Three-electrode Assembly Research Articles

1,2,4-Triazole (Htrz) functionalised 2D-manganese-organic framework (UPMOF-5) as a battery-type electrode for supercapattery

Metal-organic frameworks (MOFs) have attracted a lot of attention in the field of energy storage and conversion due to their unique properties, including large specific surface areas, adjustable pore sizes and stable porous structures. Herein, we report a novel porous Mn-based MOF that was prepared through a facile solvothermal method using 1,2,4-triazole (Htrz) organic linker in the presence of N, N’-dimethylacetamide (DMA) as a solvent. The novel [Mn(Htrz)(DMA)Br] denoted as UPMOF-5 crystallised in a monoclinic P21 space group showing a two-dimensional (2D) structure and a large BET surface area of 1725 m2/g. For the first time, the synthesised manganese-1,2,4-triazolate framework (UPMOF-5) was used as an electrode in supercapattery device assembly. Impressively, a battery-graded nature was shown in the three-electrode assembly of the UPMOF-5, which had a decent specific capacity of 160.17 C/g at 0.4 A/g. The designed supercapattery device with UPMOF-5 as a positive electrode and activated carbon as a negative electrode delivered a good specific capacity of 132.40 C/g at 0.4 A/g with 24.77 Wh/kg of specific energy at 538.91 W/kg of specific power. After 10,000 cycles, the device showed promising capacity retention of 70.3 %. The structural stability and porous character of UPMOF-5 are credited with the decent electrochemical performance.

Facile synthesis of hierarchical ZnS@FeSe2 nanostructures as new energy-efficient cathode material for advanced asymmetric supercapacitors

We have effectively synthesized ZnS, FeSe2, and their nanocomposite using a straightforward and affordable solvothermal process. We also investigated for the first time their ideal electrochemical performance for supercapacitors. The ZnS and FeSe2 positive electrodes exhibit capacitances of 266.2 F g−1 and 294.3 F g−1, respectively, with fascinating nanostructures and morphology. Their respective nanocomposites, AZ-1, AZ-2, and AZ-3, deliver capacitances of 356.8, 444.4, and 326.1 F g−1 with significant rate performance in aqueous solution in a three-electrode assembly. The lowest ESR and Rct values of AZ-2 electrodes, which improved conductivity and charge transport kinetics and created a synergistic effect between ZnS and FeSe2 electrodes, are responsible for their exceptional capacitative performance. We built an asymmetric supercapacitor (AZ-2/AC) with an optimal voltage of 1.6 V, which demonstrated great power density (6250 W kg−1) and energy density (33 Wh kg−1) with remarkable cycling stability (88.1%) in an aqueous electrolyte after 12,000 cycles. As a result, FeSe2-based nanocomposites are strong contenders for realizing high energy and power delivery for practical applications.

Inside–outside OH– incursion involved in the fabrication of hierarchical nanoflake assembled three-dimensional flower-like α-Co(OH)2 for use in high-performance aqueous symmetric supercapacitor applications

