417 results found
Wu B, Ibrahim KA, Brandon NP, 2016, Electrical conductivity and porosity in stainless steel 316L scaffolds for electrochemical devices fabricated using selective laser sintering, Materials and Design, Vol: 109, Pages: 51-59, ISSN: 1873-4197
Battery electrode microstructures must be porous, to provide a large active surface area to facilitate fast charge transfer kinetics. In this work, we describe how a novel porous electrode scaffold, made from stainless steel 316L powder can be fabricated using selective laser sintering by proper selection of process parameters. Porosity, electrical conductivity and optical microscopy measurements were used to investigate the properties of fabricated samples. Our results show that a laser energy density between 1.50–2.00 J/mm2 leads to a partial laser sintering mechanism where the powder particles are partially fused together, resulting in the fabrication of electrode scaffolds with 10% or higher porosity. The sample fabricated using 2.00 J/mm2 energy density (60 W–1200 mm/s) exhibited a good electrical conductivity of 1.80 × 106 S/m with 15.61% of porosity. Moreover, we have observed the porosity changes across height for the sample fabricated at 60 W and 600 mm/s, 5.70% from base and increasing to 7.12% and 9.89% for each 2.5 mm height towards the top surface offering graded properties ideal for electrochemical devices, due to the changing thermal boundary conditions. These highly porous electrode scaffolds can be used as an electrode in electrochemical devices, potentially improving energy density and life cycle.
Budinis S, Krevor S, Mac Dowell N, et al., 2016, Can technology unlock unburnable carbon?
In 2015, the Conference Of the Parties in Paris (COP21) reached a universal agreement on climate change with the aim of limiting global warming to below 2 °C. In order to stay below 2 °C, the total amount of carbon dioxide (CO2) released, or ‘carbon budget’ must be less than 1,000 gigatonnes (Gt) of CO2. At the current emission rate, this budget will be eroded within the next thirty years. Meeting this target on a global scale is challenging and will require prompt and effective climate change mitigation action.The concept of ‘unburnable carbon’ emerged in 2011, and stems from theobservation that if all known fossil fuel reserves are extracted and converted to CO2 (unabated), it would exceed the carbon budget and have a very significant effect on the climate. Therefore, if global warming is to be limited to the COP21 target, some of the known fossil fuel reserves should remain unburnt.Several recent reports have highlighted the scale of the challenge, drawing on scenarios of climate change mitigation and their implications for the projected consumption of fossil fuels. Carbon capture and storage (CCS) is a critical and available mitigation opportunity that is often overlooked. The positive contribution of CCS technology to timely and cost-effective decarbonisation of the energy system is widely recognised. However, while some studies have considered the role of CCS in enabling access to more fossil fuels, no detailed analysis on this issue has been undertaken.This White Paper presents a critical review focusing on the technologies that can be applied to enable access to, or ‘unlock’, fossil fuel reserves in a way that will meet climate targets and mitigate climate change.The paper includes an introduction to the key issues of carbon budgets and fossil fuel reserves, a detailed analysis of the current status of CCS technology, as well as a synthesis of a multi-model comparison study on global climate change mitigation strat
Blanga R, Berman M, Biton M, et al., 2016, Peculiarities of ion transport in confined-in-ceramics concentrated polymer electrolytes, Electrochimica Acta, Vol: 208, Pages: 71-79, ISSN: 1873-3859
Polyethylene-oxide/lithium-aluminate films were deposited by electrophoretic deposition. Films impregnated with lithium iodide formed highly concentrated polymer-in-ceramic solid electrolytes. Solid-state NMR, FIB-SEM tomography with modelling, and EIS studies showed that only a few percent of the interfacial lithium in the sample is capable of inducing a fast ion-migration path in the system. We suggest that despite suppressed crystallinity of PEO confined in ceramics the ion transport in the polymer medium impedes the total conductivity of the composite electrolyte at near-ambient temperatures. After melting of the polymer and its complexes, the interfacial conduction through perpendicular LiAlO2/LiI grain boundaries becomes feasible. This, together with ion transport via molten, confined polymer electrolyte is followed by the increase of the overall conductivity of the composite system.
