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As a cathode in aqueous zinc-ion capacitors (ZICs), nitrogen-doped carbon with a 2D bimetallic chalcogenide (NbMo6S8/NC) was used. The assembled ZIC demonstrated exceptional electrochemical stability and energy efficiency over thousands of charge–discharge cycles.

Transition metal selenides (TMS) have excellent research prospects and significant attention in supercapacitors (SCs) owing to their high electrical conductivity, superior electrochemical activity and excellent structural stability. However, the commercial utilization of TMS remains challenge due to their elaborate synthesis. Present study designed a hierarchical cobalt selenide (CoSe2) nanowire array on Ni-foam to serve as a positive electrode for asymmetric SCs (ASCs). The nanowires-like morphology of CoSe2 was highly advantageous for SCs, as it offered enhanced electrical conductivity, plenty of surface sites, and short ion diffusion. The as-obtained, CoSe2 nanowire electrode demonstrated outstanding electrochemical features, with an areal capacity of 1.08 mAh cm−2 at 3 mA cm−2, high-rate performance (69.5 % at 50 mA cm−2), as well as outstanding stability after 10,000 cycles. The iron titanium nitride@nitrogen-doped graphene (Fe-TiN@NG) was prepared as a negative electrode to construct the ASCs cell. The obtained ASCs cell illustrated an energy density of 91.8 W h kg−1 at a power density of 281.4 W kg−1 and capacity retention of 94.6% over 10,000 cycles. The overall results provide a more efficient strategy to develop redox-ambitious active materials with a high capacity for advanced energy-storage systems.

Synthesis, properties and electrochemical energy storage applications of MXenes.

Herein, a solution-free dry strategy for the growth of self-assembled ordered tricopper phosphide (Cu3P) nanorod arrays is developed and the product is employed as a high-energy, stable positive electrode for a solid-state hybrid supercapacitor (HSC). The ordered Cu3P nanorod arrays grown on the copper foam deliver an excellent specific capacity of 664 mA h/g with an energy efficiency of 88% at 6 A/g and an ultra-long cycling stability over 15,000 continuous charge–discharge cycles. These electrochemical features are attributed to the ordered growth of the Cu3P nanorod arrays, which offers a large number of accessible electroactive sites, a reduced number of ion transfer paths, and reversible redox activity. The potential of the Cu3P nanorod arrays is further explored by engineering solid-state HSCs in which the nanorods are paired with an activated carbon-based negative electrode. The constructed cell is shown to convey a specific energy of 76.85 Wh/kg at a specific power of 1,125 W/kg and an 88% capacitance retention over 15,000 cycles. Moreover, the superior energy storing and delivery capacity of the cell is demonstrated by an energy efficiency of around 65%. The versatile solution-free dry strategies developed here pave the way towards engineering a range of electrode materials for next-generation energy storage systems.

Due to their high capacity, nickel–cobalt-based cathode materials have attracted significant attention as potential components of hybrid solid-state supercapacitors (HSSCs). However, their poor cycling stability and low rate capability have impeded their implementation. In the present study, a single-step, binder-free potentiodynamic polarization approach is presented for the preparation of battery-type phosphorus-containing amorphous trimetal nickel–ruthenium–cobalt hydroxide (P@NRC-OH) nanofibers on Ni foam for use in high-energy, stable HSSCs. The phosphate dopant and the trimetal-rich electrode surface increase the intrinsic electron conductivity and redox activity and generate a large number of active defects. As a consequence, a P@NRC-OH electrode exhibited enhanced energy storage properties in terms of specific capacity (541.66 mA h g−1 at 3 mA cm−2), cycling durability (90.35% over 20 000 cycles), and rate capability (308.64 mA h g−1 at 20 mA cm−2). An assembled full-cell HSSC with P@NRC-OH nanofibers as the cathode material and porous activated carbon as the anode material produced a maximum specific energy of 90.02 W h kg−1 at a specific power of 1363 W kg−1 which remained as high as 37.87 W h kg−1 at a power density of 6818.18 W kg−1, with remarkable cycling stability over 15 000 charge–discharge cycles. The proposed approach thus represents a scalable and efficient strategy for the design of electrodes and devices with superior electrochemical performance.

