Capacitive Properties Research Articles

Hydrothermal synthesized nickel tungstate (NiWO4) microflowers for supercapacitor and water-splitting

Herein, we have synthesized nickel tungstate microflowers (NWO MFs) using the hydrothermal route and used them as an electrode in electrochemical and electrocatalytic applications. In this article, we discuss the effects of the concentration of surfactant on the NWO MFs. Additionally, the resultant products are undergone to assess the energy storage and water-splitting phenomena. In addition, NWO-SM (steel mesh) electrode demonstrates the maximum specific capacitance (Cg) and specific capacity (Csp) of 712 F/g and 158 mAh/g at 5 mV/s with ∼95% capacitive retention over the 5000 cycles. Furthermore, the fabricated device reveals the maximum performance of the capacitance and capacity of 185 F/g and 75 mAh/g at 5 mV/s and 160 F/g and 53 mAh/g with the highest energy (Ed) and power densities (Pd) of 24 Wh/kg and 1600 W/kg at 5 mA/cm2 respectively. The hybrid device shows better capacitive properties with excellent stability (94% over 5000 cycles). The NWO-SM electrodes were tested for electrocatalytic activities using different techniques. The NWO-1 SM electrode exhibited strong electrocatalytic activity with a moderate overpotential value of 302 mV, a negligible Tafel slope (118 mV/dec), an acceptable electrochemical surface area (ECSA) value of 121 cm2, and exceptional stability over 10 hours.

Enhancement of Capacitive Properties of Ce-Doped MnAl2O4 Electrode for High Performance Energy Storage Applications

Enhancement of Capacitive Properties of Ce-Doped MnAl2O4 Electrode for High Performance Energy Storage Applications

Hydrothermal synthesis of high-performance cobalt phosphate nanorod architecture as bifunctional electrocatalysts for rechargeable Zn-air batteries and supercapatteries

Transition metal phosphate bifunctional electrocatalysts demonstrate superior oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and capacitive properties owing to their high electrocatalytic and conductive activities. In this report, cobalt phosphate (Co3P2O8) nanorod (NR) electrocatalytic materials were developed via a facile one-step hydrothermal synthesis, followed by an annealing process. The unique NR structures offer superior electrocatalytic activities, continuous and quick electron transport pathways, short ion diffusion lengths, and rich active sites toward rechargeable zinc-air batteries (ZABs) and supercapatteries (SCs). The self-assembled Co3P2O8 NR electrocatalyst revealed higher current density values during the OER and ORR measurements than the commercially available Pt/C and IrO2 materials. The Co3P2O8 NR electrocatalyst exhibited an excellent OER overpotential of 180 mV. The electocatalyst also showed superior onset and half-wave potentials of 0.92 V and 0.80 V, respectively. Moreover, the fabricated Co3P2O8 NRs-based ZAB exhibited better durability than the Pt/C-based ZAB. Significantly, the Co3P2O8 NR electrode demonstrated an excellent specific capacity of 373 mAh g−1 with outstanding cycling stability of 99% after 5000 cycles. Additionally, the fabricated Co3P2O8 NRs//activated carbon SC demonstrated high specific energy and power densities of 25.62 Wh kg−1 and 2953.12 W kg−1, respectively with remarkable cycling stability of 89% after 7000 cycles. Specifically, the practical applicability of the fabricated Co3P2O8 NRs-based ZAB and SC was tested using a blue light-emitting diode nameplate energized by two devices in series. Overall, the catalytic and energy-storage properties of the Co3P2O8 NR material can provide a new pathway for high-energy electrochemical applications.

Hydrothermal preparation of N and O-rich porous carbon microspheres and their capacitance properties

In this paper, N and O-rich porous activated carbon (N-O/AC) microsphere with various pore sizes was prepared by thermal and KOH activation of g-C3N4@graphene oxide (CN@GO) microsphere. CN@GO microsphere was pre-prepared through a hydrothermal method directly from glucose and melamine, which resulted into high content and uniform doping of O and N in the final product. CN@GO microsphere was composed of GO/CN/GO sandwich nanochips, forming a porous structure with various pore sizes. The obtained N-O/AC has high energy density (33.19 Wh/kg) and high power density (499.93 W/kg), in company with excellent cyclic stability (remaining 98.64 % after 1000 cycles). The N-O/AC derived from the hydrothermal method provides a low-cost way of constructing porous carbon matrix composites with pseudo-capacitance.