Jamil Z, Ruiz-Trejo E, Boldrin P, et al., 2016, Anode fabrication for solid oxide fuel cells: Electroless and electrodeposition of nickel and silver into doped ceria scaffolds, International Journal of Hydrogen Energy, Vol: 41, Pages: 9627-9637, ISSN: 1879-3487
A novel fabrication method using electroless and electrodeposited Ni/Ag/GDC for SOFC anodes is presented. First a porous Ce0.9Gd0.1O2−x (GDC) scaffold was deposited on a YSZ electrolyte by screen printing and sintering. The scaffold was then metallized with silver using Tollens' reaction, followed by electrodeposition of nickel from a Watt's bath. The electrodes (Ni/Ag/GDC) were tested in both symmetrical and fuel cell configurations. The microstructures of the Ni/Ag/GDC anodes were analyzed using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX). Nano-particles of Ni formed in the porous GDC scaffold provided triple phase boundaries (TPB). The electronic conductivity of the Ni/Ag/GDC (3.5/24.7/71.8 vol%) electrode was good even at relatively low Ni volume fractions. The electrochemical performance was examined in different concentrations of humidified hydrogen (3% H2O) and over a range of temperatures (600–750 °C). The total area specific resistance (ASR) of the anode at 750 °C in humidified 97 vol% H2 was 1.12 Ω cm2, with low-frequency polarization (R_l) as the largest contributor. The electrodes were successfully integrated into a fuel cell and operated in both H2 and syngas.
Chen Z, Brandon N, 2016, Inkjet Printing and Nanoindentation of Porous Alumina Multilayers, Ceramics International, Vol: 42, Pages: 8316-8324, ISSN: 0272-8842
The objectives of this study were to analyse the effect of inkjet 3-D printing parameters,particularly the splat overlap distance, for the fabrication of defect-free porous Al2O3 ceramicmultilayers, and to correlate the resulting porosities with the mechanical properties measured usingnanoindentation. An aqua-based alumina ink was used in this study to fabricate the multilayers ondense alumina substrates by inkjet printing. The as-printed specimens were dried and sintered at 1200– 1500 °C. The resulting microstructural features of each specimen and their corresponding porositieswere studied using FIB-SEM. Elastic modulus and hardness were determined using the sphericalnanoindentation technique. Results showed that defect-free porous alumina multilayers with excellentlayer to layer and layer to substrate integrity were successfully fabricated. The porosity-dependence ofthe elastic modulus and hardness was shown to be consistent with values predicted using empiricalexpressions, despite the presence of abnormal grain growth at higher temperatures.
Lanzini A, Guerra C, Leone P, et al., 2016, Influence of the microstructure on the catalytic properties of SOFC anodes under dry reforming of methane, MATERIALS LETTERS, Vol: 164, Pages: 312-315, ISSN: 0167-577X
Bahadori L, Hashim MA, Manan NSA, et al., 2016, Investigation of ammonium- and phosphonium-based deep eutectic solvents as electrolytes for a non-aqueous all-vanadium redox cell, Journal of the Electrochemical Society, Vol: 163, Pages: A632-A638, ISSN: 0013-4651
The charge/discharge characteristics for vanadium acetylacetonate in deep eutectic solvents were evaluated using an H-cell with an anion-exchange membrane separator for the first time. Coulombic (CE) and energy efficiencies (EE) of the electrolyte containing V(acac)3/0.5 M TEABF4 in DES3 (a hydrogen bonded eutectic between choline chloride and ethylene glycol) were obtained as 49–52% and 25–31%, respectively, when charging from 0 to 50% of theoretical maximum state-of-charge for 12 cycles. The low CE may be due to the crossover of the active species through the separator, or to the loss of active vanadium due to a parasitic reaction. However, the CE was similar to that for acetonitrile (CH3CN) indicating the promise of DESs as suitable electrolytes for future evaluation. Charge and discharge voltages are respectively higher and lower than the formal cell potential obtained by voltammetry. Ohmic drop in the DES results from the low conductivity of the electrolyte and the relatively large distance between the two electrodes in the H-cell. Further studies require investigation in a flow cell with analyses of polarization curves and impedance to determine the loss mechanisms in sufficient detail.
