Institute of Fundamental Technological Research

Utilization of CoO@Co3O4-x-Ag (x denotes 1, 3, and 5 wt% of Ag) nanocomposites as supercapacitor electrodes is the main aim of this study. A new low-temperature wet chemical approach is proposed to modify the commercial cobalt oxide material with silver nanoparticle (NP) balls of size 1–5 nm. The structure and morphology of the as-prepared nanocomposites were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption–desorption measurements. Hydrogels known to be soft but stable structures were used here as perfect carriers for conductive nanoparticles such as carbons. Furthermore, hydrogels with a large amount of water in their network can give more flexibility to the system. Fabrication of an electrochemical cell can be achieved by combining these materials with a layer-by-layer structure. The performance characteristics of the cells were examined by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge discharge (GCD). Cobalt oxide modified with 5 wt% Ag gave the best supercapacitor results, and the cell offers a specific capacitance of ∼38 mF cm−2 in two-electrode configurations.

The sustainable transformation of bio-waste into usable, material has gained great scientific interest. In this paper, we have presented preparation of an activated carbon material from a natural mushroom (Suillus boletus) and explor its properties for supercapacitor and dye adsorption applications. The produced cell exhibited a single electrode capacitance of ∼247 F g−1 with the energy and power density of ∼35 Wh kg−1 and 1.3 kW kg−1, respectively. The cell worked well for ∼20,000 cycles with ∼30% initial declination in capacitance. Three cells connected in series glowed a 2.0 V LED for ∼1.5 min. Moreover, ultrafast adsorption of methylene blue dye onto the prepared carbon as an adsorbent was recorded with ∼100% removal efficiency in an equilibrium time of three minutes. The performed tests indicate that the mushroom-derived activated carbon has the potential to become a high-performance electrode material for supercapacitors and an adsorbent for real-time wastewater treatment applications.

Activated carbon, Amorphous material, Biomass, Polymer gel electrolyte, Supercapacitor, Dye adsorption

The electrochemical properties of metal oxides are very attractive and fascinating in general, making them a potential candidate for supercapacitor application. Vanadium oxide is of particular interest because it possesses a variety of valence states and is also cost effective with low toxicity and a wide voltage window. In the present study, vanadium oxide nanorods were synthesized using a modified sol–gel technique at low temperature. Surface morphology and crystallinity studies were carried out by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy analysis. To the best of our knowledge, the as-prepared nanorods were tested with magnesium ion based polymer gel electrolyte for the first time. The prepared supercapacitor cell exhibits high capacitance values of the order of ~ 141.8 F g−1 with power density of ~ 2.3 kW kg−1 and energy density of ~ 19.1 Wh kg−1. The cells show excellent rate capability and good cycling stability.

Vanadium dioxide (VO2) received tremendous interest lately due to its unique structural, electronic, and optoelectronic properties. VO2 has been extensively used in electrochromic displays and memristors and its VO2 (B) polymorph is extensively utilized as electrode material in energy storage applications. More studies are focused on VO2 (B) nanostructures which displayed different energy storage behavior than the bulk VO2. The present review provides a systematic overview of the progress in VO2 nanostructures syntheses and its application in energy storage devices. Herein, a general introduction, discussion about crystal structure, and syntheses of a variety of nanostructures such as nanowires, nanorods, nanobelts, nanotubes, carambola shaped, etc. are summarized. The energy storage application of VO2 nanostructure and its composites are also described in detail and categorically, e.g. Li-ion battery, Na-ion battery, and supercapacitors. The current status and challenges associated with VO2 nanostructures are reported. Finally, light has been shed for the overall performance improvement of VO2 nanostructure as potential electrode material for future application.