IntroductionThe energy industry has been challenged by the current high population and high energy consumption, forcing the development of effective and efficient supercapacitor devices. The crucial issues until now have been high production cost, deprived cyclic stability, and squat energy density. To resolve these problems, various approaches have been taken, such as the development of long-life electrode materials with high capacity, rapid charging, and slow discharging to overcome poor life cycle stability. ObjectivesIn the present work we focus on fabricating cost-effective unique-morphology, high-surface-area alpha-Co(OH)2 for application in an aqueous-electrolyte symmetric supercapacitor. MethodsIn this study, hierarchical nanoflakes assembled in three-dimensional (3D) flower-shaped cobalt hydroxide (HN-3DF-α-Co(OH)2) electrode were synthesized using the solvothermal method with sodium dodecylbenzene sulfonate (SDBS) and methanol as solvents. Spectroscopic and microscopic techniques were used to characterize fabricated HN-3DF-Co(OH)2, which revealed that the materials electrode exhibited the alpha phase with a hierarchical flower-like structure. A half-cell electrochemical assembly (three-electrode assemble cell) and symmetric full cell (two-electrode assemble cell) were examined in an aqueous electrolyte. ResultsIn three-electrode assembly cells, HN-3DF-α-Co(OH)2 exhibited 719.5 Fg−1 specific capacitance (Csp) at 1 Ag−1 with excellent cyclic retention stability of approximately 88% after 3000 cycles. In two-electrode symmetric supercapacitive systems, HN-3DF-α-Co(OH)2 achieved a maximum Csp of 70.3 Fg−1 at 0.4 Ag−1 with the highest energy density of approximately 6.25 Wh/kg at a power density of 328.94 W/kg. The fabricated two-electrode assembly cell with the HN-3DF-α-Co(OH)2 electrode retained cyclic stability of approximately 85% after 5000 repeated charge and discharge cycles. ConclusionSolvothermally-synthesized, optimized HN-3DF-α-Co(OH)2 showed outstanding electrochemical performance results in three- and two-electrode systems. This unique aqueous symmetric supercapacitor can be used to design cost-effective symmetric capacitors based on metal hydroxide.

Smart Bandage to Monitor Combat Wounds and Control Bacterial Infections During Military Operations

In the United States Army, nearly 50% of soldiers experience 1 or more injuries a year during deployment and mission operations. The most common injuries during these operations can be classified between saturable wounds, such as lacerations and punctures, and non-saturable wounds, such as blast wounds, gunshot wounds, head injuries, bone fractures, burns, and ulcers. In all cases, the leading post-wound treatment are complications associated with wound infections; with sepsis being the leading cause of death in after wound care. Gram-positive, gram-negative, and fungal infections are the most prevalent types of infections seen in the U.S. Army, with Staphylococcus aureus (s. aureus) being the most common infection recorded in about 20% of soldiers. Present techniques are limited to using pressure pads and antibacterial gels for preventing infections. These approaches cannot be integrated into a wearable construct and do not offer a reliable method of management. Therefore, monitoring and treating infection in combat wounds is a major healthcare challenge in wound care management for army application.Our work focuses on developing a wearable smart bandage that can detect a change in pH and lactate using an electrochemical sensing approach that responds as a function of bacterial infection and can monitor in real-time using data generated by sensors. Further, the pH sensing causes a triggered release of drug molecules that control bacterial infection in the wound bed. The electrochemical pH sensors were fabricated by printing commercial flexible inks onto a stretchable thermoplastic polyurethane (TPU, TE-11C DuPontTM) film, and subsequently heat laminating over a cotton gauze (thickness: 100 μm). A conventional three-electrode cell assembly consisting of SPCE, Ag/AgCl as a reference electrode, and a Pt wire as a counter electrode was used for the experiments. CV was performed to assess the performance of the electrodeposited polyaniline. The measurements were performed at a scan rate of 0.02 V s-1 in a potential window of 1 V and -0.2 V. Sensor stability was characterized under room temperature and physiological conditions (RT) over 3 days. In case of the triggered drug release, we synthesized chitosan-pH responsive polymer using an ionic gelation process and drug ampicillin and kanamycin were encapsulated with a 64% efficiency. The polymer released drug above pH 6.5 which correlated to 105 bacterial CFU/ml, thus was incorporated in the bandage matrix and served as a controlled release when infection occurs. It was observed that pH tends to rise as infection progress therefore ideal for drug release in an alkaline environment.Finally, the sensor was able to detect bacterial cells ranging from 102-105 cells and the drug release showed an 82% reduction in cell number. The work carried out highlights an integrated sensor to sense bacterial infections and simultaneously trigger drug release. In light of current findings, this study allowed us to understand the dynamic interaction occurring between the sensor surface and wound bed and the sensor data showed a direct correlation to bacterial infection. The sensor can be integrated into a multiplex wearable device detecting different biomarkers to simultaneously monitor and manage infection in combat as well as chronic wounds.