Maher RC, Shearing PR, Brightman E, et al., 2016, Reduction Dynamics of Doped Ceria, Nickel Oxide, and Cermet Composites Probed Using In Situ Raman Spectroscopy, Advanced Science, Vol: 3, ISSN: 2198-3844
The redox properties of gadolinium doped ceria (CGO) and nickel oxide (NiO) composite cermets underpin the operation of solid oxide electrochemical cells. Although these systems have been widely studied, a full comprehension of the reaction dynamics at the interface of these materials is lacking. Here, in situ Raman spectroscopic monitoring of the redox cycle is used to investigate the interplay between the dynamic and competing processes of hydrogen spillover and water dissociation on the doped ceria surface. In order to elucidate these mechanisms, the redox process in pure CGO and NiO is studied when exposed to wet and dry hydrogen and is compared to the cermet behavior. In dry hydrogen, CGO reduces relatively rapidly via a series of intermediate phases, while NiO reduces via a single-step process. In wet reducing atmospheres, however, the oxidation state of pure CGO is initially stabilized due to the dissociation of water by reduced Ce(III) and subsequent incorporation of oxygen into the structure. In the reduction process involving the composite cermet, the close proximity of the NiO improves the efficiency and speed of the composite reduction process. Although NiO is already incorporated into working cells, these observations suggest direct routes to further improve cell performance.
Chen Z, Wang X, Atkinson A, et al., 2016, Spherical Indentation of Porous Ceramics: Elasticity and Hardness, Journal of the European Ceramic Society, Vol: 36, Pages: 1435-1445, ISSN: 1873-619X
A combined experimental and numerical approach is used to characterise the elastic and plastic deformation of a porous bulk ceramic material (La0.6Sr0.4Co0.2Fe0.8O3, LSCF) with porosities in the range 5–45 vol%, undergoing spherical indentation. The Gurson model was used in FEM simulations to describe the densification of the porous material in the plastic zone under the indenter. The simulated indentation response curves, extracted elastic modulus, hardness and densification in the plastic zone all showed good agreement with corresponding experimental observations. The results show that the hardness increases with maximum indentation depth over a representative depth that depends on porosity. In this particular ceramic the hardness, at sufficiently large penetration depth, is approximately 1.7 times the uniaxial yield stress of the porous material.
Wu B, Merla Y, Yufit V, et al., 2016, Novel application of differential thermal voltammetry as an in-depth state-of-health diagnosis method for lithium-ion batteries, Journal of Power Sources, Vol: 307, Pages: 308-319, ISSN: 1873-2755
Understanding and tracking battery degradation mechanisms and adapting its operation have become a necessity in order to enhance battery durability. A novel use of differential thermal voltammetry (DTV) is presented as an in-situ state-of-health (SOH) estimator for lithium-ion batteries.Accelerated ageing experiments were carried on 5Ah commercial lithium-ion polymer cells operated and stored at different temperature and loading conditions. The cells were analysed regularly with various existing in-situ diagnosis methods and the novel DTV technique to determine their SOH. The diagnosis results were used collectively to elaborate the degradation mechanisms inside the cells. The DTV spectra were decoupled into individual peaks, which each represent particular phases in the negative and positive electrode combined. The peak parameters were used to quantitatively analyse the battery SOH.A different cell of the same chemistry with unknown degradation history was then analysed to explore how the cell degraded. The DTV technique was able to diagnose the cell degradation without relying on supporting results from other methods nor previous cycling data.
Millan M, Lorente E, Boldrin P, et al., 2016, Integration of gasification and fuel cells: Interaction between the anode and contaminants in the syngas
© 2016 International Pittsburgh Coal Conference. All rights reserved. Fouling due to carbon deposition on the fuel cell anode reduces the performance of the cell. • The addition of steam above S/C of 1 was found to reduce carbon deposition from tars but not fully suppress coke formation. • A combination of high S/C=ratio and current density may effectively inhibit carbon formation, maintaining cell performance. • Benzene and toluene represent a "worst-case scenario" as tar models and light fractions are more likely to produce carbon deposits.