Metal–organic frameworks (MOFs) serve as expedient self-templated precursors to derive hybrid materials with various functionalities. This study develops a bimetallic MOF-derived approach for the facile synthesis of nitrogen-doped carbon integrated nickel–cobalt mixed metal phosphide (NiCoP/NC) using a controlled experimental procedure for supercapacitors. Here, the nitrogen-doped carbon nanosheet functions as a conductive framework and protective layer for NiCoP nanostructures and offers facile pathways for easy charge transfer, abundant surface active sites and improves the stability of the electrode. The marigold flower-like morphology of NiCoP nanostructures stores a large number of ions in their petals and shortens the ion diffusion length. The electrochemical analysis demonstrates that the as-designed NiCoP/NC electrode possesses a high specific capacity of 690.6 mA h g−1 (6.22 F cm−2) at 1 A g−1, high rate capability and excellent cycling stability. Additionally, a hybrid supercapacitor built with NiCoP/NC and activated carbon as positive and negative electrodes shows a maximum specific energy of 47 W h kg−1 at a specific power of 1666 W kg−1 and good capacity retention over 10 000 charge–discharge cycles. The present multicomponent approach combines the virtues of efficient redox chemistries of each element and N-doped carbon providing abundant surface active sites while stabilizing the active electrode material during repeated cycling.

A two-dimensional (2D) layered material-based p-n diode is an essential element in the modern semiconductor industry for facilitating the miniaturization and structural flexibility of devices with high efficiency for future optoelectronic and electronic applications. Planar devices constructed previously required a complicated device structure using a photoresist, as they needed to consider non-abrupt interfaces. Here, we demonstrated a WSe2 based lateral homojunction diode obtained by applying a photo-induced effect in BN/WSe2 heterostructures upon illumination via visible and deep UV light, which represents a stable and flexible charge doping technique. We have discovered that with this technique, a field-effect transistor (FET) based on p-type WSe2 is inverted to n-WSe2 so that a high electron mobility is maintained in the h-BN/n-WSe2 heterostructures. To confirm this hypothesis, we deduced the work function values of p-WSe2 and n-WSe2 FETs by conducting Kelvin probe force microscopy (KPFM) measurements, which revealed the decline of the Fermi level from 5.07 (p-WSe2) to 4.21 eV (n-WSe2). The contact potential difference (CPD) between doped and undoped junctions was found to be 165 meV. We employed ohmic metal contacts for the planar homojunction diode by utilizing an ionic liquid gate to achieve a diode rectification ratio up to ∼105 with n = 1. An exceptional photovoltaic performance is also observed. The presence of a built-in potential in our devices leads to an open-circuit voltage (Voc) and short-circuit current (Isc) without an external electric field. This effective doping technique is promising to advance the concept of preparing future functional devices.

openaire: EC/H2020/834742/EU//ATOP Two-dimensional (2D) transition metal dichalcogenides have attracted vibrant interest for future solid-state device applications due to their unique properties. However, it is challenging to realize 2D material based high performance complementary devices due to the stubborn Fermi level pinning effect and the lack of facile doping techniques. In this paper, we reported a hybrid Gr/Ni contact to WS2, which can switch carrier types from n-type to p-type in WS2. The unorthodox polarity transition is attributed to the natural p-doping of graphene with Ni adsorption and the alleviation of Fermi level pinning in WS2. Furthermore, we realized asymmetric Ni and Gr/Ni hybrid contacts to a multilayer WS2 device, and we observed synergistic p-n diode characteristics with excellent current rectification exceeding 104, and a near unity ideality factor of 1.1 (1.6) at a temperature of 4.5 K (300 K). Lastly, our WS2 p-n device exhibits high performance photovoltaic ability with a maximum photoresponsivity of 4 × 104 A W-1 at 532 nm wavelength, that is 108 times higher than that of graphene and 50 times better than that of the monolayer MoS2 photodetector. This doping-free carrier type modulation technique will pave the way to realize high performance complementary electronics and optoelectronic devices based on 2D materials.

Current progress in the advancement of energy-storage devices is the most important factor that will allow the scientific community to develop resources to meet the global energy demands of the 21st century. Nanostructured materials can be used as effective electrodes for energy-storage devices because they offer various promising features, including high surface-to-volume ratios, exceptional charge-transport features, and good physicochemical properties. Until now, the successful research frontrunners have focused on the preparation of positive electrode materials for energy-storage applications; nevertheless, the electrochemical performance of negative electrodes is less frequently reported. This review mainly focuses on the current progress in the development of tungsten oxide-based electrodes for energy-storage applications, primarily supercapacitors (SCs) and batteries. Tungsten is found in various stoichiometric and nonstoichiometric oxides. Among the different tungsten oxide materials, tungsten trioxide (WO3 ) has been intensively investigated as an electrode material for different applications because of its excellent charge-transport features, unique physicochemical properties, and good resistance to corrosion. Various WO3 composites, such as WO3 /carbon, WO3 /polymers, WO3 /metal oxides, and tungsten-based binary metal oxides, have been used for application in SCs and batteries. However, pristine WO3 suffers from a relatively low specific surface area and low energy density. Therefore, it is crucial to thoroughly summarize recent progress in utilizing WO3 -based materials from various perspectives to enhance their performance. Herein, the potential- and pH-dependent behavior of tungsten in aqueous media is discussed. Recent progress in the advancement of nanostructured WO3 and tungsten oxide-based composites, along with related charge-storage mechanisms and their electrochemical performances in SCs and batteries, is systematically summarized. Finally, remarks are made on future research challenges and the prospect of using tungsten oxide-based materials to further upgrade energy-storage devices.

