In Situ Electrochemical Cobalt Doping in Perovskite-Structured Lanthanum Nickelate Thin Film Toward Energy Conversion Enhancement of Polymer Solar Cells

This study demonstrates that the electrochemical doping of lanthanum nickelate (LNO) with cobalt ions is a promising strategy for enhancing its physical and electrochemical properties, which are critical for energy storage and conversion devices. LNO emerges as a promising hole transport layer (HTL) in solar cells due to its stability, large band gap, and high transparency. Nevertheless, its low conductivity and improperly aligned band positions are persistent problems. Here, in a pioneering endeavor, Co-doped LNO thin films were synthesized electrochemically and applied as the HTL in polymer solar cells (PSCs). Characterization revealed the impact of Co doping on the electrochemical, structural, morphological, and optical properties of LNO thin films. Depending on the Co doping level, PSCs based on 10 mol % Co-doped LNO outperformed pure LNO, achieving a champion efficiency of 6.11% with enhanced short-circuit current density (12.84 mA cm-2), fill factor (68%), open-circuit voltage (0.70 V), and external quantum efficiency (82.6%). This enhancement resulted from decreased series resistance, refined surface morphology, minimized trap-assisted recombination, enhanced conductivity, increased charge carrier production, favorable energy level alignment, and improved current extraction facilitated by LNC0.10O HTL. Moreover, the unencapsulated PSC-LNC0.10O long-term stability notably improved and retained 86% of its initial PCE after 450 h storage in ambient air, 82% after being continuously heated to 85 °C for 300 h, and 80% after operating at maximum power point for 300 h. These findings offer a straightforward approach to enhancing PSC performance through Co doping of LNO, supported by density functional theory (DFT) calculations that validate the experimental results and confirm the improvement in optical properties and stability of PSCs as an HTL.

Resent Development of Binder-Free Electrodes of Transition Metal Oxides and Nanohybrids for High Performance Supercapacitors - A Review

The entire world is aware of the serious issue of global warming and therefore utilizing renewable energy sources is the most encouraging steps toward solving energy crises, and as a result, energy storage solutions are necessary. The supercapacitors (SCs) have a high-power density and a long cycle life, they are promising as an electrochemical conversion and storage device. In order to achieve high electrochemical performance, electrode fabrication must be implemented properly. Electrochemically inactive and insulating binders are utilized in the conventional slurry coating method of making electrodes to provide adhesion between the electrode material and the substrate. This results in an undesirable "dead mass," which lowers the overall device performance. In this review, we focused on binder-free SCs electrodes based on transition metal oxides and composites. With the best examples providing the critical aspects, the benefits of binder-free electrodes over slurry-coated electrodes are addressed. Additionally, different metal-oxides used in the fabrication of binder-free electrodes are assessed, taking into account the various synthesis methods, giving an overall picture of the work done for binder-free electrodes. The future outlook is provided along with the benefits and drawbacks of binder-free electrodes based on transition metal oxides.

Redox active pyridine-3,5-di-carboxylate- and 1,2,3,4-cyclopentane tetra-carboxylate-based cobalt metal-organic frameworks for hybrid supercapacitors

In the pursuit of developing superior energy storage devices, an integrated approach has been advocated to harness the desirable features of both batteries and supercapacitors, particularly their high energy density, and high-power density. Consequently, the emergence of hybrid supercapacitors has become a subject of increasing interest, as they offer the potential to merge the complementary attributes of these two technologies into a single device, thereby surpassing the limitations of conventional energy storage systems. In this context the Metal-Organic Frameworks (MOFs), consisting of metal centers and organic linkers, have emerged as highly trending materials for energy storage by virtue of their high porosity. Here, we investigate the electrochemical performance of cobalt-pyridine-3,5-di-carboxylate-MOF (Co-PDC-MOF) and cobalt-1,2,3,4-cyclopentane tetra-carboxylate-MOF (Co-CPTC-MOF). In the setup involving the analysis of Co-PDC-MOF and Co-CPTC-MOF materials, a configuration comprising three electrodes was utilized. Drawing upon the promising initial properties of CPTC, a battery device was fabricated, comprising Co-CPTC-MOF, and activated carbon (AC) electrodes. Retaining a reversible capacity of 97% the device showcased impressive energy and power density of 20.7 W h g^-1 and 2608.5 W kg^-1, respectively. Dunn's model was employed, to gain deeper insights into the capacitive and diffusive contributions of the device.

