Instytut Podstawowych Problemów Techniki

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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.

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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.

Słowa kluczowe:

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

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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.

Słowa kluczowe:

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

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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.

Słowa kluczowe:

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

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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.

Słowa kluczowe:

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

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