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The composites of NiCo2O4 with unique structures were substantially investigated as promising electrodes. In this study, the unique structured nanosheets anchored on nickel foam (Ni foam) were prepared under the hydrothermal technique of NiCo2O4 and subsequent preparation of Co(OH)2. The Co(OH)2@NiCo2O4 nanosheet composite has demonstrated higher specific capacitances owing to its excellent specific surface region, enhanced rate properties, and outstanding electrical conductivities. Moreover, the electrochemical properties were analyzed in a three-electrode configuration to study the sample material. The as-designed Co(OH)2@NiCo2O4 nanosheet achieves higher specific capacitances of 1308 F·g−1 at 0.5 A·g−1 and notable long cycles with 92.83% capacity retention over 6000 cycles. The Co(OH)2@NiCo2O4 nanosheet electrode exhibits a long life span and high capacitances compared with the NiCo2O4 and Co(OH)2 electrodes, respectively. These outstanding electrochemical properties are mainly because of their porous construction and the synergistic effects between NiCo2O4 and Co(OH)2. Such unique Co(OH)2@NiCo2O4 nanosheets not only display promising applications in renewable storage but also reiterate to scientists of the unlimited potential of high-performance materials.

Herein, we synthesized 1D bimetallic hydrogen phosphate [CoxNix(HPO4)] nanorods by using a simple and effective chemical bath deposition method for supercapacitor applications. The prepared CoxNix(HPO4) was analyzed by Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) pattern. The surface morphology was envisaged by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. The porous nature and surface area of the materials were characterized by nitrogen sorption isotherm and a high specific surface area of 153 m2 g-1 was found to be for Co0.75Ni0.25(HPO4). The Co0.75Ni0.25(HPO4) displays a maximum specific capacity of 475 mA h g-1 at 1 A g-1 in a three-electrode configuration using 3 M KOH as the electrolyte. Co0.75Ni0.25(HPO4) exhibits almost 94.8% of its initial specific capacity over 5000 GCD cycles at 10 A g-1. Furthermore, the fabricated asymmetric supercapacitor (ASC) with Co0.75Ni0.25(HPO4) and activated carbon (AC) showed a high specific capacitance of 182.5 F g-1 at 0.5 A g-1. The ASC device delivered a maximum energy density of 64.88 Wh kg-1 at a power density of 800 W kg-1.

Hematite nanoparticles of average size 20 nm were synthesized using the sol-gel method, and the structural characterizations were conducted using XRD and TEM. The XRD profile revealed a small fraction of the maghemite phase and the main hematite phase. Mössbauer spectroscopy was used to study the magnetic structure of the particles and revealed a third but very slight non-magnetic phase. Mössbauer spectrum shows 35% of the nanoparticles exhibiting superparamagnetism. The weighted average Morin transition temperature for the particles determined by Mössbauer is 262 K, which is remarkably similar to the bulk value and higher than the Morin transition determined by VSM (about 250 K). The reported findings on the hematite nanoparticles will help understand the enhanced ferromagnetic behavior of the hematite nanoparticles at room temperature, which is crucial for potential applications.

Single crystalline Mn3O4 nanowires have been synthesized with tetragonal hausmannite structure using a solvothermal method. The structural and morphological evolution of Mn3O4 nanowires have been characterized using powder X-ray diffraction, transmission electron microscopy, and electron resonance spectroscopy. The nanowires were grown uniformly along the (200) direction with a diameter of 5–10 nm range. A relatively broad and intense electron spin resonance (ESR) signal was observed at room temperature, with the g ≈ 2.0. As the synthesis temperature increases from 150 to 250 °C, a decrease in ESR signal intensity and line widths were observed. Mn3O4 displayed a positive Curie-Weiss temperature, θ, which decreases with the increase of synthesis temperature.

In this work, first 13X zeolite was prepared by the hydrothermal method. Then, the composite electrode was fabricated by using 13X zeolite and aniline monomer in nickel foam by electropolymerization technique in an acidic medium (13X/PANI). The synthesized 13X zeolite was characterized by physicochemical characterization techniques such as Fourier transform infra-red (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD) pattern and nitrogen sorption isotherm. 13X/PANI composite was further analyzed by XRD, XPS and FE-SEM techniques. Furthermore, the catalyst activity of the synthesized 13X, PANI and 13X/PANI composite electrodes was evaluated in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) by using linear square voltammetry (LSV) and Tafel slope method. The Tafel slopes of HER were found to be 203 mV dec−1, 440 mV dec−1 and 282 mV dec−1 for 13X, PANI and 13X/PANI-15 electrodes respectively. While the OER Tafel slopes were found to be 423 mV dec−1, 310 mV dec−1 and 168 mV dec−1 for 13X, PANI and 13X/PANI-15, respectively. 13X/PANI-15 electrodes show excellent catalytic performance about the overpotential at 10 mA cm−2 for HER and the overpotential at 20 mA cm−2 for OER. The obtained results suggest fabricated novel electrodes are a potential candidate for HER and OER reaction and can be open new avenue for other electrochemical reactions.

