Electrochemical Capacitive Behavior Research Articles

Leaf‐Inspired Hetero‐Structure WS2/WO3 In Situ Embedded on Pomelo Peel Derived Carbon for Supercapacitor and Capacitive Deionization

AbstractComposite materials have occupied a reliable position in electrochemical energy storage and conversion due to their double electric layer and pseudocapacitance. In this work, a leaf‐like heterostructure composite, obtained by peeling – carbonizing – in situ sulfuration/oxidation approach for the first time, is investigated as electrode material for electrochemical capacitance behavior. The thin and highly active transition metal WS2 acts as an energetic “blade” to trap free ions, which are then transported across the material through a strong “tendon skeleton” WO3. The derived carbon PPC with a large aspect ratio holds up the overall leaf structure, also as a “warehouse” for ion storage, thus enhancing the conductivity and wettability of the material. The above three (WS2+WO3+PPC) synergistically provide outstanding double‐layer capacitance and pseudocapacitance. In particular, the vacancy defects, constructed at the heterogenous interface from WS2‐WO3 in situ growth, can still achieve superior ion absorption/desorption ability even under large current density and high concentration brackish solution.

Enhanced dye-sensitized solar cell performance and electrochemical capacitive behavior of bi-functional ZnO/NiO/Co3O4 ternary nanocomposite prepared by chemical co-precipitation method

Increasing prerequisites for sustainable energy storage and conversion technologies have necessitated the exploration of advanced materials with improved properties. Here, we present the synthesis and characterization of ZnO nanoparticles (NPs), ZnO/NiO, ZnO/Co3O4 and ZnO/NiO/Co3O4 NCs as promising bi-functional materials for dye-sensitized solar cell (DSSC) and electrochemical energy storage applications. A facile chemical co-precipitation approach was followed to synthesize pure ZnO NPs, ZnO/NiO, ZnO/Co3O4 and ZnO/NiO/Co3O4 NCs. The structural and morphological analyses revealed the successful integration of ZnO, NiO, and Co3O4 NPs and also the formation of well-defined core-shell and homogenous nanocomposite structures. The XRD and HRTEM analyses confirmed the crystalline nature and nanoscale morphology of synthesized materials, respectively. The photovoltaic performance of DSSC fabricated using ternary ZnO/NiO/Co3O4 NC photoanode showed optimum dye-loading and best solar to electrical energy conversion efficiency with Jsc of 11.29 mA cm−2 and ƞ of 4.66%, which was considerably higher than the DSSC fabricated using pure ZnO NPs photoanode (ƞ = 2.01%). The increment in photocurrent density (Jsc) could be ascribed to the perfect band alignment of NiO and Co3O4 NPs in the ternary NC. Further, the ZnO/NiO/Co3O4 NC photoanode integrated DSSC disclosed 97% retainment in energy conversion efficiency even after 10 days of operation. The electrochemical performance of supercapacitor fabricated using ternary ZnO/NiO/Co3O4 NC showed high specific capacitance of 534.7 Fg−1 at 1 Ag−1 with favourable rate ability (∼52% at 16 Ag−1), good cyclic stability (91.07%) and low internal resistance. Moreover, the ZnO/NiO/Co3O4 NC at a current density of 2 Ag−1 exhibited a significantly high capacitance value of 463.1 Fg−1, which was 1.93, 1.58 and 1.22 times greater than ZnO NPs, ZnO/Co3O4 NC and ZnO/NiO NC, respectively.

Electrochemical capacitance and hydrogen adsorption behavior of activated carbon derived from cattail fiber

