Carbon-based Nanomaterials for Energy Storage and Sensing Applications

This chapter reviews carbon-based nanomaterials and their potential applications in energy storage and sensing. Several methods of synthesizing carbon nanomaterials have been developed over the years. They include exfoliation, thermal decomposition, chemical vapor deposition, chemical-based techniques (including Hummer’s method), laser abrasion, and arc-discharge method. There are several synthesis methods developed over the years for carbon nanomaterials. There are mainly three different approaches to the chemical vapor deposition (CVD) technique, namely, atmospheric pressure CVD, low pressure CVD, and plasma enhanced CVD (e.g., microwave plasma enhanced CVD). Chemical-based techniques are the chemical extraction of graphene films from graphite, unlike the liquid phase exfoliation technique. Laser ablation relies on the laser exfoliation or ablation of amorphous graphite, and is sometimes called pulsed laser deposition. In the field of materials science, electrochemical energy storage has become a big challenge due to the rising need for portable electronic devices and systems

Single-route synthesis of binary metal oxide loaded coconut shell and watermelon rind biochar: Characterizations and cyclic voltammetry analysis

Generally, the type of biomass precursors is one of the key factors affecting the properties of synthesized biochar. This novel study therefore examined the single-route preparation of coconut shell and watermelon rind biochar with the combination of two types of binary metal oxide, iron nickel oxide (Fe2NiO4), and cobalt iron oxide (CoFe2O4) by employing a novel vacuum condition in an electric muffle furnace. The samples were characterized by several methods such as Fourier transform infrared (FTIR), field emission scanning electron microscope (FESEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) Surface Area. The optimum pyrolysis temperature for producing a high surface area of 322.142 m2/g and 441.021 m2/g for coconut shell biochar and watermelon rind biochar, respectively, was recorded at 600 °C. FTIR analysis revealed lesser adsorption bands found in FTIR spectrum of the samples with higher pyrolysis temperature (500–700 °C). In addition, FESEM results also revealed the surface changes of the samples with the impregnation of CoFe2O44 and Fe2NiO4. Furthermore, the value added application of biochar in electrochemical energy storage has been explored in the present work. In typical three-electrode configuration, WR-BMO 600 exhibits about 152.09 Fg−1 with energy density about 19.01 Wh kg−1

Assessing the progression of metal concentrations in plastic components and printed wiring boards of end-of-life mobile cell phones

This study assessed the progression of Pb, Cd and Cr concentrations in plastic components (PCs) and printed wiring boards (PWBs) of 59 end-of-life (EoL) mobile phones (MPs) produced between 2000 and 2015 by two leading original equipment manufacturers (OEMs) patronized by Nigerians. This was done to study the behavior of OEMs in complying with some widely acceptable regulations. Metals in PCs and PWBs of MPs were extracted following EPA 3050B method and extracts were analyzed using atomic absorption spectrophotometry technique. Furthermore, Toxicity Characteristic Leaching Procedure (TCLP) test was conducted on selected samples to assess metal leachability in landfill conditions. Summary of results (mg/kg) for PCs and PWBs for MPs produced by OEM 1 and OEM 2 in brackets ranged thus: PCs, Pb: 5.00 –195 (LOD-1750), Cr: LOD-6050 (LOD-2170) and Cd: LOD-1.00 (LOD-5.75) while PWBs, Pb:129-9750 (5.00-12125), Cr: LOD-5488 (LOD-4000) and Cd: LOD-1.00 (0.25-1.00). There were no regular trends for all metals for both OEMs. Results suggest that a greater percentage of MPs produced till 2015 contained Pb and Cr higher than RoHS and TTLC limits. Furthermore, 50% of TCLP extracts contain Pb higher than EPA limit of 5 mg/L. Therefore, EoL MPs arising in Nigeria should be handled as hazardous materials

Characterization of crystallized struvite on wastewater treatment equipment: Prospects for crystal fertilizer production