Nowadays, bioactive nanomaterials have been attracted the researcher’s enthusiasm in various fields. Herein, Diplocyclos palmatus leaf extract-derived green-fluorescence carbon dots (DP-CDs) were prepared using the hydrothermal method. Due to the strong fluorescence stability, the prepared DP-CDs were coated on filter-paper to make a fluorometric sensor-strip for Fe3+ detection. After, a bandgap-narrowed DP-CDs/TiO2 nanocomposite (DCTN) was prepared using the methanolic extract of D. palmatus. The prepared DCTN exhibited improved photocatalytic bacterial deactivation under sunlight irradiation. The DCTN-photocatalysis slaughtered V. harveyi cells by the production of reactive oxygen species, which prompting oxidative stress, damaging the cell membrane and cellular constituents. These results suggest the plausible mode of bactericidal action of DCTN-photocatalysis under sunlight. Further, the DCTN has shown potent anti-biofilm activity against V. harveyi, and thereby, DCTN extended the survival of V. harveyi-infected shrimps during the in vivo trial with Litopenaeus vannamei. Notably, this is the first report for the disinfection of V. harveyi-mediated acute-hepatopancreatic necrosis disease (AHPND) using nanocomposite. The reduced internal-colonization of V. harveyi on the hepatopancreas as well as the rescue action of the pathognomonic effect in the experimental animals demonstrated the anti-infection potential of DCTN against V. harveyi-mediated AHPND in aquaculture.

Hydrothermal method successfully produced a new cesium-metal borate (CsKB4O5(OH)4·2H2O). The crystals are grown in the P21/c space group with a monoclinic lattice, a = 10.7298 (13) Å, b = 8.1521 (11) Å, c = 13.2690 (15) Å, β = 108.325 (9)°, and Z = 4. The structure is composed of [B4O5(OH)4]2- groups connected to 8-coordinated potassium, 12-coordinated cesium ions, and water molecules forming the final 3D framework. FTIR and Raman spectra identified the type and nature of the borate groups within the structure. UV-Vis- NIR diffuse reflection spectra have studied the transmission property, whereas TG-DSC analyses revealed the thermal stability of the crystals. In addition, theoretical calculations have been executed to understand the density of states and band structure.

High electrocatalytic activity and low charge transfer resistance are the key factors of coutner electrodes (CEs) for high-performance quantum dot-sensitized solar cells (QDSSCs). Hence, it is challenging and highly deisrable to fabricate the CEs with high catalytic activity and low charge transfer resistance for QDSSCs. To address these issues, here, we design and prepare a new catalytic electrode by doping of nickel (Ni) ion in CuS for use as CEs in QDSSCs. The Ni-doped CuS CEs are fabricated via a facile chemcial bath deposition method. Scanning electron microscope study reveals that the Ni-doped CuS exhibits the surface morphology of nanoparticles over nanoflake structrues, while the CuS delivers the nanoflake structures. The Ni-doped CuS provides abundant active sites for reduction of polysulfide redox couple, higher electrical conductivity and offers excellent pathways for electron transfer, which yields the high electrocatalytic activity and delivers the lower charge transfer resistance at the interface of CE/electrolyte. As a result, the TiO2/CdS/CdSe QDSSCs with Ni–CuS yield a power conversion efficiency (η) of 4.36% with short circuit current density (JSC) of 13.78 mA cm−2, open-circuit voltage (VOC) of 0.567 V, and fill factor (FF) of 0.558, which are much superior to that of device with CuS CE (η = 3.24%; JSC = 10.63 mA cm−2; VOC = 0.567; FF = 0.546) under one sun illumination (AM 1.5G, 100 mW cm−2). Present work determines that Ni-doped CuS could be a promising CE material for QDSSCs due to its high electrical conductivity, excellent electrocatalytic activity, and lower charge transfer resistance.

Over the past few decades, the application of new novel materials in energy storage system has seen excellent development. We report a novel MnCo2O4/NiO nanostructure prepared by a simplistic chemical bath deposition method and employed it as a binder free electrode in the supercapacitor. The synergistic attraction from a high density of active sites, better transportation of ion diffusion and super-most electrical transportation, which deliver boost electrochemical activities. X-ray diffraction, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy have been used to investigate the crystallinity, morphology, and elemental composition of the as-synthesized precursors, respectively. Cyclic voltammetry, galvanostatic charge/discharge, and electron impedance spectroscopy have been employed to investigate the electrochemical properties. The unique nanoparticle structures delivered additional well-organized pathways for the swift mobility of electrons and ions. The as-prepared binder-free MnCo2O4/NiO nanocomposite electrode has a high specific capacity of 453.3 C g−1 at 1 Ag−1, and an excellent cycling reliability of 91.89 percent even after 4000 cycles, which are significantly higher than bare MnCo2O4 and NiO electrodes. Finally, these results disclose that the as-fabricated MnCo2O4/NiO electrode could be a favored-like electrode material holds substantial potential and supreme option for efficient supercapacitor and their energy storage-related applications.

Background: Cadmium sulfide (CdS) based semiconductors are of great interest for different high-end applications because they pose a direct bandgap (2.42 eV). CdS are used as the main constituent material in many applications, namely solar cells, electroluminescent, and quantum dot light-emitting diodes. Transition metal-doped CdS revealed considerable influence in the bandgap, photoluminescence properties and peak energy upon increasing the metal content. Objective: In this work, we study the single-phase cubic structure of CdS. Photoluminescence spectra revealed a strong blue emission peak located at about 445 nm. Methods: We investigate the Co-doping CdS semiconductor nanoparticles prepared via the chemical co-precipitation method using thiophenol as template, 300 °C/2h in vacuum optimum temperature and period of annealing to yield nanosized particles. Morphology and structural studies of the particles were using XRD, and TEM, respectively. Results: XRD and TEM studies for the calcined samples revealed a cubic structure. The crystalline size was in the range of 10-17 nm. Thermogravimetric analysis (TGA) was employed to stabilize the temperature of annealing for the samples. The blue shift in the spectra and the band gap value of Codoped CdS nanoparticles were estimated using UV-vis absorption spectra. Photoluminescence spectra revealed a strong blue emission peak around 445 nm indicating the presence of surface states within the bandgap region, which is a characteristic feature of nanoparticles. Conclusion: XRD analysis indicated zinc blend structure and the intensity decreased with increasing Co content. TEM images show that the particles are spherical in shape with average sizes around 13 nm. Luminescence of the synthesized nanoparticles exhibited blue emission between 400 – 500 nm with the peak located at about 445 nm. The emission intensity increased with the increase in Co concentration.