Pseudocapacitive Effects of Multi-Walled Carbon Nanotubes-Functionalised Spinel Copper Manganese Oxide.

Spinel copper manganese oxide nanoparticles combined with acid-treated multi-walled carbon nanotubes (CuMn2O4/MWCNTs) were used in the development of electrodes for pseudocapacitor applications. The CuMn2O4/MWCNTs preparation involved initial synthesis of Mn3O4 and CuMn2O4 precursors followed by an energy efficient reflux growth method for the CuMn2O4/MWCNTs. The CuMn2O4/MWCNTs in a three-electrode cell assembly and in 3 M LiOH aqueous electrolyte exhibited a specific capacitance of 1652.91 F g−1 at 0.5 A g−1 current load. Similar investigation in 3 M KOH aqueous electrolyte delivered a specific capacitance of 653.41 F g−1 at 0.5 A g−1 current load. Stability studies showed that after 6000 cycles, the CuMn2O4/MWCNTs electrode exhibited a higher capacitance retention (88%) in LiOH than in KOH (64%). The higher capacitance retention and cycling stability with a Coulombic efficiency of 99.6% observed in the LiOH is an indication of a better charge storage behaviour in this electrolyte than in the KOH electrolyte with a Coulombic efficiency of 97.3%. This superior performance in the LiOH electrolyte than in the KOH electrolyte is attributed to an intercalation/de-intercalation mechanism which occurs more easily in the LiOH electrolyte than in the KOH electrolyte.

Electrochemical Testing of Carbon Materials as Bromine Electrodes for the Hydrogen-Bromine Redox Flow Battery

Hydrogen-bromine (H2-Br2) redox flow batteries (RFBs) have gained a lot of interest due to their advantages in mitigating the performance shortcomings of conventional zinc-bromine and vanadium flow batteries. Various carbon materials have been tested in H2-Br2 RFBs as bromine electrodes. However, a comparative study among the different carbon materials has not been reported in the literature. This work reports, for the first time, an evaluation of carbon papers, felt and cloth in a three-electrode half-cell setup as potential bromine electrodes, in pristine and thermally treated state. A systematic evaluation was performed by comparing the surface morphologies, kinetic parameters, polarisation curves and stability tests of different carbon electrodes. Thermally treated graphite felt electrode demonstrated the best electrochemical performance as bromine electrode owing to its improved surface area, hydrophilicity and intrinsic activity. Further in-depth studies will shed important insights, which will help understand the electrode characteristics for future bromine battery design. The current study will assist in evaluating the performance of upcoming novel electrode materials in a three-electrode assembly.

Microwave-mediated synthesis of tetragonal Mn3O4 nanostructure for supercapacitor application.

The development of electrode materials plays a vital role in energy storage applications to save and store energy. In the present work, the synthesis of nanorod shaped Mn3O4 supported with amorphous carbon (Mn3O4/AC) is reported by the microwave method for supercapacitor application. The as-prepared electrode material was then characterized using microscopic and spectroscopic techniques. The electrochemical supercapacitor performance of Mn3O4/AC was examined by the cyclic voltammetry and galvanostatic charge-discharge method inside the three-electrode assembly cell. The results showed that the Mn3O4/AC delivers the excellent capacitance value of the 569.5 Fg-1 at the current load of 1 Ag-1, higher than the previously reported Mn3O4 based electrodes. The better performance of the Mn3O4/AC is credited to the excellent redox behaviour of the Mn3O4 and the presence of the amorphous carbon, which facilitated the fast ion interaction between the electrode and electrolyte during the electrochemical reaction.

