Cobalt Sulfide/Spongy functionalized Graphene nanostructured electrodes for High-Performance Supercapacitors

A simple approach is illustrated for the preparation of functionalized spongy graphene/cobalt sulfide (FG-CoS) nanocomposites as unified, porous 3-dimensional (3D) network crinkly sheets. These crinkly sheets contain the reduced spongy graphene oxide (SGO) sheets and the intercalated CoS nanoparticles within the spongy graphene. The fabricated FG-CoS composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy. The synthesized materials were examined as supercapacitor materials in an aqueous electrolyte (3M KOH) using cyclic voltammetry (CV) at a wide range of potential scan rates, and galvanostatic charge/discharge at various current densities. The FG-CoS electrode yielded a maximum specific capacitance of 1072 F/g at a scan rate of 1 mV/s. In addition, it showed outstanding cyclability retention of 117% after the 1000th cycle at 100mV/s. The obtained energy density is 35.2 Wh/kg along with a power density of 250 W/kg at 1.0 A/g. Such high performance can be attributed to the synergistic effect of graphene and CoS, where CoS is sandwiched between graphene nanosheets. This makes the FG/CoS composite a promising electrode material for a superior-performance supercapacitor

A Review of Supercapacitors: Materials Design, Modification, and Applications

This is the final version. Available on open access from MDPI via the DOI in this recordSupercapacitors (SCs) have received much interest due to their enhanced electrochemical performance, superior cycling life, excellent specific power, and fast charging–discharging rate. The energy density of SCs is comparable to batteries; however, their power density and cyclability are higher by several orders of magnitude relative to batteries, making them a flexible and compromis-ing energy storage alternative, provided a proper design and efficient materials are used. This review emphasizes various types of SCs, such as electrochemical double-layer capacitors, hybrid su-percapacitors, and pseudo-supercapacitors. Furthermore, various synthesis strategies, including sol-gel, electro-polymerization, hydrothermal, co-precipitation, chemical vapor deposition, direct coating, vacuum filtration, de-alloying, microwave auxiliary, in situ polymerization, electro-spin-ning, silar, carbonization, dipping, and drying methods, are discussed. Furthermore, various func-tionalizations of SC electrode materials are summarized. In addition to their potential applications, brief insights into the recent advances and associated problems are provided, along with conclu-sions. This review is a noteworthy addition because of its simplicity and conciseness with regard to SCs, which can be helpful for researchers who are not directly involved in electrochemical energy storage.Saudi Aramco Chair ProgrammeEngineering and Physical Sciences Research Council (EPSRC

Inorganic Nanostructures Decorated Graphene

Additional information is available at the end of the chapte

SULFURIZATION OF NANOSTRUCTURED COBALT OXIDE FOR ENERGY STORAGE APPLICATIONS

Development of energy storage devices with high energy performance, power density, fast charge-discharge capability and long cyclability is needed to meet the increasing demand for energy, power and environmental protection in our daily life. Supercapacitors have great potential in future energy storage devices with magnificent properties. Recently, researchers have shown great progress for the improvement of supercapacitor performance by fabrication of nanostructured transition metal chalcogenides materials. One of the main objectives of this thesis is to synthesize nanostructured cobalt oxide and then converte them to cobalt sulfide using a facile hydrothermal method. The synthesized cobalt oxide and cobalt sulfide were structurally and electrochemically characterized. The structural characterizations were performed using X-ray diffraction and scanning electron microscopy. The electrochemical properties were studied using a standard three-electrode cell containing a platinum wire as a counter electrode, saturated calomel electrode as a reference electrode, and synthesized materials as a working electrode. The energy storage capacity was investigated using cyclic voltammetry (CV) and galvanostatic charge-discharge techniques. Cobalt oxide and cobalt sulfide showed specific capacitances of 983 and 7358 mF/cm2 at 2 mA/cm2, 5 respectively. The electrochemical properties of cobalt oxide have been improved significantly after converting to cobalt sulfide. Moreover, the effect of temperature on the electrochemical properties of the supercapacitor device fabricated using cobalt sulfide was studied. It was observed that the charge storage capacity of the device increased with increase in the temperature, which could be due to decrease in series resistance of the device. Our results suggest that cobalt sulfide could be used as an advanced material for energy storage applications

