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Abstract: The use of Ni–MH batteries for traction applications in electric and hybrid vehicles is increasingly attractive and reliable. Besides the energy and power handling, and the cost issues, high tolerance to abuse is an important aspect of the Ni–MH technology. Thus, the ability to reduce charging time and to absorb regenerative breaking is highly desirable in these traction applications. This requires an accurate control of the charge termination. To facilitate an easy and reliable charging control and to avoid battery premature failure or ageing it is very important to know the behavior of the battery under a range of charging conditions. In this paper, we described the performance of high capacity commercial Ni–MH traction batteries (12V, 109Ah modules) when subjected to different charging rates (0.1, 0.2, 0.5, and 1.0C) from 100% depth of discharge (DOD). Changes in battery voltage and temperature during charging were monitored, with a particular emphasis on the detection of the presence of hydrogen near the battery. This unique hydrogen detection outside the battery was used as the method for the end-of-charge termination to prevent overcharging of the battery. Relevant parameters, such as charge acceptance, energy efficiency, and charging time, were analyzed for comparison. [Copyright &y& Elsevier]

Abstract: The Institute for Energy and Environment (IEE) at the University of Strathclyde has developed various fuel cell (FC) systems for stationary and vehicular applications. In particular the author is involved in the development of alkaline fuel cell (AFC) systems. To understand the dynamic behaviour of the system''s key element, the alkaline fuel cell stack, a dynamic model was developed allowing the characterisation of the electrochemical parameters. The model is used to forecast the behaviour of the fuel cell stack under various dynamic operating conditions. The so-called Nernst potential, which describes the open circuit voltage of the stack, is calculated using thermodynamic theory. Electrochemistry theory has been used to model the sources of the electric losses within the FC, such as activation, ohmic and concentration losses. The achievable value of this paper is the first publication of a detailed dynamic AFC based on mass balance, thermodynamics and electrochemical theory. The effects of the load changes on various fuel cell parameters, such as electrolyte concentration and concentrations of dissolved hydrogen and oxygen were covered in this investigation using the author''s model. The model allows a detailed understanding of the dynamic effects within the AFC during load change events, which lead to the experienced electric response of the overall FC stack. [Copyright &y& Elsevier]

Abstract: Recent advances in super-iron batteries, based on an unusual Fe(VI) cathodic charge storage, are presented. Fe(VI) cathodes that have been demonstrated in super-iron batteries include the synthesized Fe(VI) compound with three-electron cathodic charge capacity Na2FeO4, K2FeO4, Rb2FeO4, Cs2FeO4 (alkali Fe(VI) salts), alkali earth Fe(VI) salts BaFeO4, SrFeO4, and also a transition Fe(VI) salt Ag2FeO4 which exhibits a five-electron cathodic charge storage. This paper focus on the primary alkaline Fe(VI) charge storage in aqueous electrolyte systems. Primary alkaline super-iron batteries exhibit a higher capacity than conventional alkaline batteries. Configuration optimization, enhancement and mediation of Fe(VI) cathode charge transfer of primary Fe(VI) alkaline batteries are summarized. Composite Fe(VI)/Mn(IV or VII), Fe(VI)/Ag(II) and zirconia coating stabilized Fe(VI)/Ag(II) cathode alkaline batteries are also illustrated. [Copyright &y& Elsevier]

Abstract: The paper treats investigation of the desulphurization process of damped Pb-paste by Na2CO3 or NaOH. There is determined the effect of Na2CO3 (NaOH) concentration and the liquid–solid phase ratio on the process parameters (degree of desulphurization and degree of Na2CO3 (NaOH) utilization in function of the temperature and process duration). The optimum conditions for carrying out desulphurization of Pb-pastes by Na2CO3 or NaOH are determined in dependence of the used reactors (common reactor with laboratory agitator and rotary reactor of drum type). The content of inclusions in the solutions is examined with the purpose of producing sufficiently pure crystalline Na2SO4 for the industry. [Copyright &y& Elsevier]

Abstract: This paper describes the characteristics and performance of a fuel cell powered unmanned aircraft. The aircraft is novel as it is the largest compressed hydrogen fuel cell powered airplane built to date and is currently the only fuel cell aircraft whose design and test results are in the public domain. The aircraft features a 500W polymer electrolyte membrane fuel cell with full balance of plant and compressed hydrogen storage incorporated into a custom airframe. Details regarding the design requirements, implementation and control of the aircraft are presented for each major aircraft system. The performances of the aircraft and powerplant are analyzed using data from flights and laboratory tests. The efficiency and component power consumption of the fuel cell propulsion system are measured at a variety of flight conditions. The performance of the aircraft powerplant is compared to other 0.5–1kW-scale fuel cell powerplants in the literature and means of performance improvement for this aircraft are proposed. This work represents one of the first studies of fuel cell powered aircraft to result in a demonstration aircraft. As such, the results of this study are of practical interest to fuel cell powerplant and aircraft designers. [Copyright &y& Elsevier]