AbstractIn this paper, we have reported the synthesis of activated carbon (AC) from biomass cattail fiber through hydrothermal carbonization, followed by chemical activation, and its electrochemical capacitance and hydrogen storage properties. The AC exhibits a Brunauer‐Emmett‐Teller (BET) surface area (SBET) of 1597.5 m2g−1, determined from the low‐pressure N2 adsorption isotherm at 77 K using a BET‐multipoint plot. The AC sample shows a reversible hydrogen adsorption capacity of 0.25 wt.% H2 (1.25 mmol H2 g−1) at 293 K and 74 atm. The capacitance performance of AC was investigated with various conductive additives such as carbon nanotubes (CNTs), carbon black (CB), and reduced graphene‐oxide (rGO). From galvanostatic charge discharge (GCD) and cyclic voltammetry (CV) measurements, the as‐derived AC with polymer binder exhibits a specific capacitance (Cs) of 245.2 F g−1 at 0.2 A g−1 and 158.1 F g−1 at 5 mV s−1. Among the investigated conductive additives, AC with CNTs in KOH electrolyte exhibit highest Cs of 326 F g−1 at 0.2 A g−1 and 173 F g−1 at 5 mV s−1. Furthermore, the symmetrical two‐electrode device fabricated using AC with CNTs (as a conductive additive) in 1 M aq. Na2SO4 electrolyte shows a Cs of 97.2 F g−1 at 0.1 A g−1. The energy and power densities of the two‐electrode device were observed to be 28 kW kg−1 and 2.64 Wh kg−1, respectively.

Direct Synthesis of MOF-74 Materials on Carbon Fiber Electrodes for Structural Supercapacitors.

The use of fossil fuels has contributed significantly to environmental pollution and climate change. For this reason, the development of alternative energy storage devices is key to solving some of these problems. The development of lightweight structures can significantly reduce the devices' weight, thereby reducing energy consumption and emissions. Combining lightweight structures with alternative energy storage technologies can further improve efficiency and performance, leading to a cleaner and more sustainable system. In this work, for the first time, MOF-74 materials with different divalent metal ions have been synthesized directly on carbon fiber, one of the most widely used materials for the preparation of electrodes for supercapacitors with structural properties. Different techniques, such as nitrogen adsorption-desorption isotherms, cyclic voltammetry or galvanostatic charge-discharge, among others, were used to evaluate the influence of the metal cation on the electrochemical capacitance behavior of the modified electrodes. The Co-MOF-74 material was selected as the best modification of the carbon fibers for their use as electrodes for the fabrication of structural supercapacitors. The good electrochemical performance shown after the incorporation of MOF materials on carbon fibers provides a viable method for the development of carbon fiber electrodes, opening a great variety of alternatives.

Molten‐Salt Synthesis of Anthracite‐Based Porous Carbon for Microscale Supercapacitors and Strain Sensors

AbstractThe molten‐salt synthesis and electrochemical capacitive behaviors of porous carbon are reported using anthracite as the precursor. Upon synthesis, the binary KCl/K2CO3 molten salt not only exfoliates bulky anthracite to carbon nanosheets but also creates rich micro‐ and mesopores in the structure. The resulting porous carbon shows a large surface area of 1399.7 m2 g−1 and a total pore volume of 1.50 cm3 g−1. In 6.0 mol L−1 KOH aqueous electrolyte, it delivers a high specific capacitance of 245.6 F g−1 at a current density of 0.5 A g−1. Flexible micro‐supercapacitors with this porous carbon are assembled following an interdigitated design. The micro‐supercapacitor affords an area capacitance of 18.0 mF cm−2 and an energy density of 1.58 µWh cm−2 at a power density of 20 µW cm−2, and sustains 89.6% of the capacitance after 2000 cycles. Furthermore, the strain sensor fabricated by replacing the current‐collecting fluid at both ends of the electrode provides consistent and stable signal output, regardless of the degree of bending and the number of cycles. This study demonstrates the great potential of anthracite‐based porous carbon in flexible energy and electronic microdevices.

Boosted electrochemical performance of magnetic caterpillar-like Mg0.5Ni0.5Fe2O4 nanospinels as a novel pseudocapacitive electrode material

