Oxygen Reduction Reaction

In this chapter, the oxygen reduction reaction (ORR), which is one of the most important reactions in energy conversion systems such as fuel cells, including its reaction kinetics, is presented. Recent developments in electrocatalysts for ORR in fuel cells, including low and non-Pt electrocatalysts, metal oxides, transition metal macrocycles and chalgogenides, are discussed. Understanding of the interdependence of size, shape and activity of the electrocatalysts is evaluated. The recent development of ORR electrocatalysts with novel nanostructures is also reported. The mechanism catalysed by these electrocatalysts is presented. Finally, the perspectives of future trends for ORR are discussed

Fuel Cell Thermodynamics

Thermodynamics is the study of energy change from one state to another. The predictions that can be made using thermodynamic equations are essential for understanding fuel cell performance, as a fuel cell is an electrochemical device that converts the chemical energy of a fuel and an oxidant gas into electrical energy. When a fuel cell is operating, some of the input is used to create electrical energy, but another portion is converted into thermal energy, depending on the type of fuel cell. Based on the first and second laws of thermodynamics, one can write down thermodynamic potentials to specify how energy can be transferred from one form to another. This chapter examines how electrical energy and thermal energy are transferred in the hydrogen fuel cell system. It also defines how reversible fuel cell voltages, which are the maximum fuel cell performances, are affected by departures from the standard state. Basic thermodynamic concepts allow one to predict states of the fuel cell system, including the potential, temperature, pressure, volume and moles of a fuel cell. The specific topics explored in this chapter include enthalpy, entropy, specific heat, Gibbs free energy, net output voltage irreversible losses in fuel cells and fuel cell efficiency

Materials, components, assembly and performance of flexible polymer electrolyte membrane fuel cell: A review

With emerging demand of potable and wearable electronic devices, reliable and flexible energy suppliers are inevitable. Polymer electrolyte membrane fuel cells (PEMFCs) attract great attention due to high energy density and sustainability. However, non-bendability limits their application in flexible electronic devices. To make PEMFCs adaptable and flexible, considerable efforts have been devoted to developing various bendable com- ponents or advanced techniques. This review, therefore, focuses on the advancement of components and relative techniques of flexible PEMFCs, which determine the performance and durability, while achieved little concern in other reviews. The components and techniques include membrane, flexible catalytic layer, flexible gas diffusion layer, flexible bipolar plates, assembly of single cell or stack, store or supply of fuel and oxidant. In each section, the materials or techniques commonly used in conventional PEMFCs are summarized firstly, followed by the reasons why they aren’t appliable to flexible PEMFCs and then proceeding to the development of flexible components and relevant techniques of flexible PEMFCs. Subsequently, the flexible PEMFCs’ performance and durability are presented, reaching to 100–200 mW cm and dozens of hours, respectively, still far lower than those of conventional PEMFCs. Finally, a brief perspective on remaining challenges and future development of flexible PEMFCs are provide

Sugar Cane Bagasse Ash: An Agricultural Residue with Potential Rubber Filler Applications

South Africa produces approximately 7 million tons of sugarcane bagasse annually as an agricultural residue, which is treated as waste and its disposal is known to have negative impacts on the environment. To lessen reliance on petroleum and polymers, consideration is given on use of sugarcane bagasse ash as substitute materials for the development of fillers for rubber and other large-scale commodity polymers. This work reports on the mechanical, physiochemical, and structural properties of sugarcane bagasse ash to define the compatibility with the specific polymers that will pave way to the engineering of composites to utilize the potential benefits of these residue-derived fillers. The structural and morphological properties of the untreated and treated sugarcane bagasse ash were performed using XRD, FTIR, and SEM-EDX, respectively. The obtained results confirmed the successful treatment of the sugarcane bagasse ash. The study was successful in showing that sugarcane bagasse ash as potential filler in rubber polymer matrix is a natural resource of silica, which is sustainable and cost-effective, thus should be harnessed for industrial purposes in South Africa

Solar energy materials-evolution and niche applications: A literature review

The demand for energy has been a global concern over the years due to the ever increasing population which still generate electricity from non-renewable energy sources. Presently, energy produced worldwide is mostly from fossil fuels, which are non-renewable sources and release harmful by-products that are greenhouses gases. The sun is considered a source of clean, renewable energy, and the most abundant. With silicon being the element most used for the direct conversion of solar energy into electrical energy, solar cells are the technology corresponding to the solution of the problem of energy on our planet. Solar cell fabrication has undergone extensive study over the past several decades and improvement from one generation to another

Green synthesis of crystalline silica from sugarcane bagasse ash: Physico-chemical properties

