Nazanin Hamnabard

Performance evaluation of highly conductive graphene (RGOHI–AcOH) and graphene/metal nanoparticle composites (RGO/Ni) coated on carbon cloth for supercapacitor applications

The application of graphene (RGO)-based composites as electrode materials in supercapacitors can be limited by the fabrication complexity and costs, and the non-environmentally friendly nature of the production process. This study examined the effectiveness of a highly conductive graphene material (RGOHI–AcOH) compared to the hydrazine-produced RGO and graphene nanoparticle composite (RGO/Ni) materials on a carbon cloth substrate in supercapacitors. The composites were synthesized at different mass ratios (1 : 1, 2 : 1, 4 : 1, 10 : 1 and 1 : 2) of RGO to Ni nanoparticles. All synthesized samples were characterized using X-ray diffraction, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The methylene blue method was used for determining the specific surface area. The RGOHI–AcOH electrode exhibited a higher electrochemical performance (40 F g−1 at 10 mV s−1 and 70 F g−1 at 0.2 A g−1) and stability (∼94%) than the other electrodes examined. Among the prepared composites, the composite with a RGO to Ni nanoparticle mass ratio of 1 : 1 showed a better electrochemical performance (30 F g−1 at 10 mV s−1, and 27 F g−1 at 0.2 A g−1) than the hydrazine-produced RGO and the other composite electrodes. Overall, RGOHI–AcOH as a first priority electrode material (particularly, coated on a carbon cloth substrate) has potential applications in energy storage devices.

Enhanced electrochemical performance of morphology-controlled titania-reduced graphene oxide nanostructures fabricated via a combined anodization-hydrothermal process

Titania nanotubes (TNTs) synthesized by an anodization process were used as a basic substrate material to create different morphologies of quasi-1D (nanoribbons), 2D (nanoflakes), and 3D (nanoparticles) structures via an alkali-controlled hydrothermal route. Graphite oxide was introduced to the hydrothermal unit to fabricate graphene oxide/reduced graphene oxide–titania nanostructure hybrid materials. The presence of NaOH and graphene oxide in the hydrothermal environment had a profound effect on the surface morphology of the nanostructures. NaOH acted as both an etchant to convert TNT surfaces into low-dimensional structures and as a reducing agent to convert graphene oxide into reduced graphene oxide. Graphene oxide inhibited the etching rate to tune the surface morphologies into 1D, 2D, and 3D nanostructures. The electrochemical supercapacitance of all the nanostructures was characterized. Among the prepared samples, the nanostructured hybrid sample of reduced graphene oxide, titania nanoflakes, and TNT exhibited enhanced electrochemical performance with quite high specific capacitance. This superior electrochemical performance is attributed to the specific nanostructure, which provides short pathways for fast transport of salt ions and improved specific surface area for more adsorption sites for the formation of an electrical double layer, which leads to fast charge transfer.

Synthesis of amorphous manganese oxide nanoparticles – to – crystalline nanorods through a simple wet-chemical technique using K+ ions as a ‘growth director’ and their morphology-controlled high performance supercapacitor applications

Highly crystalline manganese-oxide nanostructures are fabricated by acidic reduction of KMnO4 solution followed by air-annealing. During annealing, the nanostructures are converted from nanoparticles (diameters ∼ 100 nm) to nanorods (width ∼ 20 nm), which depends on the K+ ion content within the samples. K+ ions are considered to act as a ‘growth-director’ for the nanoparticle-to-nanorod conversion process. By controlling the K+ content through a simple rinsing step, the nanostructures are effectively controlled to be either only nanorod structures, or of pure nanoparticle structure or a mixture of both. Electrochemical characterization of these three types of nanostructures revealed that nanorod–nanoparticle mixture samples have superior electrochemical performance compared to others, which is attributed to their unique morphology, with a combination of highly crystalline 1D-nanorods and the porous structure of 3D-nanoparticles. This provides a high active surface area in the pores of nanoparticles and high surface-to-volume ratio in the nanorods for considerably higher utilization of the active materials during electrochemical performance.

A novel visible-light Nd-doped CdTe photocatalyst for degradation of Reactive Red 43: Synthesis, characterization, and photocatalytic properties

Abstract Novel high-efficiency visible-light-sensitive Nd-doped CdTe nanoparticles were prepared with various doping concentrations of neodymium ion by a facile hydrothermal method. The reaction products were analyzed via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoelectron spectroscopy (XPS), and UV-Vis diffuse reflectance spectroscopy techniques. Red shift was seen in the absorption band edge peak in the UV-Vis absorbance spectrum with increasing Nd content. The XRD and XPS results confirmed that Nd ions successfully replaced Cd atoms and were incorporated into the crystal lattice of CdTe. SEM and TEM images indicated spherical structure and high crystallinity. Even at a very low Nd/CdTe molar ratio of 2 mol.%, Nd doping could greatly enhance the photocatalytic activity of CdTe. The photocatalytic activity of Nd-doped CdTe nanoparticles was evaluated by monitoring the decolorization of RRed 43 in aqueous solution under visible-light irradiation. The color removal efficiency of Nd 0.08 Cd 0.92 Te and pure CdTe were 83.14% and 14.32% after 100 min of treatment, respectively. Among different amounts of the doping agent, 8 mol.% Nd indicated the highest decolorization. The presence of radical scavengers such as Cl − , CO 3 2− , SO 4 2− , and buthanol was found to reduce the decolorization efficiency.