Ni-incorporated MgFe2O4 (Mg0.5Ni0.5Fe2O4) porous nanofibers were synthesized using the sol–gel electrospinning method. The optical bandgap, magnetic parameters, and electrochemical capacitive behaviors of the prepared sample were compared with pristine electrospun MgFe2O4 and NiFe2O4 based on structural and morphological properties. XRD analysis affirmed the cubic spinel structure of samples and their crystallite size is evaluated to be less than 25 nm using the Williamson–Hall equation. FESEM images demonstrated interesting nanobelts, nanotubes, and caterpillar-like fibers for electrospun MgFe2O4, NiFe2O4, and Mg0.5Ni0.5Fe2O4, respectively. Diffuse reflectance spectroscopy revealed that Mg0.5Ni0.5Fe2O4 porous nanofibers possess the band gap (1.85 eV) between the calculated value for MgFe2O4 nanobelts and NiFe2O4 nanotubes due to alloying effects. The VSM analysis revealed that the saturation magnetization and coercivity of MgFe2O4 nanobelts were enhanced by Ni2+ incorporation. The electrochemical properties of samples coated on nickel foam (NF) were tested by CV, GCD, and EIS analysis in a 3 M KOH electrolyte. The Mg0.5Ni0.5Fe2O4@Ni electrode disclosed the highest specific capacitance of 647 F g−1 at 1 A g−1 owing to the synergistic effects of multiple valence states, exceptional porous morphology, and lowest charge transfer resistance. The Mg0.5Ni0.5Fe2O4 porous fibers showed superior capacitance retention of 91% after 3000 cycles at 10 A g−1 and notable Coulombic efficiency of 97%. Moreover, the Mg0.5Ni0.5Fe2O4//Activated carbon asymmetric supercapacitor divulged a good energy density of 83 W h Kg−1 at a power density of 700 W Kg−1.

2H-MoS2 as an electrode material for oxygen reduction reaction and supercapacitor applications

Molybdenum Disulfide (MoS2) is a two-dimensional material having hexagonal crystal structure, which is widely used as a catalyst in various electrochemical reactions. In the present work, 2H-MoS2 nano-structures are synthesized in the exfoliated form by a facile hydrothermal synthesis route and are studied as electrode material for electrochemical devices. Formation of 2H-MoS2 phase has been confirmed by XRD and is also supported by the presence of E12g and A1g bands in Raman spectroscopy which appears due to the formation of layered MoS2 sheets. The FESEM images show MoS2 sheets in the form of flower-like microstructures. The ORR limiting current density obtained from polarization curves is 3.51 mA/cm2 at 2400 rpm with an onset potential of 0.06 V vs RHE. The specific capacitance of 2H-MoS2 as determined from CV and GCD are 115.42 F/g (at a scan rate of 10 mV/s) and 57.69 F/g (at current density 0.5 A/g) respectively and the samples retain 71.5 % of specific capacitance after 5000 CV cycles. The sample exhibited an electrochemical double layer capacitive (EDLC) behavior with partial pseudo-capacitance. The results suggest that the MoS2-based materials are potential candidates as electrodes in the electrochemical devices.

Enhanced electricity generation and storage by nitrogen-doped hierarchically porous carbon modification of the capacitive bioanode in microbial fuel cells

Microbial fuel cells (MFCs) can potentially be utilized for power generation, but their low power density and low energy storage capabilities remain major bottlenecks for their large-scale development. In this research, a simplistic nitrogen-doped hierarchically porous carbon material (HPC-A) was developed through a one-step carbonization and activation process and was successfully hot-pressed on the carbon cloth (CC) substrate. This process fabricates capacitive bioanodes (HPC-A-CC) that can enhance electricity generation and storage in MFCs. The as-prepared HPC-A-CC anode delivered a power density of 2043.6 mW·m−2 and a cumulative total charge (Qm) of 426.4 ± 13.4C·m−2 at each cycle, which was 2.1 and 34.8 times higher than that of the plain CC anode, respectively. This was a result of the hierarchical and interconnected porous structure, improved hydrophilic surface, and increased number of active centers which host the bacteria for enhanced electron transfer. Electrochemical measurements indicated the superior electrochemical activity and capacitive behavior of the HPC-A-CC anode. Furthermore, biofilm analysis revealed that the HPC-A-CC biofilm exhibited higher cell viability and a more uniform spatial distribution. These findings not only demonstrate the potential of HPC-A-CC for power enhancement in MFCs but also provide a feasible solution to the problem of power generation and demand mismatch in MFC applications.

