Synthesis of sponge like Gd3+ doped vanadium oxide/2D MXene composites for improved degradation of industrial effluents and pathogens

Current report is based on the synthesis of Gd⁺³ doped V₂O₅ nanostructures (GVO) along with fabrication of GVO/MXene binary nanocomposite. As synthesized GVO and GVO/MXene were characterized by XRD (X-ray diffraction), FESEM (Field emission scanning electron microscopy), EDX (Energy dispersive X-ray), BET (Brunauer Emmett Teller technique) and UV–Visible spectroscopy. Diffraction and elemental analysis confirmed the substitution of Gd⁺³ ions in VO layers. Orthorhombic phase of VO was observed in both GVO and GVO/MXene samples with crystallite size range of 17.02–17.51 nm. FESEM analysis indicated asymmetrical VO particles and sheets distributed on MXene layers, giving out a sponge like appearance. Surface area of GVO and GVO/MXene was enhanced to 20.46 and 23.69 nm, respectively. Effect of Gd⁺³ contents was significant on optical properties, which reduced the band gap energy of VO to 2.33 eV. The photocatalytic performance of prepared samples was analysed by the degradation of Methylene blue (MB) under direct sunlight. Gd⁺³ ion doping was found useful to enhance degradation of MB up to ～71%. Among all samples, GVO/MXene showed maximum degradation (～92%) within 120 min. Meanwhile, GVO/MXene showed good recyclability for successive five cycles. In addition, GVO and GVO/MXene were effective antibacterial agents against Gram positive (S. aureus) and Gram negative (P. vulgaris) strains of bacteria. The results suggested that the GVO and GVO/MXene could serve as potential candidates for large scale treatment of organic pollutants and pathogens.     

Structural and electrochemical properties of mixed calcium-zinc spinel ferrites nanoparticles

In the current work, we provide the electrochemical (EC) characteristics and considerable size of Ca-doped ZnFe₂O₄ nanoparticles. Mixed transition metal oxides are widely used as excellent electrode materials in superior supercapacitors because of their superior capacitance, low cost, and environmental friendliness. The prepared nanoparticles were characterized by X-ray diffraction (XRD), Field-emission scanning electron microscope (FE-SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS), and EC methods. The results exhibited that the as-synthesized nanoparticles had a cubic spinel crystal structure and efficient EC properties. The EC properties of the prepared electrodes were explored by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) studies. The Ca_0.1Zn_0.9Fe₂O₄ electrode demonstrated a specific capacitance (SC) ～208 Fg^-1 at a 2 mV/s scan rate due to significant morphological behavior. Therefore may be the prepared materials are the finest electrodes for supercapacitor applications.     

Synthesis of rGO/nanoclay/PVK nanocomposites,electrochemical performances of supercapacitors

ABSTRACT

In this study, graphene oxide (GO) was chemically reacted with sodium borohydride (NaBH₄) to form reduced graphene oxide (rGO). rGO, Montmorillonite nanoclay, and polyvinylcarbazole (PVK) were used to form a ternary nanocomposite via chemical reaction. These nanocomposite qualities were described via scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy-attenuated transmission reflectance (FTIR-ATR). In addition, these materials were used in supercapacitor device as an active material to test electrochemical performances via cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). The rGO/nanoclay/PVK nanocomposite shows significantly improved specific capacitance (C_sp = 168.64 Fg^?1) compared to that of rGO (C_sp = 63.26 Fg^?1) at the scan rate of 10 mVs^?1 by CV method. The enhanced capacitance results in high power density (P = 5522.6 Wkg^?1) and energy density (E = 28.84 Whkg^?1) capabilities of the rGO/nanoclay/PVK nanocomposite material. The addition of nanoclay and PVK increased the specific capacitance of rGO material due to a dopant effect for supercapacitor studies. Ragone plots were drawn to observe energy and power density of supercapacitor devices. The C_sp of rGO/nanoclay/PVK nanocomposite has only 86.4% of initial capacitance for charge/discharge performances obtained by CV method for 5000 cycles.     

