Ruthenium sulfide nanoparticles as a new pseudocapacitive material for supercapacitor

Thermo-Electric Powered High Energy-Density Hybrid Supercapattery for Driving Overall Water Splitting: A Novel Trifunctional Builder for Self-Powered Hydrogen Production

Integrated electrochemical energy devices with multifunctionality are evolving as an auspicious way to lift up energy technology. However, the challenge is utilizing a single-electrode material for multifunctional applications is essential to minimize the manpower and overall cost of the system. Herein, a novel and cost-effective self-powered aqueous electrochemical energy device (SAEED) is proposed via integrating asymmetric supercapattery (ASD) and water-splitting (WS) devices utilizing Cu₃Mo₂O₉ (CMD) nanostructures on Ni-foam (prepared via hydrothermal method) as a trifunctional electrode. First, the Cu3Mo2O9/Ni electrode is examined for the supercapacitor, which shows the faradaic-type of charge-storage behavior with a superior specific capacity of 588.88 mAh g-1. The Cu3Mo2O9ǁgraphene ASD is constructed, which shows high energy storage performance with high device capacitance and energy/power densities and 98% retention capacitance over 5000 cycles. Second, the electrocatalyst behavior of the Cu₃Mo₂O₉/Ni electrode is explored, which reveals impressive HER/OER performance with lower overpotential (HER-120 mV at 10 mA cm⁻²/OER-310 mV at 50 mA cm⁻²) values. As a proof-of-concept, an SAEED was developed that contains a thermoelectric generator, Cu₃Mo₂O₉ǁgraphene ASD, and a beaker-type electrolyzer operating at a voltage of 1.58 V to eliminate power loss and intermittent issues for sustainable and uninterrupted production of H₂.

Unveiling the charge storage mechanisms of Co-based perovskite fluoride in a mild aqueous electrolyte

This study is an in-depth exploration of the charge storage mechanisms of KCoF3 in 1 M Na2SO4 mild aqueous electrolytes via an array of ex situ/in situ physicochemical/electrochemical methods, especially the electrochemical quartz crystal microbalance (EQCM) technique, showing a combination of conversion, insertion/extraction and adsorption mechanisms. Specifically, during the first charge phase, Co(OH)2 is formed/oxidized into amorphous CoOOH and Co3O4, and then CoOOH undergoes partial proton extraction to yield CoO2, which is simultaneously accompanied by the transformation of Co3O4 into CoOOH and (hydrated) CoO2. During the first discharge process, the partial insertion of H+ into (hydrated) CoO2 leads to the formation of CoOOH and Co3O4, with the conversion of Co3O4 into CoOOH and both Co3O4 and CoOOH undergoing further transformations into (hydrated) Co(OH)2via the insertion of H+. This work offers valuable references for the development of aqueous energy storage.

Electrodeposition of porous metal-organic frameworks for efficient charge storage

Efficient charge storage is a key requirement for a range of applications, including energy storage devices and catalysis. Metal-organic frameworks are potential materials for efficient charge storage due to their self-supported three-dimensional design. MOFs are high surface area materials made up of coordination of appropriate amounts of metal ions and organic linkers, hence used in various applications. Yet, creating an effective MOF nanostructure with reduced random crystal formation continues to be a difficult task. The energy efficiency and electrochemical yield of bulk electrodes are improved in this study by demonstrating an effective technique for growing MOFs over a conducting substrate utilizing electrodeposition. An exceptionally stable asymmetric supercapacitor is created when activated carbon cloth is combined with the resulting MOF structure that was directly synthesized via an electrochemical method resulting in 97% stability over 5k cycles which is higher than conventional processes. High performance in supercapacitors is ensured by this practical approach for producing MOF electrodes, making it a suitable structure for effective charge storage.

