Electrochemical capacitive properties of nickel oxide and nickel tetra-aminophthalocyanine based electrodes

This study reports on an electrochemical capacitive properties of nickel tetraaminophthalocyanine (NiTAPc), nickel tetraaminophthalocyanine incorporated with Nickel oxide (NiTAPc-NiO) and nickel oxide incorporated with multi-walled carbon nanotubes (NiO-MWCNT), using three different techniques known as successive ionic layer adsorption reaction (SILAR), electrodeposition and dip-dry. This study also reports on the effect of undoped polymer of poly-pyrrole on NiTAPc. The physical properties of the synthesised materials were investigated using SEM and EDX and the electrochemical properties were investigated using cyclic voltammetry (CV), charge-discharge (CD) and electrochemical impedance spectroscopy (EIS). The supercapacitive properties of NiTAPc film on nickel foam showed a maximum specific capacitance of 416.0 Fg-1, a maximum power density of 15.50x103 WKg-1 and a maximum specific energy of 66.0 WhKg-1. The NiO-MWCNT film on nickel foam gave a maximum specific capacitance of 1034.0 Fg-1, a maximum power density of 10.41x103 WKg-1 and a maximum specific energy of 132.0 WhKg-1. The NiTAPc-NiOE film on nickel foam was found to possess a maximum specific capacitance of 1117.0 Fg-1, a maximum power density of 20.48x103 WKg-1 and a maximum specific energy of 119.0 WhKg-1. The NiTAPc-NiOE-S film on nickel foam gave a maximum specific capacitance of 1279.0 Fg-1, a maximum power density of 26.96x103 WKg-1 and a maximum specific energy of 114.0 WhKg-1. Finally, the NiO mixed with an oxidant (NiOS-ox) film on nickel foam gave a maximum specific capacitance of 1403.0 Fg-1, power density of 14.44x103 WKg-1 and a maximum specific energy of 147.0 WhKg-1. In addition, the electrodes were found to be very stable even after repetitive cycling. These electrodes have clearly proved that they may be suitable for use as potential supercapacitors. Further research is necessary to fully explore their supercapacitive behaviour in single cell (2-electrode)systems. CopyrightDissertation (MSc)--University of Pretoria, 2012.Chemistryunrestricte

Structural elucidation of magnetic biochar derived from recycled paper waste sludge

Partially treated wastewater released into natural water bodies leads to eutrophication which poses a threat to aquatic animals and water supply security. The recovery of nutrients from wastewater, and their subsequent recycling in other agricultural applications contribute to nutrient recycling and utilization. Biochar derived from biomass waste is increasingly seen as a multifunctional material for the adsorption of various pollutants from wastewater. This is due to its low production cost and carbon footprint. Recycled paper waste sludge (RPWS) is another abundant type of woody biomass that yields biochar as a by-product during pyrolysis processes. This material has emerged as a feedstock to produce several liquid fuels such as bio-oils and alcohols. However, there has been little application of the material as an adsorbent for the removal of nutrients and pollutants from wastewater. Two variants of RPWS were available for this work, primary sludge from screening processes and secondary sludge from a clarification plant were used as feedstocks to produce biochar products via slow pyrolysis at 550 °C, and 650 °C. Furthermore, a step to produce magnetic biochar was added through impregnation with Fe3+ and Fe2+ and subsequent co-pyrolysis. The biochar yields are promising for the pyrolysis of RPWS. The structural analysis and morphological characterization of the samples (before and after pyrolysis) were done through thermogravimetric analysis (TGA), Scanning Electron Microscopy (SEM-EDS), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and Brunauer-Emmet Teller (BET). The residues after pyrolysis showed good physical and chemical qualities that can be beneficial for the adsorption of nutrients in wastewater treatment.http://www.aidic.it/cetam2022Chemical Engineerin

The crystal structure of fac-tricarbonyl(6-bromo-2,2-bipyridine-κ2 N,N)-(nitrato-κO)rhenium(I), C13H7BrN3O6Re

Please read abstract in the article.NRFhttps://www.degruyter.com/view/j/ncrsChemistr

Surfactant assisted synthesis of copper oxide (CuO) leaf-like nanostructures for electrochemical applications

Three different copper oxide (CuO) leaf-like nanostructures have been synthesised by micelles micro emulsion method using a surfactant of copper dodecyl sulphate (Cu(DS)2) by varying the concentration of sodium hydroxide (NaOH). This study was carried out to investigate the effect of NaOH concentration on the stability, crystalline domain and pseudocapacitance behaviour of the leaf-like nanostructures. The samples were characterized by X-ray diffraction (XRD), thermogravimetry analysis (TGA), Raman spectroscopy, Fourier-Transform Infrared (FTIR), scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). It was observed that the crystalline domain size (12 nm-18 nm) and size distribution of the as-synthesized nanocrystals decreases with increasing concentration of NaOH. The interactions mechanism and formation of the leaf-like structure have been elucidated and correlated with various analytical techniques. The domain size and NaOH concentration tend to influence the charge transfer resistance.South African Research Chairs Initiative of the Department of Science and Technology (DST) and the National Research Foundation (NRF). University of Pretoria and NRF.http://journal.sapub.org/materialshb201