The rational design and development of highly conductive hierarchical nanostructured materials are of great importance to improve the electrochemical performance of supercapacitors. Great efforts have been committed to the development of positive electrodes for asymmetric supercapacitors (ASC). However, it is still necessary to develop better negative electrodes for practical applications. In present investigation, a multi-walled carbon nanotubes-tungsten trioxide (MWCNT-WO3) hybrid nanostructure is prepared as a negative electrode for ASC. The MWCNT-WO3 hybrid electrode is prepared using a simple two-step approach, which involves coating of MWCNTs on carbon cloth substrates followed by hydrothermal treatment to deposit WO3 nanorods on the MWCNT-coated carbon cloth. The MWCNT-WO3 hybrid electrode exhibits a maximum specific capacitance (areal capacitance) of 429.6 F g−1 (1.55 F cm−2) and capacity retention of 94.3% after 5000 cycles, which are higher than the 155.6 F g−1 (0.43 F cm−2) and 84.9% shown by pristine WO3 in 1 M LiClO4 electrolyte. A flexible all-solid-state ASC is self-assembled with MWCNT-WO3 as a negative electrode, MnO2 as a positive electrode, and PVA-LiClO4 as a gel electrolyte. The MnO2//MWCNT-WO3 ASC achieve specific capacitance of 145.6 F g−1 at a current of 2 mA and specific energy of 39.63 Wh kg−1 at a specific power of 546 W kg−1. Specifically, the ASC exhibits superior long-term cycling stability (77% over 10000 cycles) and excellent mechanical flexibility with less capacitance loss. These remarkable results demonstrate the potential of using MWCNT-WO3 hybrid nanostructures for the fabrication of high-performance energy storage devices.

Hexagonal WO3 nanorod thin films have been successfully synthesized by a simple hydrothermal method using ammonium sulfate ((NH3)2SO4) as a structure directing agent. The effect of structure directing agent on structural, morphological and electrochemical properties of WO3 thin films is investigated. The nanorods with diameters of 50–200 nm and length up to several micrometers are obtained. The results demonstrate that the concentration of (NH3)2SO4 plays an important role in the growth direction and formation of self-assembled WO3 nanorods. The electrochemical measurements show that WO3 thin films demonstrate excellent electrochemical performance with a maximum specific capacitance of 538 F g−1 at 5 mV s−1, high power performance and good cycling stability (85% over 2000 CV cycles). The present work may provide a facile and versatile approach to tune the morphology and capacitive performance of WO3 thin films required for high-performance energy storage devices.

Two-dimensional (2D) transition metal dichalcogenides have attracted vibrant interest for future solid-state device applications due to their unique properties. However, it is challenging to realize 2D material based high performance complementary devices due to the stubborn Fermi level pinning effect and the lack of facile doping techniques. In this paper, we reported a hybrid Gr/Ni contact to WS2, which can switch carrier types from n-type to p-type in WS2. The unorthodox polarity transition is attributed to the natural p-doping of graphene with Ni adsorption and the alleviation of Fermi level pinning in WS2. Furthermore, we realized asymmetric Ni and Gr/Ni hybrid contacts to a multilayer WS2 device, and we observed synergistic p-n diode characteristics with excellent current rectification exceeding 104, and a near unity ideality factor of 1.1 (1.6) at a temperature of 4.5 K (300 K). Lastly, our WS2 p-n device exhibits high performance photovoltaic ability with a maximum photoresponsivity of 4 × 104 A W-1 at 532 nm wavelength, that is 108 times higher than that of graphene and 50 times better than that of the monolayer MoS2 photodetector. This doping-free carrier type modulation technique will pave the way to realize high performance complementary electronics and optoelectronic devices based on 2D materials.