Diffusion control and surface control mechanism in hierarchical nanostructured porous zinc‐basedMOFmaterial for supercapattery

In this paper, we are reporting the zinc-based metal-organic framework nanomaterials for their application as a supercapattery device. The facile hydrothermal technique had been utilized to synthesize the MOF material. The surface morphology, crystallinity, and porosity were investigated with X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller, and energy dispersive X-ray analysis. To study the ability of the synthesized material for the storage of charges, electrochemical characterizations such as cyclic voltammetry (CV), galvanostatic charge (GCD), and electrochemical impedance spectroscopy (EIS) were performed in 1.0 M potassium hydroxide electrolyte. The specific capacity has been calculated from GCD curves and the material delivers 200 C/g at a current density of 0.7 A/g. This material revealed excellent performance in three-electrode assembly and therefore coupled with activated carbon (Zn-MOF//AC) to analyze the real energy and power density. This asymmetric assembly (supercapattery) had been tested with CV, GCD, and EIS. From all these characterizations, it was founded that the device was able to store charges of 172 C/g along with the excellent energy density and power density of 38.05 Wh/kg and 240 W/kg, respectively. The supercapattery revealed exceptional cyclic stability of 93.6% even after 2500 GCD cycles along with 100% of columbic efficiency. Furthermore, the diffusion-controlled and surface-controlled contributions were investigated for the assembled supercapattery, and it is found that the device stores energy through both the contributions. The maximum diffusive contribution by the device was 70.13% at the scan rate of 10 mV/s, which reaches to 42.75% at 100 mV/s scan rate. Likewise, the surface control contribution of the device was 29.86% at 10 mV/s, which rises up to 57.24% at 100 mV/s scan rate. These variations are attributed to the scan rates, which allow the ions to interact fast/slow with electrodes. Our analysis indicates that the synthesized material can be utilized as an interesting high-performance electrode material for supercapattery devices.

Wrinkle-Shaped Nickel Sulfide Grown on Three-Dimensional Nickel Foam: A Binder-Free Electrode Designed for High-Performance Electrochemical Supercapacitor Applications

Recently, three-dimensional nickel foam (3D-Nf) has been increasingly studied; however, further modifications in nanoscale surface modification are necessary for particular applications. In this work, three-dimensional hierarchically porous nanogranular NiS (NiS-3D-Nf) and wrinkle-shaped NiS (w-NiS-3D-Nf) structures were fabricated directly on nickel foam by a simple one-step solvothermal process using two different solvents. Several characterization techniques, including X-ray diffraction pattern, X-ray photoelectron spectroscopy, and scanning electron microscopy, were used to characterize the samples’ properties. To prove their applicability, supercapacitor electrodes were tested directly in a three-electrode assembly cell. The resulting w-NiS-3D-Nf electrodes exhibited greater capacitive activity than the NiS-3D-Nf electrodes. The optimized w-NiS-3D-Nf electrodes delivered an excellent specific capacitance of 770 Fg−1, at a current density of 1 Ag−1, compared with the NiS-3D-Nf electrodes (162.0 Fg−1 @ 1 Ag−1), with a cyclic stability of over 92.67% capacitance retention after 2200 cycles. The resultant unique structure with integrated hierarchical three-dimensional configuration can not only enhance abundant accessible surface areas but also produce strong adhesion to the 3D-Nf, facilitating the fast transportation of ions and electrons for the electrochemical reaction via the conductive 3D-Nf. This set of results suggests that the modification of 3D-Nf surfaces with a suitable solvent has highly significant effects on morphology, and ultimately, electrochemical performance. Additionally, the current preparation approach is simple and worthwhile, and thus offers great potential for supercapacitor applications.

Facile hydrothermal synthesis of high-performance binary silver-cobalt-sulfide for supercapattery devices