Effect of Substrate Temperature on the Electrochemical and Supercapacitance Properties of Pulsed Laser-Deposited Titanium Oxynitride Thin Films

Abstract Electrocatalytically active titanium oxynitride (TiNO) thin films were fabricated on commercially available titanium metal plates using a pulsed laser deposition (PLD) method for energy storage applications. The elemental composition and nature of bonding were analyzed using x-ray photoelectron spectroscopy (XPS) to reveal the reacting species and active sites responsible for the enhanced electrochemical performance of the TiNO electrodes. Symmetric supercapacitor devices were fabricated using two TiNO working electrodes separated by an ion-transporting layer to analyze their real-time performance. The galvanostatic charge-discharge studies on the symmetric cell have indicated that TiNO films deposited on the polycrystalline titanium plates at lower temperatures are superior to TiNO films deposited at higher temperatures in terms of storage characteristics. For example, TiNO films deposited at 300°C exhibited the highest specific capacity of 69 mF/cm2 at 0.125 mA/cm2 with an energy density of 7.5 Wh/cm2. The performance of this supercapacitor (300°C TiNO) device is also found to be ∼ 22 % better compared to that of a 500°C TiNO supercapacitor with a capacitance retention ability of 90% after 1000 cycles. The difference in the electrochemical storage and capacitance properties is attributed to the reduced leaching away of oxygen from the TiNO films by the Ti plate at lower deposition temperatures, leading to higher oxygen content in the TiNO films and, consequently, a high redox activity at the electrode/electrolyte interface.

A Remarkable Pt Doped CNT Catalyst as a Double Functional Material: Its Application for Hydrogen Production and Supercapacitor

In this study, by producing bifunctional material, hydrolysis, and supercapacitor applications were investigated. The carbon nanotube-supported Pt catalyst was prepared using the sodium borohydride (NaBH<sub>4</sub>) reduction. Surface characterization of the synthesized Pt/CNT catalyst was performed using scanning electron microscopy-energy dıstrıbutıon X-ray spectrometer (SEM-EDX), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Hydrolysis experiments were performed after deciding on the appropriate atomic ratio from the Pt/CNT catalysts synthesized in different nuclear ratios. The parameters affecting the hydrogen production from NaBH<sub>4</sub> were examined. As a result of the kinetic calculations, the initial rates of reaction for 30°C and 60°C were calculated as 21949,69 mlH<sub>2</sub>g<sub>cat</sub>min<sup>-1</sup> and 70018,18 mlH<sub>2</sub>g<sub>cat</sub>min<sup>-1</sup>. Galvastonic charge-discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used as characterization techniques for the use of Pt/CNT catalysts as electrodes in supercapacitor applications. The specific capacitance value of 7% Pt/CNT catalyst at 1 A/g current density was calculated as 57,78 F/g. Energy and power density were calculated as 8,025 Wh/kg and 963 W/kg, respectively. Therefore, this catalyst is called a “cap-cat” with capacitor properties. The catalyst used in this study is promising for this recently studied topic.

Anisotropic Semicrystalline Homopolymer Dielectrics for High‐Temperature Capacitive Energy Storage

AbstractHigh‐temperature dielectric polymers are in high demand for powering applications in extreme environments. Here, we have developed high‐temperature homopolymer dielectrics with anisotropy by leveraging the hierarchical structure in semicrystalline polymers. The lamellae have been aligned parallel to the surface in the dielectric films. This structural arrangement resembles the horizontal alignment of nanosheet fillers in polymer nanocomposites and nanosheet‐like lamellae in block copolymers, which has been proven to provide the optimal topological structure for electrical energy storage. The unique ordering of lamellae in our dielectric films endue a significantly increased breakdown strength and a reduced leakage current compared to amorphous films. This novel approach of enhancing the capacitive energy storage properties by controlled orientation of lamellae in homopolymer offers a new perspective for the design of high‐temperature polymer dielectrics.

Anisotropic Semicrystalline Homopolymer Dielectrics for High-Temperature Capacitive Energy Storage.

High-temperature dielectric polymers are in high demand for powering applications in extreme environments. Here, we have developed high-temperature homopolymer dielectrics with anisotropy by leveraging the hierarchical structure in semicrystalline polymers. The lamellae have been aligned parallel to the surface in the dielectric films. This structural arrangement resembles the horizontal alignment of nanosheet fillers in polymer nanocomposites and nanosheet-like lamellae in block copolymers, which has been proven to provide the optimal topological structure for electrical energy storage. The unique ordering of lamellae in our dielectric films endue a significantly increased breakdown strength and a reduced leakage current compared to amorphous films. This novel approach of enhancing the capacitive energy storage properties by controlled orientation of lamellae in homopolymer offers a new perspective for the design of high-temperature polymer dielectrics.