Herein, we have designed and prepared the battery-type redox behavior enabled hybrid V2O5@NiCo2O4 heterostructures on nickel foam by a simple one-step chemical bath deposition method. The structural and compositional analyses confirmed the presence of V2O5 and NiCo2O4 in the as-prepared hybrid V2O5@NiCo2O4 composite. The electrochemical studies reveal that the V2O5@NiCo2O4 composite electrode exhibited a high specific capacity of 184.49 mA h g−1 at 1 A g−1 and excellent rate capability of 88.5% at 12 A g−1 with good cycling stability (94.3% capacity retention over 3000 cycles), which are superior to the NiCo2O4 electrode. The results demonstrate that the hybrid V2O5@NiCo2O4 composite have a wide range of applications in the energy storage field.

Cone-shaped CuS@MnS nanostructures were grown on Ni foam with robust adhesion using a one-step hydrothermal method and efficiently served as binder-free battery-type material for high-performance supercapacitors. The synergic effects of the unique nanostructure and great adhesion is advantageous for enhancing the surface area on the Ni foam substrate, increasing the storage and charge accumulation, increasing the electrochemical activity between CuS and MnS, and accelerating electron and electrolyte ion transfer. As a result, as a battery-type material, the CuS@MnS/NF composite electrode exhibited excellent electrochemical performance, including high specific capacity (89.77 mA h g−1 at a current density of 1 A g−1), good cycling stability (95.9% capacity retention after 3000 cycles), and outstanding rate capability compared to that of CuS/NF (45.73 mA h g−1) and MnS/NF (3.8 mA h g−1). This study sheds new light on the composites, and demonstrates that the CuS@MnS/NF electrode is an ideal material for electrochemical energy storage.

Quantum dot sensitized solar cell (QDSSC) performance is primarily limited by the recombination of charges at the interfaces of TiO2/quantum dot (QD) sensitizer/electrolyte. Hence, blocking or suppressing the charge recombination is an essential requirement to elevate the QDSSC performance to the next level. To retard the charge recombination, herein, we propose the introduction of a SnO2 nanograss (NG) interlayer on the surface of TiO2 using the facile chemical bath deposition method. The SnO2 NG interlayer not only inhibits the interfacial recombination processes in QDSSCs but also enhances the light-harvesting capability in generating more excitons. Hence, the TiO2/SnO2 NG/CdS QDSSCs can achieve the power conversion efficiency of 3.15%, which is superior to that of a TiO2/CdS device (2.16%). Electrochemical impedance spectroscopy, open-circuit voltage decay and dark current analyses confirm that the recombination of charges at the photoanode/electrolyte interface is suppressed and the life time is improved by introducing the SnO2 NG interlayer between the TiO2 and CdS QD sensitizer.

Layer-by-layer approach for NiS, CoS and PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) is being fabricated. Metal sulfides have always been chosen for their remarkable electrochemical characteristics and wide beneficial domains, such as electrochemical energy conversion and storage. This work presents the preparation of cost-effective metal sulfides (NiS, NiS/CoS, NiS/CoS/PEDOT:PSS) developed on nickel foam sheets for supercapacitor (SC) applications. The assembled NiS/CoS/PEDOT:PSS array SC device exhibits an utmost energy density of 30.3 W h kg−1 and specific capacitance of 353 F g−1. All wet processing methods of fabrication accompanied with superior performance characteristics make these SCs very attractive for the next generation flexible energy storage systems.

Binder-free hierarchical nanosheet manganese cobaltate@manganese cobaltate nanosheet arrays (NS MnCo2O4@MnCo2O4 NSAs) heterostructures have been successfully deposited on nickel (Ni) foam surface using a facile two-step hydrothermal process. Scanning electron microscope characterization illustrate that the as-developed composite exhibits a growth of smaller MnCo2O4 nanosheet structures anchored on the surface of MnCo2O4 NSAs that provide abundant reactive sites and effective electronic transmission, endowing the NS MnCo2O4@MnCo2O4 NSAs an outstanding electrochemical performance. The electrochemical measurements reveal that the as-prepared NS MnCo2O4@MnCo2O4 NSAs delivers a Faradic battery-type redox behavior, which is distinct from the behaviors of carbon-based materials. As a battery-type material, NS MnCo2O4@MnCo2O4 NSAs exhibits an outstanding specific capacity (135.15 mA h g−1 at 2 A g−1) and remarkable rate capability (82.93%), which are much higher than that of bare MnCo2O4 NSAs. Moreover, NS MnCo2O4@MnCo2O4 NSAs delivers an excellent cycling stability of 88.74% over 5000 cycles. Hence, these electrochemical results suggest that the as-developed NS MnCo2O4@MnCo2O4 NSAs can serve as an advanced battery-type electrode material for supercapacitor applications.