Chemical adsorption of NiO nanostructures on nickel foam-graphene for supercapacitor applications

Few-layer graphene was synthesized on a nickel foam template by chemical vapor deposition. The resulting three-dimensional (3D) graphene was loaded with nickel oxide nanostructures using the successive ionic layer adsorption and reaction technique. The composites were characterized and investigated as electrode material for supercapacitors. Raman spectroscopy measurements on the sample revealed that the 3D graphene consisted of mostly few layers, while X-ray diffractometry and scanning electron microscopy revealed the presence of nickel oxide. The electrochemical properties were investigated using cyclic voltammetry, electrochemical impedance spectroscopy, and potentiostatic charge–discharge in aqueous KOH electrolyte. The novelty of this study is the use of the 3D porous cell structure of the nickel foam which allows for the growth of highly conductive graphene and subsequently provides support for uniform adsorption of the NiO onto the graphene. The NF-G/NiO electrode material showed excellent properties as a pseudocapacitive device with a high-specific capacitance value of 783 F g-1 at a scan rate of 2 mV s-1. The device also exhibited excellent cycle stability, with 84 % retention of the initial capacitance after 1000 cycles. The results demonstrate that composites made using 3D graphene are versatile and show considerable promise as electrode materials for supercapacitor applications.South African Research Chairs Initiative of the Department of Science and Technology (SARChI-DST) and the National Research Foundation (NRF). University of Pretoria.http://link.springer.com/journal/11665hb201

Effects of carbon nanomaterials on the performance of symmetric pseudocapacitors

This thesis reports on the study of carbon nanomaterials integrated with nanostructured birnessite-type MnO2 and tetragonal hausmannite-type Mn3O4 as electrode materials for enhanced performance in symmetric pseudocapacitors. This work further explores the synergistic effect of graphene oxide decorated with particles of nickel (II) tetraaminophthalocyanine as electrode materials for improved performance (power and energy densities) in symmetrical pseudocapacitor device. Physical properties of the synthesised electrode materials were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), gas adsorption technique (BET), infra-red spectroscopy, Raman spectroscopy and thermogravimetric analysis (TGA) techniques. Electrochemical properties of synthesised electrode materials were investigated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). From the study of carbon nanomaterials integrated with nanostructured birnessite-type MnO2, it has been discovered that OLC/MnO2 nanohybrid exhibited better performance (regarding specific capacitance, rate capability, and energy density) compared to other nanohybrids such as CNT/MnO2, GO/MnO2, and AC/MnO2. This device gave maximum specific capacitance of 255 F g-1, the specific energy density of 5.6 Wh kg-1 and excellent power density of 74.8 kW kg-1. The CNT/MnO2, exhibited a maximum specific capacitance, energy and power density of 174 F g-1, 4.9 Wh kg-1, and 55.1 kW kg-1, respectively, while, the GO/MnO2 displayed 135 F g-1, 3.9 Wh kg-1, and 35.8 kW kg-1, and AC/MnO2 was 110 F g-1, 3.3 Wh kg-1, and 30.0 kW kg-1, respectively. From the study of carbon nanomaterials integrated with nanostructured tetragonal hausmannite-type Mn3O4, OLC/Mn3O4 nanohybrid exhibited better performance (regarding specific capacitance, rate capability, and energy density) compared to other nanohybrid electrode materials (i.e., CNT/Mn3O4 GO/Mn3O4, and AC/Mn3O4). This device exhibited a maximum specific capacitance of 195 F g-1, the specific energy density of 4.3 Wh kg-1 and power density of 52 kW kg-1. The CNT/Mn3O4 exhibited a maximum specific capacitance, energy and power density of was 180 F g-1, 3.9 Wh kg-1, and 33 kW kg-1, respectively. While the GO/Mn3O4 displayed values of 160 F g-1, 3.6 Wh kg-1, 24 kW kg-1 and AC/Mn3O4 was 124 F g-1, 2.8 Wh kg-1, 18 kW kg-1, respectively. The study on the synergistic effect of graphene oxide (GO) decorated with particles of nickel (II) tetraaminophthalocyanine (NiTAPc) resulted in GO/NiTAPc nanohybrid displaying better pseudocapacitive performance relative to its precursor (i.e., GO and NiTAPc). This pseudocapacitor device exhibited a maximum specific capacitance of 163 F g-1, the specific energy density of 3.6 Wh kg-1 and high-power density of 140 kW kg-1. These values are much higher than those of its individual precursors NiTAPc (60 F g-1 and 1.3 Wh kg-1) and GO (15 F g-1 and 0.3 Wh kg-1). This excellent capacitive performance shows promising opportunities for the development of aqueous-based pseudocapacitors made of carbon nanomaterials with transitional metal oxides and metallophthalocyanine (MPc) complexes (N4-macrocyclic metal compounds). Interestingly, this study also shows the significance of the use of novel carbon nanomaterials apart from the well-studied activated carbon for the development of high-power electrochemical capacitors.Thesis (PhD)--University of Pretoria, 2016.tm2016ChemistryPhDUnrestricte