Effect of SiO2/Al2O3 ratio on the electrochemical performance of amorphous zeolite loaded with cobalt oxide grown via steam-assisted crystallization method

Improving the performance of a supercapacitor is one of the main approaches to solve the energy shortage problem. Electrode material is one of the key components limiting the efficiency of a supercapacitor. Discovering, tuning, and improving electrode materials are very important. This work reports the effect of SiO₂/Al₂O₃ ratio on electrochemical performances of amorphous zeolites ZSM5 (AZ) and H-ZSM5 (H-AZ) loaded with cobalt oxide. Two SiO₂/Al₂O₃ ratios (1 = 6.2 and 2 = 8.3) of AZ₁, AZ₂ and H-AZ₁, H-AZ₂ were synthesized by a facile impregnation method. Then, controlled masses of cobalt oxide were introduced to enhance the supercapacitive performances of the amorphous zeolite. Investigation of the SiO₂/Al₂O₃ ratio in the cobalt oxide/zeolite composite (Co/AZ and Co/H-AZ) was carried out to unveil its effect on the electrochemical properties. Worthy of note is the fact that the resulting electrode materials exhibited supercapacitive behavior that is effective over a potential window ranging from 0 to 0.5 V in potassium hydroxide (1 M KOH) aqueous electrolyte. Results from Galvanometry Charging and Discharging (GCD) analyses show that the modified Ni-foam electrodes loaded with Co/H-AZ₁ and Co/H-AZ₂ are capable of delivering a relatively high specific capacity from 45.97 mA h g^-1 to a high value of 72.5 mA h g^-1 at 1 A g^-1 and Ni-foam electrodes loaded with Co/AZ₁ and Co/AZ₂ exhibited values from 26 mA h g^-1 to 52.83 mA h g^-1 respectively. It is clearly shown that, when the mass ratio SiO₂/Al₂O₃ increases, the specific capacity increases as well. It was also noticed that after 2000 cycles, Co/H-AZ₁ and Co/AZ₁ have a poor coulombic efficiency while Co/H-AZ₂ and Co/AZ₂ exhibited 98% for coulombic efficiency. Finally, this study shows that to fabricate high performance supercapacitors with amorphous zeolite loaded with cobalt oxide, one should keep the ratio of SiO₂/Al₂O₃ as high as possible during synthesis.

Metal organic framework derived NiO x nanoparticles for application as a hole transport layer in perovskite solar cells

NiO _x as a hole transport layer (HTL) has gained a lot of research interest in perovskite solar cells (PSCs), owing to its high optical transmittance, high power conversion efficiency, wide band-gap and ease of fabrication. In this work, four different nickel based-metal organic frameworks (MOFs) using 1,3,5-benzenetricarboxylic acid (BTC), terephthalic acid (TPA), 2-aminoterephthalic acid (ATPA), and 2,5-dihydroxyterephthalic acid (DHTPA) ligands respectively, have been employed as precursors to synthesize NiO _x NPs. The employment of different ligands was found to result in NiO _x NPs with different structural, optical and morphological properties. The impact of calcination temperatures of the MOFs was also studied and according to field emission scanning electron microscopy (FESEM), all MOF-derived NiO _x NPs exhibited lower particle size at lower calcination temperature. Upon optimization, Ni-TPA MOF derived NiO _x NPs calcined at 600 °C were identified to be the best for hole transport layer application. To explore the photovoltaic performance, these NiO _x NPs have been fabricated as a thin film and its structural, optical and electrical characteristics were analyzed. According to the findings, the band energy gap (E _g) of the fabricated thin film has been found to be 3.25 eV and the carrier concentration, hole mobility and resistivity were also measured to be 6.8 × 10¹⁴ cm^-3; 4.7 × 10¹⁴ Ω cm and 2.0 cm² V^-1 s^-1, respectively. Finally, a numerical simulation was conducted using SCAPS-1D incorporating the optical and electrical parameters from the thin film analysis. FTO/TiO₂/CsPbBr₃/NiO _x /C has been utilized as the device configuration which recorded an efficiency of 13.9% with V _oc of 1.89 V, J _sc of 11.07 mA cm^-2, and FF of 66.6%.