Abstract: Polymer electrolyte membrane fuel cells (PEMFCs) show great promise in portable, automotive, and stationary applications. They have reached the test and demonstration phase in automotive and power markets today. This paper is focused on a stand-alone residential PEMFC power system that provides the electricity needs of the house. A novel stochastic sizing methodology is developed that considers both fuel cell system dynamics and residential load dynamics in overall system sizing for the stand-alone residential fuel cell power system. Understanding the nature of demand side is critical in stand-alone system sizing. Thus, experimental measurements have been completed to capture the load side dynamics in detail. No such data is found in the current literature. The Threshold Bootstrap method is used to model the residential load demand and to produce many realistic load profiles. Matlab/Simulink is used to run system simulations to determine system sizes based on parameters defined through a designed experiment. Comparison between the proposed sizing method and a possible worst case scenario sizing is given. The new sizing methodology can be used together with sophisticated demand analysis programs to obtain customized sizing for each user as stand-alone power systems become more viable. [Copyright &y& Elsevier]

Abstract: Water management remains a leading challenge in the implementation of small polymer electrolyte membrane (PEM) fuel cells for portable electronic applications. At present there are many excellent models for the distribution of water within PEM fuel cells, but little quantitative data on the water distribution that can be compared to models. In this paper magnetic resonance imaging (MRI) is used to examine the water distribution in the flow fields of an operating PEM fuel cell. While previous workers have used MRI to do qualitative measurements of the water distribution, we use MRI to quantitatively measure the water distribution for the first time. We find that even with Teflon® flow fields the GDL is so hydrophobic, that water is drawn away from the cathode GDL and accumulates at the bottom of the flow field. The flow pattern in the flow field seems to be wavy-stratified flow rather than plug flow as previously supposed. Additionally, we find that water is transported from the cathode to the anode. Thus, diffusional forces and hydrophobic capillary pressures appeared to dominate electroosmotic forces, at low current densities. [Copyright &y& Elsevier]

Abstract: Metallic bipolar plates look promising for the replacement of graphite due to higher mechanical strength, better durability to shocks and vibration, no gas permeability, acceptable material cost and superior applicability to mass production. However, the corrosion and passivation of metals in environments of proton exchange membrane fuel cell (PEMFC) cause considerable power degradation. Great attempts were conducted to improve the corrosion resistance of metals while keeping low contact resistance. In this paper, a simple, novel and cost-effective high-energy micro-arc alloying process was employed to prepare compact titanium carbide as coatings for the type 304 stainless steel bipolar plates with a metallurgical bonding between the coating and substrate. It was found that TiC coating increased the corrosion potential of the bare steel in 1M H2SO4 solution at room temperature by more than 200mV, and decreased significantly its corrosion current density from 8.3μAcm−2 for the bare steel to 0.034μAcm−2 for the TiC-coated steel. No obvious degradation was observed for the TiC coatings after 30-day exposure in solution. [Copyright &y& Elsevier]

Abstract: Fuel cell applications become increasingly attractive. Therefore, comprehensive models, simulation software and analysis tools are required to characterize fuel cell behavior. This paper introduces a model capable of representing the static and dynamic (dynastatic) behavior of PEM fuel cells. The model approximates the theoretical current–voltage description with an equivalent electric circuit. The parameter values of the model are found by analyzing small-signal measurement results from electrochemical impedance spectroscopy, together with the steady-state electric characteristic and large-signal behavior from step-response measurements. Because the modeling approach is completely based on measurements on the fuel cell electric output terminals, electrochemical aspects like temperature dependency, charge double layer and adsorption effects are implicitly covered. [Copyright &y& Elsevier]

Abstract: In this paper, a transient two-phase non-isothermal PEM fuel cell model has been developed based on the previously established two-phase mixed-domain approach. This model is capable of solving two-phase flow and heat transfer processes simultaneously and has been applied herein for two-dimensional time-accurate simulations to fully examine the effects of liquid water transport and heat transfer phenomena on the transient responses of a PEM fuel cell undergoing a step change of cell voltage, with and without condensation/evaporation interfaces. The present numerical results show that under isothermal two-phase conditions, the presence of liquid water in the porous materials increases the current density over-shoot and under-shoot, while under the non-isothermal two-phase conditions, the heat transfer process significantly increases the transient response time. The present studies also indicate that proper consideration of the liquid droplet coverage at the GDL/GC interface results in the increased liquid saturation values inside the porous materials and consequently the drastically increased over-shoot and under-shoot of the current density. In fact, the transient characteristics of the interfacial liquid droplet coverage could exert influences on not only the magnitude but also the time of the transient response process. [Copyright &y& Elsevier]