Facile synthesis of Sm2S3 diffused nanoflakes and their pseudocapactive behavior

The Sm₂S₃ thin films with diffused nanoflakes morphology are prepared by an environment-friendly facile chemical synthesis method and used in electrochemical supercapacitors. The structural, elemental and surface morphological characterization are carried out using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and wettability techniques. The FESEM images show tree root like distribution of flakes with average flake width of about 80 nm. The film surface is lyophilic with propylene carbonate contact angle of 21°. The supercapacitive measurements are carried out through cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) techniques. The Sm₂S₃ film electrode exhibited a highest specific capacitance (C_s) of 213 Fg⁻¹ at 5 mVs⁻¹ scan rate in LiClO₄-propylene carbonate electrolyte. Asymmetric nature of charge–discharge curves confirmed pseudocapacitive behavior of electrode with energy and power densities of 39.39 Whkg⁻¹ and 4.33 kWkg⁻¹, respectively. An equivalent series resistance of 0.44 Ωcm⁻² indicated negligible ohmic losses in charge storage. An electrochemical stability of 81.47% is retained after 1000 cycles indicating that Sm₂S₃ is a promising candidate for supercapacitor application.     

Hydrothermally synthesised nickel oxide nanostructures on nickel foam and nickel foil for supercapacitor application

Nickle-based oxides exhibit seamless redox activity and show undisputed parameter optimization flexibility, which makes them a candidate of choice for various scientific analysis and multipurpose execution. The communique addresses the domain of energy storage of hydrothermally fabricated nickel oxide nanostructures by analysing the capacitive behaviour of the sample. The crystal geometry, chemical composition and bonding state of the material were carried out through XRD and XPS analysis, respectively. Electron microscopy showed systematically aligned nano-needles, which in aggregate represent an urchin. A comparative study of specific capacitance (Cs) at a scan rate of 1 mVs^?1 showed an enhanced Cs of nickel oxide embedded Ni-foam (1125 Fg^-1) against nickel oxide deposited Ni-foil (454 Fg^-1). At a current density of 8 mAcm ^?2, the nickel oxide based Ni-foam electrode exhibited an energy density of 23 Whkg^?1 and a power density of 259 Wkg^-1 which makes it instrumental in electrochemical devices. The Ni-foam electrode also showed less ‘cycle fatigue’ as its charge/discharge stability dipped by just 12% even after 5000 cycles. The novel supercapacitor electrode developed in this study exhibits excellent specific capacitance, high stability, high power density, and low impedance, demonstrating its promising practical functionality.     

Facile Fabrication of Binder-Free CoZn LDH/CFP Electrode with Enhanced Capacitive Properties for Asymmetric Supercapacitor

CoZn layered double hydroxide (LDH) or Co(OH)₂ pseudocapacitive material has been prepared on the current collector of carbon fiber paper (CFP) using an eco-friendly one-step electrodeposition. Benefiting from its unique structural feature, the binder-free CoZn LDH/CFP electrode material realizes high specific capacitance of 1156 Fg^?1 at a current density of 1 Ag^?1 and excellent rate capability of 80% retention with 16 fold current density increment, which is much better than that of Co(OH)₂ (617 Fg^?1, 65%). Notably, the CoZn LDH/CFP can retain an outstanding electrochemical stability with a capacitance degradation of only 6% after 6000 charge–discharge cycles at 32 Ag^?1. Moreover, an asymmetric supercapacitor (ASC) using CoZn LDH/CFP as a positive electrode and AC/CFP as a negative electrode has been assembled. The ASC exhibits a superior energy density of 30.0 Whkg^?1 at a power density of 800 Wkg^?1 with a specific capacitance up to 84.4 Fg^?1 and a potential window wide to 1.6 V. These encouraging results indicate that CoZn LDH/CFP composite material has a great potential for next-generation energy conversion/storage devices.