Supercapacitors: An Efficient Way for Energy Storage Application

To date, batteries are the most widely used energy storage devices, fulfilling the requirements of different industrial and consumer applications. However, the efficient use of renewable energy sources and the emergence of wearable electronics has created the need for new requirements such as high-speed energy delivery, faster charge-discharge speeds, longer lifetimes, and reusability. This leads to the need for supercapacitors, which can be a good complement to batteries. However, one of their drawbacks is their lower energy storage capability, which has triggered worldwide research efforts to increase their energy density. With the introduction of novel nanostructured materials, hierarchical pore structures, hybrid devices combining these materials, and unconventional electrolytes, significant developments have been reported in the literature. This paper reviews the short history of the evolution of supercapacitors and the fundamental aspects of supercapacitors, positioning them among other energy-storage systems. The main electrochemical measurement methods used to characterize their energy storage features are discussed with a focus on their specific characteristics and limitations. High importance is given to the integral components of the supercapacitor cell, particularly to the electrode materials and the different types of electrolytes that determine the performance of the supercapacitor device (e.g., storage capability, power output, cycling stability). Current directions in the development of electrode materials, including carbonaceous forms, transition metal-based compounds, conducting polymers, and novel materials are discussed. The synergy between the electrode material and the current collector is a key factor, as well as the fine-tuning of the electrode material and electrolyte.

Effect of Annealing Temperature on the Structural and Electrochemical Properties of Hydrothermally Synthesized NiCo2O4 Electrodes

In this study, a porous Ni-foam support was employed to enhance the capacitance of nickel cobaltite (NiCo2O4) electrodes designed for supercapacitors. The hydrothermal synthesis method was employed to grow NiCo2O4 as an active material on Ni-foam. The NiCo2O4 sample derived from hydrothermal synthesis underwent subsequent post-heat treatment at temperatures of 250 °C, 300 °C, and 350 °C. Thermogravimetric analysis of the NiCo2O4 showed that weight loss due to water evaporation occurs after 100 °C and enters the stabilization phase at temperatures above 400 °C. The XRD pattern indicated that NiCo2O4 grew into a spinel structure, and the TEM results demonstrated that the diffraction spots (DSs) on the (111) plane of the sample annealed at 350 °C were more pronounced than those of other samples. The specific capacitance of the NiCo2O4 electrodes exhibited a decrease with increasing current density across all samples, irrespective of the annealing temperature. The electrode annealed at 350 °C recorded the highest specific capacitance value. However, the capacity retention rate of the NiCo2O4 electrode revealed a deteriorating trend, declining to 88% at 250 °C, 75% at 300 °C, and 63% at 350 °C, as the annealing temperature increased.

Dependence of Transition-Metal Telluride Phases on Metal Precursor Reactivity and Mechanistic Implications

Modern bottom-up synthesis to nanocrystalline solid-state materials often lacks the reasoned product control that molecular chemistry boasts from having over a century of research and development. In this study, six transition metals including iron, cobalt, nickel, ruthenium, palladium, and platinum were reacted with the mild reagent didodecyl ditelluride in their acetylacetonate, chloride, bromide, iodide, and triflate salts. This systematic analysis demonstrates how rationally matching the reactivity of metal salts to the telluride precursor is necessary for the successful production of metal tellurides. The trends in reactivity suggest that radical stability is the better predictor of metal salt reactivity than hard-soft acid-base theory. Of the six transition-metal tellurides, the first colloidal syntheses of iron and ruthenium tellurides (FeTe₂ and RuTe₂) are reported.

3D/2D Heterojunction Fabricated from RuS2 Nanospheres Encapsulated in Polymeric Carbon Nitride Nanosheets for Selective Photocatalytic CO2 Reduction to CO

Micro/nanostructure control of heterostructures is still a challenge for achieving high efficiency and selectivity of photocatalytic CO₂ conversion. In this work, a new three-dimensiona/two-dimensional (3D/2D) heterostructure is fabricated by encapsulating RuS₂ nanospheres in the interlayer of mesoporous polymeric carbon nitride (PCN) nanosheets based on an in situ growth and polymerization strategy. The unique microstructure of the obtained 3D/2D RuS₂/PCN heterojunction can effectively improve the transfer and separation efficiency of photogenerated charge carriers, reduce the mass transfer resistance of CO₂ toward active sites, and provide a confined reaction space, thus propelling the photocatalytic CO₂ reduction to CO with high selectivity. The CO yield over the optimal 5%-RuS₂/PCN sample reaches 4.2 and 2.8 times as high as that of single PCN and RuS₂ within 4 h, respectively. Furthermore, the plausible charge transfer mechanism and CO₂ reduction path are revealed by time-dependent in situ Fourier transform infrared (FT-IR) spectra combined with photophysical, electrochemical, and photoelectrochemical techniques and density functional theory (DFT) calculations. This work develops the microstructural engineering design strategy of PCN-based heterojunctions for selective photocatalytic CO₂ fuel conversion.