Nanoparticles Functionalised with Re(I) Tricarbonyl Complexes for Cancer Theranostics

Globally, cancer is the second (to cardiovascular diseases) leading cause of death. Regardless of various efforts (i.e., finance, research, and workforce) to advance novel cancer theranostics (diagnosis and therapy), there have been few successful attempts towards ongoing clinical treatment options as a result of the complications posed by cancerous tumors. In recent years, the application of magnetic nanomedicine as theranostic devices has garnered enormous attention in cancer treatment research. Magnetic nanoparticles (MNPs) are capable of tuning the magnetic field in their environment, which positively impacts theranostic applications in nanomedicine significantly. MNPs are utilized as contrasting agents for cancer diagnosis, molecular imaging, hyperfusion region visualization, and T cell-based radiotherapy because of their interesting features of small size, high reactive surface area, target ability to cells, and functionalization capability. Radiolabelling of NPs is a powerful diagnostic approach in nuclear medicine imaging and therapy. The use of luminescent radioactive rhenium(I), 188/186Re, tricarbonyl complexes functionalised with magnetite Fe3O4 NPs in nanomedicine has improved the diagnosis and therapy of cancer tumors. This is because the combination of Re(I) with MNPs can improve low distribution and cell penetration into deeper tissues

Highlighting the Importance of Characterization Techniques Employed in Adsorption Using Metal–Organic Frameworks for Water Treatment

The accumulation of toxic heavy metal ions continues to be a global concern due to their adverse effects on the health of human beings and animals. Adsorption technology has always been a preferred method for the removal of these pollutants from wastewater due to its cost-effectiveness and simplicity. Hence, the development of highly efficient adsorbents as a result of the advent of novel materials with interesting structural properties remains to be the ultimate objective to improve the adsorption efficiencies of this method. As such, advanced materials such as metal–organic frameworks (MOFs) that are highly porous crystalline materials have been explored as potential adsorbents for capturing metal ions. However, due to their diverse structures and tuneable surface functionalities, there is a need to find efficient characterization techniques to study their atomic arrangements for a better understanding of their adsorption capabilities on heavy metal ions. Moreover, the existence of various species of heavy metal ions and their ability to form complexes have triggered the need to qualitatively and quantitatively determine their concentrations in the environment. Hence, it is crucial to employ techniques that can provide insight into the structural arrangements in MOF composites as well as their possible interactions with heavy metal ions, to achieve high removal efficiency and adsorption capacities. Thus, this work provides an extensive review and discussion of various techniques such as X-ray diffraction, Brunauer–Emmett–Teller theory, scanning electron microscopy and transmission electron microscopy coupled with energy dispersive spectroscopy, and X-ray photoelectron spectroscopy employed for the characterization of MOF composites before and after their interaction with toxic metal ions. The review further looks into the analytical methods (i.e., inductively coupled plasma mass spectroscopy, ultraviolet-visible spectroscopy, and atomic absorption spectroscopy) used for the quantification of heavy metal ions present in wastewater treatment

Ethylenediamine functionalized waste polyethylene terephthalate-derived metal-organic framework for adsorption of palladium ions from aqueous solutions

The recovery of palladium metal is essential in order to meet its growing global demand and also to address water pollution crisis. Herein, MIL-101(Cr)/ED was fabricated from waste polyethylene terephthalate (PET) bottles and modified using ethylenediamine (ED) to retrieve divalent palladium (Pd(II)) metal ions from aqueous environment. The successful grafting of ED moieties onto MIL-101(Cr) was established by the appearance of broad bands at around 2800–3300 cm−1 on the Fourier transform infrared spectrum which was supported by the increase in binding energy using density functional theory. The adsorption experiments revealed that higher Pd(II) ion intake occurred using 30 mg of MIL-101(Cr)/ED in acidic media of pH = 3.0. The data fit better on the Langmuir isotherm with the correlation coefficient (R2) 0.9089. At 25 °C, the MIL-101(Cr)/ED achieved a substantial enhancement in the intake capacities of 454.2 mg.g−1. Kinetics data demonstrated to comply with pseudo-second order, achieving a rapid rate of Pd(II) adsorption by the MIL-101(Cr)/ED in less than 3 min given by the rate constant k2 = 0.02065 g.mg−1.min−1. The MIL-101(Cr)/ED has high affinity for Pd(II) ions as more than 80% removal was achieved even in presence of other ions. These observations revealed the potential utilization of MIL-101(Cr)/ED as an adsorbent to efficiently extract Pd(II) ions from wastewater

The crystal structure of fac-tricarbonyl(4,4-dimethyl-2,2-dipyridyl-κ2N,N′)- (pyrazole-κN)rhenium(I) nitrate, C18H16O3N4Re

C18H16O3N4Re, monoclinic, P21/c (no. 14), a = 9.8409(6) Å, b = 14.0933(9) Å, c = 13.9153(9) Å, β = 90.558(2)°, V = 1929.8(2) Å3, Z = 4, Rgt(F) = 0.0266, wRref(F2) = 0.0584, T = 100(2) K