performed by sandwiching the polyvinyl alcohol-sodium perchlorate based hydrogel membrane between two symmetrical supercapacitor electrodes. CVDNG symmetrical supercapacitor device delivers an enhanced areal capacitance of 26.75 mF cm−2 with a high energy density of 2.14 mWh cm−2 with a power density of 72 mW cm−2 at 0.05 mA cm−2. The device shows excellent flexibility by retaining 91.1% of its capacitance at extreme bending (180° angle) conditions and excellent specific capacitance retention (90.6%) after 10,000 charge-discharge cycles. [Display omitted] • Nitrogen-doped Bernal graphene through the LPCVD approach for flexible supercapacitors. • A novel PMMA free approach to transfer the graphene, enabling the reusability of copper. • NaClO 4 -PVA based quasi-solid-state hydrogel membrane electrolyte. • The device shows excellent flexibility by retaining 91.1% of its capacitance at extreme bending (180° angle) conditions. • Excellent specific capacitance retention (90.6%) after 10,000 charge-discharge cycles. [ABSTRACT FROM AUTHOR]

Transition metal oxides, as well as multivalent metal oxides like Co 3 O 4 , have attracted huge attention for energy-storing materials. Combining Co 3 O 4 with carbon materials is of interest to improve the limited electrical conductivity and electrochemical performance of Co 3 O 4 composites. However, most synthesis methods of those Co 3 O 4 and carbon composites commonly need plenty of chemicals with long calcination and release many harmful byproducts. Thus, our green strategy based on laser sintering to synthesize a carbon-Co 3 O 4 composite from a single source – cobalt acetate – is proposed. With a low-power laser, our method is applicable to making flexible devices. A demonstration of flexible supercapacitor cells formed on a silver-nanowires-coated polyimide substrate is presented. Furthermore, the effects of laser pulse duration and current collector conductance on the device performance are investigated. As tested in Na 2 SO 4 and KOH electrolytes, these cells can deliver specific capacitances of 13.2 F g−1 (at 0.08 A g−1) and 48.2 F g−1 (at 1 A g−1), respectively, with a remarkable cycling behavior of 90% after 3000 cycles. Notably, the usability of our composite with the neutral Na 2 SO 4 electrolyte is worth exploring for eco-friendly energy storage. Altogether, our study shows opportunities to create green composites of carbon and multivalent metal oxides quickly and cost-effectively. [Display omitted] [ABSTRACT FROM AUTHOR]

Among the electrode materials of supercapacitors, transition metal oxides have been widely used because of their low price, high theoretical capacitance and good cycle stability, and MnO 2 is one of the typical representative materials. However, the actual specific capacitance of MnO 2 is low because of its poor conductivity, easy agglomeration in the preparation process and large volume change in the process of repeated charge and discharge. Attapulgite can not only provide a large specific surface area for transition metal oxide materials, but also provide a skeleton on which nano-sized materials can be grown or dispersed. Therefore, the electrochemical performance of electrode materials can be improved by designing nanostructures and compounding a variety of materials with different properties. Herein, a new type of composites electrode material is prepared by simple one-step hydrothermal method. As an electrode material, the ATP-MnO 2 composites exhibited a high specific capacitance of 138.2 F/g at a current density of 0.5 A/g, which was 13.4% higher than that of pure MnO 2 nanoflowers. Under the current density of 3 A/g, the capacitance retention of ATP-MnO 2 composites was 89.4% after 5000 cycles. • Provides a new idea for the application of clay-based materials in electrochemistry. • Composites can be prepared by a simple hydrothermal method. • Attapulgite can disperse the agglomeration of MnO 2 and improve the adsorption. • The capacitance and cyclic stability of the composites can be improved by attapulgite. [ABSTRACT FROM AUTHOR]

In this study, the performance of a fixed-wing PEMFC/SC hybrid UAV with an SRM thruster is investigated by different flight levels. Flight levels negatively affect the PEMFC due to changing ambient conditions such as air temperature and pressure. Hence, the international standard atmosphere (ISA) model for PEMFC voltage-current-power ratings is derived with 100 m intervals for 0–7500 m. The demanded electrical power by UAV increases at high altitudes due to the compressor used for air pressurization of PEMFC. Therefore, a maximum power point tracking (MPPT) model of PEMFC should be utilized in case of overshooting the maximum power level that can be provided. While the main power source of the UAV is PEMFC, the auxiliary power source is SC. The SC is preferred for DC bus voltage stabilization, avoiding maximum power point overshoot, and preventing high instantaneous current that shortens the lifespan of PEMFC. The proposed UAV model is verified at MATLAB/Simulink and the results prove that the system is satisfying. • The maximum power generation point of the fuel cells changes with altitude of the unmanned aerial vehicles. • The international standard atmospheric model is used to estimated air pressure, and temperature by altitude. • High instantaneous currents cause some problems in the 4-phase switched reluctance motor powered with the fuel cells. • Hybrid power system with fuel cell and super capacitor is a good combination for the unmanned aerial vehicles. [ABSTRACT FROM AUTHOR]