Charge storage mechanism in vanadium telluride/carbon nanobelts as electroactive material in an aqueous asymmetric supercapacitor

A novel one-step method for fabricating vanadium telluride nanobelt composites for high-performance supercapacitor applications is reported. The nanobelts are realized by direct tellurization of vanadium oxide in-situ formed via decomposition of ammonium metavanadate in argon atmosphere. Use of melamine as precursor helps in forming graphitic carbon layers during pyrolization on which the nanobelts are grafted. Morphological analysis suggests interconnected nanobelts of ∼23.0 nm width coming out of carbon structure. As pseudocapacitive electrode, vanadium telluride/carbon (C) composite exhibits interesting electrochemical performance within a potential window of 0-1.0 V in 1.0 M sodium sulfate electrolyte along with excellent capacitance retention during 5000 cycles. In-depth analysis suggests that the charge storage mechanism in the composite is governed by both diffusion-controlled and diffusion-independent processes with the former dominating at slower scan rates and later at faster scan rates. The asymmetric supercapacitor assembled using vanadium telluride/C and activated charcoal (AC) as respective positive and negative electrodes exhibited an energy/power combination of 19.3 Wh/kg and 1.8 kW/kg within a potential window of 0-1.8 V in aqueous electrolyte. This strategy to improve capacitance along with potential window in an aqueous electrolyte would facilitate development of high-performance energy storage devices with metal chalcogenides.

Dry Synthesis of Binder-Free Ruthenium Nitride-Coated Carbon Nanotubes as a Flexible Supercapacitor Electrode

Ruthenium nitride was successfully deposited on a multiwalled carbon nanotube (MWCNT) forest grown on a stainless-steel mesh substrate by radiofrequency plasma-assisted pulsed laser deposition. This novel dry fabrication method for flexible supercapacitor electrodes eliminates toxic byproducts and the need for any binder component. Experimental results show a successful thin film coating of the individual MWCNTs with RuN_x under various synthesis conditions. The electrochemical characterization demonstrates a significant improvement in capacitance of the synthesized RuN_x-MWCNT electrode compared to the bare MWCNT forest, with a large potential window of 1.2 V. Capacitance values as high as 818.2 F g^-1 (37.9 mF cm^-2) have been achieved.

Synergistic phase and crystallinity engineering in cubic RuSe2 catalysts towards efficient hydrogen evolution reaction

Herein, cubic RuSe2 electrocatalysts with different 1T phase ratios (ranging from 20.53% to 64.97%) and crystallinities (ranging from 1.72% to 89.10%) were developed by a fast and efficient microwave-assisted synthesis method.

Flexible nickel disulfide nanoparticles-anchored carbon nanofiber hybrid mat as a flexible binder-free cathode for solid-state asymmetric supercapacitors

Nickel disulfide nanoparticles (NiS₂NPs)-anchored carbon nanofibers (NiS₂NPs@CNF) hybrid mats were fabricated via the sequential process of stabilization and carbonization of electrospun polyacrylonitrile-based fibers followed by hydrothermal growth of NiS₂NPs on the porous surface of CNFs. The vertical growth of NiS₂NPs on entire surfaces of porous CNFs appeared in the SEM images of hybrid mat. The hierarchical NiS₂NPs@CNF core-shell hybrid nanofibers with 3D interconnected network architecture can endow continuous channels for easy and rapid ionic diffusion to access the electroactive NiS₂NPs. The conductive and interconnected CNF core could facilitate electron transfer to the NiS₂shell. Moreover, the porous CNF as a buffering matrix can resist volumetric deformation during the long-term charge-discharge process. The NiS₂NPs@CNF electrode can yield high specific capacitance (916.3 F g^-1at 0.5 A g^-1) and reveal excellent cycling performances. The solid-state asymmetric supercapacitor (ASC) was fabricated with NiS₂NPs@CNF mat as a binder-free positive electrode and activated carbon cloth as a negative electrode. As-assembled ASC not only produce high specific capacitance (364.8 F g^-1at 0.5 A g^-1) but also exhibit excellent cycling stability (∼92.8% after 5000 cycles). The ASC delivered a remarkably high energy density of 129.7 Wh kg^-1at a power density of 610 W kg^-1. These encouraging results could make this NiS₂NPs@CNF hybrid mat a good choice of cathode material for the fabrication of flexible solid-state ASC for various flexible/wearable electronics.