A Facile Microwave Hydrothermal Synthesis of ZnFe2O4/rGO Nanocomposites for Supercapacitor Electrodes

As a typical binary transition metal oxide, ZnFe₂O₄ has attracted considerable attention for supercapacitor electrodes due to its high theoretical specific capacitance. However, the reported synthesis processes of ZnFe₂O₄ are complicated and ZnFe₂O₄ nanoparticles are easily agglomerated, leading to poor cycle life and unfavorable capacity. Herein, a facile microwave hydrothermal process was used to prepare ZnFe₂O₄/reduced graphene oxide (rGO) nanocomposites in this work. The influence of rGO content on the morphology, structure, and electrochemical performance of ZnFe₂O₄/rGO nanocomposites was systematically investigated. Due to the uniform distribution of ZnFe₂O₄ nanoparticles on the rGO surface and the high specific surface area and rich pore structures, the as-prepared ZnFe₂O₄/rGO electrode with 44.3 wt.% rGO content exhibits a high specific capacitance of 628 F g^-1 and long cycle life of 89% retention over 2500 cycles at 1 A g^-1. This work provides a new process for synthesizing binary transition metal oxide and developing a new strategy for realizing high-performance composites for supercapacitor electrodes.

NiO/Ni Nanowafer Aerogel Electrodes for High Performance Supercapacitors

Transition metal oxide aerogels are a fascinating class of compounds that have received considerable attention in the last decade owing to their unique and exceptional properties, including high porosity, large surface area, and ultralow density. In this study, α-Ni(OH)₂ aerogels and annealed NiO/Ni aerogels were used to design and fabricate a two-electrode supercapacitor device. The physicochemical properties of the as-synthesized aerogels were characterized through X-ray diffraction, scanning electron microscopy, transmission electron microscopy, the Brunauer-Emmett-Teller theory, and X-ray photoelectron spectroscopy studies. The annealed NiO/Ni aerogels showed a (specific capacitance of 1060 F/g) specific capacity of 422 C/g at 1 A/g current density and with good cycling stability (up to 10,000 cycles). The supercapacitor also demonstrated an energy density of 32.4 Wh/kg and power density of 1800 W/kg at a current density of 2 A/g. The specific capacitance of NiO/Ni aerogels was more than twice that of the α-Ni(OH)₂ aerogels. The practical applications of the aerogel were demonstrated by fabricating a two-electrode device.

Nickel Oxide-Incorporated Polyaniline Nanocomposites as an Efficient Electrode Material for Supercapacitor Application

This work reports the facile, controlled, and low-cost synthesis of a nickel oxide and polyaniline (PANI) nanocomposites-based electrode material for supercapacitor application. PANI-NiO nanocomposites with varying concentrations of NiO were synthesized via in-situ chemical oxidative polymerization of aniline. The XRD and FTIR support the interaction of PANI with NiO and the successful formation of the PANI-NiO-x nanocomposite. The SEM analysis showed that the NiO and PANI were mixed homogenously, in which the NiO nanomaterial was incorporated in porous PANI globular nanostructures. The multiple phases of the nanocomposite electrode material enhance the overall performance of the energy-storage behavior of the supercapacitor that was tested in 1 M H2SO4 using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). Among the different nanocomposites, PANI-NiO-3 exhibit the specific capacitance of a 623 F g−1 at 1 A g−1 current density. Furthermore, the PANI-NiO-3 electrode retained 89.4% of its initial capacitance after 5000 cycles of GCD at a 20 A g−1 current density, indicating its significant cyclic stability. Such results suggest that PANI-NiO nanocomposite could be proposed as an appropriate electrode material for supercapacitor applications.

Adsorptive removal of some Cl-VOC's as dangerous environmental pollutants using feather-like γ-Al2O3 derived from aluminium waste with life cycle analysis

Herein, we designed a cost-effective preparation method of nanocomposite γ-Al₂O₃ derived from Al-waste. The produced material has a feather-like morphology, and its adsorption of some chlorinated volatile organic compounds (Cl-VOC's) such as benzyl chloride, chloroform and carbon tetrachloride (C₇H₇Cl, CHCl₃ and CCl₄) was investigated due to their potential carcinogenic effect on humans. It showed a characteristic efficiency towards the adsorptive removal of these compounds over a long period, i.e., eight continuous weeks, at ambient temperature and atmospheric pressure. After 8-weeks, the adsorbed amounts of these compounds were determined as: 325.3 mg C₇H₇Cl, 247.6 mg CHCl₃ and 253.3 mg CCl₄ per g of γ-Al₂O_3, respectively. CCl₄ was also found to be dissociatively adsorbed on the surface of γ-Al₂O₃, whereas CHCl₃ and C₇H₇Cl were found to be associatively adsorbed. The prepared γ-Al₂O₃ has a relatively high surface area (i.e., 192.2 m². g^-1) and mesoporosity with different pore diameters in the range of 25-47 Å. Furthermore, environmental impacts of the nanocomposite γ-Al₂O₃ preparation were evaluated using life cycle assessment. For prepartion of adsorbent utilising 1 kg of scrap aluminium wire, it was observed that potential energy demand was 288 MJ, climate change potential was 19 kg CO₂ equivalent, acidification potential was 0.115 kg SO₂ equivalent and eutrophication potential was 0.018 kg PO₄^3- equivalent.