Core-shell metal-semiconductor nanostructures have established worldwide interest due to their magnificent chemical, optical and electrical behavior as compared to their monometallic analogous. Wet chemically synthesized gold-copper oxide (Au@Cu2O) core-shell nanostructures were studied for catalytic activity for the degradation of dyes such as crystal violet (CV) and congo red (CR) and the reduction of organic pollutant, 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) and compared with Au nanoparticles (Au NPs). The Au@Cu2O nanostructures show ten times higher reduction rate for 4-NP than that of monometallic Au NPs. The adsorption followed by degradation of CV, and CR dyes in aqueous solution has been investigated with Au NPs and Au@Cu2O core-shell nanostructures. Kinetics study has been performed using Au NPs and Au@Cu2O core-shell nanostructure for the 4-NP reduction, CV and CR degradation. The synergistic effect in Au@Cu2O core-shell nanostructure facilitates catalytic activity compared to the monometallic Au NPs.

Au@Cu2O, Core-shell nanostructure, 4-Nitrophenol, 4-Aminophenol, Dye degradation

The rapid, ultralow detection, degradation, and complete removal of pesticides demand the design of potential substrates. Herein, we discussed gold nanorods (Au NRs) as the potential substrate for the naked eye detection and degradation of two common and broad-spectrum pesticides, chlorpyrifos (CPF) and malathion (MLT), up to 0.15 ppt concentration within 2 min. Under certain environmental conditions, both the pesticides degraded and adsorbed on the surface of Au NRs. The degraded moieties of CPF and MLT on the surface of Au NRs formed side-to-side and end-to-end interactions, respectively, leading to a long-range assembly. This shows that no external agent is required, and only CPF and MLT analytes are quite enough for the formation of assembly of Au NRs. Assembly of Au NRs is confirmed by transmission electron microscopy (TEM) analysis, and degradation is supported by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and gas chromatography-mass spectrometry (GC-MS) analyses. Au NRs were recovered and reused for four consecutive cycles. The fast and ultralow detection of pesticides demonstrates that Au NRs are a potential substrate for the detection and degradation of pesticides.

gold nanorods, chlorpyrifos, malathion, pesticides, degradation, side to side interaction, end to end interaction

The conversion of biomass into valuable carbon composites as an efficient non-precious energy storage electrode material has elicited extensive research interest. An as-synthesized partially graphitized iron oxide-carbon composite material (Fe3O4/Fe3C@C) shows excellent properties as an electrode material for supercapacitor applications. X-ray diffraction analysis, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller analysis are used to study the structural, compositional and surface areal properties. The electrode material shows a specific surface area of 827.4 m2/g. Owing to the synergistic effect of the graphitic layers with iron oxide/carbide, Fe3O4/Fe3C@C hybrid electrode materials display a high performance when used in supercapacitors, with an excellent capacity of 878 F/g at a current density of 5 A/g (3-electrode) and 211.6 F/g at a current density of 0.4 A/g (2-electrode) in 6 M KOH electrolyte with good cyclic stability.

Bagasse, supercapacitor, composite material, iron carbide, iron oxide

Here, we report a non-precious mesoporous adsorbent obtained from the carbonization of bagasse. The material shows pH dependent an impressive adsorbent property for cationic, anionic and commercially used dyes along with an organic contaminant (4-nitrophenol) in water. The adsorbent shows specific surface area of ~462 m2 g-1 and the porous layered structure as confirmed by gas adsorption and microscopic techniques, respectively. Further, pH triggered adsorption of Methylene blue (MB, cationic dye), Congo red (CR, anionic dye) and commercial hair dye were studied. The results show >96% adsorption for CR and MB within 24 min at pH 2 and pH 8, respectively. Moreover, fast adsorption response, 92.6% in 20 min, was obtained for a commercially used hair dye and demonstrates the practical applicability of the material for waste water remediation. Under experimental conditions, adsorbent shows ultrafast adsorption kinetics (4 min to achieve equilibrium state with 99.5% adsorption) for 4-nitrophenol from water. Notably, the adsorbent show structural stability, easily separable with an external magnetic field and recyclability with ~85% efficiency even after 5th cycle.

Iron-carbon composite, adsorption, bagasse, hair dye, Methylene blue, Congo Red, 4-Nitrophenol

Supercapacitors, MWCNTs, Polymer gel electrolyte, Surface modification