Facile synthesis of PEDOT-rGO/HKUST-1 for high performance symmetrical supercapacitor device

A novel poly(3,4-ethylenedioxythiophene)-reduced graphene oxide/copper-based metal-organic framework (PrGO/HKUST-1) has been successfully fabricated by incorporating electrochemically synthesized poly(3,4-ethylenedioxythiophene)-reduced graphene oxide (PrGO) and hydrothermally synthesized copper-based metal-organic framework (HKUST-1). The field emission scanning microscopy (FESEM) and elemental mapping analysis revealed an even distribution of poly(3,4-ethylenedioxythiophene) (PEDOT), reduced graphene oxide (rGO) and HKUST-1. The crystalline structure and vibration modes of PrGO/HKUST-1 were validated utilizing X-ray diffraction (XRD) as well as Raman spectroscopy, respectively. A remarkable specific capacitance (360.5 F/g) was obtained for PrGO/HKUST-1 compared to HKUST-1 (103.1 F/g), PrGO (98.5 F/g) and PEDOT (50.8 F/g) using KCl/PVA as a gel electrolyte. Moreover, PrGO/HKUST-1 composite with the longest charge/discharge time displayed excellent specific energy (21.0 Wh/kg), specific power (479.7 W/kg) and an outstanding cycle life (95.5%) over 4000 cycles. Thus, the PrGO/HKUST-1 can be recognized as a promising energy storage material.

Metal Sulfide Nanoparticles: Precursor Chemistry

Fascination with and the need for evermore increasing efficiency, power, or strength have been the cornerstones for developing new materials and methods for their creation. Higher solar cell conversion efficiencies, increased battery storage power, and lightweight strong materials are some that have been at the forefront of attention for these efforts. Materials created for most applications start as simple chemical compounds. A study of how these chemicals have been used in the past can be used to create new materials and new methods of production. Herein, a class of materials that are valuable in a multitude of applications, metal sulfide nanoparticles, are examined, along with how they are being produced and how new methods can be established that will help to standardize and increase production capabilities. Precursor–solvent combinations that can be used to create metal sulfide nanoparticles in the gas phase are also explored.

Bismuth metal organic framework-derived Bi2Se3@C for high performance supercapacitors

The synthesis of Bi2Se3@C materials for high performance supercapacitors through a bismuth metal organic framework (CAU-17) assisted hydrothermal selenization method followed by carbonized annealing.

Design of a ZnMoO4 porous nanosheet with oxygen vacancies as a better performance electrode material for supercapacitors

A ZnMoO₄ porous nanosheet with oxygen vacancies (ZnMoO₄-OV) was synthesized which delivers a preferable energy storage performance.

Cost-effective single-step synthesis of flower-like cerium-ruthenium-sulfide for the determination of antipsychotic drug trifluoperazine in human urine samples

Nanostructured binary metal sulfides are considered as a promising electrode material because of their excellent electron transfer and good sensing behavior rather than metal oxides. As a result, the binary metal sulfides were applied in energy and electrochemical sensor applications. Herein, we propose the electrochemical sensor method based on flower-like cerium-ruthenium sulfide nanostructure (Ce-Ru-S NS) for the electrochemical sensing of trifluoperazine (TFPZ). The Ce-Ru-S NS prepared using the cost-effective one-pot hydrothermal synthesis technique. Then, the resultant materials were characterized through suitable spectrophotometric techniques and the electrocatalytic properties of the fabricated sensor were investigated by EIS, CV, and amperometric (i-t) techniques. The Ce-Ru-S material has good electrocatalytic activity towards the electrochemical oxidation of TFPZ. Significantly, the fabricated sensor demonstrates the distinct amperometric response with the lowest limit of detection (LOD) of 0.322 nM (S/N = 3), high sensitivity 2.682 μA μM^-1 cm^-2 and lowest oxidation potential of +0.64 V (Ag/AgCl). Furthermore, the Ce-Ru-S NS displays excellent selectivity, good reproducibility, and long-term stability. The practicability of the TFPZ sensor tested in a human urine sample.

