KOH Aqueous Electrolyte Research Articles

Novel hierarchical yolk-shell α-Ni(OH)2/Mn2O3 microspheres as high specific capacitance electrode materials for supercapacitors

For high performance supercapacitors, novel hierarchical yolk-shell α-Ni(OH)2/Mn2O3 microspheres were controllably synthesized using a facile two-step method based on the solvothermal treatment. The unique α-Ni(OH)2 based yolk-shell microstructures decorated with numerous interconnected nanosheets and the heterocomposition features can synergistically enhance reactive site exposure and electron conduction within the microspheres, facilitate charge transfer between electrolyte and electrode materials, and release structural stress during OH− chemisorption/desorption. Moreover, the Mn2O3 sediments distributed over the α-Ni(OH)2 microspheres can serve as an effective protective layer for electrochemical reactions. Consequently, when tested in 1 mol·L−1 KOH aqueous electrolyte for supercapacitors, the yolk-shell α-Ni (OH)2/Mn2O3 microspheres exhibited a considerably high specific capacitance of 2228.6 F·g−1 at 1 A·g−1 and an impressive capacitance retention of 77.7% after 3000 cycles at 10 A·g−1. The proposed α-Ni(OH)2/Mn2O3 microspheres with hetero-composition and unique hierarchical yolk-shell microstructures are highly promising to be used as electrode materials in supercapacitors and other energy storage devices.

Activated Graphene Deposited on Porous Cu Mesh for Supercapacitors.

A porous Cu (P-Cu) mesh was used as a current collector and its morphological effect on the supercapacitor performance was investigated. A porous surface was obtained by thermally annealing the Cu mesh using ammonia gas. Hierarchically porous activated graphene (AG) with a high specific surface area (SSA) was deposited on the P-Cu mesh using electrophoretic deposition, aided by graphene oxide (GO). GO was thermally converted to electrically conductive reduced graphene oxide (rGO). The AG/rGO that was deposited on the P-Cu mesh achieved a high specific capacitance of up to 140.0 F/g and a high energy density of up to 3.11 Wh/kg at a current density of 2 A/g in 6 m KOH aqueous electrolyte. The high SSA of AG and the porous surface morphology of the Cu mesh allowed efficient electric double-layer formation and charge transport. This work offers an alternative to improve supercapacitors by combining a porous metallic current collector with porous AG.

Hydrothermal liquefaction (HTL) processing of unhydrolyzed solids (UHS) for hydrochar and its use for asymmetric supercapacitors with mixed (Mn,Ti)-Perovskite oxides

In this study, the unhydrolyzed solid (UHS) derived from corn stover was hydrothermally processed to generate heavy bio-oil (HBO) and hydrochar. In particular, hydrothermal liquefaction (HTL) was carried out in a 300 mL high temperature and high pressure reactor with the slurry of UHS in de-ionized (DI) water, and the effect of reaction temperature, initial nitrogen pressure, reaction time, and UHS to solvent ratio on hydrochar generation was investigated. HTL processed slurries were filtered to recover the solid residue, which was extracted with acetone to recover heavy bio-oil (HBO). The solid residue was thermally treated further at 400 °C to produce hydrochar, which was thoroughly characterized by BET, SEM/EDX, FTIR and Raman spectroscopy. Results indicated that as temperature of HTL process increased from 250 to 300 °C, hydrochar yield decreased. Increase in HTL temperature also resulted in decrease in BET specific surface area (SSA) and pore volume; however, increase in pore diameter. HTL parameters such as initial N2 pressure, reaction time, and UHS:water ratio was found to influence the yield, BET SSA, pore volume and pore diameter. SEM images showed porous structure whereas surface functional groups with O-H, >CC< and C–H stretching vibrations were observed with FTIR spectroscopy. Fully characterized hydrochar obtained under different HTL processing conditions was used with sol-gel synthesized (Mn,Ti)-oxide electrode and aqueous KOH electrolyte to fabricate asymmetric supercapacitors (ASC), which were tested with cyclic voltammetry to determine specific capacitance. A maximum specific capacitance was observed for the hydrochar electrode materials obtained at the HTL processing conditions of 275 °C temperature, 1 h reaction time, and UHS:water ratios of 1:30 and 1:10 with initial nitrogen pressure of 100 psig and 150 psig, respectively.