Whether or not specific ion effects determine the charge storage properties of aqueous graphene and graphite-based supercapacitors remains a highly debated topic. In this work we present a multiscale quantum mechanics – classical molecular dynamics (QMMD) investigation of aqueous mono- and divalent salt electrolytes in contact with fully polarizable charged graphene sheets. By computing both the electrochemical double layer (EDL) and quantum capacitance we observe a constant electrode specific capacitance with cationic radii and charge. Counterintuitively, we determine that a switch in the cation adsorption mechanism from inner to outer Helmholtz layers leads to negligible changes to the EDL capacitance, this appears to be due to the robust electronic structure of the graphene electrodes. However, the ability of ions (such as K+) with a relatively low hydration free energy to penetrate the inner Helmholtz plane and adsorb directly on the electrode surface is found to slow their diffusion parallel to the interface. Ions in the outer Helmholtz layer are found to have higher diffusivity at the surface due to their position in ion channels between water layers. Our results show that surface effects such as the surface polarization and the partial dehydration and local structuring of ions on the surface underpin the behaviour of cations at the interface and add a vital new perspective on trends in ion mobilities seen under confinement. [Display omitted] [ABSTRACT FROM AUTHOR]

After being undervalued for a long-time, the potential use of lignins have gained interest as a source of wealth from waste. Despite the complexity of lignins chemical structure, its high carbon content compared to cellulose and sugars makes lignin a very promising precursor for the development of nanocarbons for broad range applications, including supercapacitors for energy storage. High performing supercapacitors have been made using dimensionally different nanocarbon entities (zero-to three), such as carbon nanoparticles, carbon nanodots, carbon fibers, and carbon nanosheets with modular and interconnected pore structures, which are prepared from lignins of various types with and without use of templates, porogens and chemical agents. Control of physicochemical and electrochemical properties in such nanocarbons remains the key for their high energy density, flexibility, and long-term stability. To this end, nanocarbons conductivity, porosity and surface areas are controlled by various synthesis approaches while detailed adjustment of pore structure, pore width and pore distribution have been made to improve electrolyte access, ions confinement, and transportation. To compare performances of nanocarbons made from different lignin types, we must do meaningful investigations on the lignin's structure, composition, and purity to understand how their structure-property relationships are influenced by pyrolysis, carbonization and activation methods/conditions used. In this review, a clear overview of the lignins structure, classification, and properties is presented, wherein we compared the structure-property-performance relationships of nanostructured carbons from lignins for improvement of supercapacitor device performances with recent advances. Separation processes of lignin from wood, steps involved in preparing dimensionally different nanocarbon entities (zero -to three), and electrolytes for the fabrication of sustainable and flexible supercapacitor devices. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, NiCo 2 S 4 , nickel-cobalt layered double hydroxides (NiCo-LDH) and CoS 2 electrodes are successfully prepared by using ZIF-67 as the precursor, the results show that NiCo-LDH and NiCo 2 S 4 are nano-flower-like structures and CoS 2 exhibits a nano-cage structure. The electrochemical properties of the hybrid supercapacitor assembled with NiCo 2 S 4 and activated carbon (AC) as electrodes were tested. As the positive electrode of NiCo 2 S 4 //AC hybrid supercapacitor, the NiCo 2 S 4 electrode has the largest specific capacity of 2934 mAh g−1 at a current density of 1 A g−1. The NiCo 2 S 4 //AC capacitor generates the highest energy density of 38.8 Wh kg−1 when the power density is 993.0 W kg−1 and has a nice cycling performance with a capacity retention rate of 81.2% after 10,000 cycles at 5 A g−1. • Nano-flower-like structures NiCo 2 S 4 is successfully prepared by using ZIF-67 as the precursor. • NiCo 2 S 4 shows nice performance as the cathode of NiCo 2 S 4 //AC (activated carbon) hybrid supercapacitor. • NiCo 2 S 4 //AC (activated carbon) hybrid supercapacitor shows practical potential. [ABSTRACT FROM AUTHOR]