FeS2/SRGO nanocomposite: Synthesis, characterization and comprehensive study of supercapacitor behavior in different electrolytes

In this study, fine FeS2 nanoparticles were synthesized using novel, easy and efficient methods. Graphene oxide was reduced and sulfur-doped in one step by a new simple chemical method and used to prepare the (pyrite- sulfur doped reduced graphene oxide) FeS2-SRGO nanocomposite. The prepared samples were characterized and approved by using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning- electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) mapping, transmission electron microscopy (TEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods. The FeS2-SRGO nanocomposite was coated on a carbon paste electrode substrate and the electrochemical capacitive behavior of the electrode was studied by CV and galvanostatic charge-discharge (GCD) method in different electrolytes including 6 M KOH, 1 M H2SO4, 1 M Na2SO4, 1 M NaCl, 1 M NaNO3, 1 M KCl, 3 M NaOH. Experimental results and specific capacitance calculations showed that the electrode in 1 M H2SO4 electrolyte with a specific capacity of 277 F g−1 has the best supercapacitor performance. The capacity retention is about 90 % of the initial capacity even after 200 charge and discharge cycles.

High performance nanostructured symmetric reduced graphene oxide/polyaniline supercapacitor electrode: effect of polyaniline morphology

The synergetic impact of reduced graphene oxide (rGO) with different morphologies of polyaniline (PANI) has been studied for the energy storage devices. The electrode materials are synthesized via in-situ polymerization method at a low molar concentration (0.1 M) of an aqueous H2SO4 electrolyte medium in order to enhance the electrochemical capacitive behavior of rGO/PANI nanocomposites. The aim of this work is to enhance the overall capacitive behavior of rGO by incorporating different PANI morphologies (granular and flakes). The work aims at overcoming the limitations present in the PANI and rGO that deteriorates their electrochemical performances. The electrochemical analysis showed that the maximum specific capacitance of 681 F/g is for rGO/flakes PANI with a good retention rate of 63 %, high energy and power density (9 Wh Kg −1 and 1100 W Kg -1), high coulombic efficiency of 86 % as compared to the granular morphology with a maximum capacitance of 478 F/g at a scan rate of 10 mV/s. The large specific surface area is provided by rGO/f-PANI (41.96 m2/g) and rGO/g-PANI (33.10 m2/g) than their individual constituents. A low internal resistance provided by rGO/f-PANI (0.51 Ω) results in a large interfacial area for the enhancement of capacitive behavior of an electrode material. Considering the supercapacitor performance of rGO material with PANI morphologies and its ease of synthesis as well as affordability rGO/g-PANI and rGO/f-PANI, the nanocomposite seems to be a promising electrode material for next generation supercapacitors.

Characterisation of Novel Nitrogen Doped Reduced Graphene Oxide

The utilisation of fuel cells in everyday life is of critical importance for the introduction of clean energy and departure from carbon-based economy. The oxygen reduction reaction (ORR) rate on the cathode is the key factor for effective polymer electrolyte membrane fuel cells. Therefore, novel cathode catalysts have to be designed to reduce the ORR over voltage. One of the most efficient ways to increase the ORR rate is to use nitrogen doping of carbon materials.1 Such materials are also promising for applications in supercapacitors and other energy storage devices.2 In this work, experimental results based on a nitrogen-doped reduced graphene oxide are presented. The nitrogen-doped reduced graphene oxide has been produced by Sea Further SARL using a biological micro-organisms and non-toxic chemicals.3 The material has been characterised by several physical methods: particle size distribution analysis, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, gas adsorption method, and electrical conductivity measurements. X-ray diffraction data reveal the presence of peaks characteristic to reduced graphene oxide. The specific surface area of the bulk material is around 2.4 m2 g− 1 based on the nitrogen adsorption method. The bulk sample, in powder form, exhibited considerable specific conductance under pressure.Additionally, electrochemical measurements have been conducted in 0.1 M HClO₄ and 0.1 M KOH solutions. The electrochemical stability, capacitive behaviour, and ORR activity of nitrogen-doped reduced graphene oxide have been determined using cyclic voltammetry, rotating disc electrode and electrochemical impedance spectroscopy methods. The material under discussion has a good electrochemical stability within the investigated potential region in both media. The measurement data show that the ORR kinetics in alkaline media is much faster than in acidic media. Surprisingly, this material has a high gravimetric capacitance. Therefore, nitrogen-doped reduced graphene oxide has high potential for energy storage devices and is promising co-catalyst material in fuel cell. Acknowledgements This work was supported by the EU through the European Regional Development Fund under project TK 141 “Advanced materials and high-technology devices for energy recuperation systems” (grant number 2014 2020.4.01.15 0011); and by the Estonian Research Council (grant number PUT PRG 676). References N. Daems, X. Sheng, I.F.J. Vankelecom, and P.P. Pescarmona, J. Mater. Chem. A, 2, 4085 (2014).N.A. Elessawy, J.E. Nady, W. Wazeer, and A.B. Kashyout, Sci. Rep., 9, 1129 (2019).V. Iakimov, International Patent Application No. WO2021/059152, WIPO, April 1st 2021.