In the context of constant growth in the utilization of the Li-ion batteries, there was a great surge in the quest for electrode materials and predominant usage that lead to the retiring of Li-ion batteries. This review focuses on the recent advances in the anode and cathode materials for the next-generation Li-ion batteries. To achieve higher power and energy demands of Li-ion batteries in future energy storage applications, the selection of the electrode materials plays a crucial role. The electrode materials, such as carbon-based, semiconductor/metal, metal oxides/nitrides/phosphides/sulfides, determine appreciable properties of Li-ion batteries such as greater specific surface area, a minimal distance of diffusion, and higher conductivity. Various classifications of the anode materials such as the intercalation/de- intercalation, alloy/de-alloy, and various conversion materials are illustrated lucidly. Further, the cathode materials, such as nickel-rich LiNixCoyMnzO2 (NCM), were discussed. NCM members such as NCM 333, NCM 523 that enabled to advance for NCM622 and NCM81are reported. The nanostructured materials bridged the gap in the realization of next-generation Li-ion batteries. Li-ion batteries’ electrode nanostructure synthesis, performance, and reaction mechanisms were considered with great concern. The serious effects of Li-ion batteries disposal need to be cut significantly to reduce the detrimental effect on the environment. Hence, the recycling of spent Li-ion batteries has gained much attention in recent years. Various recycling techniques and their effect on the electroactive materials are illustrated. The key areas covered in this review are anode and cathode materials and recent advances along with their recycling techniques. In light of crucial points covered in this review, it constitutes a suitable reference for engineers, researchers, and designers in energy storage applications.

Binder-free nanorice-like featured CuS@WS2 structures have been synthesized using a simple and cost-effective chemical bath deposition approach and their application as electroactive material for high-performance supercapacitors. The surface properties of morphology, structure and composition of the as-prepared electrodes are examined using the scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The nanorice-like featured CuS@WS2 electrode exhibits nanorice-like structures, which provides the abundant active sites for redox reactions and facilitates the electrolyte diffusion. The electrochemical performance of the supercapacitor electrodes was examined by cyclic voltammetry and galvanostatic charge–discharge studies. From the electrochemical tests, the CuS@WS2 electrode exhibits a higher specific capacitance (Cs) of 887.15 F g−1 at a current density of 3.75 A g−1 with greater energy density and excellent rate capability compared to bare CuS (588.0 F g−1) and WS2 (19.40 F g−1) electrodes. Overall, these results demonstrate that the as-synthesized CuS@WS2 could be a promising material for next-generation high-performance electrochemical energy storage applications.

Nanosheet-like tungsten diselenide (WSe2)/reduced graphene oxide (rGO) hybrid has been developed for the first time by facile one-step hydrothermal route for supercapacitor applications. Electrochemical measurements show that the WSe2/rGO-based supercapacitor electrode exhibits a maximum specific capacitance of 389 F g−1 at 1 A g−1 with capacitance retention of 98.7% after 3000 charge/discharge cycles at a high current density of 7 A g−1, and delivered a energy density of 34.5 W h kg−1 at 400 W kg−1 and 22.4 W h kg−1 at a high power density of 4000 W kg−1.

Quantum dot sensitized solar cell (QDSSC) performance is primarily limited by the recombination of charges at the interfaces of TiO

Herein, for the first time, we demonstrate the fabrication of Fe2O3@LiCoO2 hybrid nanostructures on Ni foam substrate by facile one-step hydrothermal technique. Morphological studies reveal that aggregated Fe2O3 nanoflakes anchored on the surface of sphere-like LiCoO2 nanoflakes. Electrochemical studies are used to examine the performance of the supercapacitor electrodes. The composite Fe2O3@LiCoO2 electrode exhibited excellent electrochemical performance than Fe2O3 and LiCoO2 electrodes, such as a low charge transfer resistance, a high specific capacitance of 489 F g−1 at 5 mA cm−2 and an enhanced capacity retention of 108% over 3000 cycles at 15 mA cm−2. The composite Fe2O3@LiCoO2 holds great promise for electrochemical applications due to well-defined hierarchical morphology, synergetic effect of Fe2O3 and LiCoO2, enhanced electrical conductivity, efficient electrolyte penetration and fast electron transfer.

Copper sulfide is an important multifunctional semiconductor that has attracted considerable attention owing to its outstanding properties and multiple applications, such as energy storage and electrochemical energy conversion. This paper describes a cost-effective and simple low-temperature solution approach to the preparation of copper sulfide for supercapacitors (SCs) and quantum-dot sensitized solar cells (QDSSCs). X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy confirmed that the nickel foam with a coriander leaf like nanostructure had been coated successfully with copper sulfide. As an electrode material for SCs, the CC-3 h showed excellent specific capacitance (5029.28 at 4 A g−1), energy density (169.73 W h kg−1), and superior cycling durability with 107% retention after 2000 cycles. Interestingly, the QDSSCs equipped with CC-2 h and CC-3 h counter electrodes (CEs) exhibited a maximum power conversion efficiency of 2.52% and 3.48%, respectively. The improved performance of the CC-3 h electrode was attributed mainly to the large surface area (which could contribute sufficient electroactive species), good conductivity, and high electrocatalytic activity. Overall, this work delivers novel insights into the use of copper sulfide and offers an important guidelines for the fabrication of next level energy storage and conversion devices.

Nanoparticle-featured MoS2 and WS2 have been synthesized using a facile one-step hydrothermal approach and their application as electroactive materials for high-performance supercapacitors has been investigated. The electrochemical results of the MoS2 electrode exhibit a higher specific capacitance (Cs) of 1531.2 F g−1 at 5 mA cm−2 with good cycling stability (up to 81.6% retention over 3000 cycles). The WS2 electrode delivers a high Cs of 1439.5 F g−1 at 5 mA cm−2 and excellent cycling stability with 77.4% retention after 3000 cycles. The outstanding performance of the MoS2 and WS2 electrodes indicates their potential in next-generation high-performance supercapacitor applications.