Fabrication of High-Performance Asymmetric Supercapacitor Consists of Nickel Oxide and Activated Carbon (NiO//AC)

Exploring faster, safer, and more efficient energy storage devices will motivate scientists to develop novel energy storage products with high performance. Herein, we report porous NiO nanoparticles have been prepared by a simple hydrothermal method with CTAB and laboratory tissue paper as a template followed by calcination at three different temperatures (300, 500, and 700 °C). The electrochemical characteristics of the prepared materials were examined in a three-electrode cell configuration using aqueous potassium hydroxide (2.0 M KOH) electrolyte. The NiO-300 electrode displayed the supreme capacitance of 568.7 F g−1 at 0.5 A g−1. The fascinating NiO morphology demonstrates a crucial part in offering simple ion transport, shortening electron, and ion passage channels and rich energetic spots for electrochemical reactions. Finally, the asymmetric supercapacitor (ASC), NiO//AC was constructed using positive and negative electrode materials of NiO-300 and activated carbon (AC), respectively. The assembled ASC displayed excellent supercapacitive performance with a high specific energy (52.4 Wh kg−1), specific power (800 W kg−1), and remarkable cycle life. After quick charging (25 s), such supercapacitors in the series will illuminate the light emitting diode for an extended time, suggesting improvements in energy storage, scalable integrated applications, and ensuring business efficacy. This work will lead to a new generation of high-performance ASCs to portable electronic displays and electric automobiles.

Toward Enhanced Electrochemical Performance by Investigation of the Electrochemical Reconstruction Mechanism in Co2V2O7 Hexagonal Nanosheets for Hybrid Supercapacitors

As for hybrid supercapacitors, it is important to enhance the long cycling performance and high specific capacitance. In this paper, cobalt vanadate (Co₂V₂O₇) hexagonal nanosheets on nickel foam are manufactured by a facile hydrothermal method and then transformed into numerous smaller size interconnected hierarchical nanosheets without any shape change via electrochemical reconstruction. Benefiting from the favorable architecture of hierarchical nanosheets via electrochemical reconstruction, the Co₂V₂O₇ hexagonal nanosheet electrode exhibits a remarkable long cycling performance with 272% specific capacitance retention after 100,000 cycles at a current density of 5 A g^-1 and then displays an increasing specific capacitance of 1834 F g^-1 (tested at 1 A g^-1). Furthermore, an aqueous hybrid supercapacitor device based on the Co₂V₂O₇ hexagonal nanosheet electrode exhibits a high energy density of 35.2 Wh kg^-1 at a power density of 1.01 kW kg^-1 and an excellent cyclic stability with 71.4% capacitance retention after 10,000 cycles at 5 A g^-1. These results offer a practicable pathway for enhancing the electrochemical properties of other metal oxides through electrochemical reconstruction.

Investigating the Impact of the Washing Steps of Layered Double Hydroxides (LDH) on the Electrochemical Performance

The washing of layered double hydroxides (LDH) material is mostly purposed to discard the unreacted products after the reaction has been completed. However, this study demonstrated that the washing stage can also be targeted to optimise the electrochemical performance of LDH by using an appropriate solvent. Solvents, namely, ethanol, acetone, and an ethanol-acetone solution (2:1) were used for the washing of LDH and the impacts thereof on the structural, physical, chemical, morphological, and electrochemical properties were investigated. Using Williamson-Hall analysis, we observed modifications on the crystalline domain. The specific surface area and pore parameters for all the samples were also differently affected. The Fourier transform infrared (FTIR) measurements displayed evident changes in the basic sites. The electrochemical performances of samples were analysed. The sample washed with the ethanol-acetone solution exhibited a specific capacitance of 1807.26 Fg-1 at 10 mVs-1, which is higher than that of other samples as well as low internal resistance compared to its counterpart. This demonstrates that the use of an appropriate solvent during the washing stage of LDH affects the electrochemical properties.