Samsatli S, Ramos A, Matchett M, et al., 2016, Whole-Systems Modelling of Alternatives for Future Domestic Transport, Editors: Kravanja, Bogataj, Publisher: ELSEVIER SCIENCE BV, Pages: 457-462
Torija S, Castillo-Castillo A, Brandon NP, 2015, The prospects for biogas integration with fuel cells in the United Kingdom, Fuel Cells, Vol: 16, Pages: 55-79, ISSN: 1615-6854
Anaerobic digestion (AD) presence is emerging in the UK because it has numerous environmental benefits as a waste management strategy and produces valuable biogas. This work shows that up to 5.5% of UK primary energy could be met by biogas, representing 14.4% of gas consumption. Fuel cells (FCs) are the most efficient and environmentally benign energy convertor of any device of equivalent scale and in addition are well suited for biogas utilization, which has worldwide led to the emergence of numerous integrated commercial applications. Thus, biogas coupling with fuel cells is proposed as a unique and virtuous AD scheme. A techno-economic model has been developed for the two types of AD plants with the highest development prospects in the UK, namely livestock and food waste plants, whose performance and feasibility at different scales are scrutinized under several policy scenarios, some of which incorporate supportive mechanisms for the introduction of FCs. Results confirm that conventional AD projects can already be profitable in the current market environment, while projects involving FCs proved environmentally superior, virtually suppressing harmful pollutant emissions and decreasing the CO2 emissions from using grid electricity and natural gas, at a reasonable avoided carbon cost in the best suited cases.
Kishimoto M, Lomberg M, Ruiz-Trejo E, et al., 2015, Numerical modeling of nickel-infiltrated gadolinium-doped ceria electrodes reconstructed with focused ion beam tomography, Electrochimica Acta, Vol: 190, Pages: 178-185, ISSN: 1873-3859
A one-dimensional numerical model of a nickel-infiltrated gadolinium-doped ceria (Ni-GDC) electrode has been developed to investigate the effects of electrode microstructure on performance. Electrode microstructural information was obtained with focused ion beam tomography and microstructural parameters were quantified, such as tortuosity factor, surface area and particle/pore sizes. These have been used to estimate the effective transport coefficients and the electrochemical reaction rate in the electrodes. GDC was considered as a mixed ionic and electronic conductor and hence the electrochemical reaction is assumed to occur on the GDC-pore contact surface, i.e. double-phase boundaries (DPBs). Sensitivity analysis was conducted to investigate the effect of electrode microstructure on both transport properties and electrochemical activity, including the effect of DPB density, GDC tortuosity factor and pore size. The developed model offers a basis to understand the microstructure-performance relationships and to further optimize the electrode microstructures.
Patsios C, Wu B, Chatzinikolaou E, et al., 2015, An integrated approach for the analysis and control of grid connected energy storage systems, Journal of Energy Storage, Vol: 5, Pages: 48-61, ISSN: 2352-152X
This paper presents an integrated modelling methodology which includes reduced-order models of alithium ion battery and a power electronic converter, connected to a 35-bus distribution network model.The literature contains many examples of isolated modelling of individual energy storage mediums,power electronic interfaces and control algorithms for energy storage. However, when assessing theperformance of a complete energy storage system, the interaction between components gives rise to arange of phenomena that are difficultto quantify if studied in isolation. This paper proposes an integratedelectro–thermo–chemical modelling methodology that seeks to address this problem directly byintegrating reduced-order models of battery cell chemistry, power electronic circuits and grid operationinto a computationally efficient framework. The framework is capable of simulation speeds over100 times faster than real-time and captures phenomena typically not observed in simpler battery andpower converter models or non-integrated frameworks. All simulations are performed using real systemload profiles recorded in the United Kingdom. To illustrate the advantages inherent in such a modellingapproach, two specific interconnected effects are investigated: the effect of the choice of battery floatstate-of-charge on overall system efficiency and the rate of battery degradation (capacity/power fade).Higher state-of-charge operation offers improved efficiency due to lower polarisation losses of thebattery and lower losses in the converter, however, an increase in the rate of battery degradation isobserved due to the accelerated growth of the solid-electrolyte interphase layer. We demonstrate thatgrid control objectives can be met in several different ways, but that the choices made can result in asubstantial improvement in system roundtrip efficiency, with up to a 43% reduction in losses, orreduction in battery degradation by a factor of two, depending on battery system use ca