Nitrogen-doped RuS2 nanoparticles containing in situ reduced Ru as an efficient electrocatalyst for hydrogen evolution

The production of hydrogen via water electrolysis brings hope for the realization of hydrogen economy, but there is still a lack of highly efficient and appropriate electrocatalysts for the generation of hydrogen in practical applications. In particular, reasonable construction and feasible preparation strategies are the essential requirements for excellent electrocatalysts. Herein, the heterostructures of N-RuS₂/Ru nanoparticles were designed by annealing the RuS₂ nanoparticles in ammonia. By introducing a nitrogen dopant and single-phase Ru metal simultaneously, high-efficiency electrocatalytic performance for hydrogen evolution reaction (HER) was implemented, where the electrocatalyst of N-RuS₂/Ru exhibited a low onset overpotential of 76 mV and small overpotential of 120 mV at 10 mA cm⁻² in an acidic electrolyte. Besides, it displayed a low Tafel slope of 53 mV dec⁻¹, a small interface charge transfer resistance, and long-time stability and durability, suggesting its remarkable properties as a promising HER electrocatalyst candidate.

The reasonable design that N-doping and in situ reduced Ru metal enhances the performance of N-RuS₂/Ru for HER.

Porous spherical NiO@NiMoO4@PPy nanoarchitectures as advanced electrochemical pseudocapacitor materials

In this work, a rational design and construction of porous spherical NiO@NiMoO₄ wrapped with PPy was reported for the application of high-performance supercapacitor (SC). The results show that the NiMoO₄ modification changes the morphology of NiO, and the hollow internal morphology combined with porous outer shell of NiO@NiMoO₄ and NiO@NiMoO₄@PPy hybrids shows an increased specific surface area (SSA), and then promotes the transfer of ions and electrons. The shell of NiMoO₄ and PPy with high electronic conductivity decreases the charge-transfer reaction resistance of NiO, and then improves the electrochemical kinetics of NiO. At 20Ag^-1, the initial capacitances of NiO, NiMoO₄, NiO@NiMoO₄ and NiO@NiMoO₄@PPy are 456.0, 803.2, 764.4 and 941.6Fg^-1, respectively. After 10,000 cycles, the corresponding capacitances are 346.8, 510.8, 641.2 and 904.8Fg^-1, respectively. Especially, the initial capacitance of NiO@NiMoO₄@PPy is 850.2Fg^-1, and remains 655.2Fg^-1 with a high retention of 77.1% at 30Ag^-1 even after 30,000 cycles. The calculation result based on density function theory shows that the much stronger Mo-O bonds are crucial for stabilizing the NiO@NiMoO₄ composite, resulting in a good cycling stability of these materials.

Amorphous RuS2 electrocatalyst with optimized active sites for hydrogen evolution

Transition metal chalcogenides have attracted much attention as high-performance electrocatalysts for hydrogen evolution reaction (HER). Here, we synthesized an efficient HER electrocatalyst of amorphous ruthenium sulfide (A-RuS₂), exhibiting an overpotential of 141 mV at the current density of 10 mA cm^-2 and a Tafel slope of 65.6 mV dec^-1. Experiments demonstrate amorphous RuS₂ has much better catalytic activity than that of its crystalline counterparts. Our study shows that amorphous RuS₂ has increased intrinsic activity and active sites. This work provides a feasible strategy for the development of HER electrocatalysts in amorphous state.

Hydrothermal Synthesis of Cobalt Ruthenium Sulfides as Promising Pseudocapacitor Electrode Materials

In this paper, we report the successful synthesis of cobalt ruthenium sulfides by a facile hydrothermal method. The structural aspects of the as-prepared cobalt ruthenium sulfides were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. All the prepared materials exhibited nanocrystal morphology. The electrochemical performance of the ternary metal sulfides was investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy techniques. Noticeably, the optimized ternary metal sulfide electrode exhibited good specific capacitances of 95 F g−1 at 5 mV s−1 and 75 F g−1 at 1 A g−1, excellent rate capability (48 F g−1 at 5 A g−1), and superior cycling stability (81% capacitance retention after 1000 cycles). Moreover, this electrode demonstrated energy densities of 10.5 and 6.7 Wh kg−1 at power densities of 600 and 3001.5 W kg−1, respectively. These attractive properties endow proposed electrodes with significant potential for high-performance energy storage devices.

Synergistic activity of binary metal sulphide WS2–RuS2 nanospheres for the electrochemical detection of the antipsychotic drug promazine

Schematic presentation for the synthesis of tungsten disulfide–ruthenium disulfide (WS₂–RuS₂) nanospheres and application for the electrochemical determination of antipsychotic drug promazine.