Preparation and Capacitive Properties of Ni-Doped Zinc Cobaltate/Carbon Fiber Composite Porous Mesh Materials

Nickel-element-doped zinc cobaltate/carbon fiber composites (Ni-ZnCo2O4/CF) were prepared on carbon cloth (made of a combination of carbon fibers) conductive substrates using a simple ambient stirring method combined with heat treatment. Characterization tests of the materials revealed that the prepared products were porous Ni-ZnCo2O4/CF mesh structures. This porous network structure increases the surface area of the material and helps shorten the diffusion path of ions and electrons. The samples were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) methods to investigate the effect of Ni elemental doping on the stability of the materials. The results show that there are no other impurity peaks and no other impurity elements in the Ni-ZnCo2O4/CF electrode material, which indicates that the sample purity is high. Meanwhile, the electrochemical properties of Ni-ZnCo2O4/CF electrode materials were studied. Under the condition of 15 A·g−1, the specific capacitance of Ni-ZnCo2O4/CF electrode material is 1470 F·g−1, and after 100 cycles, its specific capacity reaches 1456 F·g−1, which is 99.0% of the specific capacity of 1470 F·g−1, indicating that the electrode material has good stability. In addition, we assembled asymmetric supercapacitors (Ni-ZnCo2O4/CF//CNTs) with Ni-ZnCo2O4/CF as the positive material and carbon nanotubes (CNTs) as the negative material. In the cyclic stability experiment of Ni-ZnCo2O4/CF/CNTs devices, when the current density was 1 A·g−1, the specific capacitance was 182 F·g−1. After 10,000 cyclic charge–discharge tests, the specific capacity became 167 F·g−1, which was basically unchanged compared with the initial specific capacity, reaching 91.8%. It shows that it has higher charge–discharge performance and higher cycle stability.

A review of EDLC and pseudocapacitance with synergistic integration of carbon-based and metal oxide materials for enhanced electrochemical energy storage

This paper provides a comprehensive analysis of the recent advancements in electrochemical double-layer capacitors (EDLCs) and pseudocapacitance, emphasizing the pivotal role of carbon-based materials, metal oxides, conducting polymers, and composites in augmenting the energy storage landscape. Through a systematic collection of electrochemical performance metrics, we elucidate the inherent advantages of these materials, such as superior electrical conductivity, enhanced surface area, and chemical robustness, which are instrumental in the development of next-generation supercapacitors. We discuss the integration of novel materials like reduced graphene oxide/hexagonal boron nitride composites, carbon onions, and various metal oxides that contribute to a significant increase in energy density and cycling stability. This work also highlights innovative fabrication techniques and synthesis methodologies that have resulted in electrodes with remarkable performance enhancements. Furthermore, the exploration of synergistic effects between different materials has led to hybrid structures that exhibit improved capacitive properties and operational efficiency.

A reconfigurable integrated smart device for real-time monitoring and synergistic treatment of rheumatoid arthritis.

Rheumatoid arthritis (RA) is a global autoimmune disease that requires long-term management. Ambulatory monitoring and treatment of RA favors remission and rehabilitation. Here, we developed a wearable reconfigurable integrated smart device (ISD) for real-time inflammatory monitoring and synergistic therapy of RA. The device establishes an electrical-coupling and substance delivery interfaces with the skin through template-free conductive polymer microneedles that exhibit high capacitance, low impedance, and appropriate mechanical properties. The reconfigurable electronics drive the microneedle-skin interfaces to monitor tissue impedance and on-demand drug delivery. Studies in vitro demonstrated the anti-inflammatory effect of electrical stimulation on macrophages and revealed the molecular mechanism. In a rodent model, impedance sensing was validated to hint inflammation condition and facilitate diagnosis through machine learning model. The outcome of subsequent synergistic therapy showed notable relief of symptoms, elimination of synovial inflammation, and avoidance of bone destruction.