Selective fabrication of carbon materials with developed specific surface area and hierarchical porous structure is essential for high-performance carbon-based supercapacitors. Direct carbonization of organic acid salts represents a strategy that can produce porous carbon with high specific surface area, but it is still hindered by low carbon yield, impeding its large-scale application. Herein, a biomass-derived hierarchical porous carbon with large specific surface area is prepared via a facile one-pot calcination method. The optimal SCPC-4 sample presents three-dimensional interconnected network structure and plentiful heteroatom content. Hence, it delivers a large specific capacitance of 321 F g−1 at a current density of 1 A g−1, and negligible capacitance loss after 10,000 cycles at 10 A g−1. In addition, the assembled SCPC-4 based symmetric supercapacitor exhibits an energy density of 21.2 Wh kg−1 at a power density of 900 W kg−1. This cost-effective binary biomass carbon source route provides a great possibility for the mass production of high-yield porous carbon materials. [Display omitted] • A hierarchical porous carbon with 3D interconnected network structure was successfully synthesized. • The porous carbon exhibits a large specific surface area of 1781 m2g−1. • Excellent electrochemical performance of 321 F/g at 1 A/g was obtained. • The assembled symmetric supercapacitor shows energy density of 21.2 Wh/kg at the power density of 900 W/kg. [ABSTRACT FROM AUTHOR]

Nickel metal organic frameworks (Ni MOFs) were synthesized employing microwave technique for supercapacitor applications using Ni(NO 3) 2 ·6H 2 O (=M) and p-benzenedicarboxylic acid (=L) in M:L ratios of 1:1–4:1, 150–200 °C. Flakes, plates, nanoflowers, and globules are obtained and arranged in M:L-Temperature space to yield morphological stability map. Flakes appear at all M:L, 150 °C; plates form at M:L = 1:1, ≥ 165 °C; nanoflowers are seen at M:L ≥ 2:1, 165 °C; globules form at M:L ≥ 2:1, ≥ 180 °C. Cyclic voltammograms from these morphologies within 0 and + 0.6 V vs SCE at 10–100 mV s−1 show redox peaks corresponding to partial diffusion control, substantiated by galvanostatic charge-discharge (GCD) curves. From GCD, globules at M:L = 3:1 exhibit the highest specific capacitance (C sp) of 1361–600 F g−1 at 0.5–5.0 A g−1. This is attributed to their smallest size, presence of monoclinic and γ-NiOOH phases. Further, globules exhibit the lowest charge transfer resistance as estimated from the Nyquist plots showing two incomplete depressed semicircles. This work presents a systematic approach to select suitable Ni MOF morphologies for supercapacitor applications using morphological stability map. Also, it answers the question: "why does a particular morphology exhibit superior charge storage performance?" [ABSTRACT FROM AUTHOR]

Supercapacitors exhibit fast charging/discharging ability and have attracted considerable attention within the automotive, aerospace, and telecommunication industries. Porous carbons, prized for their high electrical conductivity and high surface area, have been attractive candidates for supercapacitor electrodes. Moving to thick electrodes is one strategy to further increase energy density due to a higher volume fraction of active material. However, thick electrodes suffer from sluggish charged species transport, which is why thin electrodes are currently favored. In this work, we investigate the use of computational optimization and additive manufacturing to design and fabricate thick porous electrodes with improved performance. Electrode performance was maximized by designing their morphologies via topology optimization and printing by projection micro stereolithography (PμSL) using commercial resin (PR48). The PR48 resin was then pyrolyzed (PR48-P) to create the final conductive electrode. The optimized PR48-P electrodes exhibited 99% improvement in capacitance compared to control electrodes printed with cubic lattice morphologies. To further improve performance, we formulated a resin combining graphene oxide (GO) and trimethylolpropane triacrylate (TMPTA). Electrodes printed with 3 wt% GO in TMPTA exhibited improved capacitance retention after pyrolysis compared to the PR48-P electrodes. This work demonstrates the benefits of using topology optimization to design electrodes and material development to improve functional properties of 3D printable electrodes. [Display omitted] • 3D printing of complex shaped electrodes by projection micro stereolithography. • Topology optimization is used to design porous electrodes with optimal energy density. • Adding graphene oxide into photocurable resin improves the capacitance retention of supercapacitors. [ABSTRACT FROM AUTHOR]