     

Electrochemical recycling of cobalt from spent cathodes of lithium-ion batteries: its application as supercapacitor

The supercapacitive behavior of the metallic cobalt recycled from Li-ion batteries has been studied in this work. The reversibility of both redox process (Co^II/Co^III) and (Co^III/Co^IV) in KOH 6 mol L⁻¹ is very high and promising for capacitive applications in electrochemical devices. The specific capacitances calculated from cyclic voltammetry and electrochemical impedance spectroscopy show a good agreement, giving the value of 625 Fg⁻¹. The electrode morphology presents a high porosity, thus an electrical equivalent circuit composed of two parallel resistance and capacitance elements in series was proposed. The specific capacitance values calculated from charge/discharge curves at 0.23 and 2.3 mA/cm² are 601 and 384 Fg⁻¹, respectively. Thereby, it was observed that metallic cobalt recycled from ion-Li batteries is compatible with other supercapacitive materials. This shows that cobalt recycling from Li-ion batteries is economically and environmentally viable for application in supercapacitor devices.     

Synthesis of cross-linked graphene aerogel/Fe2O3 nanocomposite with enhanced supercapacitive performance

In this work, cross-linked graphene aerogel (CL-GA) and its composite with Fe₂O₃ nanoparticles (NPs) were synthesized through a one-step hydrothermal procedure by using p-phenylenediamine (PPD). Structural characterizations revealed that in the preparation of the composite PPD acts as a cross-liker and provides high surface area by decreasing restacking of graphene sheets and functions as nitrogen source simultaneously. The electrochemical characteristics of the nanocomposite were investigated by cyclic voltammetry (CV), galvanostatic charge/discharge, electrochemical impedance spectroscopy (EIS) and Fast Fourier transform continues cyclic voltammetry (FFTCCV). The results show that cross-linked graphene aerogel/Fe₂O₃ (CL-GA/Fe₂O₃) nanocomposite displays enhanced supercapacitive performance, where it has capacitance of 445 at 1 A g⁻¹, high energy density of 63 W h Kg⁻¹, and 89% capacitance retention after 5000 cycles in 3 M KOH. Presence of PPD considerably improved supercapacitive performance of nanocomposite as a result it could be promising material in synthesis of efficient graphene/metal oxide-based electrode material for high performance supercapacitors.     

Microwave-polyol synthesis of nanocrystalline ruthenium oxide nanoparticles on carbon nanotubes for electrochemical capacitors

The ruthenium oxide nanoparticles dispersed on multi-wall carbon nanotubes (CNTs) were successfully synthesized via microwave-polyol process combined with forced hydrolysis without additional thermal oxidation or electrochemical oxidation treatment. The HRTEM, Raman spectra and TGA curve indicate that CNTs were uniformly coated with crystalline and partially hydrous RuO₂·0.64H₂O nanoparticles of 2 nm diameter and the loading amount of ruthenium oxide in the composite could be controlled up to 70 wt.%. The specific capacitance was 450 Fg⁻¹ of ruthenium oxide/CNT composite electrode with 70 wt.% ruthenium oxide at the potential scan rate of 10 mV s⁻¹ and it decreased to 362 Fg⁻¹ by 18% at 500 mV s⁻¹. The specific capacitance of ruthenium oxide in the composite was 620 Fg⁻¹ of ruthenium oxide at 10 mV s⁻¹. The ruthenium oxide nanoparticles in ruthenium oxide/CNT nanocomposite electrode had a high ratio of outer charge to total charge of 0.81, which confirmed its high-rate capability of the composite through the preparation of the nano-sized ruthenium oxide particles on the external surface of CNTs.     

