Aluminium–air cells are high-energy density (<400 W h kg−1) primary batteries developed in the 1960s. This review shows the influence of the materials, including: aluminium alloy, oxygen reduction ...catalyst and electrolyte type, in the battery performance. Two issues are considered: (a) the parasitic corrosion of aluminium at open-circuit potential and under discharge, due to the reduction of water on the anode and (b) the formation of a passive hydroxide layer on aluminium, which inhibits dissolution and shifts its potential to positive values. To overcome these two issues, super-pure (99.999 wt%) aluminium alloyed with traces of Mg, Sn, In and Ga are used to inhibit corrosion or to break down the passive hydroxide layer. Since high-purity aluminium alloys are expensive, an alternative approach is to add inhibitors or additives directly into the electrolyte. The effectiveness of binary and ternary alloys and the addition of different electrolyte additives are evaluated. Novel methods to overcome the self-corrosion problem include using anionic membranes and gel electrolytes or alternative solvents, such as alcohols or ionic liquids, to replace aqueous solutions. The air cathode is also considered and future opportunities and directions for the development of aluminium–air cells are highlighted.
► Discussion of the rationale to choose a suitable alloy for Al–air battery. ► Effect of the properties and preparation route to enhance the oxidation of Al. ► Effect of the inhibitors on the anode oxidation in the alkaline electrolyte. ► Comparison of the performance of high-activity oxygen reduction electrodes.
Graphene (GN) has many beneficial properties that encourage wide applications. Various manufacturing procedures are detailed in the literature but most are unable to produce GN flakes in bulk and ...usually result in toxic discharges. These techniques are also time-consuming and involve operations at high temperatures. A ‘greener’, simpler and a one-step synthesis of the material may be realised by electrochemical oxidation (or reduction) of the graphite host leading to intercalation of ions from the electrolyte (which may be aqueous, organic or an ionic liquid) followed by electrochemical exfoliation. Single- or multi-layered GN flakes can easily be produced in short periods of time, typically within 30min. This paper reviews the state-of-the-art methods reported in the literature regarding electrochemical synthesis of GN flakes as well as their properties (determined via sophisticated analytical methods such as AFM, TEM, SEM or Raman spectroscopy). This is followed by a discussion on the applications of electrochemically prepared GN flakes. Challenges and opportunities are briefly considered leading to the conclusion that the cathodic intercalation of lithium ions into graphite can produce the highest yield (>70%) of pristine GN flakes in organic electrolytes. Future work is recommended with ternary eutectic melts as electrolytes.
Fuzzy logic is used to define a new quantity called the battery working state (BWS), which is based on both battery terminal voltage and state of charge (SOC), to overcome the problem of battery ...over-discharge and associated damage resulting from inaccurate estimates of the SOC. The BWS is used by a fuzzy logic energy-management system of a plug-in series hybrid electric vehicle (HEV) to make a decision on the power split between the battery and the engine, based on the BWS and vehicle power demand, while controlling the engine to work in its fuel economic region. The fuzzy logic management system was tested in real time using an HEV simulation test bench with a real battery in the loop. Simulation results are presented to demonstrate the performance of the proposed fuzzy logic energy-management system under different driving conditions and battery SOCs. The results indicate that the fuzzy logic energy-management system using the BWS was effective in ensuring that the engine operates in the vicinity of its maximum fuel efficiency region while preventing the battery from over-discharging.
Over the last twenty years, there has been a resurgent research interest in direct borohydride fuel cells (DBFCs) highlighting the fundamental aspects that need to be addressed to achieve their ...optimal performance. The main problem is the hydrolysis of borohydride ions, which generates hydrogen, decreases the energy efficiency and reduces the power density. The electrons released during borohydride oxidation, the cell potential difference and the power output are strongly influenced by the choice of anode and cathode, including three-dimensional and nanostructured electrodes, the electrolyte composition and the operating conditions. Extensive investigations on various anodic electrocatalysts and their effect on the oxidation and hydrolysis have been quantified as well as the cathode catalyst and its influence on the overall fuel cell performance. Computational methods such as ab-initio and physical modelling could play prominent roles in the design and fundamental characterisation of DBFCs but are currently underused and only small number of studies in well-defined materials such as Pt (111) or Au (111) exist. Cell design and configuration have also been considered but the basic requirement to engineer a selective catalyst able to suppress the hydrogen evolution and the elucidation of the mechanism of borohydride ion oxidation, remain.