The specific surface area (SSA) and pore structure are two critical factors that determine the energy storage performance of carbon-based supercapacitors. However, for biobased carbon electrodes, it is difficult to simultaneously control the pore structures and achieve high SSA. Herein, highly porous carbons (HPCs) with ultrahigh SSA and controllable pore structures are produced through hydrogel-controlled carbonization and activation process for glucose. Polyacrylamide (PAM) is used as the pore-forming agent, and pore structures can be regulated by controlling the content of PAM. The highest SSA of the HPCs reaches 3381 m2 g−1 with a 60% PAM content. Compared with the sample without PAM, the specific capacitance of HPCs-60 shows a 63% increase, reaching 441 F g−1 at a current density of 0.25 A g−1. Moreover, a KOH/PVA symmetric supercapacitor assembled from HPCs-60 not only exhibits an excellent energy density (10.9 Wh kg−1 at a power density of 125 W kg−1) but also has high cycling stability (∼10% loss over 20,000 cycles) and good flexibility. The as-prepared supercapacitors can provide stable power supplies for multiple electronic devices, indicating that the HPCs have enormous potential for use in high-performance electrochemical energy storage devices. Highly porous carbons with ultrahigh specific surface areas and controllable pore structures were obtained by hydrogel-controlled carbonization and activation of glucose. [Display omitted] [ABSTRACT FROM AUTHOR]

Bundled V 2 O 5 nanobelts decorated with Fe 3 O 4 nanoparticles (F3V nanostructures) were successfully synthesized to develop a low-cost electrode material for energy storage applications. The synthesized samples were subjected to structural, morphological and electrochemical studies. The Fe 3 O 4 nanoparticles decorated over bundled V 2 O 5 nanobelts exhibited better electrochemical properties than the pristine Fe 3 O 4 nanoparticles and V 2 O 5 nanobelts. The electrochemical behavior of the fabricated electrodes was investigated in an electrolyte of 3 M KOH, demonstrated an exceptional specific capacity values of 750.1, 660.3, and 1519 F g–1 for V 2 O 5 , Fe 3 O 4 , and F3V respectively at a current density of 15 A g–1. The assembled F3V symmetric supercapacitor (SSC) device exhibited an excellent specific capacitance of 93 F g–1 at a current density of 0.5 A g–1, delivering energy and power densities of 13 Wh.kg–1 and 1530 W kg–1, respectively, and superior long-term cycling stability of ∼84% capacity retention over 5000 galvanostatic charge–discharge cycles. These findings demonstrate the extraordinary electrochemical characteristics of the F3V nanostructures, indicating their potential use in energy storage applications. [ABSTRACT FROM AUTHOR]

It is not an easy way to design composite electrodes with a high concentration of the constituent. This study cleverly exploited the phase transformation of molybdenum oxide to synthesize three-dimensional carbon-based endogenous-exogenous MoO 2 composites (EEC) by a two-step process. MC-15 exhibited the most outstanding electrochemical performance among EEC, with a specific capacitance up to 411.1 F g−1 in Na 2 SO 4 , due to the design of MoO 2 , which could be highly loaded with three-dimensional carbon. In addition, the electrode capacitance remains up to 94.1% after 5000 cycles, attributed to the synergy effect of three-dimensional carbon and molybdenum dioxide by providing an abundance of active sites for MoO 2 and overcoming its stacking. In this way, the electrochemical properties of the EEC electrode are not compromised by the volume expansion during the electrochemical process. The energy density of the asymmetric supercapacitor using this material as the negative electrode and MnO 2 @CC is 14 W h kg−1 at a power density of 802 W kg−1, showing a significant increase in energy density over the asymmetric supercapacitor with a conventional negative electrode (activated carbon, energy density of 3.36 W h kg−1 and power density of 700 W kg−1). Its specific capacitance remained 84.9% after 2500 cycles. In addition, an overpotential of only 348 mV was required to drive oxygen evolution in alkaline electrolytes with a Tafel slope as low as 88.7 mV dec−1; the 20 h stability test retains almost 100%. The results show that the design optimization of the negative electrode material provides a simple and effective strategy to increase the energy density of supercapacitors, and EEC electrode materials are a great candidate to be utilized in supercapacitors with excellent performance as well as electrolytic water. [ABSTRACT FROM AUTHOR]

A hybrid ZnCo 2 O 4 @CoMoO 4 heterogeneous structure deposited onto nickel foam was synthesized via a two-step hydrothermal process. The results demonstrate that the hybrid architecture exhibits excellent electrochemical performance, including the specific capacitance of 1040C g−1 at 1 A g−1 for hybrid structures, high energy density of 87.3 Wh kg−1 at a power density of 2700 W kg−1 for an as-assembled supercapacitor and excellent cycle stability with a capacity retention of 99% undergoing 8000 charge-discharge for the device. Moreover, it also shows favorable electrocatalytic activity with low overpotentials of 237 mV at 20 mA cm−2 for oxygen evolution reaction and 114 mV at 10 mA cm−2 for hydrogen evolution reaction, and low cell voltage of 1.54 V at 10 mA cm−2 for overall water splitting. In addition, the stability maintains well for the long-term use of 13 h. We believe that this hybrid ZnCo 2 O 4 @CoMoO 4 heterogeneous structure could be a promising candidate for future energy storage and conversion. [ABSTRACT FROM AUTHOR]