Abstract: The present paper presents a study of the Ru x Cr y Se z chalcogenide electrocatalyst based on physical–chemical characterization through scanning electron (SEM), atomic force (AFM) microscopy and energy dispersion elemental analysis (EDS), thermal stability using differential scanning calorimeter (DSC), electrochemical kinetics towards the oxygen reduction reaction (ORR) in acid media by rotating ring-disk electrode (RRDE) and single and three-stack membrane-electrode assembly (MEA) performance as a function of catalyst loading (10%, 20% and 40%W from 0.2 to 2mgcm−2). Results indicate an electrocatalyst with chemical composition of Ru6Cr4Se5. AFM images showed 80–160nm nanoparticle agglomerates. Good thermal stability of the cathode Ru6Cr4Se5 was established after 100h of continuous operation. The electrochemical kinetics study (RRDE) resulted in a electrocatalyst with high activity towards the ORR, preferentially proceeding via 4e− charge transfer pathway towards water formation (i.e., O2+4H++4e−→2H2O), with a maximum of 2.8% H2O2 formation at 25°C. Finally, MEA tests revealed a maximum power density of 220mWcm−2 with a catalyst loading of 20wt% at 1.6mgcm−2. [Copyright &y& Elsevier]

Abstract: In this work, ruthenium oxide films containing platinum nanoparticles were prepared using the polymeric precursor method on Ti substrates with several molar ratios. This paper aims at presenting the characterization of the Pt content effect in the methanol electrochemical oxidation reaction. The films were physically characterized using X-ray diffraction and both Pt and RuO2 (rutile) phases were observed. The mean crystallite sizes were 6nm for Pt and 25nm for RuO2. The X-ray photoelectronic results indicated that on the electrodes surfaces, depending on the substrate, there was RuO2, Ru metal and Pt metal. Besides, it was not observed the formation of PtRu alloys. The atomic force microscopy images of the films showed highly rough surfaces. A decrease in the roughness mean square values is observed as the Pt content increases. These last results are similar to electroactive surface area values calculated by redox-couple (K4FeCN6/K3FeCN6). There was an increase in the globular size observed on the electrode surface and lower particle dispersion as the Pt content is increased from 12.5 to 75mol%. Regarding the eletrode electrocatalytical behavior for methanol oxidation, it was observed that the onset oxidation overpotential is displaced towards more negative values as Pt content is decreased. Besides, an increase has been shown in the current density for methanol oxidation of 600% using a Ti/RuO2-Pt (87.5:12.5) electrode compared to polycrystalline Pt. [Copyright &y& Elsevier]

Abstract: This article is an examination of the CO poisoning and cleaning (stripping) phenomenon that occur in a PEM fuel cell operating on an impure hydrogen stream such as reformed hydrocarbons or alcohols. A range of experimental results including cell polarization curves, measurements of spontaneous and transient oscillations of the anode potential and current pulsing behaviour are presented. Detailed examination of the pulsing process has shown that optimization of both the pulse width and pulse initiation potential will have an important impact on the overall fuel cell efficiency. To optimize these processes, the development of a mathematical model to understand and control the poisoning and cleaning processes is going to be important. In this paper, we have extended the model of Zhang et al. [J. Zhang, Investigation of CO tolerance in proton exchange membrane fuel cells, PhD thesis, Worcester Polytechnic Institute, June, 2004; J. Zhang, R. Datta, J. Electrochem. Soc. 149 (2002) A1423; J. Zhang, J.D. Fehribach, R. Datta, J. Electrochem. Soc. 151 (2004) A689] to include mass transfer effects. It is shown that this new model gives results that are in reasonable agreement with our experimental data. [Copyright &y& Elsevier]

Abstract: A cobalt oxide coating was deposited on porous nickel by a potentiostatic electrochemical technique and studied in molten (Li0.52Na0.48)2CO3 eutectics at 650°C under an atmosphere of CO2:Air (30:70). The structural and morphological characteristics of this coating before and after immersion in the molten electrolyte were described in a previous paper, showing that the initial Co3O4 layer is rapidly transformed into LiCoO2 and afterwards probably into LiCo1−y Ni y O2. In the present part, the electrical and electrochemical behaviour of this promising novel MCFC cathode material was thoroughly analysed during 50h by impedance spectroscopy. A porous nickel cathode was tested in the same conditions and taken as a reference. The oxidation and lithiation reactions are accelerated by the presence of cobalt. The charge transfer resistance is higher with the coated cathode but the diffusion resistance through this new material is lower in comparison with the state-of-the-art cathode. [Copyright &y& Elsevier]