Unraveling Synergistic Redox Interactions in Tetraphenylporphyrin-Polyluminol-Carbon Nanotube Composite for Capacitive Charge Storage.

Organic redox-active materials, combined with high-surface-area carbonaceous substrates, form sustainable and low-cost composites with greatly enhanced electrochemical charge storage capacities. The electrochemical capacitive behavior of a composite electrode containing tetraphenylporphyrin sulfonate (TPPS), Chemically polymerized luminol (CpLum), and carbon nanotubes (TPPS-CpLum-CNT) was studied and compared with individual TPPS-CNT and CpLum-CNT composites. The dual-layer TPPS-CpLum had a combined contribution to the electrochemical charge storage, which led to an increased volumetric capacitance over the bare CNT and individual TPPS-CNT and CpLum-CNT composites. The synergistic interactions in the composite enabled faster charge storage kinetics and great stability. Spectroscopic analyses revealed that TPPS and CpLum interact electronically through noncovalent π-π and van der Waals bonds, which facilitates the transfer of electrons during charge and discharge. The synergy in charge storage was confirmed by density functional theory computational analysis, which suggested favorable physisorption and interfacial electronic interactions for TPPS adsorbed to a CpLum-carbon substrate. The combined insights from experimental and computational characterizations show that superimposing redox-active organic layers can be an effective and sustainable approach to design and engineer the surface of carbonaceous materials for capacitive charge storage.

Preparation, Characterization, and Electrochemical Performance of the Hematite/Oxidized Multi-Walled Carbon Nanotubes Nanocomposite.

In this research work, a hematite (α-Fe2O3) nanoparticle was prepared and then mixed with oxidized multi-walled carbon nanotubes (O-MWCNT) to form a stable suspension of an α-Fe2O3/O-MWCNTs nanocomposite. Different characterization techniques were used to explore the chemical and physical properties of the α-Fe2O3/O-MWCNTs nanocomposite, including XRD, FT-IR, UV-Vis, and SEM. The results revealed the successful formation of the α-Fe2O3 nanoparticles, and the oxidation of the MWCNT, as well as the formation of stable α-Fe2O3/O-MWCNTs nanocomposite. The electrochemical behaviour of the α-Fe2O3/O-MWCNTs nanocomposite was investigated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV), and the results revealed that modification of α-Fe2O3 nanoparticles with O-MWCNTs greatly enhanced electrochemical performance and capacitive behaviour, as well as cycling stability.

Semi-Polycrystalline–Polyaniline Empowered Electrochemical Capacitor

We report on the formation of semi-polycrystalline polyaniline, a novel electroactive polymeric material synthesized by a modified surfactant-free chemical route and its enhanced electrochemical capacitive behavior. The material exhibits uniformly arranged spindle-shaped morphology in scanning electron microscopy and well-defined crystallographic lattices in the high-resolution transmission electron microscopy images. The X-ray diffraction spectrum reveals sharp peaks characteristic of a crystalline material. The characteristic chemical properties of polyaniline are recorded using Fourier transform infrared technology and laser Raman spectroscopies. The cyclic voltammetry curves exhibit features of surface-redox pseudocapacitance. The specific capacitance calculated for the material is 551 F g−1 at a scan rate of 10 mV s−1. The cycle stability and the coulombic efficiency recorded at a current density of 12 A g−1 exhibited good stability (90.3% and 99.5%, respectively) over 3000 cycles.