In the current work, cost-effective NiO nanosheets decorated with NiS nanoparticles were successfully fabricated on Ni foam by following a facile two-step hydrothermal route, and investigated as an efficient electrode material for supercapacitor applications for the first time. The obtained NiO/NiS hybrid electrode was found to deliver rapid diffusion of ions and fast electron transport, due to the high electrical conductivity, large surface area, and unique surface morphology of the NiO/NiS. As a result, this electrode exhibited a high specific capacitance of 386.7 F g−1 at 1 A g−1 and good cycling stability, specifically retaining 97.6% of the initial capacitance after 3000 charge–discharge cycles at 5 A g−1. These results indicated NiO/NiS to be a promising electrode material for supercapacitor applications.

In this work, we report a facile and cost-effective two-step hydrothermal method to fabricate the unique hierarchical CdMn2O4@CdMn2O4 structures on Ni foam for the first time. The CdMn2O4 diamond structures are fully covered on mesoporous CdMn2O4 nanoparticles. Compared with the bare CdMn2O4 nanoparticles, the composite CdMn2O4@CdMn2O4 electrode exhibits higher pseudocapacitive behaviors in 2 M KOH, which delivers a greatly enhanced specific capacitance of 3885 F g−1 at a current density of 1.5 A g−1. In addition, composite CdMn2O4@CdMn2O4 electrode shows superior cycling stability, retaining 99.8% of the initial capacitance after 2000 cycles at a current density of 5 A g−1.

MnNi2O4–PbS composites have been successfully deposited on a nickel (Ni) foam substrate using a simple and cost-effective two-step hydrothermal route for application as supercapacitor electrode materials in energy storage devices. The morphological, structural and physical behaviors of the as-prepared composite were evaluated, and the results indicate that the PbS nanoparticles were successfully anchored onto the surface of MnNi2O4 nanoflakes. The electrochemical studies reveal that the MnNi2O4–PbS composite exhibits a higher supercapacitor performance with a high specific capacitance of 1176.76 F g−1 at 1 A g−1 and improved cycling stability with 98.86% retention after 4000 cycles, which are much higher than that of the MnNi2O4 electrode. The improved electrochemical performance of the composite electrode is mainly due to its unique hierarchical structure, which provides a better contact of the electrolyte and electrode surface, and a large number of active sites. These results suggest that the unique MnNi2O4–PbS electrode would be a promising electrode for high-performance supercapacitor applications.

A rational and multicomponent design of hierarchical CoFe2Se4 (CFS) nanorods adhered to CoNiSe2 (CNS) microsphere composites is prepared for the first time via facile and eco-friendly synthesis methods. The hierarchical CFS–CNS robust architectures enhance the specific surface area and porosity and also increase the availability of electrochemically active sites, which provides ideal pathways for electrolyte diffusion and facilitates electron transportation. As a result, the as-prepared fabric-based CFS–CNS electrode delivers a maximum specific capacity of 183.4 mA h g−1 at a current density of 1 A g−1, with an excellent rate capability of 172.4 mA h g−1 at 8 A g−1 and outstanding cycling stability with 99.2% retention over 3000 cycles in aqueous 3 M KOH electrolyte solution. Moreover, the assembled fabric-based CFS–CNS//CFS–CNS symmetric SC achieves a high energy density of 80.2 W h kg−1 at 1000 W kg−1 and delivers an exceptional cycling stability with 97.02% retention over 3000 cycles as well as exhibiting excellent flexibility to sustain various deformations including bending and twisting. Utilizing the outstanding energy storage performance, the symmetric SC can light up a light-emitting diode for real-time applications.

Novel ZnO@CoFe2O4 and CoFe2O4 nanocomposites have potential applications on account of their high surface area and electrical properties. These two nanocomposite electrodes on nickel foam were developed for high performance electrochemical supercapacitor applications using a low-cost and facile one-step hydrothermal approach. The surface morphologies and electrochemical properties of the ZnO@CoFe2O4 and CoFe2O4 nanocomposites were examined by field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, galvanostatic charge–discharge cycling, and electrochemical impedance spectroscopy. The electrochemical tests indicated that the ZnO@CoFe2O4 nanocomposite electrode achieved a high specific capacitance of 4050.4 F g−1 at 10 mA cm−2 with a high energy density of 77.01 W h kg−1 in a 3 M KOH aqueous solution. This electrode exhibited attractive cycling stability and specific capacitance with approximately 90.9% capacity retention after 1000 cycles. On the other hand, the CoFe2O4 electrode showed lower specific capacitance (3499.9 F g−1) and cycling stability (50.07%) than the ZnO@CoFe2O4 nanocomposite electrode. These results highlight the potential of these ZnO@CoFe2O4 nanocomposite electrodes as electrodes for next generation supercapacitor applications in high energy density storage systems.

In this study, we report a facile two-step fabrication of honeycomb-like NiMoO4@NiWO4 nanocomposites on Ni foam as the electrode for high-performance supercapacitor applications. Structural characterization and compositional analysis of the as-prepared NiMoO4@NiWO4 nanocomposites was performed using scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, cyclic voltammetry, galvanostatic charge–discharge cycling, and electrochemical impedance spectroscopy. The electrochemical properties of the as-synthesized NiMoO4@NiWO4 nanocomposites were studied in a 3 M KOH electrolyte solution for application as electrode material of supercapacitors. A maximum specific capacitance of 1290 F g−1 was achieved for NiMoO4@NiWO4 at a current density of 2 A g−1. This electrode exhibits excellent long cycle-life stability with 93.1% specific capacitance retention after 3000 cycles at a current density of 6 A g−1. Our studies indicate that the as-synthesized NiMoO4@NiWO4 nanocomposites could be a promising candidate as the electrode material in high-performance electrochemical energy storage applications.