Enhanced supercapacitive behavior by CuO@MnO2/carboxymethyl cellulose composites

The exploration of biocompatible materials has received greater significance in the research area of energy storage tools. In the present work, a composite material consisting of carboxymethyl cellulose (CMC) with CuO@MnO₂ is synthesized via thermal reduction protocol. The resulting composite material exhibited unique morphology and excellent electrochemical properties. The electrochemical properties were premeditated by CV, GCD, and spectral impedance analysis. Electrochemical analyses of the composite materials indicated the extraordinary specific capacitance in a three-electrode configuration. The composite displayed the value of ~414 F/g at a current density of 0.5 A g⁻¹ and the electrodes retaining 96.2% capacitance after 5000 cycles. Therefore, our study demonstrated the synergistic effect of CuO@MnO₂ nanoparticles with porous CMC network structures show enhanced electrochemical properties in the presence of 3 M KOH as an electrolyte.     

Facile three-step strategy to design CdS@Bi2Se3 core-shell nanostructure: An efficient electrode for supercapacitor application

In this study, we utilized a successive ionic layer adsorption and reaction (SILAR) route to attach bismuth selenide (Bi₂Se₃) nanoparticles on one dimensional (1D) cadmium sulfide nanowires (CdS NWs) at ambient temperature (27 °C) to design CdS@Bi₂Se₃ core-shell nanostructure towards active electrode for supercapacitor application. To verify and explore the retrieved surface configuration, structural, elemental, compositional, and surface morphological investigations were performed. The designed CdS@Bi₂Se₃ core-shell nanostructure not only offers the tremendous number of active areas, but also a continuous and quick one directional electron transport channels, demonstrating noticeable electrochemical performance with specific capacitance of 198 F g⁻¹ (aerial capacitance 59.5 mF/cm²) with 80% cyclic retention @ 2000 cycles. Superior electrochemical activity was enhanced through the mutualistic involvement of Na⁺ ion insertion/extraction via non-stoichiometric bismuth selenide, which was well supported through electrochemical impedance (EIS) studies.     

Capacitive behavior of polycarbazole- and poly(N-vinylcarbazole)-coated carbon fiber microelectrodes in various solutions

The electrochemical behavior of polycarbazole (PCz) and poly(N-vinyl carbazole) P(NVCz) was investigated by means of electrochemical impedance spectroscopy (EIS). Supporting electrolytes made from various combinations of solvents (acetonitrile and propylene carbonate) and salts (sodium perchlorate, lithium perchlorate, and tetraethyl ammonium perchlorate) were employed in the investigation. Information on the double layer capacitance (C_dl) and specific capacitance (C_sp) of P(NVCz) was achieved by cyclic voltammetry (CV), chronoamperometry and chronopotentiometry. Carbon fiber microelectrodes (CFME) were electrocoated by cyclic voltammetry in a monomer-free solution and displayed film thicknesses in the range ~200 nm to ~4.8 μm. The capacitive behavior of the PCz- and P(NVCz)-coated carbon fiber microelectrodes was also investigated by CV. The effects of the type of electrolyte and solvent on the electrochemical impedance spectroscopic data were subsequently fitted with an ((R(C(R(Q(RW))))(CR))-equivalent circuit model to calculate the numerical values of the proposed components. The obtained experimental C_sp values for PCz/CFME and P(NVCz)/CFME, as measured in LiClO₄/ACN, were 280.5 mF g⁻¹ and 294.1 mF g⁻¹, respectively.     

Usefulness of a composite electrode with a carbon surface modified by electrosynthesized polypyrrole for supercapacitor applications

Thin polypyrrole (PPy) films (thickness = 5–10 nm) were electrochemically deposited in situ on a carbon paste (97% of graphite plus 3% of Teflon) by means of cyclic voltammetry (CV), from an acetonitrile solution of pyrrole (0.2 M) and NaClO₄ (0.1 M). The obtained PPy/graphite composite electrode was investigated by CV and chronopotentiometry in 0.3 M NaClO₄ aqueous electrolytic solution. The capacitance of a composite electrode, calculated by CV, was about 10 F g⁻¹. The capacitance value of the composite electrode was approximately nine times larger than that of pure graphite. The massic charge and discharge capacity (Q) values, calculated by chronopotentiometry, were considerably higher for the composite electrode—by more than 60 times—than for the pure graphite electrode. Electrochemical impedance spectroscopy (EIS) measurements, performed under stationary conditions, led to an interfacial capacitance value intermediate between that of pure graphite and that of the composite electrode.     