Carbyne-enriched carbon anchored on nickel foam: A novel binder-free electrode for supercapacitor application

Carbon- and carbon derivatives are widely employed as efficient electrode materials for supercapacitor applications. Herein, we demonstrate a cost-effective dip-coating process followed by dehydrohalogenation of PVDF-Ni for the preparation of carbyne enriched carbon anchored on nickel (CEC-Ni) as high-performance electrode material. The removal of halogens in the prepared CEC-Ni were widely characterized using XRD, XPS, Laser Raman, and FT-IR analysis. The occurrence of carbon-carbon vibration in the prepared CEC-Ni foam was confirmed using FT-IR spectroscopy. Laser Raman analysis confirms that the CEC-Ni foam contains both sp and sp² hybridized carbon. The electrochemical properties of prepared carbyne enriched carbon anchored on nickel foam electrode (CEC-NiE) showed an ideal capacitive properties and delivered a maximum specific capacitance of about 106.12 F g^-1 with excellent cyclic retention. Furthermore, the mechanism of charge-storage in the CEC-NiE was analyzed using Dunn's method. In additon, the asymmetric supercapacitor device was fabricated using CEC-NiE as positive and rGO as negative electrode achieved a remarkable energy density of 33.57 Wh Kg^-1 with a maximal power density of 14825.71 W Kg^-1. These results suggested that the facile preparation of CEC-NiE could be a promising and effective electrode material for future energy storage application.

Biomimetic Nitrogen Fixation Catalyzed by Transition Metal Sulfide Surfaces in an Electrolytic Cell

The nitrogen reduction reaction was investigated on the surfaces of 18 different stable transition metal sulfides using density functional theory calculations. YS, ScS, and ZrS were modeled in the rocksalt structure with the (1 0 0) facet; TiS, VS, CrS, NbS, NiS, and FeS in NiAs-type structure with the (1 1 1) facet; and MnS₂ , CoS₂ , IrS₂ , CuS₂ , OsS₂ , FeS₂ , RuS₂ , RhS₂ , and NiS₂ in pyrite structure for both the (1 0 0) and (1 1 1) orientations. As the first step towards determination of sulfides that are less prone to hydrogen evolution, the competition between adsorption of NNH and H (for the associative mechanism), and between adsorption of N and H (for the dissociative mechanism) on these surfaces was considered. The catalytic activity through both the associative and dissociative mechanisms was explored and the overpotential required for electrochemical ammonia formation is reported. The scaling relations and volcano plots were constructed with free energy of adsorption of NNH or N on the surface as the descriptor. RuS₂ was observed as the most active sulfide that could catalyze nitrogen reduction to ammonia at potentials around -0.3 V through the associative mechanism. NbS, CrS, TiS, and VS are also promising candidates for both the associative and dissociative mechanisms with overpotentials for nitrogen reduction around 0.7-1.1 V.

A high-performance asymmetric supercapacitor electrode based on a three-dimensional ZnMoO4/CoO nanohybrid on nickel foam

A two-step hydrothermal route was employed to fabricate a ZnMoO₄/CoO nanohybrid supported on Ni foam. The ZnMoO₄/CoO nanohybrid shows a three-dimensional criss-crossed structure. The specific surface area is enhanced from 45 m² g^-1 of ZnMoO₄ to 67 m² g^-1 of the ZnMoO₄/CoO nanohybrid. Furthermore, the existence of electroactive CoO is in favor of reducing the charge transport resistance. The ZnMoO₄/CoO nanohybrid electrode possesses a high capacitance of 4.47 F cm^-2 at 2 mA cm^-2, which is much higher than those of ZnMoO₄ (1.07 F cm^-2) and CoO (2.47 F cm^-2). The ZnMoO₄/CoO nanohybrid electrode also exhibits an ultrahigh cycling stability with 100.5% capacitance retention after 5000 cycles at 20 mA cm^-2. In addition, an asymmetric all-solid-state supercapacitor was assembled using the ZnMoO₄/CoO nanohybrid as the positive electrode and exfoliated graphite carbon paper as the negative electrode. The asymmetric supercapacitor exhibits a superior energy density of 58.6 W h kg^-1 at a power density of 800 W kg^-1 and a considerable cycling stability with 81.8% capacitance retention after 5000 cycles at 5 A g^-1. The ZnMoO₄/CoO nanohybrid demonstrates its tremendous advantages and possibilities as a positive electrode material in energy storage applications. Moreover, for a better understanding of the electrochemical behavior, a combined study of experimental measurements and density functional theory calculations is also applied to illustrate the high-performance of the ZnMoO₄/CoO nanohybrid.