Heterogeneous Catalysis in Organic Transformations

In this study, we report a series of carbon/nickel-based composites. The composites are prepared through a facile one-pot solution combustion method by using nickel nitrate hydrate (Ni(NO3)2·6H2O) as an oxidizer and glucose (C6H12O6) as a fuel material. The phase, component and electrochemical capacitive behavior of the as-prepared samples are investigated. The component of the obtained composites could be simply controlled by changing the ratio of NO3−/C6H12O6. Novel C/Ni3(NO3)2(OH)4 composites are obtained at high molar ratio of NO3−/C6H12O6 (larger than 9) for the first time. The as-prepared C/Ni3(NO3)2(OH)4 composite shows battery-type behavior and exhibits a specific capacity of 630 C g−1 (1260 F g−1) at the current density of 1 A g−1, which is ca. 2–10 fold higher than those of C/NiO composite (414 C g−1, 828 F g−1) and C/NiO/Ni composite (65 C g−1, 129 F g−1). In addition, C/Ni3(NO3)2(OH)4 composite exhibits an excellent rate performance (448 C g−1, 996 F g−1 at 10 A g−1) and good cyclic stability. The results indicate that the C/Ni3(NO3)2(OH)4 composite is a potential electrode material for electrochemical supercapacitor. This work also suggests that the solution combustion process is promising for large-scale production of materials for supercapacitors.

Influence of free electron charge and free extra framework anions in calcium aluminate@ rGO (CA@ rGO) cement composites with enhanced dielectric and electrochemical properties

Nowadays, the metal oxide-based composites loaded with reduced graphene oxide (rGO) nano sheets are believed to enhance both the electrochemical and dielectric properties. In this study, therefore, the effect of rGO loading contents on the calcium aluminate (CA), namely CA@ rGO, cement composites with high dielectric and electrochemical properties is presented. CA@ rGO composites were successfully synthesized via a simple direct mixing of CA cement with various contents of graphene oxide (GO) precursors followed by a conventional thermal reduction method. Based on XRD and Raman spectroscopy results, all prepared CA@ rGO composites clearly confirmed both the structure of the pristine CA cement as well as the complete conversion of GO precursors to rGO after thermal reduction, and the existence of rGO nano sheets on the surface of CA@ rGO composites. The impedance value results revealed that the enhancement of a high dielectric constant was achieved in the CA@ rGO composites due to both typical interface polarization and the micro-capacitor of CA cement and rGO nano sheets. Meanwhile, the prepared CA@ rGO-4 composite electrode exhibited the highest of electrochemical double-layer capacitive behavior with the specific capacitance (Csc) value of 79.33 F g−1 at 0.2 A g−1. The enhanced super-capacitive performance of CA@ rGO composite can be improved by the synergistic effect of free electron transfer and electron diffusion between the CA cement interface and rGO nano sheets.

DNA-Assisted Stabilization of Graphene Sheets and Its Application as Supercapacitors Electrode

This work reports on the formation of rGO/ssDNA composite by stabilization of rGO sheets in an aqueous solution containing ssDNA extracted from baker’s yeast culture. The as-formed rGO/ssDNA composite was verified using spectroscopic and microscopic techniques, including Fourier transform infrared (FTIR), Raman, and photoluminescence (PL) spectroscopies, and field emission scanning electron microscopye (FESEM). Physical investigations showed the successful stabilization of rGO suspension by ssDNA for more than a month without the rGO sheets precipitating. The highly charged backbone of ssDNA comprising phosphate groups, nucleic-bases, and sugar molecules contributed to the rGO stabilization and this could be a potential electrode material for a charge storage supercapacitor. Electrochemical investigations confirmed the electrochemical double-layer capacitance behavior of rGO/ssDNA composite in KOH electrolyte, where a nearly 2-fold capacitance enhancement was observed compared to pure rGO. The oxygen residues on ssDNA were shown to contribute to the electrochemically active surface area of rGO/ssDNA. By virtue of the approach simplicity of its preparation and its being environmentally benign, it the proposed material can be considered as a promising candidate for practical applications of as a bio-supercapacitors after further processing.