Graphene Nanosphere as Advanced Electrode Material to Promote High Performance Symmetrical Supercapacitor.

To get carbon electrode with both excellent gravimetric and volumetric capacitances at high mass loadings is critical to supercapacitors. Herein, cracked defective graphene nanospheres (GNS) well meet above requirements. The morphology and structure of the GNS are controlled by polystyrene sphere template/glucose ratio, microwave heating time, and Fe content. The typical GNS with specific surface area of 2794 m2 g-1 , pore volume of 1.48 cm3 g-1 , and packing density of 0.74g cm-3 performs high gravimetric and volumetric capacitances of 529 F g-1 and 392 F cm-3 at 1A g-1 with a capacitance retention of 62.5% at 100 A g-1 in a three-electrode system in 6mol L-1 KOH aqueous electrolyte. In a two-electrode system, the GNS possesses energy density of 18.6Wh kg-1 (13.8Wh L-1 ) at the power density of 504 W kg-1 , which is higher than all reported pure carbon materials in gravimetric energy density and higher than all reported heteroatom-doped carbon materials in volumetric energy density, in aqueous solution, as far as it is known. A structural feature of carbon materials that possess both high energy density and high power density is pointed out here.

Preparation of Cobalt Oxide-Reduced Graphitic Oxide Supercapacitor Electrode by Photothermal Processing.

We report a photonic technique to instantaneously synthesize cobalt oxide reduced graphitic oxide (CoOx-rGO) supercapacitor electrodes. The electrode processing is achieved through rapidly heating the precursor material by irradiation of high-energy pulsed mostly visible light from a xenon lamp. Due to the short duration of the light pulse, we prepared the electrodes at room temperature instantaneously (ms), thus eliminating the several hours of processing times of the conventional techniques. The as-prepared electrodes exhibited a highly porous morphology, allowing for enhanced ionic transport during electrochemical interactions. The electrochemical properties of the CoOx-rGO electrodes were studied in 1 M KOH aqueous electrolyte. The non-rectangular cyclic voltammetry (CV) curves with characteristic redox peaks indicated the pseudocapacitive charge storage mechanism of the electrodes. From the discharge curves at 0.4 mA/cm2 and 1.6 A/g constant current densities, the electrode showed areal specific capacitance of 17 mF/cm2 and specific capacitance of 69 F/g, respectively. Cyclic stability was tested by performing 30,000 galvanostatic charge–discharge (GCD) cycles and the electrode exhibited 65% capacitance retention, showing its excellent electrochemical performance and ultra-long cycle life. The excellent electrochemical electrode properties are attributed to the unique processing technique, optimum processing parameters, improved conductivity due to the presence of rGO, and highly porous morphology which offers a high specific surface area. The novel photonic processing we report allows for high-temperature heating of the precursor films achieved via non-radiative recombination of photogenerated electron holes pairs during irradiation. Such extremely quick (ms) heating followed by instantaneous cooling results in the formation of a dense and robust bottom layer of the electrode, resulting in a long cycle life.