Sugarcane bagasse South Africa is an agricultural waste that poses many environmental and human health problems. Sugarcane bagasse dumps attract many insects that harm the health of the population and cause many diseases. Sugarcane ash is a naturally renewable source of silica. This study presents for the first time the extraction of nanosilica from sugar cane bagasse ash using L-cysteine hydrochloride monohydrate acid and Tetrapropylammonium Hydroxide. The structural, morphological, and chemical properties of the extracted silica nanoparticles was cross examined using XRD, FTIR, SEM, and TGA. SEM analysis presents agglomerates of irregular sizes. It is possible to observe the structure of nanosilica formed by the presence of agglomerates of irregular shapes, as well as the presence of some spherical particles distributed in the structure. XRD analysis has revealed 2 angles at 20, 26, 36, 39, 50, and 59 which shows that each peak on the xrd pattern is indicative of certain crystalline cubic phases of nanosilica, similar to results reported in the literature by Jagadesh et al. in 2015

Antibacterial and photodegradation of organic dyes using lamiaceae-mediated zno nanoparticles: A review

The green synthesis of zinc oxide nanoparticles (ZnO NPs) using plant extracts has been receiving tremendous attention as an alternative to conventional physical and chemical methods. The Lamiaceae plant family is one of the largest herbal families in the world and is famous for its aromatic and polyphenolic biomolecules that can be utilised as reducing and stabilising agents during the synthesis of ZnO NPs. This review will go over the synthesis and how synthesis parameters affect the Lamiaceae-derived ZnO NPs. The Lamiaceae-mediated ZnO NPs have been utilised in a variety of applications, including photocatalysis, antimicrobial, anticancer, antioxidant, solar cells, and so on. Owing to their optical properties, ZnO NPs have emerged as potential catalysts for the photodegradation of organic dyes from wastewater. Furthermore, the low toxicity, biocompatibility, and antibacterial activity of ZnO against various bacteria have led to the application of ZnO NPs as antibacterial agents. Thus, this review will focus on the application of Lamiaceae-mediated ZnO NPs for the photodegradation of organic dyes and antibacterial applications

A review of the green synthesis of zno nanoparticles utilising Southern African indigenous medicinal plants

Metal oxide nanoparticles (NPs), such as zinc oxide (ZnO), have been researched extensively for applications in biotechnology, photovoltaics, photocatalysis, sensors, cosmetics, and pharmaceuticals due to their unique properties at the nanoscale. ZnO NPs have been fabricated using conventional physical and chemical processes, but these techniques are limited due to the use of hazardous chemicals that are bad for the environment and high energy consumption. Plant-mediated synthesis of ZnO NPs has piqued the interest of researchers owing to secondary metabolites found in plants that can reduce Zn precursors and stabilise ZnO NPs

Development of adsorptive materials for selective removal of toxic metals in wastewater: A review

Removal of toxic metals is essential to achieving sustainability in wastewater purification. The achievement of efficient treatment at a low cost can be seriously challenging. Adsorption methods have been successfully demonstrated for possession of capability in the achievement of the desirable sustainable wastewater treatment. This review provides insights into important conventional and unconventional materials for toxic metal removal from wastewater through the adsorption process. The importance of the role due to the application of nanomaterials such as metal oxides nanoparticle, carbon nanomaterials, and associated nanocomposite were presented. Besides, the principles of adsorption, classes of the adsorbent materials, as well as the mechanisms involved in the adsorption phenomena were discussed

Underpotential deposition of SnBi thin films for sodium ion batteries: The effect of deposition potential and Sn concentration

Bimetallic SnBi film was deposited on a Cu foil substrate via the electrochemical atomic layer deposition (E-ALD) technique. The deposition attainment of Sn and Bi were investigated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The deposition potential of Bi was varied in the underpotential deposition (UPD) region and the concentration of Sn was varied in the SnBi bimetallic material. The materials were characterised using field emission scanning electron microscopy coupled with energy dispersive spectroscopy (FE-SEM/EDS) for morphology and elemental distribution, focused ion beam scanning electron microscopy (FIBSEM) for thickness, X-ray diffraction (XRD) for crystallinity and inductively coupled plasma mass spectroscopy (ICP-MS) for composition measurements. Bi deposited at different UPD regions was structurally different. The deposits were crystalline SnBi materials containing Sn, Bi and other phases of Cu and Sn. Bi was concentrated on the surface, while Sn was distributed evenly across the film. The SnBi electrodes were tested as anode materials in Na-ion batteries using galvanostatic cycling (GC), CV and electrochemical impedance spectroscopy (EIS). Initial discharge capacities of 1900 mAh g 1 for SnBi (1:1) and 341 mAh g 1 for SnBi (3:1) electrodes at 38.5 mA g 1 were obtained, while the electrodes suffered capacity loss after 10 cycles