Synthesis and characterization of polyphenols functionalized graphitic hematite nanocomposite adsorbent from an agro waste and its application for removal of Cs from aqueous solution

In this study, Polyphenols functionalized Graphitic Hematite Nanocomposite (PGHN) was used as an adsorbent to remove Caesium (Cs) ions from a simulated solution. The nanocomposite was produced by synthesizing iron oxide nanoparticles using orange peel extract (OPE) as the reducing and capping agent in the presence of graphite produced from sugarcane bagasse. The nanocomposite exhibited a scaly morphology and the mean particle size of rhombohedral structured hematite nanoparticles was found to be 148.9 nm. The simulated solution of Cs ions was treated with PGHN and the treatment conditions were optimized by batch method. The concentration of Cs ion in the treated solution was determined using atomic emission spectroscopy (AES). The maximum Cs adsorption of 97.95% was attained at an optimum condition of pH - 9.0 and adsorbent dose - 70 mg/mL for treatment period of 110 min. The experimental data of adsorption fitted well with pseudo 1st order kinetics and was favorable for both Langmuir and Freundlich isotherm models. The study reports a facile method for the production of nanocomposite using agro-wastes such as sugarcane bagasse and orange peels. The synthesized nanocomposite was used as an adsorbent for the removal of toxic Cs and can be further used for industrial wastewater treatment.

Optimization of hydrogen-ion storage performance of tungsten trioxide nanowires by niobium doping

The transport and storage of ions within solid state structures is a fundamental limitation for fabricate more advanced electrochemical energy storage, memristor, and electrochromic devices. Crystallographic shear structure can be induced in the tungsten bronze structures composed of corner-sharing WO₆octahedra by the addition of edge-sharing NbO₆octahedra, which might provide more storage sites and more convenient transport channels for external ions such as hydrogen ions and alkali metal ions. Here, we show that Nb₂O₅·15WO₃nanowires (Nb/W = 0.008) with long length-diameter ratio, smooth surface, and uniform diameter have been successfully synthesized by a simple hydrothermal method. The Nb₂O₅·15WO₃nanowires do exhibit more advantages over h-WO₃nanowires in electrochemical hydrogen ion storage such as smaller polarization, larger capacity (71 mAh g^-1, at 10C, 1C = 100 mA g^-1), better cycle performance (remain at 99% of the initial capacity after 200 cycles at 100C) and faster H⁺ions diffusion kinetics. It might be the crystallographic shear structure induced by Nb doping that does result in the marked improvement in the hydrogen-ion storage performance of WO₃. Therefore, complex niobium tungsten oxide nanowires might offer great promise for the next generation of electrochemical energy and information storage devices.

Biogenesis and Application of Nickel Nanoparticles: A Review

Biogenic synthesis of Nanoparticles (NPs) is attractive due to their ecological benefits and cheap, rapid, and sustainable nature. Among them, Nickel Oxide NPs (NiO-NPs) are acquired for their varied catalytic and clinical applications, as they have antibacterial, antifungal, cytotoxic, anticancer, antioxidant, remediation, and enzyme inhibition properties. Though several chemical-dependent methods were applied for the fabrication of nanoparticles, due to their substantial disadvantages, mainly toxicity and higher cost synthesis methods, the more secure, greener, eco-friendly, cost-effective, and synthetic methods are in demand. Greener approaches can take away the arduousness and complications of physicochemical methods. The present review is aimed at displaying the recent advancement related to the catalytic activity, antimicrobial activity, cytotoxicity, and antioxidant application of green synthesized Nickle. In this study, nickle oxide nanoparticles have been highlighted along with their sustainable synthesis options.

Porous and nanowire-structured NiO/AgNWs composite electrodes for significantly-enhanced supercapacitive and electrochromic performances

NiO/AgNWs composite films which specially contain both porous and one-dimensional (1D) nanowire structures are prepared uniformly via a simple chemical bath deposition method. The supercapacitive electrodes constructed by the as-prepared NiO/AgNWs composite films exhibit a high specific capacitance (980 F g^-1at 1 A g^-1), much higher than that of the pure NiO films. Particularly, a large optical modulation (84.3% at 550 nm) and short switching times for the coloration and bleaching (5.4 and 6.5 s) are also observed if these NiO/AgNWs films serve as the electrochromic materials. The superior capacitive and electrochromic properties of the NiO/AgNWs composite films are attributed to the large electrochemically effective surface areas and enhanced conductivity induced by the addition of 1D AgNWs, which efficiently shorten the ions/electrons diffusion paths and accelerate the reversible redox reactions. Therefore, the NiO/AgNWs composite films hold a great potential for applications as a novel electrode material in supercapacitive and electrochromic devices.