Direct Synthesis of cubic shaped Ag2S on Ni mesh as Binder-free Electrodes for Energy Storage Applications

A facile approach of chemical bath deposition was proposed to fabricate direct synthesis of silver sulphide (Ag₂S) on nickel (Ni) mesh without involvement for binders for supercapacitor electrodes. The phase purity, structure, composition, morphology, microstructure of the as-fabricated Ag₂S electrode was validated from its corresponding comprehensive characterization tools. The electrochemical characteristics of the Ag₂S electrodes were evaluated by recording the electrochemical measurements such as cyclic voltammetry and charge/discharge profile in a three electrode configuration system. Ag₂S employed as working electrode demonstrates notable faradaic behaviour including high reversible specific capacitance value of 179 C/g at a constant charge/discharge current density of 1 A/g with high cyclic stability which is relatively good as compared with other sulphide based materials. The experimental results ensure fabricated binder-free Ag₂S electrodes exhibits better electrochemical performance and suitable for potential electrodes in electrochemical energy storage applications.

A ruthenium(IV) disulfide based non-enzymatic sensor for selective and sensitive amperometric determination of dopamine

An electrochemical dopamine (DA) sensor has been fabricated by modifying a glassy carbon electrode (GCE) with ruthenium disulfide (RuS₂) nanoparticles (NPs). FESEM and TEM micrographs show the NPs to have an average size of ~45 nm. XRD, Raman and EDS, in turn, confirm the successful formation of cubic phased RuS₂ NPs. The modified GCE displays has attractive features of merit that include (a) an ultra-low detection limit (73.8 nM), (b) fast response time (< 4 s), (c) a low oxidation potential (0.25 V vs. Ag|AgCl), (d) excellent reproducibility and stability, (e) an electrochemical sensitivity of 18.4 μA μM^-1 cm^-2 and 1.8 μA.μM^-1.cm^-2 in the linear ranges from 0.1-10 μM of DA (R² = 0.97) and 10-80 μM of DA (R² = 0.99), respectively. The sensor exhibits excellent specificity over potential interferents like ascorbic acid, glucose and uric acid. The superior performance of the sensor is attributed to its high electrical conductivity, large electro-active surface, and large numbers of exposed catalytically active sites resulting from the presence of unreacted sulfur atoms. Graphical abstract A ruthenium disulfide modified electrochemical sensor material was obtained by single-step hydrothermal synthesis. Sensitive and highly selective detection of dopamine is demonstrated.

Understanding the Thermal Treatment Effect of Two-Dimensional Siloxene Sheets and the Origin of Superior Electrochemical Energy Storage Performances

Two-dimensional siloxene sheets are an emerging class of materials with an eclectic range of potential applications including electrochemical energy conversion and storage sectors. Here, we demonstrated the dehydrogenation/dehydroxylation of siloxene sheets by thermal annealing at high temperature (HT) and investigated their supercapacitive performances using ionic liquid electrolyte. The X-ray diffraction analysis, spectroscopic (Fourier transform infrared, laser Raman, and X-ray photoelectron spectroscopy) studies, and morphological analysis of HT-siloxene revealed the removal of functional groups at the edges/basal planes of siloxene, and preservation of oxygen-interconnected Si₆ rings with sheet-like structures. The HT-siloxene symmetric supercapacitor (SSC) operates over a wide potential window (0-3.0 V), delivers a high specific capacitance (3.45 mF cm^-2), high energy density of about 15.53 mJ cm^-2 (almost 2-fold higher than that of the as-prepared siloxene SSC), and low equivalent series resistance (compared to reported silicon-based SSCs) with excellent rate capability and long cycle life over 10 000 cycles.

Copper molybdenum sulfide nanoparticles embedded on graphene sheets as advanced electrodes for wide temperature-tolerant supercapacitors

A novel copper molybdenum sulfide-graphene (Cu₂MoS₄-rGO) hybrid is investigated as an electrode for temperature tolerant supercapacitor.

Synthesis of MnO2 nanostructures with MnS-deposits for high performance supercapacitor electrodes

We report the synthesis of MnO₂ nanostructures with MnS deposits via a facile one-step hydrothermal process for high-performance supercapacitor applications.

Facile synthesis of crystalline RuSe2 nanoparticles as a novel pseudocapacitive electrode material for supercapacitors

Crystalline RuSe₂ nanoparticles were firstly utilized as a pseudocapacitive electrode material for supercapacitors, and superior capacitive behaviors were observed.