Electrode materials exhibiting nanostructural design, high surface area, tunable pore size, and efficient ion diffusion/transportation are essential for achieving improved electrochemical performance. In this study, we successfully prepared cobalt phosphide and cobalt nanoparticles embedded into nitrogen-doped nanoporous carbon (CoP-CoNC/CC) using a simple precipitation method followed by pyrolysis-phosphatization. Subsequently, we employed CoP-CoNC/CC as the electrode for supercapacitor applications. Notably, the resultant CoP-CoNC/CC displayed a high surface area with tunable porosity. Based on the benefits of the CoP in CoNC/CC, improved electrochemical performance was achieved with a specific capacitance of 975 F g-1 at 1 mA cm-2 in a 2 M KOH electrolyte. The assembled hybrid supercapacitor using CoP-CoNC/CC (positive electrode) and activated carbon (AC) (negative electrode) exhibited a specific capacitance of 144 F g-1, a specific energy of 39.2 W h kg-1 at 1960 W kg-1 specific power, with better cyclic stability. The higher performance can be attributed to the synergetic effect between CoP, Co metal, and the nitrogen-doped nanoporous carbon in three-dimensional carbon cloth (CC). These excellent properties make CoP-CoNC/CC a promising electrode for developing future energy-storage devices.

A rational combination of metal cations is necessary to obtain a synergistic effect leading to improved electrochemical energy storage performance of bimetal compounds. So, the effect of concentration variation of reactants (nickel and cobalt ratio) in nickel cobalt phosphate material and their influence on physicochemical properties and electrochemical capacitive performances are investigated. The morphological evolution from microflowers (nickel phosphate) to microsheets (cobalt phosphate) is observed with increasing cobalt content in nickel cobalt phosphate thin films. The optimum nickel and cobalt composition (∼1:1) in nickel cobalt phosphate (Ni1.38Co1.62(PO4)2·8H2O) thin film electrode demonstrate maximum specific capacitance (capacity) of 1116 F g−1 (446 C g−1) at 0.5 A g−1 current density. Also, a fabricated hybrid asymmetric aqueous device consists of nickel cobalt phosphate thin film as cathode and rGO as an anode in 1 M KOH electrolyte delivers a higher specific capacitance of 120 F g−1 with a high energy density of 42.3 Wh kg−1 at a power density of 1 kW kg−1. Moreover, a hybrid asymmetric solid-state device fabricated using PVA-KOH gel electrolyte exhibits a maximum specific capacitance of 102 F g−1 with an energy density of 36.2 Wh kg−1 at 160 W kg−1 power density and 83.7 % initial capacitance retention after 4000 GCD cycles. Such excellent electrochemical capacitive performance of hybrid asymmetric devices is attributed to the synergy between nickel and cobalt species in nickel cobalt phosphate thin film electrodes, suggesting its potential application as a cathode in hybrid energy storage devices.

Electrocatalytic water splitting is a very promising and sustainable approach for generating hydrogen as a clean carbon-free fuel. To develop an efficient electrocatalyst for water splitting, the overpotential for this reaction must be minimized by using a capable electrocatalyst that can support the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). In this study, we prepared a unique core–shell structure, Co-metal–organic framework (MOF) derived cobalt diselenide laminated with molybdenum diselenide (MOF-CoSe2@MoSe2) and assessed its performance as a bifunctional electrocatalyst for the HER and OER in alkaline media. The CC/MOF-CoSe2@MoSe2 core–shell structure fabricated directly on a flexible carbon cloth substrate demonstrated low overpotentials (η10) of 109.87 and 183.81 mV for the HER and OER, respectively, and a low voltage of 1.53 V for overall water splitting activity with an electrolyzer cell with symmetric CC/MOF-CoSe2@MoSe2 electrodes. The developed CC/MOF-CoSe2@MoSe2 catalyst had excellent stability over 24 h for OER, HER, and overall water splitting activity. These results suggest that lamination of MOF with a transition metal dichalcogenide is an effective route for developing the highly efficient and sustainable bifunctional electrocatalyst for overall water splitting activity.