Synthesis of two-dimensional porous carbon nanosheets for high performance supercapacitors

• Two-dimensional porous carbon nanosheets was prepared by a simple way. • The optimized electrode shows good electrochemical performance. • The symmetric supercapacitor delivers high energy density. Two-dimensional (2D) porous carbon nanosheets (PCNs) have drawn tremendous concern due to they possess large specific surface area, reduced ion transportation resistance and shorten ion diffusion distance. However, the traditional template method is complex and time-consuming. Here, we reported a convenient strategy to synthesize 2D PCNs derived from cationic starch using graphene oxide (GO) as template through an electrostatic self-assembly strategy with KOH activation. Due to the unique 2D highly interconnected nanosheet-like porous framework with suitable specific surface area, the as-prepared PCNs-1 electrode delivers high specific capacitance (232.1 F g −1 at 2 mV s −1 ) and impressive electrochemical stabilization (100.3% retention after 10,000 cycles) in 6 M KOH aqueous electrolyte. Meanwhile, the constructed PCNs-1//PCNs-1 symmetrical supercapacitor shows an energy density of 19.2 Wh kg −1 and remarkable electrochemical stabilization (93.7% retention after 10,000 cycles) in 1 M Na 2 SO 4 aqueous electrolyte. The strategy provides a novel and convenient approach to construct porous carbon nanosheets for supercapacitors.

Cobalt-iron spinel/reduced graphene oxide composite material for supercapacitor applications

Cobalt–iron spinel/reduced graphene oxide composite material was obtained by one-step hydrothermal synthesis. XRD, low temperature nitrogen adsorption, Mossbauer spectroscopy, micro-Raman spectroscopy and cyclic voltammetry were used for materials characterization. The influence of the annealing temperature and graphene component presence on the properties of composite materials was investigated. The contribution of pseudocapacitance component in total electric capacitance of the composite-based supercapacitors in 1 M KOH aqueous electrolyte was analyzed.

Simple and Cost-Effective Synthesis of Activated Carbon Anchored by Functionalized Multiwalled Carbon Nanotubes for High-Performance Supercapacitor Electrodes with High Energy Density and Power Density

We prepared a composite using activated carbon and functionalised multiwalled carbon nanotubes by a simple and cost-effective process and investigated its use for supercapacitor application. The electrochemical performance of the prepared composite has been investigated by galvanostatic charge-discharge (GCD) and cyclic voltammetry (CV) measurements in a three-electrode set-up. The composite resulted in maximum specific capacitance of 395 F/g at 5 mV/s as measured by CV, and of 372 F/g at 60 A/g by GCD measurement in 3M KOH aqueous electrolyte. High power and energy density of 75.27 kW/kg and 25.31 W·h/kg at 60 A/g have been respectively obtained for composite using GCD measurement. The long-term charge-discharge stability has been performed for the composite electrodes, and it is observed that 89% of capacitance is retained even after 5000 cycles. The achieved results suggest that the prepared activated carbon/multiwalled carbon nanotube composite can be a potential electrode material in high-performance supercapacitors for energy storage applications.

Liquid-Phase Deposition Synthesis of ZIF-67-Derived Synthesis of Co3O4@TiO2 Composite for Efficient Electrochemical Water Splitting

In this article, a novel Co3O4@TiO2 composite is synthesized by applying two-step methods. ZIF-67 is synthesized and used as a template for the synthesis of the composite. The composite is designed by using the effective photocatalytic properties of Co3O4 and TiO2. The resulting synthesized composite is supposed to offer superior properties compared to their counterparts. The synthesized Co3O4@TiO2 composite is characterized by powder X-ray diffraction (PXRD), Brunauer–Emmet–Teller (BET), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Electrochemical water splitting, including hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) studies on the Co3O4@TiO2 composite, is evaluated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) analysis in a 2M aqueous KOH electrolyte. The current generation stability of these samples is deliberated by chronoamperometric measurements. It is observed, from LSV results at a 1 mV/s scan rate, that metal oxides incorporated on other metal oxides have a higher current density and lower onset potential as compared to pure metal oxides. From the obtained results, it has become evident that synthesized studies on the Co3O4@TiO2 composite possess significant potential for electrochemical water splitting with the lowest onset potential, highest current density, better OER, and HER activity.