To enable a society based on carbon-free electricity, electric energy storage is crucial. In this regard, the development of novel supercapacitors with high capacity and long cycling stability is critical as supercapacitors have a higher power density than batteries. A promising group of supercapacitors is chalcogenide-based materials as they show excellent ionic conductivity and stability. Moreover, ternary chalcogenides are earth-abundant, low-cost, non-hazardous materials, and the third constituting element can optimize the structural and electrochemical properties leading to improved performances. However, so far, only a few ternary chalcogenide-based supercapacitors have been developed. Herein, we have synthesised and characterized Cu 3 Sb(S/Se) 4 , Cu 9 S 5 , and Cu 2-x Se using the same solution-based method at 150°C. We compare the electric properties of all four compounds to check their suitability as supercapacitor electrode materials. The highest capacitance and cyclic stability is found for Cu 3 SbS 4. Notably during CV studies, very high specific capacitance of 397 F/g was recorded at 5 mV/s. Motivated by this result, a coin cell based on Cu 3 SbS 4 is developed showing 21 F/g at a current rate of 0.5 A/g with excellent cyclic stability. [ABSTRACT FROM AUTHOR]

Enhancing the electrochemical performance while maintaining excellent mechanical properties of carbon nanofiber-based flexible electrodes remains a significant challenge, which blocks their potential application in advanced energy storage and conversion. Herein, taking advantage of the thermal stability difference between polyacrylonitrile and polypyrrolidone, we report a simple strategy to fabricate N-doped porous carbon nanofiber membranes with inter-fiber cross-linked structures via eccentric coaxial electrospinning combined with carbonization processes. During carbonization processes, the obstacles of large contact resistance are removed and sufficient contacts among electrospun nanofibers are formed, endowing the carbon nanofiber membranes with outstanding electrical conductivity (25.4 S cm−1) and flexibility in various forms. Further, NiCo 2 O 4 nanoneedles are in-situ decorated onto the prepared carbon nanofiber membranes to construct hybrid electrodes for improving capacitance. The hybrid electrodes (NiCo 2 O 4 @NPCNFs) achieve a competitive specific capacitance (capacity) of 1474.2 F g−1 (245.4 mAh g−1) at the current density of 0.5 A g−1, as well as good rate performance (78.0% capacitance retention at a current density of 10 A g−1). In addition, the assembled asymmetric supercapacitors exhibit a high energy density of 53.0 Wh kg−1. This study paves a promising way toward carbon nanofiber-based electrodes for application in energy storage systems. [Display omitted] • According to the different thermal stabilities of the polymers, cross-linked electrospun carbon nanofibers are prepared. • Design eccentric core-shell nanofibers to facilitate the outflow of the melting core to form abundant crosslinking points. • The novel carbon nanofiber membranes render robust flexibility and high electrical conductivity. • The assembled flexible supercapacitor can supply power stably and continuously even under severe bending states. [ABSTRACT FROM AUTHOR]

Owning a highly symmetric geometry, fullerenes are popular building blocks in nanoarchitectonics. The successful preparation of fullerene superstructures with various sizes and dimensions forms the basis for their applications. However, the lack of porosity and the limited electrical conductivity of most fullerene superstructures prevent their applications in energy-related fields such as supercapacitors. Herein, hybrid crystals with a crossed-tubular morphology and a hexagonal close packed (hcp) lattice were constructed by fullerene C 60 and its derivative, [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM), through a modified liquid-liquid interfacial precipitation method. Subsequent calcination can greatly improve the porosity of this hybrid crystals and produce mesoporous carbon with an increased BET surface area nearly 30 times (from 13.91 to 432.41 m2 g−1), which exhibited a good performance as an electrode material in supercapacitor with a capacitance retention rate of 87.3% after 2000 cycles and specific capacitances of ∼213 F g−1 at 5 mV s−1 and ∼158 F g−1 at 1 A g−1, respectively. Compared to the crystals formed solely by fullerenes, the presence of PCBM lowered the calcination temperature and induced self-doping of oxygen. In addition, rough surfaces could be produced on the superstructures by solvent etching, which increased as well the performance of the material in supercapacitor. Our work provided a new strategy to engineer fullerene-derived functional materials for applications in energy storage and expanded the knowledge on the factors regulating their performance when using as electrode materials in supercapacitors. [Display omitted] [ABSTRACT FROM AUTHOR]