The self-supported integrated structure of electrode consisting of heteroatoms is advantageous for high-performance energy storage applications. Herein, we developed heteroatomic Ni-Co4N nanoparticles laminated on highly conductive nitrogen-doped carbon (NC) matrix through in-situ nitridation for high energy and stable hybrid supercapacitor (HSC). The plenty of rendering electrochemically active sites, specifically, single-atom Ni, Co4N nanoparticles, and heteroatomic N-doped carbon matrix, and their several synergistic effects facilitate fast electron transfer and superior electrochemical performance. Benefiting from these merits, the resultant Ni-Co4N@NC electrode demonstrates robust electrochemical activity with high specific capacity of 397.5 mA h g−1, high rate capability of 72.4% and superior cycling stability over 10,000 cycles. The heteroatomic Ni-Co4N@NC electrode is further employed for the HSC cell beside with the activated carbon (AC) electrode, which establish the specific energy of 57.2 Wh kg−1 at a specific power of 843.8 W kg−1 and cyclic stability of 89.7% after 15,000 cycles. The present study highlights the utilization of heteroatomic self-supported metal nitrides for the high energy HSCs cell, paving the way to the expansion of highly efficient electrode materials for the future energy storage systems.

In present work, the vertically aligned NiS nano-flakes composed thin film is prepared by anionic exchange process in which hydrothermally prepared Ni(OH)2 is used as a parent thin film and Na2S as a sulfide ion source. This synthesis process produced fully transformed and shape-controlled nano-flakes of NiS from nano-flowers of Ni(OH)2. The electrochemical supercapacitor properties of NiS electrode are studied with cyclic voltammetry (CV), galvonostatic charge discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques. Highly porous surface area (85 m2/g) of NiS nano-flakes makes large material contribution in electrochemical reaction stretching specific capacitance (Cs) of 880 F/g at scan rate of 5 mV/s and 90% electrochemical stability up to 4000 CV cycles in 2 M KOH electrolyte. Further, the flexible solid-state symmetric supercapacitor device (NiS/PVA–LiClO4/NiS) has been fabricated using NiS electrodes with polyvinyl alcohol (PVA)–lithium perchlorate (LiClO4) gel electrolyte. The NiS/PVA–LiClO4/NiS device exhibits specific capacitance of 56 F/g with specific energy of 14.98 Wh/kg and excellent cycling stability after 2000 cycles. In addition, the NiS/PVA–LiClO4/NiS device demonstrates illumination of red light emitting diode (LED) for 60 s, which confirms the practical applicability of NiS/PVA–LiClO4/NiS device in energy storage.

A simplistic and economical chemical way has been used to prepare highly efficient nanostructured, manganese oxide (α-MnO2) and hexagonal copper sulfide (h-CuS) electrodes directly on cheap and flexible stainless steel sheets. Flexible solid-state α-MnO2/flexible stainless steel (FSS)/polyvinyl alcohol (PVA)–LiClO4/h-CuS/FSS asymmetric supercapacitor (ASC) devices have been fabricated using PVA–LiClO4 gel electrolyte. Highly active surface areas of α-MnO2 (75 m2 g–1) and h-CuS (83 m2 g–1) electrodes contribute to more electrochemical reactions at the electrode and electrolyte interface. The ASC device has a prolonged working potential of +1.8 V and accomplishes a capacitance of 109.12 F g–1 at 5 mV s–1, energy density of 18.9 Wh kg–1, and long-term electrochemical cycling with a capacity retention of 93.3% after 5000 cycles. Additionally, ASC devices were successful in glowing seven white-light-emitting diodes for more than 7 min after 30 s of charging. Outstandingly, real practical demonstration suggests...

In present study, new strategy is employed to build composite nanostructure and asymmetric configuration to enhance the capacitive performance of supercapacitor device. The WO3-MnO2 composite with mesoporous structure is prepared by single-step hydrothermal method and used to gain superior electrochemical performance in asymmetric configuration. A binder-free and additive-less WO3-MnO2 composite electrode exhibits high specific capacitance of 609 F g−1 at a scan rate of 5 mV s−1. The flexible asymmetric supercapacitor device with WO3-MnO2 as a positive electrode and WO3 as a negative electrode demonstrates stable operating potential window of 1.4 V with specific capacitance of 103 F g−1 at a scan rate of 5 mV s−1 and energy density of 24.13 Wh kg−1 at power density of 915 W kg−1. Furthermore, WO3-MnO2//WO3 device exhibits good cycle life with capacity retention of 95% after 2500 cycles and excellent mechanical flexibility. These results reveal the potential of WO3-MnO2 composite electrode for fabrication of high-performance supercapacitors.