NiCo2O4 (NCO) nanosheet decorated MnCo2O4 (MCO) nanoflakes are successfully prepared on a nickel foam surface using a one-step chemical bath deposition route for supercapacitor applications. The unique nanoflakes with nanosheet structures provide efficient pathways for rapid electron and ion transportation. As a result, the MCO–NCO composite electrode exhibits a higher specific capacitance of 1152 F g−1 at 1 A g−1, excellent rate capability and superior cycling stability (95.38% retention after 3000 cycles) compared to individual MCO nanoflakes and NCO nanosheets. These results show that the as-fabricated MCO–NCO composites are promising candidates for electrochemical supercapacitors.

Unique ZnMn2O4@ZnFe2O4 microspheres were fabricated on Ni foam using a facile and cost-effective hydrothermal method for high-performance supercapacitor applications. The resulting ZnMn2O4@ZnFe2O4 electrode was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electrochemical techniques. The ZnMn2O4@ZnFe2O4 electrode exhibited a microsphere-like morphology with a mean size of ∼50–115 nm. The electrochemical performance of the ZnMn2O4@ZnFe2O4 electrode was investigated and the results showed that the ZnMn2O4@ZnFe2O4 electrode exhibits a high specific capacitance of 1024.66 F g−1 at 10 mA cm−2, low internal resistance, and remarkable cycling stability with 95.8% capacitance retention after 3000 charge–discharge cycles, which was superior to those of the ZnMn2O4 and ZnFe2O4 electrodes. Such enhanced electrochemical performance and the facile synthetic method of ZnMn2O4@ZnFe2O4 electrode materials offer great promise in next generation supercapacitor applications.

In the present study, pores enriched high surface area of carbon electrode obtained from hypercross-linked polymer of poly(divinylbenzene-co-vinylbenzyl chloride) [P(DVB:VBC)] for supercapacitor application. First, hypercross-linking reaction was carried out in [P(DVB:VBC)] via. simple Friedel-Crafts alkylation method (HCP) followed by pyrolysis at 800 °C (HCP-800). The surface morphology of the synthesized HCP and HCP-800 materials was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) technique. HCP-800 showed a remarkable surface area of 1027 m2 g−1 with the abundance of micropores. In addition, the oxidation state of the porous carbon was assessed by x-ray photo electron spectroscopy (XPS). In a three-electrode and symmetric two-electrode configurations, electrodes exhibited a supreme specific capacitance of 272 and 145 F g−1 in aqueous electrolyte, respectively. Specific energy of 39.47 Wh kg−1 at specific power of 699.96 W kg−1 is yielded from the symmetric supercapacitor device (SSCD). Furthermore, SSCD retains more than 94% of its residual capacitance after 5000 GCD cycles at a current density of 5 A g−1 suggests a good cyclic stability.

Binder-free hierarchical core-shell-like CoMn2O4@MnS heterostructures have been successfully grown on the surface of nickel (Ni) foam using facile two-step hydrothermal deposition route. In supercapacitor applications, the as-prepared core-shell-like CoMn2O4@MnS composite electrode has been used successfully as a battery-type material. Scanning electron microscope (SEM) and transmission electron microscope characterizations reveal that the as-prepared CoMn2O4@MnS electrode delivers a dandelion-like heterostructures that contains the MnS nanoparticles grown on the surface of CoMn2O4 nanowire arrays (NWAs), resulting a core-shell-like structure. In addition to increasing electrochemical behaviour and precise surface area, the novel core-shell-like heterostructures provide superhighways for the ultra-fast transfer of electrons and ions. The probable plateaus of cyclic voltammetry and galvanostatic charge-discharge experiments suggest that Faradic battery-type redox activity is given by the as-prepared core-shell-like CoMn2O4@MnS NWAs electrode. As a battery-type material, core-shell-like CoMn2O4@MnS NWAs electrode exhibits a outstanding specific capacity of (~213.0 mA h g−1 at 2 Ag−1), remarkable rate capability (~89.91% retains even at 10 A g−1), and excellent cycling stability (~91.42% at 6 A g−1 over 5000 cycles), which are much higher than those of the bare CoMn2O4 electrode. The excellent energy storage performance corroborates that CoMn2O4@MnS NWAs can serve as an advanced battery-type electrode material for supercapacitor applications.