Preparation of porous nitrogen-doped activated carbon derived from rice straw for high-performance supercapacitor application

Environmental-friendly and low-cost biomass-derived materials have been attracted many attentions to produce porous activated carbon (AC) with high surface area for supercapacitor (SC) application. In this study, rice straw (RS), an agricultural waste, is used to prepare ACs with a two-step process of carbonization and KOH activation. As-produced AC has a high specific surface area (SSA) of 2651 m2g-1 with hierarchical pore structure. In order to enhance the performance of SC, nitrogen-doping strategy is carried out to increase nitrogen functional groups in the AC using melamine as a precursor. The SSA of the nitrogen-doped AC is 2537 m2g-1 and the capacitance of 324 F/g is achieved using nitrogen-doped AC at a current density of 0.5 Ag-1 in 6 M KOH aqueous electrolyte. The capacitance retention is 95% after 10,000 charge and discharge cycles at a current density of 5.0 Ag-1. In addition, ionic liquid is employed as the electrolyte for the supercapacitor. The energy density of 48.9 Wh/kg at a power density of 750 W/kg can be achieved using EMI-TFSI electrolyte. We think that the proposed method can be used for a variety of biomass for preparation of ACs with high specific surface area and nitrogen functional groups for the energy storage applications.

Surfactant assisted morphological transformation of rod-like ZnCo2O4 into hexagonal-like structures for high-performance supercapacitors

Objectives: To develop the microstructures of rod-shaped ZnCo2O4 (ZCOUrea) and hexagonal-shaped ZnCo2O4 (ZCO-NH4F) through the change of surfactants such as urea and NH4F in the reaction and to investigate the physicochemical and electrochemical properties for high-performance supercapacitors. Methods: The structural and morphological characteristics of two prepared samples were analyzed through X-ray diffraction analysis (XRD), Scanning electron microscope (SEM) analysis, and Transmission electron microscope (TEM) analysis, respectively. The electrochemical performance was evaluated using Cyclic voltammetry (CV), Galvanostatic charge-discharge (GCD), and Electrochemical impedance spectroscopy (EIS) analysis. Findings: The crystalline nature and phase purity of the as prepared samples were confirmed from XRD, and the structural parameters such as lattice parameter (a), microstrain (e ), dislocation density (d ), cell volume (v), and average crystalline size (D) for both the samples were determined. The SEM and TEM analysis revealed morphological characteristics of the samples. The electrochemical analysis of ZCO-Urea and ZCO-NH4F electrodes were tested for supercapacitor application in 1M of aqueous KOH electrolyte and exhibit an areal capacitance of 31 mF cm-2, and 41.43 mF cm-2, respectively, obtained at a current density of 10 mA cm-2. And also showed outstanding cyclic stability over 1000 charge-discharge cycles. Applications: The simple and inexpensive method of synthesized surfactant-assisted morphological transformation of ZCO microstructures will introduce new directions in this emerging energy field. Keywords: ZnCo2O4; Urea; NH4F; areal capacitance; supercapacitors

One-pot facile synthesis and electrochemical evaluation of selenium enriched cobalt selenide nanotube for supercapacitor application

The present study emulates a one-pot facile synthesis of selenium-enriched CoSe nanotube using a chemical bath deposition (CBD) procedure. Schematic incorporation of 3D Ni foam current collectors as substrates for the growth of CoSe–Se nanotubes helped us achieve a binder-less thin film coating. The controlled synthesis of CoSe–Se nanotube was carried out by optimizing the temperature and time of the deposition. CoSe–Se nanotubes were grown on a porous Ni foam substrate using lithium chloride as a shape directing agent. The study found that the one dimensional structure of the nanotubes with porous nature results in an uninterrupted network of electroactive sites. Due to the superior conductivity, the as-fabricated material exhibited excellent rate capability and a higher degree of electrolyte ion diffusion across the CoSe–Se crystal structure. The CoSe–Se@Ni foam electrodes exhibited a specific capacitance of 1750.81 F g−1 at 1 A g−1. The electrode exhibited excellent cycling stability and showed a capacitance retention of 95% after 4000 charge-discharge cycles. Finally, an asymmetric supercapacitor (ASC) device was fabricated with the as-synthesized CoSe–Se@Ni foam electrode as the cathode, activated carbon@Ni foam electrode as the anode, and a thin filter paper separator soaked in 1 M aqueous KOH electrolyte solution. The ASC device showed a specific capacitance value of 106.73 F g−1 at 0.5 A g−1, and achieved an energy density of 37.94 Wh kg−1 at a power density of 475.30 W kg−1. The ASC device was utilized in an extended potential window of 1.6 V. The fabricated device displayed exceptional cycling stability with a capacitance retention of 93% after 5000 charge-discharge cycles.