The current problem of the relatively low energy density and cycling stability of supercapacitors can be effectively addressed by designing an all-solid-state high performance asymmetric supercapacitor (ASSCs) using chemically deposited beta-manganese oxide (β-MnO2) as a positive active electrode and orthorhombic-tin sulfide (O-SnS) as a negative electrode material on a stainless steel (SS) substrate with a poly(vinyl alcohol)-lithium perchlorate (PVA-LiClO4) solid gel polymer electrolyte and as a separator. Time-dependent surface morphological modification and its subsequent effect on electrochemical performance of the O-SnS negative electrode has been examined. Electrodes prepared at deposition time periods of 120, 240, and 360 min provide specific surface areas (SSA) of 36.7, 78.3, and 65.6 m2 g–1, respectively. Superior nanostructures of both the β-MnO2 and O-SnS electrodes offer high specific capacitance (Cs) of 994 and 1203 F g–1 at 5 mV s–1 and energy and power densities (ED and PD) of 83.3, 69.2 W...

The mesoporous nanostructured metal oxides have a lot of capabilities to upsurge the energy storing capacity of the supercapacitor. In present work, different nanostructured morphologies of MnO2 have been successfully fabricated on flexible carbon cloth by simple but capable hydrothermal method at different deposition temperatures. The deposition temperature has strong influence on reaction kinetics, which subsequently alters the morphology and electrochemical performance. Among different nanostructured MnO2 thin films, the mesoporous weirds composed thin film obtained at temperature of 453 K exhibits excellent physical and electrochemical features for supercapacitor application. The weirds composed MnO2 thin film exhibits specific surface area of 109 m2 g−1, high specific capacitance of 595 F g−1 with areal capacitance of 4.16 F cm−2 at a scan rate of 5 mV s−1 and high specific energy of 56.32 W h kg−1. In addition to this, MnO2 weirds attain capacity retention of 87 % over 2000 CV cycles, representing better cycling stability. The enhanced electrochemical performance could be ascribed to direct growth of highly porous MnO2 weirds on carbon cloth which provide more pathways for easy diffusion of electrolyte into the interior of electroactive material. The as-fabricated electrode with improved performance could be ascribed as a potential electrode material for energy storage devices.

Carbon dioxide gas (CO2) sensing properties of La2O3 thin films synthesized by spray pyrolysis method are reported. La2O3 thin films deposited at different substrate temperatures (573–623 K) are characterized for their structural, surface morphology, optical and electrical properties and used for CO2 gas response measurements. SEM analyses indicate porous surface morphology. The deposited La2O3 films are crystalline with pronounced orientation along (110) plane, uniform and adhere to the glass substrate. From optical absorbance studies, the optical band gap is found to be 4.2 eV. With porous surface morphology, the maximum response of 18% at 623 K substrate temperature is recorded on exposure of 350 ppm of CO2 gas.

Present work portrays surface morphology alteration of CuS thin film with increase in reaction bath temperature. The porous nanoflowers like morphology of CuS offers higher electron transfer and shorten ion diffusion pathway, which facilitates transfer of electrolyte ions. Nanoflowers like morphology of CuS electrode exhibits specific capacitance (Cs) of 1818.2 F g−1 at scan rate of 5 mV s−1 with electrochemical cycling stability of 92%. The symmetric FSS-SCs-PVA-LiClO4 device demonstrates Cs of 172.5 F g−1, specific power density of 1750 W kg−1 and capacity retention of 93% after 2000 CV cycles. More importantly, this device glows the panel of 200 red LEDs.

In present article, temperature dependent surface morphological modification and its subsequent influence on electrochemical performance of hexagonal WO3 (h-WO3) thin films has been investigated. The nanostructured h-WO3 films are synthesized on carbon cloth substrate using simple hydrothermal method. It is observed that h-WO3 thin films prepared at temperature of 413, 433 and 453 K display nanogranule-like, nanoplate-like and nanorod-like suface morphology. The X-ray diffraction study discloses the prominent orientation along (001) and (200) planes which reveals the preferential growth direction of h-WO3 along c and a-axis, respectively. The h-WO3 film prepared at 453 K shows good surface area, pore volume and uniform pore size distribution. The electrochemical measurements exhibit high specific capacitance of 694 F g−1, energy density of 25 Wh Kg−1 and long term cycling performance (87 % capacitance retention after 2,000 cycles) for h-WO3 thin film. The results indicate that h-WO3 nanorods could be a promising electrode material for high performance energy storage devices.