Characterization and performance evaluation of electrodeposition synthesized cobalt-nickel layered double hydroxide and composites for high-efficiency hybrid capacitor applications

Thesis (PhD (Physics))--University of Pretoria, 2022.In this thesis, “Characterization and performance evaluation of electrodeposition synthesized cobalt-nickel layered double hydroxide and composites for high-efficiency hybrid capacitor applications”, an efficient binder-free electrodeposition process was used to prepare cobalt nickel layered double hydroxide and its composites. Cobalt nickel layered double hydroxide (CN-LDH) benefits from a unique 2D layered structure with large interlayer spacing for ion transport. However, it suffers from restacking of layers leading to low electrical conductivity. Sulphur reduced graphene oxide increases mechanical strength, electrical conductivity, and wettability, while Hausmannite, manganese cobaltite and chromite improves the redox active capability and ion diffusion to improve the electrochemical performance of CN-LDH. The asymmetric supercapacitors fabricated using CN-LDH composites as positive electrodes and activated carbon as negative electrodes, exhibited excellent specific energy and power ranging from 55.8 to 80.2 W h kg -1 and 515 to 1117.7 W kg -1 , respectively, in 2 M KOH electrolyte within a cell voltage of 1.65 V.National Research FoundationPhysicsPhD (Physics)Unrestricte

Synthesis of graphene based materials and other applications as energy storage materials and Ni (II) ions adsorbant

PhD ThesisToday, with the increasing global concern regarding energy savings, CO2 emission and environmental protection, the development of low cost and environmentally friendly materials for electrodes in energy storage devices and adsorbent in wastewater treatment becomes important. Graphene, as a new materials, has attracted lots of attention due to its high current carrying capacity and high surface area. These properties give graphene the huge potential to be used as electrode materials for energy storage devices and adsorbant materials for heavy metal ions. However, the complicate synthesis methods and long reaction time limit its industrial scale up application. In this thesis, the research is focused on development of graphene based composite materials produced by fast, green and energy saving synthesis methods and study their usage as electrodes and for Ni (II) ions removal by analysing the electrochemical properties and Ni (II) ions absorb capacity. Beside graphene, bismuth has also been considered as safe and non-toxic material. In addition, a large amount of bismuth is produced as a by-product of the copper and tin refining industry. The long Fermi wavelength and high Hall coefficient give bismuth the possibility to reach high electronic conductivity with controlled structure. Therefore, bismuth compounds were selected to decorate graphene for the electrode materials. In this study, reduced graphene oxide bismuth composite (rGO/Bi, Bi2O3-GO, rGO/Bi2O2CO3) were synthesis at 60 C or room temperature with short reaction time of 3 hrs. These composite materials exhibit nano-structure and good electrochemical properties, such as high specific capacity and long cycling life. In the rGO/Bi composite materials, bismuth particles with size around 20 to 50 nm were wrapped and protected by graphene layers from oxidation. This composite materials achieves a specific capacity value of 773 C g-1, which is in the range of its theoretical value. In the Bi2O3-GO composite material, Bi2O3 shows a flower-like shape and linked by graphene oxide layer. This material reaches a specific capacity value as high as 559 C g-1. In the rGO/Bi2O2CO3 composite materials, nanosized bismuth subcarbonate were attached on the graphene layers. This composite material shows stable cycling performance even afi ter 4500 cycles. With the low cost of initial materials, simple synthesis methods, low reaction temperature, short reaction time, high specific capacity value and stable long cycling life, graphene bismuth compounds could be the promising candidates for the future electrodes used in electrochemical energy storage devices. The ability of Ni (II) ions removal by graphene oxide (GO) with sodium dodecyl sulphate (SDS) was also studied. Previous studies have proved that Ni is an excellent catalyst for carbon dioxide reforming. A robust Ni (II) ions removal absorbant is needed in order for this technology to become widely acceptable. SDS has been widely used as the industrial surfactant in toothpaste and shampoo. By adding SDS to decorate GO, it helps prevent graphene oxide sheets from stacking back together and then further enlarge the GO’s capacity of Ni (II) ions removal. In this work, SDS was added to modify graphene oxide surface by a one-step easy-to-handle method at room temperature. The effect of time on adsorption, initial concentration of Ni (II) ions and pH value of the Ni (II) ion solutions with GO and GO-SDS were analyzed. The driving force of the adsorption of Ni (II) ions on GO-SDS is proved to be by electrostatic attraction, Ni (II) ions are adsorbed on the GO surface chemically and by ion exchange. By using SDS modified GO, the Ni (II) ions adsorption capacity was increased dramatically from 20.19 mg g-1 to 55.16 mg g-1 in respect to pure GO.School of Chemical Engineering and Advanced Materials, Newcastle University, National Institute for Materials Science, Tsukuba, Japa