Preparation of 3D carbon conductive composite derived from nitrogen-rich resin/MWCNT and its application in supercapacitors

Carbon materials are considered as one of the promising materials in supercapacitors because of their distinctive electrochemical properties. In this study, N-doped carbon electrode materials, derived from melamine formaldehyde (MF) resin, a high-performance and N-rich thermosetting resin, used as an electrode active material for supercapacitor application. A simple method was adopted to fabricate the three-dimensional conductive composite materials by mixing the carbon nanotubes (CNTs) to the carbon material with different mass ratios. It was found that the reactant ratio of MF and CNT plays an important role in the improvement of electrochemical behavior. The sample of 7% CNT@MF-C showed a gravimetric specific capacitance of 319.6 F g−1 in 6 M KOH aqueous electrolyte at a current density of 0.5 A g−1, as well as capacitance retention of 97.8% after 10,000 cycles. A remarkable improvement in the electrochemical behavior was obtained by modifying the surface chemistry as well as the electrical conductivity of the carbon. The assembled symmetrical supercapacitors have a high energy density and power density of 9.53 Wh kg−1 and 400 W kg−1, respectively. The presence of porous carbon with intrinsic nitrogen-containing groups makes them more useful as high-performance supercapacitors. Overall, this simple approach exhibits great potential for carbon-based high-performance supercapacitor application.

Synthesis of heterogeneous NiO nanoparticles for high-performance electrochemical supercapacitor application

Heterostructure nickel oxide (NiO) nanoparticles have been synthesized by a facile hydrothermal route. Structural, optical, and microstructural information were investigated using XRD, UV–vis, FT-IR, FT-Raman, SEM, HR-TEM, and XPS. The X-ray diffraction and HR-TEM analysis shows that the average size of the synthesized NiO is to be 12 nm. The X-ray photoelectron spectroscopic results revealed oxidation state and elemental composition of NiO. Electrochemical examination of NiO showed attractive performance with high specific capacitance of 1358 F g−1 at 1 A g−1 in 3 M KOH aqueous electrolyte. Moreover, the results showed superior energy density of 138 W Kg−1 and power density of 1041 Wh Kg−1. The NiO-modified electrode showed high capacitive execution with high specific capacitance and excellent cycle life. The attractive electrochemical result is attributed to the heterostructure morphology and good adherence of the NiO nanoparticle on the substrates, which reduce the particle diffusion length and significantly encourage the charge movement both at the contact interfaces and inside the anode materials during the electrochemical cycle.

CoMn2O4 Nanoparticles Decorated on 2D MoS2 Frame: A Synergetic Energy Storage Composite Material for Practical Supercapacitor Applications