Transition metal nitrides have recently fascinated noteworthy research interest owing to their exclusive electronic structure with high electrical conductivity and their emerging application in energy storage and conversion devices. Herein, we have designed a freestanding Cu3N@Ni3N nanorod arrays (NRAs) integrated on copper foam (CF), which serves as an active electrode for hybrid supercapacitors (SCs). The three-dimensional (3D) nano-architecture of Cu3N@Ni3N/CF is extremely beneficial for SCs because it possesses improved electrical conductivity, numerous surface active sites, and abundant “superhighways” for charge transportation owing to the self-supported design of material and synergistic effect between each active component. As a consequence, Cu3N@Ni3N/CF electrode displays outstanding energy storage performance in terms of specific capacity (390.5 mA h g−1 (2.34 F cm−2) at 1 A g−1, cycling stability (94.9% retention over 10 000 cycles), and excellent rate capability. As-fabricated hybrid solid-state SC (HSSC) device with the Cu3N@Ni3N NRAs and activated carbon (AC) as positive and negative electrodes, respectively demonstrated a maximum specific energy of 71.8 Wh kg−1 at a specific power of 700 W kg−1 with good cycling stability over 10 000 cycles. Thus, the work signifies a scalable approach for the systematic design of electrode materials and devices for future energy storage applications.

Engineering a new class of electrode materials by combining different active components is crucial to boost the energy storage capacity of current supercapacitors. In this study, multicomponent cobalt manganese oxide@bimetallic nickel-cobalt hydroxides (CoMn2O4@NiCo-OH) and vanadium nitride@nitrogen-doped carbon (VN@NC) structures are directly grown on carbon cloth and a hybrid solid-state supercapacitor (HSSC) is designed. The integral design of the unique CoMn2O4@NiCo-OH and VN@NC electrodes offers a highly porous nanostructure, active surface sites, and facile pathways for fast electronic and ionic transportation, thereby speeding up the electrochemical reactions. As a battery-type material, CoMn2O4@NiCo-OH electrode achieves high specific capacity of 349.0 mA h g−1 at 1 mA cm−2, good rate capability, and excellent cyclic durability. Similarly, VN@NC electrode presents excellent electrochemical features in the negative potential side with specific capacity of 113.4 mA h g−1 at 2 mA cm−2. The HSSC device demonstrates a high specific energy of 68.83 W h kg−1 at a specific power of 2048 W kg−1 and an excellent cyclic durability. The overall findings present a sustainable approach for developing hierarchical multicomponent core-shell energy materials with a high capacity for the construction of future energy-storage devices.

Presently, significant attention has been paid towards the rational synthesis of nanostructured anode and cathode electrode materials for assembling high-performance supercapacitors. Despite significant progress being achieved in designing cathode electrode materials, anode electrode materials with high capacitance are hardly investigated. In the present article, a tungsten oxide (WO3) thin film is prepared on a flexible stainless steel substrate by a wet chemical method and used as an anode electrode to fabricate a flexible asymmetric supercapacitor (ASC). An electrochemical investigation of the WO3 thin film shows a maximum specific capacitance of 530 F g−1 at 1 mA cm−2 in a potential window of 0 to −0.8 V in 1 M Na2SO4 electrolyte. In addition, a highly energetic, flexible ASC device is assembled using a WO3 thin film as an anode, a MnO2 thin film as a cathode and polymer gel as an electrolyte. The as-assembled MnO2//WO3 ASC device exhibited a stable electrochemical potential window of 1.8 V and better cycling stability. What's more, the flexible MnO2//WO3 ASC device achieves a high specific capacitance of 115 F g−1 with an acceptable specific energy of 52 W h kg−1 at a current density of 3 mA. Hence, the proposed flexible MnO2//WO3 ASC device creates one more option for anode materials to develop flexible energy storage devices.

Two-dimensional (2D) layered materials and their heterostructures have opened a new avenue for next-generation spintronic applications, benefited by their unique electronic properties and high crystallinity with an atomically flat surface. Here, we report magnetoresistance of vertical magnetic spin-valve devices with multi-layer (ML) MoSe2 and its heterostructures with few-layer graphene (FLG). We employed a micro-fabrication procedure to form ultraclean ferromagnetic–non-magnetic–ferromagnetic interfaces to elucidate the intrinsic spin-transferring mechanism through both an individual material and combinations of 2D layered materials. However, it is revealed that the polarity of tunneling magnetoresistance (TMR) is independent of non-magnetic spacers whether the spin valve is composed of a single material or a hybrid structure, but it strongly depends on the interfaces between ferromagnetics (FMs) and 2D materials. We observed positive spin polarizations in ML-MoSe2 and FLG/ML-MoSe2/FLG tunnel junctions, whereas spin-valve devices comprised of FLG/ML-MoSe2 showed a reversed spin polarization and demonstrated a negative TMR. Importantly, in Co/FLG/ML-MoSe2/FLG/NiFe devices, the polarization of spin carriers in the FM/FLG interface remained conserved during tunneling through MoSe2 flakes in spin-transferring events, which is understandable by Julliere’s model. In addition, large TMR values are investigated at low temperatures, whereas at high temperatures, the TMR ratios are deteriorated. Furthermore, the large values of driving ac-current also quenched the amplitude of TMR signals. Therefore, our observations suggest that the microscopic spin-transferring mechanism between ferromagnetic metals and 2D materials played a momentous role in spin-transferring phenomena in vertical magnetic spin-valve junctions.