Flake-like MoS2 nano-architecture and its nanocomposite with reduced Graphene Oxide for hybrid supercapacitors applications

In this article, we have synthesized flake-like MoS₂ nanoarchitecture by urea assisted hydrothermal method. To improve the electrical and electrochemical properties of MoS₂ nanoarchitecture, we formed its nanocomposite (MoS₂/r-GO) with 10% r-GO. After the addition of 10% r-GO, the nanocomposite shows the electrical conductivity of 1.24 × 10⁻¹ Sm⁻¹ that is higher than the pure MoS₂ (2.2 × 10⁻⁷ Sm⁻¹). The prepared nanocomposite also showed higher specific capacitance (441 Fg^-1 at 1 Ag^-1) than the pure MoS₂ nanoarchitecture (248 Fg^-1 at 1 Ag^-1). Moreover, nanocomposite lost just 15.8% of its initial capacitance after 1000 charge-discharge cycles. The enhanced electrochemical activity of the nanocomposite is due to its unique flake-like structure and its reduced charge transfer resistance (Rct ~ 23.5 Ω). The 2-D flake-like structure of the electrode increased its contact area with the r-GO matrix and electrolyte. The higher electrical conductivity and specific surface area of the nanocomposite facilitated the faradaic and non-faradic charge storage mechanism. The r-GO matrix not only acted as a capacitive supplement but also facilitated the redox reaction because of its superior electrical conductivity. As the nanocomposite showed CV and CCD profiles in the negative potential window (−1 V to −0.53 V), therefore it has the potential to be used as a negative electrode material for hybrid supercapacitors applications. The observed results revealed the potential of the (MoS₂/r-GO) nanocomposite-based cathode for hybrid supercapacitor applications.     

Electrosynthesis and capacitive performance of polyaniline–polypyrrole composite

The composite of polyaniline and polypyrrole (PPY‐PANI) was prepared by two‐step electrochemical polymerization method. Techniques of scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and thermal gravity analysis (TG/DTG) measurements were used to characterize the morphology and structure of the composite. The electrochemical properties of the composite were investigated by cyclic voltammetry (CV), galvanostatic charge‐discharge, and electrochemical impedance spectroscopy (EIS). The results indicated that the polyaniline–polypyrrole composite showed better electrochemical capacitive performance than polypyrrole (PPY) and polyaniline (PANI). The specific capacitance of the composite electrode was 523 F/g at a current of 6 mA/cm² in 0.5 M H₂SO₄ electrolyte. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Formation and electrochemical properties of composites of the C60–Pd polymer and multi-wall carbon nanotubes

Preparation and electrochemical properties of a novel type of the composite made of multi-wall carbon nanotubes (MWCNTs) and two-component polymer of palladium and C₆₀ (C₆₀–Pd) were investigated using cyclic voltammetry, electrochemical impedance spectroscopy, and piezoelectric microgravimetry. A composite film was prepared by electrochemical deposition of C₆₀–Pd on the layer of MWCNTs immobilized on the electrode surface. The polymer forms islands of shells on the carbon multi-wall core. This composite is electrochemically active in the negative potential range due to the electroreduction of the fullerene moiety. In this potential range, specific pseudo-capacitance of the film of the MWCNT/C₆₀–Pd composite is 425 F g⁻¹ in the acetonitrile solution of tetra(n-butyl)ammonium perchlorate. The presence of MWCNTs makes the composite conductive also at potentials less negative than potentials of the C₆₀ electroreduction. The double-layer specific capacitance of this film is close to 15 F g⁻¹.     