© 2018, Desalination Publications. All rights reserved. With over-mining of the natural rock-P, food production will plummet sooner than we envisage since they are essential in agro-industry but are non-renewable. Hence, phosphate fertilizers are going to be limited in future. Struvite is a crystalline mineral substance containing equimolar amount (1:1:1) of magnesium and ammonium phosphate(V) (MgNH PO O), a good source of phosphorus and a slow-release fertilizer. In this study, a sample of the4struvite4· 6H2formed in the wastewater treatment equipment of Kilang Kelapa Sawit, Sri Senggora (Palm Oil Mill at Pahang, Malaysia) was collected and characterized to determine its suitability for use as a slow-release fertilizer for agricultural purposes. The formation of struvite in the sewage pipes of wastewater treatment facility causes bottlenecks in the operation of the plant and results in reduced pumping efficiencies and high cost of overall plant maintenance. Due to the P, N and Mg content in the palm oil wastewater streams, struvite formation is triggered, and the treatment equipment are clogged as the struvite precipitates and builds up. The results of the characterization of the struvite through SEM-EDX, FTIR, XRD and TG-DTA/DSC analyses give the morphology and atomic percentage of the different elemental composition, the absorption pattern of the different functional groups, the orthorhombic crystal structure arrangement and the loss of mass against temperature respectively. The results indicate that high quality and large quantity struvite can be recovered from the palm oil wastewater streams. The recovery of struvite will reduce the BOD and COD of the wastewater stream resulting in plant size reduction, small land space requirements and reduced cost. This phenomenon being eco-recycling of phosphorus will serve as a sustainable approach towards food security and can help mitigate the problem of eutrophication

A review of the graphene synthesis routes and its applications in electrochemical energy storage

Graphene–a carbon nanomaterial has gained huge research interest due to its intriguing and extraordinary properties such as large surface area, excellent electrical conductivity, ultra-thinness, high electron mobility, and superior mechanical strength. The combination of graphene with other inorganic nanoparticles can significantly boost its physiochemical properties and hence, opens up new frontiers of its utilization. Grapheneis significantly exploited for the energy storage systems due to its great potential for electrochemical energy storage. However, the experimental electrochemical performance of graphene is still far away from the theoretical facts. This study critically evaluated the existing synthesis routes for the production of graphene, graphene-based composites and their utilization in the energy storage applications. Furthermore, the techno-economic analysis of the synthesis methods was undertaken to determine the best routes in terms of sustainability for commercial graphene production. Lastly, the fundamental understanding of graphene growth mechanisms and the overall intricacies of the synthesis processes were highlighted and the possible way forward is proposed. Therefore, in the quest for the development of effective alternative yet sustainable energy storage devices; it is hoped that this research will give useful insights to researchers and key players in the electronics industry

Optimising the fabrication of 3D binder-free graphene electrode for electrochemical energy storage application

Herein, a one-step fabrication of three-dimensional (3D) binder-free graphene-nickel foam (G-Ni) electrode via atmospheric pressure chemical vapour deposition (APCVD) is reported. Graphene thin films were deposited on nickel foam under isobaric conditions in an inert environment. The process parameters such as temperature, time, and the gas flow rate were statistically optimised using design of experiment (DOE) to maximise the yield of graphene. The structural and morphological properties of the fabricated graphene electrode were investigated through X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDS). The electrochemical investigations were conducted through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The results confirmed few-layered graphene with good surface morphology, high purity, and crystallinity of a binder-free electrode. The statistical analysis revealed that the optimal graphene electrode fabrication conditions were 900 °C, 10 min, and 100 sccm, respectively. Moreover, the regressed model and experimental results for the graphene growth were determined to be 3.93 mg/cm2, and 4.01 mg/cm2, respectively. Electrochemically, a specific capacitance value of 62.07 F/g was recorded at a scan rate of 3 mV/s showing an excellent performance of the fabricated 3D graphene electrode for energy storage applications

Optimisation of NiO electrodeposition on 3D graphene electrode for electrochemical energy storage using response surface methodology