The rapid depletion of fossil fuel resources, along with rising energy consumption, has prompted the development of renewable energy storage systems. More focus must be placed on renewable and sustainable energy sources in order to reduce the reliance on fossil fuels for energy production. Because of their tremendous energy and great power density, batteries and supercapacitors are being intensively researched in renewable energy storage systems. In this work. We used a one-step simple hydrothermal approach to synthesize silver sulfide, cobalt sulfide, and their binary compound silver cobalt sulfide with a 50/50 weight ratio. X-ray diffraction (XRD) and scanning electron microscopy (SEM) examined the materials' crystallinity and surface morphology. Electrochemical behavior of silver sulfide AgS (S1) cobalt sulfide CoS (S2), and silver cobalt sulfide (AgCoS) was investigated in the three-electrode assembly. Cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) have been carried out to explore its electrochemical characteristics. The electrochemical analysis reveals that silver sulfide AgS (S1) provides a specific of 402 C/g at 3 mV/s while cobalt sulfide CoS (S2) provides the specific capacity of 289C/g at 3 mV/s. when combined silver sulfide and cobalt sulfide in a 50/50 weight ratio specific capacity achieved with silver cobalt sulfide AgCoS (S3) is 701.01C/g at a low scan rate of 3 mV/s. An asymmetric device (AgCoS//AC) was developed by employing activated carbon as the negative electrode and the best silver cobalt sulfide as the positive electrode. This asymmetric supercapacitor has been investigated through CV, GCD, and stability tests for 1000 consecutive cycles. The device delivered a high energy density of 22.34 Wh/kg in parallel to the high power density of 899.2 W/kg. After 1000 consecutive cycles, the columbic efficiency of this device increases to 105% while maintaining capacity retention of 82%. This study indicates that silver cobalt can be an efficient electrode material for supercapattery devices.

Effect of binder on the performance of zinc‐tin‐sulfide nano flakes for the high‐performance supercapattery devices

Here in this work, we report the role of binder concentration on the electrochemical performance of Zn-Sn-S (ZTS) mesoporous material for high-performance supercapattery devices. The desired material is synthesized through the facile hydrothermal technique followed by ultra-sonication for 1 h. Material’s morphology, crystallinity, porosity, surface area, elemental analysis, and composition were analyzed through field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The effect of binder concentration on the electrochemical properties was investigated by performing cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in three-electrode assembly while maintaining the 1 M KOH electrolyte environment. In three-electrode setup, the electrodes with a binder concentration of 50%, 25%, and 10% show a specific capacity of 69.24, 154.17, and 247.91 C/g at the current density of 1.0 A/g. Correspondingly, the series resistance observed in EIS for these three electrodes are 3.27, 2.12 and 1.29 Ω, which suggests that ZTS with 10% nafion possesses better electrochemical properties. Therefore, the electrode with a 10% binder concentration was then coupled with the activated carbon to assemble a supercapattery. This assembly (ZTS//AC) was then characterized with CV, GCD, and EIS, which delivers a specific capacity of 135.27 C/g, energy density of 30.06 Wh/kg, and 3200 W/kg of power density. At last, the device's cyclic life had been investigated by initiating GCD for 2500 continuous cycles at the current density of 3.0 A/g. We found that the material’s performance significantly got affected by the binder concentration, and it showed better performance with the optimized concentration of the binder. Furthermore, the ZTS material can be utilized as an appealing electrode material for future supercapattery devices that can deliver a high energy and power density because the material had shown a stable behavior at higher current densities.

Cobalt manganese phosphate and sulfide electrode materials for potential applications of battery-supercapacitor hybrid devices

Electrode materials with efficient electrochemical properties are always desirable for high storage energy devices. Here, due to the attractive attributes of metal phosphates and sulfides, we present a sonochemically synthesized binary composite of cobalt manganese phosphate (CoMn(PO4)2) and sulfide (CoMnS) for the real-world applications. The surface and structural properties of the synthesized materials are then investigated through X-ray diffraction (XRD) and scanning electron microscopy (SEM). Subsequently, the prepared electrode materials are optimized through electrochemical measurements performed in a three-electrode assembly. The best performing electrode, (CoMnS (S2) yielding a specific capacity (Qs) of 537 C/g at a current density js of 1 A/g) is then amalgamated with a carbonaceous electrode (activated carbon AC) for the fabrication of asymmetric (supercapattery) device. The constructed device (S2//AC) is then subjected to a two-electrode setup, providing an outstanding specific energy (Es) of 73.52 Wh/kg and a maximum specific power (Ps) of 10,200 W/kg. Afterwards, the device is analyzed for a stability test and preserved a maximum capacity retention of 90.03% against 10 A/g for 10,000 charge-discharge cycles. A semi-empirical approach via Dunn's model is next exploited to scrutinize the negative (capacitive) and positive (diffusive) electrode contributions for the device.