Bahadori L, Chakrabarti MH, Manan NSA, et al., 2015, The effect of temperature on kinetics and diffusion coefficients of metallocene derivatives in polyol-based deep eutectic solvents, PLOS One, Vol: 10, ISSN: 1932-6203
The temperature dependence of the density, dynamic viscosity and ionic conductivity of several deep eutectic solvents (DESs) containing ammonium-based salts and hydrogen bond donvnors (polyol type) are investigated. The temperature-dependent electrolyte viscosity as a function of molar conductivity is correlated by means of Walden’s rule. The oxidation of ferrocene (Fc/Fc+) and reduction of cobaltocenium (Cc+/Cc) at different temperatures are studied by cyclic voltammetry and potential-step chronoamperometry in DESs. For most DESs, chronoamperometric transients are demonstrated to fit an Arrhenius-type relation to give activation energies for the diffusion of redox couples at different temperatures. The temperature dependence of the measured conductivities of DES1 and DES2 are better correlated with the Vogel-Tamman-Fulcher equation. The kinetics of the Fc/Fc+ and Cc+/Cc electrochemical systems have been investigated over a temperature range from 298 to 338 K. The heterogeneous electron transfer rate constant is then calculated at different temperatures by means of a logarithmic analysis. The glycerol-based DES (DES5) appears suitable for further testing in electrochemical energy storage devices.
Dewage HH, Yufit V, Brandon NP, 2015, Study of Loss Mechanisms Using Half-Cell Measurements in a Regenerative Hydrogen Vanadium Fuel Cell, Journal of the Electrochemical Society, Vol: 163, Pages: A5236-A5243, ISSN: 0013-4651
The positioning of reference electrodes in redox flow batteries without disturbing the cell operation represents a great challenge. However decoupling anode and cathode processes is crucial in order to fully understand the losses in the system so it can be further optimized. The feasibility of a regenerative fuel cell based on an V(IV)/V(V) electrolyte and hydrogen gas has previously been demonstrated. In this investigation, using electrochemical impedance spectroscopy, the various losses of the cathode, anode and whole cell were established using an alternative reference electrode set-up. The findings showed that the largest irreversible losses under the conditions tested arose from diffusion limitations in the cathode and the effect of vanadium crossover and therefore adsorption onto the platinum layer of the hydrogen electrode leading to higher losses on the anode. These results highlight the potential for further improvement and optimization of cell design and materials for both electrodes in the Regenerative Hydrogen Vanadium Fuel Cell.
Tonekabonimoghadam S, Akikur RK, Hussain MA, et al., 2015, Mathematical modelling and experimental validation of an anode-supported tubular solid oxide fuel cell for heat and power generation, ENERGY, Vol: 90, Pages: 1759-1768, ISSN: 0360-5442
Balcombe P, Anderson K, Speirs J, et al., 2015, Methane and CO2 emissions from the natural gas supply chain: an evidence assessment, Publisher: Sustainable Gas Institute
Chakrabarti MH, Manan NSA, Brandon NP, et al., 2015, One-pot electrochemical gram-scale synthesis of graphene using deep eutectic solvents and acetonitrile, CHEMICAL ENGINEERING JOURNAL, Vol: 274, Pages: 213-223, ISSN: 1385-8947
Lomberg M, Boldrin P, Tariq F, et al., 2015, Additive manufacturing for solid oxide cell electrode fabrication, ECS Conference on Electrochemical Energy Conversion & Storage with SOFC-XIV, Publisher: Electrochemical Society, Pages: 2119-2127, ISSN: 1938-6737
Additive manufacturing can potentially offer a highly-defined electrode microstructure, as well as fast and reproducible electrode fabrication. Selective laser sintering is an additive manufacturing technique in which three-dimensional structures are created by bonding subsequent layers of powder using a laser. Although selective laser sintering can be applied to a wide range of materials, including metals and ceramics, the scientific and technical aspects of the manufacturing parameters and their impact on microstructural evolution during the process are not well understood. In the present study, a novel approach for electrode fabrication using selective laser sintering was evaluated by conducting a proof of concept study. A Ni-patterned fuel electrode was laser sintered on an yttria-stabilized zirconia substrate. The optimization process of laser parameters (laser sintering rate and laser power) and the electrochemical results of a full cell with a laser sintered electrode are presented. The challenges and prospects of using selective laser sintering for solid oxide cell fabrication are discussed.