RF-PECVD growth and nitrogen plasma functionalization of CNTs on copper foil for electrochemical applications

This work describes an efficient way to improve the adhesion, growth rate and density of CNTs on copper substrate using radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD). The adhesion of an alumina buffer layer to the copper substrate is critical for the successful growth of CNTs. Hydrogen plasma was performed on the copper substrate to reduce copper oxide from the surface. The effect of two intermediate layers (Ti, Ni), as individual or in combination, between alumina and copper substrate on the CNT growth has been investigated. Furthermore, a nitrogen plasma treatment was carried out to functionalize the obtained CNTs. Electrochemical measurements were performed using CNTs grown on a copper substrate as electrodes and LiClO₄ as electrolyte. The specific capacitance of the obtained electrodes increases from 49 up to 227 Fg^− 1 for untreated and nitrogen-plasma treated CNTs at a scan rate of 10 mVs^− 1, respectively.     

Experimental investigation of Co and Fe-Doped CuO nanostructured electrode material for remarkable electrochemical performance

The current research work presents a facile and cost–effective co-precipitation method to prepare doped (Co & Fe) CuO and undoped CuO nanostructures without usage of any type of surfactant or capping agents. The structural analysis reveals monoclinic crystal structure of synthesized pure CuO and doped-CuO nanostructures. The effect of different morphologies on the performance of supercapacitors has been found in CV (cyclic voltammetry) and GCD (galvanic charge discharge) investigations. The specific capacitances have been obtained 156 (±5) Fg^?1, 168(±5) Fg^?1 and 186 (±5) Fg^?1 for CuO, Co-doped CuO and Fe-doped CuO electrodes, respectively at scan rate of 5 mVs^?1, while it is found to be 114 (±5) Fg^?1, 136 (±5) Fg^?1 and 170 (±5) Fg^?1 for CuO, Co–CuO and Fe–CuO, respectively at 0.5 Ag^-1 as calculated from the GCD. The super capacitive performance of the Fe–CuO nanorods is mainly attributed to the synergism that evolves between CuO and Fe metal ion. The Fe-doped CuO with its nanorods like morphology provides superior specific capacitance value and excellent cyclic stability among all studied nanostructured electrodes. Consequently, it motivates to the use of Fe-doped CuO nanostructures as electrode material in the next generation energy storage devices.     

Pseudo-capacitance properties of porous metal oxide nanoplatelets derived from hydrotalcite-like compounds

Nanoplatelets of metal oxides with interesting porous structure were obtained by thermal treatment of Ni/Al hydrotalcite. Structural and surface properties of the porous oxides were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM and HRTEM), and N₂ adsorption–desorption. The electrochemical performance of the electrodes was investigated by cyclic voltammetry, electrochemical impedance spectroscopy and constant current charge–discharge measurements. Ni/Al hydrotalcite calcined at 450 °C (NA-450) displayed a maximum specific capacitance (419.0 F g⁻¹) due to the porous structure with the highest specific surface area (142.3 m² g⁻¹) and small pore size (4.4 nm). The present study shows the potential of NiO nanoplatelets composite material for electrochemical pseudo-capacitors.     

High-performance supercapacitor based on V2O5/carbon nanotubes-super activated carbon ternary composite

A ternary composite of V₂O₅/carbon nanotubes/super activated carbon (V₂O₅/CNTs–SAC) was prepared by a simple hydrothermal method and used as a supercapacitor electrode material. The electrochemical performance of the electrode was analyzed using cyclic voltammetry, galvanostatic charge/discharge measurements, and electrochemical impedance spectroscopy, which were performed in 2 M NaNO₃ as the electrolyte. The V₂O₅/CNTs–SAC nanocomposite exhibited a specific capacitance as high as 357.5 F g⁻¹ at a current density of 10 A g⁻¹, which is much higher than that of either bare V₂O₅ nanosheets or a V₂O₅/CNTs composite. Furthermore, the capacitance increased to 128.7% of the initial value after 200 cycles, with 99.5% of the maximum value being retained after 1000 cycles. These results demonstrated that the V₂O₅/CNTs–SAC ternary composite is suitable for use as an electrode material for supercapacitors.