Ultrasonically decorated zinc cobaltate on nanocellulose interface for supercapacitors

The strategic design of energy storage materials from renewable sources has been a keen interest for researchers, especially for energy storage applications. In the present study, ZnCo2O4 and its nanostructures were fabricated along with cellulose nanocrystals (ZnCo2O4@CNC) using the green ultrasonication technique. Structural and morphological examination of composite materials have been investigated by the aid of Field-emission transmission electron microscopy (FE-TEM), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), and Surface Brunauer-Emmett-Teller (BET) analysis revealing the existence of spherical particles arranged in a controlled nanoscale range (i.e., < 10 nm). The electrochemical properties of ZnCo2O4 and ZnCo2O4@CNC nanocomposites were performed by CV, GCD, and EIS measurements. The ZnCo2O4@CNC electrode reveals a higher specific capacitance value of 346 F/g than its pristine ZnCo2O4 (236 F/g) at 0.5 A/g (current density) in a three-electrode cell assembly. The ZnCo2O4@CNC nanocomposite electrode shows exceptional capacitance with 97% cyclic retention straight after 5000 cycles at 0.5 A/g with an energy density of 15.8 Wh kg−1 at a power density of 138.4 W kg−1, significantly superior to its pristine ZnCo2O4 composite. The increased specific capacitance of nanocomposite materials manifested by the improved surface and morphological properties convince it as capable materials for high-performance electrochemical capacitors.

Unveiling the Redox Electrochemistry of MOF-Derived fcc-NiCo@GC Polyhedron as an Advanced Electrode Material for Boosting Specific Energy of the Supercapattery.

Metal organic frameworks (MOFs), which constitute a new class of porous organic-inorganic hybrid materials, have gained considerable attention in the fields of electrochemical energy storage and conversion devices owing to their open topological structures, large surface areas, tunable morphologies, and extreme redox activity. A synthesis protocol that comprises coprecipitation followed by controlled calcination processes to design a battery-type electrode is used. This electrode consists of three-dimensional (3D), ant cave-like polyhedrons of nickel-cobalt alloy on graphitic carbon (GC; NiCo@GC) nanostructures; trimesic acid is used as a potential MOF-linker. The developed NiCo@GC sample exhibits mesoporous characteristics with the maximum surface area of 94.08 m2 g-1 at 77 K. In addition, the redox activity at different sweep rates reveals the battery-type charge storage behavior of the NiCo@GC electrode; its three-electrode assembly provides 444 C g-1 specific capacity at 2 A g-1 with long-term capacity retention. The constructed supercapattery (SC) devices (i.e., AC//NiCo@GC) achieved capacity, specific energy, and specific power are 74.3 mAh g-1 , 39.5 Wh kg-1 , and 665 W kg-1 , respectively. Owing to its reasonable electrochemical characteristics, the prepared NiCo@GC material is a promising candidate for supercapattery electrodes for portable electronic devices.

In-situ dilatometry and impedance spectroscopy characterization of single walled carbon nanotubes blended LiNi0.6Mn0.2Co0.2O2 electrode with enhanced performance