CuS counter electrodes (CEs) were prepared to fabricate efficient quantum-dot-sensitized solar cells (QDSSCs) based on a CdS/CdSe photo sensitizer. The CEs were prepared on a fluorine-doped tin oxide (FTO) glass substrate by a facile chemical bath deposition (CBD) method by dissolving CuSO 4 ·5H 2 O and CH 3 CSNH 2 in water, followed by adding 0.25 mM polyvinylpyrrolidone (PVP). The CBD was performed at 60 °C for 1 h, 2 h, and 3 h, and the samples were labeled as CuS 1 h, CuS 2 h, and CuS 3 h, respectively. The QDSSCs were assembled using prepared CuS CEs and a TiO 2 /CdS/CdSe/ZnS photoanode, and the effect of the growth time of CuS CEs on the QDSSC performance was investigated. As the CuS growth time increases, the short-circuit current density ( J sc ), fill factor (FF), and open-circuit voltage ( V oc ) of the QDSSCs gradually increases, leading to an enhanced power conversion efficiency (η). QDSSCs that use the CuS 2 h CE exhibit a high J sc of 14.31 mA cm −2 , V oc of 0.603 V, and FF of 0.49, which are higher than that using conventional Pt electrodes as well as CuS 1 h and CuS 3 h electrodes. The electrochemical impedance spectroscopy results show that the CuS 2 h CE exhibits an inferior charge transfer resistance of only 2.93 Ω, which is 33 times lesser than that of the Pt CE. The enhanced device performance of CuS 2 h is ascribed to the high catalytic activity and low charge transfer resistance of the CuS CE in the reduction process of oxidized polysulfide. Consequently, a superior power conversion efficiency of 4.27% is achieved for QDSSCs utilizing CuS 2 h.

Polymer nano-composite composed of poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) and TiO 2 nano-particles was deposited on fluorine-doped tin oxide substrate and applied as an alternative to Au counter electrode of quantum dot-sensitized solar cell (QDSC). It became surface-richer with the increase in nano-particle amount so that catalytic reaction was increased by widened catalytic interface. Electrochemical impedance spectroscopy and cyclic voltammetry clearly demonstrated the enhancement of polymer nano-composite counter electrode. A QDSC based on polymer nano-composite counter electrode showed 0.56 V of V OC , 12.24 mA cm −2 of J SC , 0.57 of FF, and 3.87% of efficiency and this photovoltaic performance was higher than that of QDSC based on Au counter electrode (3.75%).

Copper sulfide (CuS) thin films with a nanoparticle structure on a fluorine-doped tin oxide (FTO) substrate prepared by facile chemical bath deposition (CBD) at different growth times were used as the CE for QDSSCs. The morphology of the CuS CE was controlled well by the electrochemical growth time. Here, the CuS thin films deposited for 2 h (CuS2h) CE and TiO 2 /CdS/CdSe/ZnS QD sensitized cell exhibited superior electrochemical and photovoltaic performance with J sc , V oc , and FF values of 15.52 mA cm − 2 , 0.612 V, and 0.452, respectively, and an efficiency (η) of 4.29%, whereas the cell with the Au CE delivered an η of only 2.19% under the same conditions. Electrochemical impedance spectroscopy and Tafel polarization showed that the CuS film deposited at 2 h possesses fascinating electrocatalytic activity for the S 2 − /S n 2 − redox couple in a polysulfide electrolyte solution that was superior to Au CE. In addition, the stability test conducted for both CuS and Au-based devices for approximately 45 h under the one sun illumination confirmed that the long-term stability of the CuS film decreased by 12% (4.31–3.79%), whereas that of the Au based cell decreased by 9.6% (2.19–1.98%) from 0 to 45 h.

Charge recombination is considered as one of the most significant factors in hindering the photovoltaic performance of quantum dot-sensitized solar cells (QDSSCs). In addition, expand the light absorption range to the near-infrared region in QDSSCs increasing the generated photocurrent. A significant enhancement in the power conversion efficiency (PCE) of QDSSCs has been obtained by charge recombination control and enhanced light harvesting. In this respect, PbCdS layer is introduced between TiO2 and CdS QDs via a facile successive ionic layer absorption and reaction (SILAR) method in order to further improve the cell performance. For the first time a photoanode assembly composed of TiO2/PbCdS/CdS was prepared in QDSSCs. The photovoltaic parameters were significantly enhanced with the incorporation of a PbCdS intermediate layer between TiO2 and CdS QDs but varied appreciably with the SILAR cycles of PbCdS. When four SILAR cycle layer was applied, the PCE is as high as 3.35%, which is higher than the efficiency of 1.84% for the solar cell without PbCdS layer. The improved performance of the TiO2/PbCdS/CdS-based QDSSCs was attributed to the PbCdS layer can enhance the light harvesting to release more excitons. In addition, the PbCdS layer accelerates the electron injection kinetics and also functioning as a blocking layer to cover the TiO2 core from the outer QDs and redox couple, thereby reducing the recombination of electrons from the TiO2 with the electrolyte or with the QDs. Electrochemical impedance measurements has been measured and discussed in detail providing a detailed analysis of charge transport processes in QDSSCs.

This paper proposes a novel and facile strategy to synthesize hierarchical nanostructured NiCo2S4via a simple hydrothermal reaction combined with a post anion-exchange reaction that was used directly as an electrode in supercapacitor and quantum-dot sensitized solar cells. By applying the appropriate material concentration, deposition temperature, and time, the NiCo2S4 was densely deposited over the entire surface of the Ni foam with good adhesion. The NiCo2S4 electrode exhibited outstanding electrochemical performance in both the applications with a high specific capacitance of 1612.95 F g−1, energy density of 56 W h kg−1 at 5 A g−1, good cycling stability, power conversion efficiency of 3.94%, and Jsc of 12.27 mA cm−2. The NiCo2S4 electrode exhibited almost double the output values compared to NiCo2O4 (693.6 F g−1 at 6.66 A g−1 and efficiency of 1.81%) and NiCo2Se (1401.4 F g−1 at 10 A g−1 and efficiency of 3.86%), resulting from the excellent electrochemical performance of the NiCo2S4. Overall the excellent performance of the fabricated electrode was attributed mainly to the highly electrocatalytic activity, large surface area and decent conductivity of the hierarchical nanostructures of the NiCo2S4. This study shows that the NiCo2S4 nanostructures can be applied not only in high energy density fields, but also in high power density and energy harvesting applications.