Fabrication of Co3O4 from Cobalt/2,6-Napthalenedicarboxylic Acid Metal-Organic Framework as Electrode for Supercapacitor Application

In this study, cobalt-based metal-organic framework (MOF) powder was prepared via the solvothermal method using 2,6-naphthalenedicarboxylic acid (NDC) as the organic linker and N,N-dimethylformamide (DMF) as the solvent. The thermal decomposition of the pristine cobalt-based MOF sample (CN-R) was identified using a thermogravimetric examination (TGA). The morphology and structure of the MOFs were modified during the pyrolysis process at three different temperatures: 300, 400, and 500 °C, which labeled as CN-300, CN-400, and CN-500, respectively. The results were evidenced via field-emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The crystallite size of all samples was calculated using Scherrer's equation. The smallest crystallite size of 7.77 nm was calculated for the CN-300 sample. Fourier transform infrared spectroscopy (FTIR) spectra were acquired for all the samples. The graphical study of the cyclic voltammogram (CV) gave the reduction and oxidation peaks. The charge transfer resistance and ionic conductivity were studied using electrical impedance spectroscopy (EIS). The galvanostatic charge-discharge (GCD) responses of all samples were analyzed. The relatively high specific capacitance of 229 F g-1 at 0.5 A g-1 was achieved in the sample CN-300, whereby 110% of capacitance was retained after 5000 cycles. These findings highlighted the durability of the electrode materials at high current densities over a long cycle.

Nickel Cobaltite Functionalized Silver Doped Carbon Xerogels as Efficient Electrode Materials for High Performance Symmetric Supercapacitor

Introducing new inexpensive materials for supercapacitors application with high energy density and stability, is the current research challenge. In this work, Silver doped carbon xerogels have been synthesized via a simple sol-gel method. The silver doped carbon xerogels are further surface functionalized with different loadings of nickel cobaltite (1 wt.%, 5 wt.%, and 10 wt.%) using a facile impregnation process. The morphology and textural properties of the obtained composites are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen physisorption analysis. The silver doped carbon xerogels display a higher surface area and larger mesopore volume compared to the un-doped carbon xerogels and hierarchically porous structure is obtained for all materials. The hybrid composites have been utilized as electrode materials for symmetric supercapacitors in 6 M KOH electrolyte. Among all the hybrid composites, silver doped carbon xerogel functionalized with 1 wt.% nickel cobaltite (NiCo1/Ag-CX) shows the best supercapacitor performance: high specific capacitance (368 F g⁻¹ at 0.1 A g⁻¹), low equivalent series resistance (1.9 Ω), high rate capability (99% capacitance retention after 2000 cycles at 1 A g⁻¹), and high energy and power densities (50 Wh/Kg, 200 W/Kg at 0.1 A g⁻¹). It is found that the specific capacitance does not only depend on surface area, but also on others factors such as particle size, uniform particle distribution, micro-mesoporous structure, which contribute to abundant active sites and fast charge, and ion transfer rates between the electrolyte and the active sites.

Superior Pseudocapacitive Storage of a Novel Ni3Si2/NiOOH/Graphene Nanostructure for an All-Solid-State Supercapacitor

Recent developments in the synthesis of graphene-based structures focus on continuous improvement of porous nanostructures, doping of thin films, and mechanisms for the construction of three-dimensional architectures. Herein, we synthesize creeper-like Ni₃Si₂/NiOOH/graphene nanostructures via low-pressure all-solid melting-reconstruction chemical vapor deposition. In a carbon-rich atmosphere, high-energy atoms bombard the Ni and Si surface, and reduce the free energy in the thermodynamic equilibrium of solid Ni-Si particles, considerably catalyzing the growth of Ni-Si nanocrystals. By controlling the carbon source content, a Ni₃Si₂ single crystal with high crystallinity and good homogeneity is stably synthesized. Electrochemical measurements indicate that the nanostructures exhibit an ultrahigh specific capacity of 835.3 C g^-1 (1193.28 F g^-1) at 1 A g^-1; when integrated as an all-solid-state supercapacitor, it provides a remarkable energy density as high as 25.9 Wh kg^-1 at 750 W kg^-1, which can be attributed to the free-standing Ni₃Si₂/graphene skeleton providing a large specific area and NiOOH inhibits insulation on the electrode surface in an alkaline solution, thereby accelerating the electron exchange rate. The growth of the high-performance composite nanostructure is simple and controllable, enabling the large-scale production and application of microenergy storage devices.