High capacitance, long cycling life, superior energy density, and ultrafast charge-discharge rates are some of the important characteristics for energy storage systems to meet the energy demands of modern electronics. The development of new emerging class of materials is necessary to rally these key requirements. Metal organic frameworks (MOFs) are generated tremendous interest as a new class of electrode materials for applications in energy storage owing to their large specific surface area, excellent porosity, composition and functionality. Herein, layered manganese-1, 4 benzenedicarboxylic acid-based MOFs [Mn(BDC).nDMF]n (Mn-MOFs) are fabricated using hydrothermal technique for supercapacitors application. The as-obtained Mn-MOF exhibits exceptionally high specific capacity (areal capacitance) of 567.5 mA h g−1 (10.25 F cm−2) at a current density of 1 A g−1. The hybrid supercapacitor fabricated with Mn-MOFs as a cathode and reduced graphene oxide (rGO) as an anode demonstrates specific and volumetric capacitances of 211.37 F g−1 and 3.32 F cm−3, respectively, specific energy of 66 Wh kg−1 at a specific power of 441 W kg−1, and capacity retention of 81.18% over 10,000 cycles. These excellent electrochemical results illustrate potential of utilizing MOF-based materials for supercapacitor application and provide innovative direction for the development of future high-performance energy storage systems.

To obtain highly efficient supercapacitors with extraordinary capacitance, energy density, and cycle life, the design and development of new electrode materials having numerous active sites on the surface are essential. Not only the kind of material but also the surface morphology and microporous structure of the electrode plays an important role in the electrochemical performance of the supercapacitor. In the present work, a bimetallic Co/Mn-metal–organic framework (MOF) has been prepared using a simple hydrothermal method for supercapacitor application. This bimetallic MOF mainly produces a synergistic effect by connecting two kinds of metal ions through an organic ligand. The resulting bimetallic Co/Mn MOF electrode shows a high specific capacitance of 1176.59 F g−1 (2.76 F cm−2) at a current density of 3 mA cm−2 and excellent cycling stability over 5000 cycles. The constructed Co/Mn MOF//AC hybrid supercapacitor exhibits a specific energy of 57.2 Wh kg−1 at a specific power of 2000 W kg−1 and excellent capacity retention of 93.51% over 5000 cycles. These outstanding results are compared with those of similar devices in the literature, thus revealing that our approach is a desirable direction for future research on high-performance energy storage devices as well as hybrid supercapacitors.

To enhance the energy density and power performance of supercapacitors, the rational design and synthesis of active electrode materials with hierarchical mesoporous structure is highly desired. In the present work, fabrication of high-performance hierarchical mesoporous WO

Nanocrystalline cubic Cu2O thin films are developed by simple and cost-effective modified successive ionic layer adsorption and reaction method. This method increases the growth rate and reduces the overall deposition time. The synthesized Cu2O thin films were characterized for their different physico-chemical properties. The film deposited for 25 cycles exhibits optical band gap energy of 2.16 eV, phase pure cubic Cu2O structure, foggy like surface morphology and hydrophobic in nature. The photoelectrochemical device fabricated using Cu2O thin film showed an efficiency of 0.35 %.

The mesoporous nanostructured metal oxides have a lot of capabilities to upsurge the energy storing capacity of the supercapacitor. In present work, different nanostructured morphologies of MnO

To achieve the highest electrochemical performance for supercapacitor, it is very essential to find out a suitable pair of an active electrode material and an electrolyte. In the present work, a simple approach is employed to enhance the supercapacitor performance of WO3 thin film. The WO3 thin film is prepared by a simple and cost effective chemical bath deposition method and its electrochemical performance is tested in conventional (H2SO4) and redox additive [H2SO4+hydroquinone (HQ)] electrolytes. Two-fold increment in electrochemical performance for WO3 thin film is observed in redox additive aqueous electrolyte compared to conventional electrolyte. WO3 thin film showed maximum specific capacitance of 725Fg(-1), energy density of 25.18Whkg(-1) at current density of 7mAcm(-2) with better cycling stability in redox electrolyte. This strategy provides the versatile way for designing the high performance energy storage devices.