In-situ growth of MCo2O4 nanospheres (M: Mn, Ni) over g-C3N4@PPy as high-performance and novel composites for sustainable supercapacitors

Introducing and using novel conductive organic–inorganic material systems for the supercapacitor industry is rapidly emerging. In this work, the well-defined MCo2O4 nanospheres (M: Mn, Ni) are successfully grown on the graphitic carbon nitride/polypyrrole (g-C3N4@PPy) nanoparticles by hydrothermal/polymerization process. XPS, FT-IR, XRD, BET, and SEM techniques were employed to investigate the physical and chemical properties as well as the surface characteristics of MCo2O4 nanospheres. The electrochemical behavior of the developed electrode was investigated by electrochemical techniques such as cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). Moreover, owing to the advantageous proportion of aspect ratio and relatively low electrode and electrolyte resistance, the highest specific capacitance value for g-C3N4@PPy@MnCo2O4 and g-C3N4@PPy@NiCo2O4 supercapacitors was obtained as 350.00 and 258.26 F g−1, with a current density of 0.5 A g−1, respectively. Also, capacitance retention of supercapacitors after 5000 GCD cycles was achieved by 92.71 %, and 94.55 % respectively. These results demonstrate that the decorated nanospheres on g-C3N4@PPy exhibit excellent capacitive properties and stability, indicating their potential for use in the field of energy storage.

“Core–core” petrophysical relationships generation for reservoir modeling

Relevance. The need in a detailed analysis of distribution of physical properties of the formation in space. Currently, the parameters connecting the results of responses of geophysical fields and petrophysical studies of core are averaged. On the one hand, this is due to the small number of wells with cores in the fields, and on the other hand, to simplify and speed up calculations in the presence of a large number of wells with geophysical surveys of wells. However, this approach does not allow us to identify the largest number of a particular layer or section characteristics. This, in its turn, may lead to inaccuracies in calculating filtration and capacitance properties. When averaging parameters, the features of formation of the deposit in parts of the field with core sampling are lost. And this is a very big opportunity to more accurately form facies models of deposits. Aims. To generate a map of skeletal density distribution based on core data for the supra-coal strata of a terrigenous oil reservoir; analyze the resulting distribution map, identify areas with increased and decreased density values; assess the degree of change in the porosity coefficient when compared with density values; identify areas of high and low density and trends. Object. Supra-coal strata of terrigenous sediments of one of the layers of an oil field in the Tomsk region. Methods. Analysis of the petrophysical database leads to formation of an idea of the reservoir. Laboratory core studies are the source of the most reliable information about the filtration and reservoir properties of the formation. The analysis technique involves the well-by-well construction of dependencies of petrophysical parameters and determination of the value of the constant density of the skeleton. Additionally, a general relationship is built for all wells to compare values and identify maximum and minimum parameters boundaries, skeletal density distribution map and resulting zones with low- and high-density values analysis. Borehole differentiation of values leads to increased detail of the distribution of the studied parameter and identification of zones with abnormally high and low values for more detailed study and the formation of a conceptual geological model.

Ligand regulation and capacitive properties of nickel based pyrazole trinuclear copper cluster organic framework

Traditional metal organic framework (MOF) hinders its application as high-performance electrode materials for supercapacitors due to the limited electron transfer efficiency and conjugation of its ligand molecules. Therefore, in this article, highly electrochemical active pyrazole trincore-copper cluster derivatives as the core unit were covalently assembled by Schiff base reaction with organic linkers of different structures to obtain a series of structurally different electroactive ligands. It was found that ligands with multiactive metal chelation site structure with polydentate carboxylate linker and aromatic extension showed high coordination ability and high degree of conjugation. The nickel-based MOF synthesized with this novel electroactive ligand exhibited a high specific capacitance of 1804 Fg−1 at a current density of 1 Ag−1. At a power density of 747.25 W kg−1, the maximum energy density of the assembled asymmetric supercapacitor assembled with Cu-PyAc-Am2Ac-Ni is 58.95 Wh kg−1 with cycling stability of 88.95 % after 5000 charges and discharges. This means that Cu-PyAc-Am2Ac-Ni is a promising electrode material for supercapacitors.