High-performance multifunctional electromagnetic (EM) materials exhibit great potential for development, and have attracted extensive attention from the scientific field. Generally, the dielectric "genes", including conductive networks, interfaces, and defects, are the pivotal factors that determine their performance. Herein, multifunctional Ti 3 C 2 T x @polyaniline decorated MWCNT (TPMC) nanocomposites, containing generous dielectric "genes", were synthesized via the electrostatic self-assembly method. Thanks to the regulation of internal dielectric "genes", TPMC exhibited a tunable EM wave absorption (EMA) and EM interference (EMI) shielding performance. TPMC achieved a maximum reflection loss (RL) of −54.7 dB and an effective absorption bandwidth (EAB) of nearly 6 GHz at 1.5 mm. Moreover, the complete conductive networks endowed TPMC with a reliable EMI shielding capability. It exhibited a maximum EMI shielding effectiveness (SE) of 34 dB, and meanwhile, displayed an absorption-dominated green shielding performance. Furthermore, owing to the integration of the "genes", TPMC showed a high coulomb efficiency (∼98%) and excellent cycling stability (exceeded 95% retation after 8000 cycles), indicating a great potential as outstanding supercapacitor electrode material. This work provides a promising strategy for controlling the EM pollution and alleviating the energy issues. The Dielectric "genes" are the key core to regulate the multifunction of TPMC, which include defects, interfaces, functional groups and conductive networks. By regulating and patching the dielectric "genes" of TPMC, the multifunctional integration of EM wave absorption, EMI shielding and charge storage can be achieved. [Display omitted] [ABSTRACT FROM AUTHOR]

Nanostructured cobalt sulfide-based electrode materials for supercapacitors (SCs) still suffer from easy aggregation, sluggish reaction kinetics, and poor structural stability. To resolve these issues, we adopt a two-step electrochemical deposition method to fabricate CoS nanosheets decorated on polypyrrole (PPy) nanowires that grow directly on Ni foam. The PPy nanowires serve as supports for growing CoS nanosheets, which not only make the CoS nanosheets well dispersed but also reduce their size and thickness. In addition, the intensive interaction between CoS and PPy endows the nanoarchitecture with high mechanical strength. Therefore, the constructed PPy@CoS nanocomposites feature abundant electroactive sites, high charge transport and transfer efficiencies, a short ion diffusion distance, and good structural stability. As a result, the optimized PPy@CoS nanocomposites as SC electrodes demonstrate specific capacities of 860C g−1 at 1 A g−1 and 595C g−1 at 20 A g−1, as well as a 92% initial capacity retention after 5000 cycles at 10 A g−1. Furthermore, a fabricated asymmetric supercapacitor (ASC) device with PPy@CoS nanocomposites as the positive electrode realizes a specific energy of 51.1 Wh kg−1 at 800 W kg−1, suggesting a promising potential for their practical application in SCs. This work may provide a feasible strategy for fabricating other metal sulfide/conducting polymer nanocomposites with enhanced charge storage capabilities as SC electrodes. [ABSTRACT FROM AUTHOR]

Amorphous MnO 2 /CuO/ZrO 2 nanocompositeswere synthesized by facile hydrothermal method at 120 °C. The nanomaterialswere prepared from KMnO 4 with Mn, Cu and Zr aqueous salts. The mixed oxide active materials were produced through three different molar ratios. The synthesized nanocomposites demonstrated a phase mixer of tetragonal-MnO 2 , monoclinic-CuO and tetragonal-ZrO 2. The ultrahigh specific capacitance of 1964F/g at a current density of 1A/g was achieved for the nanocomposite MnO 2 /CuO /ZrO 2 synthesized at a mole ratio 1:2:1. Based on the electrochemical performance; the nanomaterial synthesized at higher mole percentage of copper has shown a high-rate capability of 20.93 Wh/kg at constant power discharge of 4013.10 W/kg. These findings interrogated that Manganese Copper, Zirconium mixed nanocomposite is proved to be an excellent electrode material for energy storage devices. [ABSTRACT FROM AUTHOR]