Solvent-Controlled Morphology of Amino-Functionalized Bimetal Metal-Organic Frameworks for Asymmetric Supercapacitors

The composition-tuned, structure-modified, and morphology-controlled nanoscale metal-organic frameworks (MOFs) are quite important to improve the electrochemical performances for supercapacitors. In this work, a solvent-controlled method to prepare amino-functionalized bimetal MOFs with various morphologies is proposed. Three different morphologies of NiCo-MOFs, such as nanospheres, nanosheet-assembled hollow spheres (NSHSs), and rhombus sheets, have been successfully synthesized by using different solvents. The as-prepared three nanoscale NiCo-MOFs are comparatively characterized and are endowed a possible mechanism on nucleation and crystal growth controlling morphology. When used as electrode materials for supercapacitors, all NiCo-MOFs have excellent electrochemical properties. Specifically, the NiCo-MOF NSHS owns the best specific capacitance, which can achieve 1126.7 F g^-1 at the current density of 0.5 A g^-1 and maintain 93% of its original capacitance at the current density of 10 A g^-1 after 3000 charge-discharge cycles. Moreover, an asymmetric supercapacitor device (NiCo-MOF NSHS//AC) assembled with NiCo-MOF NSHS as the positive electrode and activated carbon (AC) as the negative electrode achieves an energy density of 20.94 Wh kg^-1 at a power density of 750.84 W kg^-1. This work is facile and highly reproducible and can be extended to prepare other nano-MOFs in energy storage and conversion fields. In addition, it opens up an effective approach to synthesizing amino-functionalized MOFs by a solvent-controlled method without any other changes in the experimental conditions.

Ultrasonication-assisted synthesis of novel strontium based mixed phase structures for supercapattery devices

An upsurge in sustainable energy demands has ultimately made supercapattery one of the important choice for energy storage, owing to highly advantageous energy density and long life span. In this work, novel strontium based mixed phased nanostructures were synthesized by using probe sonicator with sonication power 500 W at frequency of 20 kHz. The synthesized material was subsequently calcined at different temperature ranging from 200 to 800 °C. Structural and morphological analysis of the synthesized materials reveals the formation of mixed particle and rod like nanostructures with multiple crystal phases of strontium oxides and carbonates. Crystallinity, grain size and morphology of grown nanomaterials significantly improved with the increase of calcination temperature due to sufficient particle growth and low agglomeration. The electrochemical performance analysis confirms the redox activeness of the Sr-based electrode materials. Material calcined at 600 °C show high specific capacitance of 350 F g^-1 and specific capacity of 175 C g^-1 at current density of 0.3 A g^-1 due to less particle agglomeration, good charge transfer and more contribution of electrochemical active sites for redox reactions. In addition, the developed supercapattery of Sr-based nanomaterials//activated carbon demonstrated high performance with maximum energy density of 21.8 Wh kg^-1 and an excellent power density of 2400 W kg^-1 for the lower and higher current densities. Furthermore, the supercapattery retain 87% of its capacity after continuous 3000 charge/discharge cycles. The device characteristics were further investigated by analyzing the capacitive and diffusion controlled contributions. The versatile strategy of developing mixed phased nanomaterials pave the way to synthesize other transition metal based nanomaterials with superior electrochemical performance for hybrid energy storage devices.

Hyperbranched Triphenylamine Polymer for UltraFast Battery Cathode

A novel hyperbranched poly(triphenylamine) (PHTPA) was synthesized, and the electrochemical properties of this material were studied. PHTPA was synthesized by a facile method in a one-step reaction from affordable monomers. Despite all aromatic structures, PHTPA showed good solubility in several organic solvents. The battery performance test of PHTPA showed a high discharge voltage, an ultrafast charge-discharge performance of 100-300 C, and a long cycle life of more than 5000 cycles. Moreover, the addition of the PHTPA to LiFePO₄ (LFP) improved the charge-transfer resistance and Warburg coefficient, which is related to the diffusion of lithium ions in LFP, and consequently improved the charge-discharge performance of LFP itself at a high C rate (20-100 C). This behavior is understood to be the result of the organic-inorganic charge transfer. The superior cycle performance of the PHTPA-LFP hybrid cathode was also found. PHTPA will serve as an additive for a high-performance LIB.

Advanced Energy Storage Devices: Basic Principles, Analytical Methods, and Rational Materials Design

Tremendous efforts have been dedicated into the development of high-performance energy storage devices with nanoscale design and hybrid approaches. The boundary between the electrochemical capacitors and batteries becomes less distinctive. The same material may display capacitive or battery-like behavior depending on the electrode design and the charge storage guest ions. Therefore, the underlying mechanisms and the electrochemical processes occurring upon charge storage may be confusing for researchers who are new to the field as well as some of the chemists and material scientists already in the field. This review provides fundamentals of the similarities and differences between electrochemical capacitors and batteries from kinetic and material point of view. Basic techniques and analysis methods to distinguish the capacitive and battery-like behavior are discussed. Furthermore, guidelines for material selection, the state-of-the-art materials, and the electrode design rules to advanced electrode are proposed.