Electrochemical Investigation of Lithium Perchlorate-Doped Polypyrrole Growing on Titanium Substrate

Lithium perchlorate-doped polypyrrole growing on titanium substrate (LiClO4-PPy/Ti) has been fabricated to act as electroactive electrode material for feasible electrochemical energy storage. A theoretical and experimental investigation is adopted to disclose the conductivity, electroactivity properties and interfacial interaction-dependent capacitance of LiClO4-PPy/Ti electrode. The experimental measurement results disclose that LiClO4-PPy/Ti reveals lower ohmic resistance (0.2226 Ω cm−2) and charge transfer resistance (2116 Ω cm−2) to exhibit higher electrochemical conductivity, a more reactive surface, and feasible ion diffusion to present higher double-layer capacitance (0.1930 mF cm−2) rather than LiClO4/Ti (0.3660 Ω cm−2, 65,250 Ω cm−2, 0.0334 mF cm−2). LiClO4-PPy/Ti reveals higher Faradaic capacitance caused by the reversible doping and dedoping process of perchlorate ion on PPy than the electrical double-layer capacitance of LiClO4/Ti caused by the reversible adsorption and desorption process of the LiClO4 electrolyte on Ti. Theoretical simulation calculation results prove that a more intensive electrostatic interaction of pyrrole N···Ti (2.450 Å) in LiClO4-PPy/Ti rather than perchlorate O···Ti (3.537 Å) in LiClO4/Ti. LiClO4-PPy/Ti exhibits higher density of states (57.321 electrons/eV) at Fermi energy and lower HOMO-LUMO molecule orbital energy gap (0.032 eV) than LiClO4/Ti (9.652 electrons/eV, 0.340 eV) to present the enhanced electronic conductivity. LiClO4-PPy/Ti also exhibits a more declined interface energy (−1.461 × 104) than LiClO4/Ti (−5.202 × 103 eV) to present the intensified interfacial interaction. LiClO4-PPy/Ti accordingly exhibits much higher specific capacitances of 0.123~0.0122 mF cm−2 at current densities of 0.01~0.10 mA cm−2 rather than LiClO4/Ti (0.010~0.0095 mF cm−2, presenting superior electroactivity and electrochemical capacitance properties. LiClO4-PPy/Ti could well act as the electroactive supercapacitor electrode for feasible energy storage.

Soft-template assisted morphology tuning of NiMoO4 for hybrid supercapacitors

The electrochemical performance of electrode materials depends on various physicochemical properties like particle size, morphology, porosity, etc. of materials. Herewith, a facile surfactant assisted hydrothermal route using cetyltrimethylammonium bromide (CTAB) and hexamethylenetetramine (HMT) is used to successfully synthesize nanostructured nickel molybdate (NiMoO4) with various morphologies. It is found that NiMoO4 possesses different morphologies when synthesized by using these surfactants. With change in morphology, there is a significant increase in diffusion coefficient for sample synthesized with CTAB. It is interesting to note that NiMoO4 synthesized by using CTAB exhibit a high specific capacitance of 947 F g−1 when cycled at 1 A g−1 in 1 M KOH solution as compared to that of 322 F g−1 (synthesized without CTAB), which can be ascribed to its flower-like shape with uniform porosity. Both Ni2+/Ni3+ and Mo6+/Mo4+ redox couples are involved in the capacitive characteristic of NiMoO4, as found from the XPS study. Additionally, a hybrid supercapacitor has been assembled using NiMoO4 as positive electrode and reduced grapgene oxide (rGO) as negative electrode, which can exhibit 107 F g−1 with an operating voltage of 1.6 V with excellent cycling stability of maintaining 94 % capacitance retention after 6000 cycles in 1 M KOH solution. The hybrid supercapacitor can possess an energy density of 37.7 Wh kg−1 and a power density of 8 kW kg−1. Thus, this study enables the importance of tuning the morphology to enhance the capacitance property of transition metal oxide based electrode materials for supercapacitor applications.

One-pot hydrothermal synthesis of MWCNTs/NiS/graphitic carbon nitride as next generation asymmetric supercapacitors

Fabricating new electrode materials with high capacitive properties is crucial in contemporary research. The construction of hybrid supercapacitors developed using transition metal-sulfides and carbonaceous materials provides significant surface area and distinctive charge storage characteristics. In the present work, NH2-multiwalled carbon nanotubes/NiS/g-C3N4 (MNG) hybrid was synthesized by a one-pot hydrothermal method, and pristine g-C3N4 using thermal method. The morphological studies of the hybrid materials show the presence of tube like MWCNTs, sphere-like NiS, and sheet like g-C3N4. The uniform distribution of all the components in the hybrid helps in exhibiting excellent electrochemical performances. The prepared electrode material shows a specific capacitance of 2432 F g−1 at a current density of 4 A g−1. Furthermore, following a series of 10,000 cycling tests, the hybrid ternary composite retains 98 % of its initial capacitance. An asymmetric coin cell of MNG//AC was fabricated with an exceptional energy density of 73.3 Wh kg−1 and a power density of 1599.2 W kg−1. This remarkable rate performance and cycle stability exhibited by the material indicate its potential as a highly efficient electrode material for supercapacitors.