In material science, the synergistic effect comes into the picture when the physical and/or chemical properties of a composite material improve noticeably in comparison to that demonstrated by its forming individual components. This work represents the facile synthesis of CoMn2O4 (CMO) and CoMn2O4@MoS2 (CMOS) nanocomposites via a co-precipitation synthesis approach. In this study, amounts of CMO precursors were kept constant and the effect of MoS2 addition on the electrochemical properties of the nanocomposite has been investigated. The substantial improvement in the electrochemical performance of the nanocomposite after adding MoS2 contents with CMO can be attributed to the synergistic effect. The CMOS nanocomposite synthesized using 20% MoS2 uniform dispersion (abbreviated as CMOS20) exhibits maximum improvement in the electrochemical properties which is ascribed to its higher specific surface area (74 m2 g−1) and hierarchical pore size distribution. When examined in a conventional three-electrode system with 2 M KOH aqueous electrolyte, CMOS20 nanocomposite demonstrates high specific capacitances of 422 F g−1 at 0.5 A g−1, good cyclability, high-rate capability and higher diffusion coefficients (1.96 × 10−10 cm2 s−1). An asymmetric supercapacitor device designed using CMOS20 nanocomposite cathode and activated carbon anode exhibit maximum specific energy of 37 W h kg−1 and the maximum specific power of 5000 W kg−1. This practical device can light up a red LED for more than 3 min. We believe the facile synthesis approach and promising electrochemical results assert the potential of our designed CMOS20 nanocomposite in the development of high-performance practical supercapacitor devices.

A green and economical approach to derive biomass porous carbon from freely available feather finger grass flower for advanced symmetric supercapacitors

Presently, the porous carbon derived from natural biomass wastes hold a prominent position as electrode material in supercapacitors from its wonderful features of huge surface area, cost-effectiveness, freely available precursor, easy to preparation and eco-friendly nature. Thus, in the present study, we propose a new hollow tubular-like porous carbon (HT-PC) from the more sustainable and freely available feather finger grass flower (FFGF) with high electrochemical behavior as an active electrode for supercapacitors. The combination of carbonization and KOH activation treatments were carried out to prepare HT-PC from natural FFGF. The as-prepared biomass HT-PC containing the different sized micro-pore arrangement with a huge surface area (637.1 m2 g−1) after performed KOH activation treatment at the optimized condition. The three-electrode system measurements reveal that as-prepared HT-PC provides a remarkable specific capacitance of 315 F g−1 at 1 A g−1 and 262 F g−1 at 100 A g−1 with keeping 96% of capacitance over 50,000 cycles at 50 A g−1 using 6 M KOH aqueous electrolyte. In addition to that, the HT-PC electrode-based symmetrical supercapacitor releases high specific energy of 18.75 Wh kg−1 at 0.37 kW kg−1 with losing 30% of capacitance over 10,000 cycles at 10 A g−1 using 6 M KOH electrolyte. Meanwhile, the symmetrical supercapacitor shows a good specific energy of 13.18 Wh kg−1 at 0.61 kW kg−1 without losing any capacitance over 10,000 cycles at 10 A g−1 using 1 M Et4NBF4/AN electrolyte. This study is verified that the naturally available FFGF is a talented sustainable carbon source to make more economical and effective carbon electrodes for supercapacitors.

Decoration of CeO2 nanoparticles on hierarchically porous MnO2 nanorods and enhancement of supercapacitor performance by redox additive electrolyte

Pure CeO2 nanoparticles (NPs) and MnO2 nanorods (NRs) have been prepared by the hydrothermal technique. The CeO2 NPs were uniformly coated over the MnO2 NRs through a facile ultrasonic technique. The uniform distribution of CeO2 NPs over MnO2 NRs has been analysed by scanning electron microscopy. Crystalline phases of pure CeO2, MnO2, and the formation of CeO2 NPs decorated MnO2 NRs have been studied by XRD analysis. The absence of inorganic residuals over the prepared nanomaterials was confirmed by FT-IR analysis. The surface chemical composition and the formation of CeO2 NPs decorated MnO2 NRs have been studied by XPS analysis. The electrochemical performances of the prepared sample have been studied in 3 M aqueous KOH electrolyte and 0.2 M K4[Fe(CN)6] added 3 M KOH electrolyte. CeO2 nanoparticles decorated MnO2 nanorods exhibited the superior capacitance of 1058.2 Fg−1.