Self-templated Synthesis of Nickel Silicate Hydroxide/Reduced Graphene Oxide Composite Hollow Microspheres as Highly Stable Supercapacitor Electrode Material

Nickel silicate hydroxide/reduced graphene oxide (Ni₃Si₂O₅(OH)₄/RGO) composite hollow microspheres were one-pot hydrothermally synthesized by employing graphene oxide (GO)-wrapped SiO₂ microspheres as the template and silicon source, which were prepared through sonication-assisted interfacial self-assembly of tiny GO sheets on positively charged SiO₂ substrate microspheres. The composition, morphology, structure, and phase of Ni₃Si₂O₅(OH)₄/RGO microspheres as well as their electrochemical properties were carefully studied. It was found that Ni₃Si₂O₅(OH)₄/RGO microspheres featured distinct hierarchical porous morphology with hollow architecture and a large specific surface area as high as 67.6 m² g^-1. When utilized as a supercapacitor electrode material, Ni₃Si₂O₅(OH)₄/RGO hollow microspheres released a maximum specific capacitance of 178.9 F g^-1 at the current density of 1 A g^-1, which was much higher than that of the contrastive bare Ni₃Si₂O₅(OH)₄ hollow microspheres and bare RGO material developed in this work, displaying enhanced supercapacitive behavior. Impressively, the Ni₃Si₂O₅(OH)₄/RGO microsphere electrode exhibited outstanding rate capability and long-term cycling stability and durability with 97.6% retention of the initial capacitance after continuous charging/discharging for up to 5000 cycles at the current density of 6 A g^-1, which is superior or comparable to that of most of other reported nickel-based electrode materials, hence showing promising application potential in the energy storage area.

Strong Pinned-Spin-Mediated Memory Effect in NiO Nanoparticles

After a decade of effort, a large number of magnetic memory nanoparticles with different sizes and core/shell compositions have been developed. While the field-cooling memory effect is often attributed to particle size and distribution effects, other magnetic coupling parameters such as inter- and intra-coupling strength, exchange bias, interfacial pinned spins, and the crystallinity of the nanoparticles also have a significant influence on magnetization properties and mechanisms. In this study, we used the analysis of static- and dynamic-magnetization measurements to investigate NiO nanoparticles with different sizes and discussed how these field-cooling strengths affect their memory properties. We conclude that the observed field-cooling memory effect from bare, small size NiO nanoparticles arises because of the unidirectional anisotropy which is mediated by the interfacial strongly pinned spins.

High performance of electrochemical lithium storage batteries: ZnO-based nanomaterials for lithium-ion and lithium-sulfur batteries

As one of the most promising electrode materials, zinc oxide-based nanomaterials have attracted great attention in recent decades for remarkable features such as relatively low cost, relatively high reversible capacity and good physical and chemical stability. In this article, we aim to present a general review of synthetic methods of zinc oxide-based nanomaterials and related morphologies. In addition, recent advances in lithium storage batteries are summarized and discussed (lithium-ion and lithium-sulfur batteries). Tentative conclusions and assessments aim to promote the next generation of electrochemical lithium storage devices.

Facile sonochemical synthesis of nanostructured NiO with different particle sizes and its electrochemical properties for supercapacitor application

In this work, we demonstrate the influence of nickel oxides with divergent particle sizes as the working electrodes for supercapacitor application. The nanostructured nickel oxide (NiO) is synthesized via facile sonochemical method, followed by calcination process. The crystallinity and surface purity of prepared samples are clearly examined by X-ray diffraction and Raman analysis. NiO crystallinity is significantly increased with increasing calcination temperatures. The surface analysis confirmed that the calcination at 250°C exhibited nanoclutser like NiO with average particle size of ∼6nm. While increasing the calcination temperature beyond 250°C, hexagonal shaped NiO is observed with enhanced particle sizes. The electrochemical performance confirmed the good redox behavior of NiO electrodes. Moreover, NiO with average particle size of ∼6nm exhibited high specific capacitance of 449F/g at a scan rate of 5mV/s compared to other samples with particle sizes of ∼21nm (323F/g) and ∼41nm (63F/g). This is due to the good ion transfer mechanism and effective electrochemical utilization of the working electrode.