Enhancing lithium-ion batteries (LiBs) cycle life is essential from both economic and sustainability perspective. In addition, to make their application in electric vehicles (EVs) even more feasible, the energy and power density have to be enhanced as well. Improvement in the electrical conductivity of battery electrodes can lead to an augmentation in power density and this can be achieved by using highly conductive carbon nanomaterials in the electrode fabrication. On the other hand, cycle life of LiBs is affected by dilation of both positive and negative electrodes during lithium ion (de)-insertion, and this can be also tailored by electrode design. In this work, ozonated long single walled carbon nanotubes (SWCNTs) are utilized to improve electrical conductivity of a LiNi0.6Mn0.2Co0.2O2 (NMC622) positive electrode along with enhancement of the mechanical strength. The enhancement effect of the ozone-treated SWCNTs on the NMC622 positive electrodes is demonstrated by means of electrochemical impedance spectroscopy and in-situ dilatometry. Compared to a conventional conductive carbon containing electrode, the presence of SWCNTs in an NMC622 electrode decreases irreversible height change occurring during a formation cycle from 276 nm to 86 nm and decreases overall electrode height change ∼5.5 times. Furthermore, coulombic and energy efficiencies of the Ozonated SWCNT NMC622 electrodes are improved by 1.2% and 6.4%, respectively, compared to the reference NMC622 electrode after 250 cycles in a three-electrode assembly, showing great potential for SWCNTs to be used in LiBs. Hence, addition of optimized amount of modified SWCNTs is capable of enhancing both power density and cycling stability of LiBs simultaneously.

Environmentally-assisted microstructural integrity of commercial cold drawn pearlitic steel wires

This paper deals with environmentally-assisted microstructural integrity of commercial cold drawn pearlitic steel wires to be used as prestressing steel wires for prestressed concrete in civil engineering structures. The article contains a fractographic analysis of the fracture surfaces of initially-smooth samples of commercial prestressing steel wires subjected to tensile tests in aggressive environment promoted by a corrosion cell consisting of the metallic sample and a three-electrode assembly. Two testing rates were used: one moderately fast (0,1 mm/min) and another moderately slow (0,01 mm/min). The electro-chemical potential used covers a wide range (from –400 to –1400 mV SCE), thus including from anodic to cathodic conditions. The main objective is focused on the study of the fracture surface for those specimens that failed due to the aggressive environment (inside corrosion cell). The analysis of the fracture surface is made by considering the different domains of the micro-fracture map (MFM).

Magnetron sputtered tungsten di-sulfide: An efficient battery grade electrode for supercapattery devices

Tungsten disulfide (WS2) due to its layered structure and high capacitance is an attractive electrode material for supercapattery application. In this study, different thickness of WS2 is deposited by magnetron sputtering technique. The thickness of the sputtered layer is also optimized. The sputtered WS2 is characterized by various techniques such as X-ray diffraction and atomic force microscopy to examine the structural morphology and to study the surface morphology. The electrochemical performance of sputtered WS2 is investigated through three-electrode assembly via cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. Sample S2 (WS2 with 250 nm thickness) shows the best performance in comparison with other samples. The S2 exhibits the maximum specific capacity of 346 C/g at 0.5 A/g. The hybrid device is designed by keeping S2 as positive and activated carbon as the negative electrode. The device exhibits maximal specific capacity of 190.2 C/g and after 3000 galvanostatic charge-discharge, cycles it retains 98.6% of its initial capacity. The maximum specific energy of the device is 45.2 Wh/kg which is high enough and an exceptional maximum specific power of 10,200 W/kg. Furthermore, by applying Dunn's model the diffusive and capacitive contributions of the hybrid device are studied. Moreover, b values are calculated by employing power law, the trend of b values confirms the asymmetric nature of supercapattery device. The excellent results of magnetron sputtered WS2 makes it a favorable electrode for its application in supercapattery devices.