Bio-Inspired Synthesis Of Nanostructured Materials On Substrates For Environmental And Energy Applications

It is still a challenging task to develop simple methods for facile synthesis of functional nanostructures on substrates under mild conditions without using expensive instruments. We have successfully developed a bio-inspired method using simple diaphragm-assisted system to synthesize functional nanostructures on various substrates under mild conditions. We have systematically studied the effects of experimental parameters on the formation of nanostructures under controlled conditions. The fundamental mechanism involved has been systematically studied and revealed. By growing the unique networks of nanostructures on a piece of substrate, a double-rough surface, with structures at both nanoscale and microscale, has been achieved, showing interesting roughness-induced superhydrophobicity in air and superoleophobicity in water. The double rough substrates will find important environmental applications. Additionally, nanostructures formed on substrates have been used as integrated and binder-free electrodes for energy storage. The unique structures with a large exposed surface enable the electrodes to demonstrate dramatically improved performances. Moreover, some chemically active substrates were used to build up composite materials to enhance their applications. The method and ideas outlined in the dissertation, based on diaphragm-assisted systems, will have impacts, in principle, on the synthesis of numerous functional materials or precursors under mild conditions

Conductive textiles for signal sensing and technical applications

Conductive textiles have found notable applications as electrodes and sensors capable of detecting biosignals like the electrocardiogram (ECG), electrogastrogram (EGG), electroencephalogram (EEG), and electromyogram (EMG), etc; other applications include electromagnetic shielding, supercapacitors, and soft robotics. There are several classes of materials that impart conductivity, including polymers, metals, and non-metals. The most significant materials are Polypyrrole (PPy), Polyaniline (PANI), Poly(3,4-ethylenedioxythiophene) (PEDOT), carbon, and metallic nanoparticles. The processes of making conductive textiles include various deposition methods, polymerization, coating, and printing. The parameters, such as conductivity and electromagnetic shielding, are prerequisites that set the benchmark for the performance of conductive textile materials. This review paper focuses on the raw materials that are used for conductive textiles, various approaches that impart conductivity, the fabrication of conductive materials, testing methods of electrical parameters, and key technical applications, challenges, and future potential

Enhancement of transition metal-based supercapacitor materials for improved performance

In this research work, metal-doped MoS2 of Cobalt and Manganese (Co-MoS2 and Mn-MoS2) nanocomposites of different ratios of dopant concentrations were synthesized with a facile hydrothermal technique. The samples were characterized using various instruments to elucidate the properties and novelties of the prepared nanomaterials and likewise to establish their supercapacitive suitability for energy storage devices. The bibliometric evaluation of the development of literary works involving supercapacitor devices since the use of MoS2 as the active materials in energy storage (Supercapacitor) was performed. The bibliometric analysis of the studied materials gives us perspectives on the strengths and weaknesses of the materials, which enable us to identify the area of focus and the targeted publication outlets. The Co-MoS2 electrode materials (CMS1 and CMS3) were electrochemically evaluated for their energy storage performance, the materials exhibit specific capacitances of 164 and 146 Fg-1 at 1 Ag-1 for the working electrodes, respectively. Also, the energy densities of 3.67 and 2.05 Wh/kg with power densities of 3279.97 and 2960.26 W/kg were calculated for both electrode materials, respectively. While the electrochemical performance of the Mn-doped MoS2 electrode material showed a pseudo-capacitive behavior, with a specific capacitance of 70.37 Fg−1, and with a corresponding energy density of 3.14 Whkg−1 and a power density of 4346.35 Wkg−1. The general obtained results show that the electrode materials were well prepared and the enhancement of MoS2 properties is achievable with the transition metal composites. These improved properties of MoS2 composites showing the suitability of the nanomaterials for the energy storage applications have been explained in this work with possible future works recommended in the report.PhysicsD. Phil. (Physics