Aniline (Ani) and pyrrole (Py) based copolymers (poly(Ani-co-Py)) were fabricated by varying the reaction time ranging from 4 to 8 h through chemical oxidative polymerization technique. The photocatalytic performance and the application as supercapacitors of prepared copolymers were assessed together with the studies of their morphological features. The formation of poly(Ani-co-Py) copolymers was confirmed by FTIR, UV–Vis, and photo-luminescence (PL) spectroscopy. All the copolymers demonstrated almost similar morphology, like irregular, aggregated, and spherical-shaped structures, investigated by field-emission scanning electron microscopy (FESEM). Such morphology was different from the individual polymer of PANI (rod-like) and PPy (spherical) although diameters remained similar in the range of 50–200 nm for the homo and copolymers. The prepared copolymers showed excellent photocatalytic representation towards methylene blue (MB) degradation in comparison to the PANI and PPy. The supercapacitors fabricated using poly(Ani-co-Py) copolymers also showed promising prospects for the hybrid supercapacitor. These findings may provide a new insight to fabricate poly(Ani-co-Py) photocatalysts for organic pollutants treatment as well as may have potential prospects for supercapacitor. [Display omitted] • Simple fabrication of poly(Ani-co-Py) copolymer is reported. • The morphological distinctions of the poly(Ani-co-Py) was identified in comparison to PANI and PPy. • Copolymers showed excellent photocatalytic representation towards methylene blue removal than polymer. • Supercapacitor fabricated using poly(Ani-co-Py) showed superb performance. [ABSTRACT FROM AUTHOR]

Bimetallic nanostructures within carbon-based materials can overcome the fundamental limits of energy materials, which cannot be obtained using a single material. However, their synthesis involves time-consuming and complex processes that cause phase/interface segregation and non-uniformly distributed metal elements. Herein, we report a facile combustion-driven synthesis for bimetallic Ag–Bi nanoparticle (NP)-anchored carbon nanotube (CNT) electrodes. One-step combustion wave passing through freestanding films comprising Ag 2 O and Bi powders, nitrocellulose layers within CNTs enables high-density thermochemical reactions in seconds. The rapid heating-cooling rates induce the formation of liquefied Ag–Bi and trapping of metastable Ag–Bi phases at the carbon surfaces, thereby synthesizing homogeneously mixed bimetallic Ag–Bi NPs anchored on the CNTs, along with smaller diameters (∼20 nm) and high distribution density. A supercapacitor electrode employing them exhibits outstanding specific capacitance and retention (1372-1093 Fg-1 at 2-5 mVs−1, and 101.3% of the stabilized capacitance after 10,000 cycles at 100 mVs−1). This was attributed to the large active site surface area from the small diameters and high distribution density of the bimetallic Ag–Bi NPs by low surface energy, and highly stable adhesion to the CNTs. The synthesis strategy can be extended to a scalable fabrication method of various multi-metallic nanostructures for versatile electrochemical electrodes and catalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

Electrochemical conductive hydrogels are being extensively explored in the fabrication of portable batteries and high-performance supercapacitors. Herein, the rational design of a new polyanionic electrically conductive hydrogels based on sodium alginate-g-poly(AM-co-ECA-co-AMPS) are described. rGO was incorporated into the hydrogel during the polymerization process generating rGO@ sodium alginate-g-poly(AM- co -ECA-co-AMPS) composite hydrogels to study the impact of rGO on the performance of the hydrogels. FT-IR, XRD, and SEM-EDX characterized the chemical composition, crystalline, and morphological structure of the new synthesized hydrogels. The electrochemical performance of as-synthesized hydrogels was investigated by cyclic voltammetry, galvanostatic, charge-discharge rate, and electrochemical impedance spectroscopy. The supercapacitor performance for ECH2.5 composite hydrogel showed a capacitance of 753 F. g−1 at 1 A. g−1 with good rate capability and cycling stability up to 5000 cycles. Thus, ECH2.5 hydrogel is a good candidate as electrode material in supercapacitor applications. [ABSTRACT FROM AUTHOR]

The aim of this study was to synthesize CuFe 2 O 4 together with g-C 3 N 4 and GNPs in various combinations on the surface of Ni foam for use as anode materials in supercapacitors. The fabricated electrodes were investigated by XRD, FTIR, XPS, BET, SEM and TEM for content and by CV, GCD and EIS analysis for electrochemistry. The characterization results showed that CuFe 2 O 4 was successfully synthesized together with g-C 3 N 4 and GNPs in a nanosponge-like geometry. The highest value of specific capacitance was found to be 989 mF/cm2 at 2 mA measurement in the triple combination. Moreover, the stability of this electrode was measured to be 70% after 1500 cycles at 16 mA, while the energy and power densities were calculated to be 27.8 mWh/cm2 and 300 mW/cm2, respectively. The EIS results show that the carbon-based component increased the Cs value by decreasing the charge transfer and diffusion resistances of the electrodes. Compared to its counterparts in the literature, its Cs value is quite high, but its stability is low, so it can be used in low-cycle applications. [ABSTRACT FROM AUTHOR]