Development of Binder Free Interconnected 3D Flower of NiZn2O4 as an Advanced Electrode Materials for Supercapacitor Applications

The design and development of electrode materials for energy-storage applications is an area of prime focus around the globe because of the shortage of natural resources. In this study, we developed a method for preparing a novel three-dimensional binder-free pseudocapacitive NiZn2O4 active material, which was grown directly over nickel foam (NiZn2O4@3D-NF), using a simple one-step hydrothermal process. The material was characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy techniques were employed to evaluate the pseudocapacitive performance of the NiZn2O4 active material in a three-electrode assembly cell. The prepared NiZn2O4@3D-NF electrode exhibited an excellent specific capacitance, of 1706.25 F/g, compared to that of the NiO@3D-NF (1050 F/g) electrode because it has the bimetallic characteristics of both zinc and nickel. The NiZn2O4@3D-NF electrode showed better cyclic stability (87.5% retention) compared to the NiO@3D-NF electrode (80% retention) after 5000 cycles at a fixed current density, which also supports the durability of the NiZn2O4@3D-NF electrode. The characteristics of NiZn2O4@3D-NF include corrosion resistance, high conductivity, an abundance of active sites for electrochemical reaction, a high surface area, and synergism between the bimetallic oxides, which make it a suitable candidate for potential application in the field of energy storage.

Effect of polyaniline on the performance of zinc phosphate as a battery-grade material for supercapattery

Efficient electrochemical energy storage devices are essential to address the current energy demands, as traditional energy storage devices are unable to fulfill the global energy quest due to their low energy and power density. Therefore, a hybrid approach is used to harvest the advantages of batteries and supercapacitors in a single device known as supercapattery. Herein, a cost-efficient, sustainable, and nontoxic zinc phosphate/polyaniline composite is developed for high-performance supercapattery through hydrothermal method. The morphology, and crystallinity of the prepared zinc phosphate with polyaniline composite (Zn3(PO4)2/PANI) is examined through SEM (scanning electron microscopy), and XRD (X-ray diffraction), respectively. Initially, the performance of Zn3(PO4)2/PANI is investigated in the three-electrode testing assembly using a 1 M KOH electrolyte. These results reveal an excellent performance of Zn3(PO4)2/PANI (50/50%) compared to its counterparts (Zn3(PO4)2 and PANI). A two-electrode real device (supercapattery) was fabricated by coupling the Zn3(PO4)2/PANI with activated carbon (Zn3(PO4)2/PANI // AC), and its performance is investigated through CV, GCD, and EIS. The maximum energy density of Zn3(PO4)2/PANI // AC supercapattery is found to be 25.16 W h/kg at a power density of 850 W/kg using 1.2 A/g current density. Furthermore, the electrochemical storage mechanism of the assembled device is inspected through Dunn's model to validate theoretically the experimental results. It is found that the diffusion controlled reactions are dominant at low scan rates for charge storage, whereas the diffusion-limited reactions are found dominant at higher scan rates. This contrast in the storage mechanism is due to the time available for ions to interact with the electrode material.

Synergestic effect of magnetron sputtered silver nano-islands and Co3(PO4)2 for high performance supercapattery devices

The study divulges the enhanced electrochemical performance of sonochemicaly synthesized cobalt phosphate by inclusion of magnetron sputtered Ag nano-islands. The morphological, structural, and compositional insight of materials, is analyzed by using various analytical techniques like Optical, atomic force microscopy (AFM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-Ray analysis (EDX). Initially, the electrochemical performance of the electrodes is tested in three-electrode assembly. The results reveal that Co3(PO4)2 with silver current collector (Ag- Co3(PO4)2) profits an enhanced specific capacity (Qs) of 502 Cg−1 compare to pristine (273 Ag−1) at 0.6 Ag−1. To validate the real time application supercapattery device is fabricated by coupling Ag-Co3(PO4)2 (positive electrode) with AC (negative electrode). The supercapattery holds an excellent specific energy of 65.8 Whkg−1 at corresponding specific power of 510 Wkg−1 at 0.6 Ag−1 and the maximum specific power is 6012 Wkg−1 at 7 Ag−1. The device unveiled a stability potential of 85.6% after 10,000 continuous GCD cycles. Additionally, the contribution of diffusive and capacitive mechanisms in the entire charge storage capacity of the supercapattery is estimated by employing Dunn’s analysis. The results portray the inclusion of silver as a fine drive toward high performance electrodes for potential supercapattery applications.