► We review aspects of the borohydride fuel cell that have not been revised previously. ► Aspects of the borohydride hydrolysis, modelling, simulation and recycling are discussed. ► Future trends and recommendations to improve the technology are suggested
Recent literature on the electrodeposition of metallic coatings containing nanosized particles is surveyed. The nanosized particles, suspended in the electrolyte by agitation and/or use of ...surfactants, can be codeposited with the metal. The inclusion of nanosized particles can give (i) an increased microhardness and corrosion resistance, (ii) modified growth to form a nanocrystalline metal deposit and (iii) a shift in the reduction potential of a metal ion. Many operating parameters influence the quantity of incorporated particles, including current density, bath agitation (or movement of work piece) and electrolyte composition. High incorporation rates of the dispersed particles have been achieved using (i) a high nanoparticle concentration in the electrolyte solution, (ii) smaller sized nanoparticles; (iii) a low concentration of electroactive species, (iv) ultrasonication during deposition and (v) pulsed current techniques. Compositional gradient coatings are possible having a controlled distribution of particles in the metal deposit and the theoretical models used to describe the phenomenon of particle codeposition within a metal deposit are critically considered.
Tubular and fibrous nanostructures of titanates have recently been synthesized and characterized. Three general approaches (template assisted, anodic oxidation, and alkaline hydrothermal) for the ...preparation of nanostructured titanate and TiO2 are reviewed. The crystal structures, morphologies, and mechanism of formation of nanostructured titanates produced by the alkaline hydrothermal method are critically discussed. The physicochemical properties of nanostructured titanates are highlighted and the links between properties and applications are emphasized. Examples of early applications of nanostructured titanates in catalysis, photocatalysis, electrocatalysis, lithium batteries, hydrogen storage, and solar‐cell technologies are reviewed. The stability of titanate nanotubes at elevated temperatures and in acid media is considered.
The synthesis of tubular and fibrous nanostructures of titanates and TiO2, their structure, physiochemical properties, potential applications and stability are considered. Early applications of nanostructured titanates (see figure) have taken place in the fields of catalysis, photocatalysis, electrocatalysis, lithium batteries, hydrogen storage, and solar cells.
The literature dealing with the electrochemical corrosion characteristics of unalloyed copper in aqueous chloride media is examined. The enormous quantity of polarisation and mixed/corrosion ...potential data that has been made available in the literature over the last 50 years has been compiled and discussed in a comprehensive review. For a wide range of electrode geometries, the importance of the chloride ion and the mass transport of anodic corrosion products on the corrosion behaviour of copper are made clear for both freshly polished and ‘filmed’ surfaces.
Recent developments in bio-fuel cell technology are reviewed. A general introduction to bio-fuel cells, including their operating principles and applications, is provided. New materials and methods ...for the immobilisation of enzymes and mediators on electrodes, including the use of nanostructured electrodes are considered. Fuel, mediator and enzyme materials (anode and cathode), as well as cell configurations are discussed. A detailed summary of recently developed enzymatic fuel cell systems, including performance measurements, is conveniently provided in tabular form. The current scientific and engineering challenges involved in developing practical bio-fuel cell systems are described, with particular emphasis on a fundamental understanding of the reaction environment, the performance and stability requirements, modularity and scalability. In a companion review (Part II), new developments in microbial fuel cell technologies are reviewed in the context of fuel sources, electron transfer mechanisms, anode materials and enhanced O
2 reduction.
Redox flow cells for energy conversion Ponce de León, C.; Frías-Ferrer, A.; González-García, J. ...
Journal of power sources,
09/2006, Letnik:
160, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Energy storage technologies provide an alternative solution to the problem of balancing power generation and power consumption. Redox flow cells are designed to convert and store electrical energy ...into chemical energy and release it in a controlled fashion when required. Many redox couples and cell designs have being evaluated. In this paper, redox flow systems are compared in the light of characteristics such as open circuit potential, power density, energy efficiency and charge-discharge behaviour. The key advantages and disadvantages of redox flow cells are considered while areas for further research are highlighted.
Typically, pure niobium oxide coatings are deposited on metallic substrates, such as commercially pure Ti, Ti6Al4 V alloys, stainless steels, niobium, TiNb alloy, and Mg alloys using techniques such ...as sputter deposition, sol–gel deposition, anodizing, and wet plasma electrolytic oxidation. The relative advantages and limitations of these coating techniques are considered, with particular emphasis on biomedical applications. The properties of a wide range of pure and modified niobium oxide coatings are illustrated, including their thickness, morphology, microstructure, elemental composition, phase composition, surface roughness and hardness. The corrosion resistance, tribological characteristics and cell viability/proliferation of the coatings are illustrated using data from electrochemical, wear resistance and biological cell culture measurements. Critical R&D needs for the development of improved future niobium oxide coatings, in the laboratory and in practice, are highlighted.