Elevated performance of binder-free Co3O4 electrode for the supercapacitor applications

In the present work, we have designed a symmetric supercapacitor (SS) device by synthesizing a pseudocapacitive binder-free cobalt oxide (Co3O4) thin film based electrode using reactive DC magnetron sputtering technique. The thin film electrodes were characterized by x-ray diffraction, Raman spectroscopy and x-ray photoelectron spectroscopy to reveal the crystallographic details, stoichiometry, and electronic configuration, respectively. Furthermore, Co3O4 thin film electrode is used for pseudocapacitor and electrochemically tested in 1M aqueous KOH electrolyte solution, in addition, a symmetric supercapacitor (SS) device was fabricated. It was found that the SS device exhibits tremendous electrochemical stability in terms of high capacitance and good cycling stability. The value of specific capacitance for Co3O4 thin film electrodes and the SS device was calculated to be 392 Fg−1 and 95 Fg−1, respectively, at a scan rate of 2 mAcm−2. The SS device exhibits high specific energy (29 W-hkg−1) along with comparable good specific power (4745 Wkg−1). In this work, the fabricated SS device demonstrates 91.40% cyclic and capacitance retention at 8 mAcm−2 beyond 10 000 cycles. The excellent electrochemical stability and capacitive performance of the SS device suggest that it would be an ideal and potential candidate for energy storage applications in the future.

Self-standing SnS nanosheet array: a bifunctional binder-free thin film catalyst for electrochemical hydrogen generation and wastewater treatment.

Hydrogen generation during wastewater treatment has remained a long-standing challenge for the environment preservation welfare. In the present work, we have fabricated a promising bifunctional thin film-based catalyst for hydrogen generation with concurrent wastewater treatment. The prepared catalyst film is a vertically oriented thin SnS (tin monosulfide) nanosheet array on a Ni-foam (SnS/NF) obtained via a solution process, demonstrating a promising electrocatalytic activity towards the generation of green H2 fuel at the cathodic side and the decomposition of urea waste at the anodic side. Notably, while assembling two identical electrodes as cathode and anode together with a reference electrode (i.e., SnS/NF∥SnS/NF vs. RHE assembly) in 1 M KOH aqueous electrolyte containing 0.33 M urea, the electrolyzer electrolyzed urea at a lower cell potential of 1.37 and 1.43 V (vs. RHE) to deliver a current density of 10 mA cm-2 and 50 mA cm-2, respectively, for the decomposition of urea at the anodic SnS/NF electrode and green hydrogen fuel generation at the cathodic SnS/NF electrode. This activity on electrocatalytic urea decomposition lies within the best performance to those of the previously reported sulfide-based and other catalytic materials. The promising catalytic activities of the SnS catalyst film are attributed to its combined effect of self-standing nanosheet array morphology and high crystallinity, which provides abundant active sites and a facile charge transfer path between the nanosheet arrays and the electrolyte. Thus, the present work offers a green avenue to the waste-urea treatment in water and sustainable hydrogen energy production.

Hydrothermal synthesis of MnO2@graphene/activated carbon composite electrode with enhanced electrochemical performance for supercapacitor applications

We report the preparation of an electrode material made up of MnO2/graphene/ activated carbon ternary composite by hydrothermal method for supercapacitor (SC) applications. The prepared ternary composite has been characterized by using scanning electron microscopy (SEM), powder X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and Raman spectroscopy measurements. The prepared objective electrode has been investigated using galvanostatic charge-discharge (GCD) and cyclic voltammetry (CV) measurements in a 3-electrode system using 3M KOH aqueous electrolyte for the analysis of their electrochemical performance. The prepared MnO2 /graphene/activated carbon composite results in maximum capacitance of ∼493.57 F/g at 5 mV/s using CV and moreover the highest capacitance obtained from the GCD measurement is ∼485.29 F/g at 1 A/g. The long-term cycle stability of the composite electrode is also demonstrated and it shows outstanding cyclic performance where 97% of capacitance is left over 5000 cycles at 1 A/g. Therefore, the composite shows good charge storage performance, as well as tremendous cycle stability and that, reveal the synthesized ternary composite can be a suitable electrode for SC applications.