The Cu–ZnS passivation layer is considered to be far more efficient than the most widely used ZnS passivation layer in terms of enhancement of light harvesting and suppression of surface charge recombination. As a result, a TiO2/CdS/Cu–ZnS quantum dot sensitized solar cell (QDSSC) exhibits a greatly improved efficiency of 3.35%, which is 30% and 82% higher than that of TiO2/CdS/ZnS and TiO2/CdS based QDSSCs, respectively.

Expensive and energy-consuming vacuum process of metal deposition with ambient-unstable hole transporters are incompatible with large-scale and low-cost production of perovskite solar cells (PSCs) and thus hampers their commercialization. For the first time, we demonstrate cost-effective novel carbon nanotube (CNT) paste that was applied to FTO substrate by the facile doctor blade method and processed at low temperature (100 °C). Herein we report a new method of cost-efficient perovskite solar cells with the use of conventional hole transporters by directly clamping a selective hole extraction electrode made of CNT and a TiO 2 /perovskite photoanode. Most importantly, under optimized conditions in the absence of an organic hole-transporting material and metal contact, CH 3 NH 3 PbI 3 and CNTs formed a solar cell with an efficiency of up to 7.83%. The PSC devices are fabricated in air without high-vacuum deposition which simplifies the processing and lowers the threshold of both scientific research and industrial production of PSCs. Electrochemical impedance spectroscopy demonstrates good charge transport characteristics of CEs on the photovoltaic performance of devices. The PSCs exhibited good stability over 50 h. The abundance, low cost, and excellent properties of the CNT material offer wide prospects for further applications in PSCs.

Herein, we tailor the surface morphology of nickel–manganese-layered double hydroxide (NiMn-LDH) nanostructures on 3D nickel-foam via a step-wise cobalt (Co)-doping hydrothermal chemical process. At the 10% optimum level of Co-doping, we noticed a thriving tuned morphological pattern of NiMn-LDH nanostructures (NiCoMn-LDH (10%)) in terms of the porosity of the nanosheet (NS) arrays which not only improves the rate capability as well as cycling stability, but also demonstrates nearly two-fold specific capacitance enhancement compared to Co-free and other NiCoMn-LDH electrodes with a half-cell configuration in 3 M KOH, suggesting that Co-doping is indispensable for improving the electrochemical performance of NiMn-LDH electrodes. Moreover, when this high performing NiCoMn-LDH (10%) electrode is employed as a cathode material to fabricate an asymmetric supercapacitor (ASC) device with reduced graphene oxide (rGO) as an anode material, excellent energy storage performance (57.4 Wh kg−1 at 749.9 W kg−1) and cycling stability (89.4% capacitive retention even after 2500 cycles) are corroborated. Additionally, we present a demonstration of illuminating a light emitting diode for 600 s with the NiCoMn-LDH (10%)//rGO ASC device, evidencing the potential of the NiCoMn-LDH (10%) electrode in fabricating energy storage devices.

The effect of the cobalt nitrate hexahydrate/zinc nitrate hexahydrate molar ratio on the physicochemical features of the zeolitic imidazole framework (ZIF) was studied. ZIFs were prepared by using 2-methyl imidazole as the cross-linker at room temperature without any additives in methanol solution. From the obtained results, it was found that the Co/Zn ratio has a tremendous impact on the surface area, crystallinity, pore diameter and electrochemical performance of ZIFs. Upon increasing the Co/Zn content the surface area, pore volume, pore diameter and specific capacitance decreased. The maximum BET surface area was found to be 1043.65 m2 g−1 for ZIF Co/Zn = 0.5. The present work offers a new intuition in relation to the role of the Co/Zn ratio in the synthesis method of ZIFs.

High energy density, fast charge–discharge capability, high flexibility, and sustained cycle life are the key challenges in the application of flexible supercapacitors (SCs) in modern electronics. These primary requirements could be accomplished by engineering a new class of current collectors consisting of hierarchical combinations of various active materials. This study reports the selective integration of hierarchical Ni(OH)₂ nanoneedle arrays with NiO–NiCo₂O₄ nanosheet arrays (Ni(OH)₂ NNAs@NiO–NiCo₂O₄ NSAs) on flexible fabric for high-performance electrodes. The novel core–shell-like hetero-nanoarchitectures not only enhance the electrochemical activity and specific surface area but also, more importantly, provide superhighways for the ultrafast transport of electrons and ions. As a battery-type material, the core–shell-like Ni(OH)₂ NNAs@NiO–NiCo₂O₄ NSAs display a high specific capacity of 326.7 mA h g⁻¹ at 2 A g⁻¹ in aqueous 3 M KOH; this value is 1.89, 1.23 and 1.14 times those of NiO–NiCo₂O₄, NiO@NiO–NiCo₂O₄ and Co₃O₄@NiO–NiCo₂O₄ electrodes, respectively. Most importantly, a flexible hybrid SC (FHSC, Ni(OH)₂ NNAs@NiO–NiCo₂O₄ NSAs//graphene-ink) demonstrates a superhigh energy density of 97.1 W h kg⁻¹ and a superior long cycling lifespan with 94.7% retention over 5000 cycles. Utilizing these excellent energy storage properties, the fabricated FHSC operated a multifunction electronic display and light up different colored light emitting diodes for real-time applications. This work was supported by BK 21 PLUS, Creative Human Resource Development Program for IT Convergence, Pusan National University, Busan, South Korea.