Wood with vertically aligned tracheids has many potential applications in energy storage. Carbonized wood inherits the previous tracheid structure and has good electrical conductivity, which provides favorable conditions for its application in self-supporting electrodes of supercapacitors. However, problems such as low specific surface area, low space utilization, and hydrophobicity limit the development of wood-derived carbon (WC) as an electrode material. Here, to improve the specific surface area and tracheid space utilization of WC, a porous carbon skeleton (PCS) was simply and efficiently constructed in its interior by using glucose and sodium chloride templates, and then potassium hydroxide etching treatment was used to further improve the specific surface area and hydrophilicity of the PCS, resulting in an etched porous carbon skeleton (E-PCS). The prepared E-PCS@WC electrode had an excellent area/volumetric specific capacitance of 7.29 F cm−2/145.8 F cm−3, and the supercapacitor exhibited a high volumetric capacitance and volumetric energy density of 34.99 F cm−3 and 4.86 mWh cm−3 at a power density of 2.5 mW cm−2. The supercapacitor constructed from this electrode exhibited good cycling stability with a retention rate of 98.5% over 20,000 cycles at a current density of 50 mA cm−3. This research will provide new ideas and a scientific basis for the design, construction and application of new green energy storage devices. [Display omitted] • A porous carbon skeleton was constructed inside the wood tracheid. • The hydrophilicity of the electrode was effectively improved by KOH etching. • The E-PCS@WC electrode has excellent specific capacitance of 145.8 F cm−3 • The E-PCS@WC//E-PCS@WC SC delivered a remarkable energy density of 4.86 mWh cm−3 • This strategy can be used as a platform for high-performance electrode. [ABSTRACT FROM AUTHOR]

Triple-layered boron-containing carbon nanofibers (CNFs) with hollow channels (PPMPB) are fabricated via step-by-step electrospinning for high-performance freestanding supercapacitors. Polyacrylonitrile (PAN)-based CNFs in the first layer are chosen as the support layer material because of their excellent chemical stability and electrospinnability. The well-developed hollow channels provided fast ion diffusion in the second layer of PAN/poly(methyl methacrylate) (PMMA)-based CNFs. The surface boron functional groups constituting the third layer contribute to the pseudo-capacitance. The symmetric supercapacitor of the PPMPB electrodes delivers a maximum specific capacitance of 180 Fg−1 at 1 mAcm−2, a high energy density of 22.38 Whkg−1 at a power density of 400 Wkg−1, and an excellent retention rate of 96% after 10,000 cycles in aqueous solution. The excellent electrochemical performance is attributed to the unique sandwich nanostructure with a three-layer structure, in which the factors representing the electrochemical properties of each layer do not interfere with each other. Therefore, a moderate amount of boron and the high surface area of the triple-layer structured PPMPB can be fully utilized as an excellent conductive network and electroactive sites, which is expected in a high-performance supercapacitor electrode. [Display omitted] • Triple-layered boron-containing CNFs were fabricated by step-by-step electrospinning. • The CNFs in the first layer provide active adsorption sites for EDLC. • Hollow core present in the interlayer serves as an excellent conductive network. • A moderate amount of boron in the third layer is utilized as the electroactive site. • Symmetric PPMPB(20) electrode showed good rate capability and long cycle life. [ABSTRACT FROM AUTHOR]

Understanding of the electrode/electrolyte interface interaction is crucial to electrochemical energy storage devices. In aqueous electrochemical double-layer capacitors (supercapacitors), the energy density is limited by the narrow voltage window, which is dominated by water dissociation. However, molecular-level understandings of the operating voltage window are still ambiguous because of the lacks of accurate description of this electric double layer structure and the clear picture of the adsorption structure of interfacial water molecules during electrochemical process, which makes it difficult to improve electrochemical performance. We focus on the typical graphene/aqueous electrolyte interface and employ Ab inito molecular dynamics simulations to accurately describe the electrified interface in simulation cells. Thus, a fundamental relationship between the asymmetric response of interfacial water molecules to applied electrode potentials and operating voltage window has been revealed. It is found that the response for orientation of the interfacial water molecules to varied potentials affects their adsorption structure, and the adsorption behavior determines the practical EDL region. Moreover, our calculations show that nitrogen dopants effectively adjust adsorption behavior of interfacial water molecules and thus broaden the negative voltage window. Our work provides new insights into the operating voltage window in electrochemical double-layer capacitors and efficient strategies for broadening voltage window. Ab inito molecular dynamics simulation studies to reveal the fundamental relationship between the adsorption structure of interfacial water molecules and voltage window in graphene and nitrogen doped graphene-based electrode/electrolyte EDL structure. [Display omitted] [ABSTRACT FROM AUTHOR]