In this study, NiO was electrodeposited on a 3D graphene electrode to produce a nanocomposite with enhanced electrochemical properties. The electrodeposition process parameters such as electrolyte concentration, deposition time, and deposition potential were statistically optimised using response surface methodology. The statistical analysis showed that the optimal electrodeposition conditions to be 0.3 M, 10 min, and -1.2 V for electrolyte concentration, deposition time, and deposition potential, respectively. Furthermore, the predicted model and experimental results for the specific capacity of G-NiO were determined to be 240.91 C/g and 240.58 C/g at 3 mV/s. The results show that the electrochemical deposition technique can be employed as a fast and reliable synthesis route to develop graphene-based metal oxide nanocomposites. The structural and morphological properties were determined by XRD and FESEM studies. The electrochemical measurements revealed the excellent electrochemical performance of 3D graphene NiO composite (G-NiO) for energy storage applications.This work was supported by Malaysia-Japan International Institute of Technology (MJIIT) of Universiti Teknologi Malaysia and MJIIT JICA Fund [UTM-Vot: 4B593]

Fabrication of 3D binder-free graphene NiO electrode for highly stable supercapattery

Electrochemical stability of energy storage devices is one of their major concerns. Polymeric binders are generally used to enhance the stability of the electrode, but the electrochemical performance of the device is compromised due to the poor conductivity of the binders. Herein, 3D binder-free electrode based on nickel oxide deposited on graphene (G-NiO) was fabricated by a simple two-step method. First, graphene was deposited on nickel foam via atmospheric pressure chemical vapour deposition followed by electrodeposition of NiO. The structural and morphological analyses of the fabricated G-NiO electrode were conducted through Raman spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDS). XRD and Raman results confirmed the successful growth of high-quality graphene on nickel foam. FESEM images revealed the sheet and urchin-like morphology of the graphene and NiO, respectively. The electrochemical performance of the fabricated electrode was evaluated through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in aqueous solution at room temperature. The G-NiO binder-free electrode exhibited a specific capacity of ≈ 243 C g at 3 mV s in a three-electrode cell. A two-electrode configuration of G-NiO//activated charcoal was fabricated to form a hybrid device (supercapattery) that operated in a stable potential window of 1.4 V. The energy density and power density of the asymmetric device measured at a current density of 0.2 A g were estimated to be 47.3 W h kg and 140 W kg, respectively. Additionally, the fabricated supercapattery showed high cyclic stability with 98.7% retention of specific capacity after 5,000 cycles. Thus, the proposed fabrication technique is highly suitable for large scale production of highly stable and binder-free electrodes for electrochemical energy storage devices

Fabrication of 3D binder-free graphene NiO electrode for highly stable supercapattery

Electrochemical stability of energy storage devices is one of their major concerns. Polymeric binders are generally used to enhance the stability of the electrode, but the electrochemical performance of the device is compromised due to the poor conductivity of the binders. Herein, 3D binder-free electrode based on nickel oxide deposited on graphene (G-NiO) was fabricated by a simple two-step method. First, graphene was deposited on nickel foam via atmospheric pressure chemical vapour deposition followed by electrodeposition of NiO. The structural and morphological analyses of the fabricated G-NiO electrode were conducted through Raman spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDS). XRD and Raman results confirmed the successful growth of high-quality graphene on nickel foam. FESEM images revealed the sheet and urchin-like morphology of the graphene and NiO, respectively. The electrochemical performance of the fabricated electrode was evaluated through cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) in aqueous solution at room temperature. The G-NiO binder-free electrode exhibited a specific capacity of ≈ 243 C g−1 at 3 mV s−1 in a three-electrode cell. A two-electrode configuration of G-NiO//activated charcoal was fabricated to form a hybrid device (supercapattery) that operated in a stable potential window of 1.4 V. The energy density and power density of the asymmetric device measured at a current density of 0.2 A g−1 were estimated to be 47.3 W h kg−1 and 140 W kg−1, respectively. Additionally, the fabricated supercapattery showed high cyclic stability with 98.7% retention of specific capacity after 5,000 cycles. Thus, the proposed fabrication technique is highly suitable for large scale production of highly stable and binder-free electrodes for electrochemical energy storage devices