Preparation of silk-like reduced graphene oxide/polyaniline composites using oxidant template-guided technique for supercapacitor

The large-scale utilization of supercapacitors (SCs) demands urgently for high-performance electrode materials. Herein, the silk-like reduced graphene oxide/polyaniline (rGO/PANI) composites have been prepared by oxidant template-guided technique, it is an effective method for obtaining rGO/PANI composites with respect morphologies of PANI grow on rGO nanosheets due to δ-MnO2 acts as oxidant as well as reactive template. Initially, rGO nanosheets were employed as a reducing agent and substrate for the growth of δ -MnO2; next, aniline monomers were adsorbed on the surface of δ -MnO2 within rGO/MnO2 composites, and PANI was uniformly grown on the rGO nanosheets; finally, three of rGO/PANI composites with different mass percentages of PANI (22, 34, and 68 %) were obtained due to the varying amounts of δ -MnO2 and designated as rGO/PANI-1, rGO/PANI-2, and rGO/PANI-3, respectively. The silk-like rGO/PANI-1 and rGO/PANI-2 not only outperform rGO/PANI-3 and PANI in rate performance but also cycling stability. Moreover, the silk-like rGO/PANI-1 electrode material has an extraordinarily high-rate capability, retaining 84 % (435 ∼ 364 F/g) of its initial capacitance when the current density is increased from 0.25 to 10 A/g, and 80 % of the initial capacitance is maintained after 1000 cycles at 10 A/g. As well, the assembled rGO/PANI-1 symmetric SC demonstrates high rate capability and long term cycling stability. Therefore, the silk-like rGO/PANI-1 material’s outstanding capacitive property make it a prospective candidate for high-performance SCs.

Bottom-Up Synthesis of Twisted Porous Graphene through a Heterogeneous Scholl Reaction and Its Supercapacitor Application.

Anthracene- and pyrene-based twisted porous graphene (AN-Pyre-PG) with an ordered pore structure has been synthesized through bottom-up solution phase synthesis from a conjugated microporous polymer (AN-Pyre-CMP) via a heterogeneous Scholl cyclization reaction. The regular-ordered pores embedded within the graphene structures were analyzed through a Raman spectrum, different morphological analyses, and theoretical studies. A significant change in surface area from AN-Pyre-CMP to AN-Pyre-PG was observed, from 143 to 640 m2/g, respectively. Surface area-driven capacitive properties were also observed. Twisted-structure and ordered porous graphene shows better specific capacitance compared to CMP. AN-Pyre-PG shows a specific capacitance of 629 F g-1 at 1 A g-1, with 91% retention of capacitance after 3000 charge-discharge cycles, whereas AN-Pyre-CMP shows a maximum specific capacitance of 200 F g-1 was observed at 2 A g-1.

A battery-type cathode with RuO2 modified Ni11(HPO3)8(OH)6 for asymmetric supercapacitors

Phosphates are a kind of promising electrode materials because they can provide numerous cavities and several reaction sites to be favored for storing anions and cations. However, the widespread application of phosphates are limited by their intrinsically low electronic conductivity. RuO2/hydrated RuO2 exhibits high conductivity and excellent electrochemical properties. Reducing its dosage and increasing its specific surface area are the research concerns. Combining less RuO2 to Nickel phosphate (NiP) is expected to improve the electrochemical performance. RuO2-modified NiP (NiP-RuO2) electrode material is synthesized by a one-step hydrothermal reaction and its structural morphology and capacitive properties are investigated. The results indicate that NiP-RuO2 electrode consists of hydrated RuO2 and Ni11(HPO3)8(OH)6, and exhibits excellent battery-type electrochemical supercapacitor performance with a specific capacity of 878.06 C/g at 1 A/g. According to density functional theory (DFT) analysis, Ru-doped Ni11(HPO3)8(OH)6 has a narrower forbidden band width and higher conductivity than Ni11(HPO3)8(OH)6. Furthermore, the asymmetric supercapacitor (ASC) assembled by NiP-RuO2/NF and activated carbon (AC) electrode achieves a high energy density (43.58 Wh/kg) at a power density of 923.47 W/kg. When two ASC devices are connected in series, ten light-emitting diodes (LEDs) can be illuminated for ten minutes.