Electrochemical capacitive behaviors of carbon/titania composite prepared by Tween 80-assisted sol-gel process for capacitive deionization

Hybridization of carbon with metal compounds has gained substantial attention in the development of robust electrodes for capacitive deionization (CDI). A composite of activated carbon (AC) with titania (TiO2) was concocted via Tween 80-assisted sol-gel process. The effects of Tween 80 on AC particles interaction with titanium tetraisopropoxide (TTIP) and properties of the composite were systematically scrutinized by multiple analytical techniques including scanning electron microscopy (SEM), laser diffraction (LD), contact angle (CA) measurement, X-ray diffraction (XRD), nitrogen sorption isotherms and X-ray photoelectron spectroscopy (XPS). Electrochemical characterization was conducted by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The results show the essential role of Tween 80 for homogeneous bonding of titania and altering characteristics of AC-T80/TiO2 composite. As such, the composite exhibited enhanced specific capacitance, and efficiency owing to the modulated benchmark properties (wettability, homogeneity, structure, and conductivity). Subsequently, the composite delivered the salt adsorption capacity (SAC) of 17.1 mg g−1 (26% higher than surfactant-free composite) at 1.4 V, with outstanding capacity retention (87%) over 150 cycles in oxygen saturated saline water (10 mM). This work discloses a novel strategic approach for carbon-metal compound composites synthesis with fundamental aspects for CDI application.

One-step electrochemical controllable preparation of nickel cobalt sulfide nanosheets and its application in supercapacitors

The bimetallic sulfides hold great promise for achieving high-performance supercapacitors. A facile unipolar pulse electrodeposition (UPED) method is developed to prepare nickel cobalt sulfides/polypyrrole (PPy) nanocomposites on carbon paper as electrode for supercapacitors, in which the crystalline structure, morphology and electrochemical performance of Co-Ni sulfides can be readily manipulated by simply changing the Co/Ni molar ratio in the electrodeposition electrolyte. It is demonstrated that the optimal CNS-3 electrode delivers the highest specific capacitance (2004 F g−1 at 1 A g−1), excellent rate capability and superior cycling stability. The outstanding electrochemical capacitive behavior can be ascribed to the synergistic effect of the Co-Ni sulfides, the 3D integrated porous structure of the electrode, as well as the conductivity and adhesion of PPy. Furthermore, an asymmetric supercapacitor (ASC) fabricated by the CNS-3 as positive electrode and activated carbon as negative electrode also displays remarkable electrochemical performance with ultralong cycle life and high energy density. These results manifest the great potential of CNS-3 in the development of high-performance supercapacitor electrode materials. Theoretically, the green and efficient UPED technology could also allow preparing other bimetallic or polymetallic sulfides with controllable composition, crystal structure and morphology.

Controlled synthesis, structural, morphological and electrochemical study of Cu(OH)2@Cu flexible thin film electrodes prepared via aqueous–non-aqueous routes

Copper oxide is one of the cheapest transition metal oxides used in the electrode preparation. Present work is focused on the preparation of Cu(OH)2@Cu flexible thin film electrodes (FTFEs) via aqueous and non-aqueous routes by self anodization and their comparative analysis by electrochemical analyzer for capacitive behavior. In this work, electrodes get prepared using different dispersion media at different deposition potentials by anodic electrodeposition technique. Electrodeposition was carried out on flexible Cu plates in 20 ml solution of 1 M NaOH dispersed in different medias viz. water, methanol and ethanol. These FTFEs were analyzed for structural and morphological analysis by using X-ray diffraction which confirms cubic crystal structure for all samples. All deposited electrodes exhibit hydrophilic nature. Cyclic voltammetry (CV) of these electrodes has been carried out in 1 M NaOH electrolyte. Only the electrode deposited at deposition potential 0.9 V via aqueous route exhibits good electrochemical stability and highest specific capacitance 604 F/g in 1 M NaOH at 2 mV/s. Galvanostatic charge–discharge behavior was studied to estimate specific energy (SE), specific power (SP), specific capacitance and columbic efficiency (η). Present work is important to understand the easy synthesis and suitable dispersive media for deposition of hydroxide phase of copper for better electrochemical capacitive behavior.