Boldrin P, Ruiz Trejo E, Tighe C, et al., 2015, Impregnation of nanoparticle scaffolds for syngas-fed solid oxide fuel cell anodes, ECS Conference on Electrochemical Energy Conversion & Storage with SOFC-XIV, Publisher: Electrochemical Society, Pages: 1219-1227, ISSN: 1938-6737
A strategy for fabrication of solid oxide fuel cell anodes with improved porosity and lower sintering temperatures by impregnation of nanoparticle-containing porous scaffolds of ceria-gadolinia (CGO) has been developed. The CGO scaffolds are fabricated using a screen-printed ink containing nanoparticles and commercial particles of CGO and polymeric pore formers. Scanning electron microscopy and in situ ultra-small angle X-ray scattering show that incorporation of nanoparticles increases the porosity by allowing a reduction in sintering temperature. Electrochemical characterisation of symmetrical cells shows that the cells sintered at 1000°C possess similar electrode polarisation compared to those sintered at 1300°C. Button cell testing showed that reducing the sintering temperature produced cells which perform better at 700°C and below in hydrogen, and performed better at all temperatures using syngas. This approach has the potential to allow the use of a wider range of nanomaterials, giving a finer control over microstructure.
Mazur CM, Brandon, Offer, et al., 2015, Understanding the drivers of fleet emission reduction activities of the German car manufacturers, Environmental Innovation and Societal Transitions, Vol: 16, Pages: 3-21, ISSN: 2210-4224
The current mobility system, dominated by fossil fuel poweredautomobiles, is under increasing pressure due to its environmentalimpact. To address this issue there is a need for a transitionof the system towards one that is more sustainable, including theintroduction of car technologies that allow a decrease in fuel consumptionand the substitution of fossil fuels as primary energysource. Due to the stability of the current automotive industryand the dominance of the internal combustion engine technology,it is expected that the incumbent firms and their activities willplay a crucial role in the transition. Policy makers have thereforeintroduced a variety of policies to encourage the industry to providesuitable solutions.We have conducted amicro-level analysis of howthe threemain German carmanufacturers have changed their activitiesin the field of low emission vehicle technologies in response tonational/international events and policy making. Our analysis suggeststhat policy makers only have limited influence on the typeof disruptive solution that is chosen by these individual companiesand that activities related to solutions that were not familiar to theindividual car manufacturer were mainly induced by internal or external champions. Still, while the existence of regulatory policiesallowed such activities to succeed, on its own it only encouraged theindustry to work on incremental solutions based upon the knowledgealready possessed.
Green RJ, staffell I, Hamilton IG, 2015, The residential energy sector, Domestic Microgeneration Renewable and Distributed Energy Technologies, Policies and Economics, Editors: Staffell, Brandon, Hawkes, Brett, Publisher: Routledge, Pages: 18-48, ISBN: 9781317448853
1 Overview Whilst the primary use of microgeneration is to service the energy demands of a building or a community, microgeneration technologies could also play a role in wider energy networks such as communal heating schemes or (more ...
Bahadori L, Chakrabarti MH, Hashim MA, et al., 2015, Temperature Effects on the Kinetics of Ferrocene and Cobaltocenium in Methyltriphenylphosphonium Bromide Based Deep Eutectic Solvents, Journal of the Electrochemical Society, Vol: 162, Pages: H617-H624, ISSN: 0013-4651
The oxidation of ferrocene (Fc/Fc+) and reduction of cobaltocenium (Cc+/Cc) under different temperatures has been studied by cyclic voltammetry and double potential step chronoamperometry in deep eutectic solvents (DESs) consisting of methyltriphenylphosphonium bromide salt with tri-ethylene glycol, glycerol or ethylene glycol as hydrogen bond donors. The temperature dependence of the measured physical properties of DESs (such as viscosity and conductivity) is discussed in detail. The kinetics of the redox couples are studied using cyclic voltammetry, and the standard heterogeneous electron transfer rate constant, k0 is found to be of the order of 10−5 to 10−4 cms−1 at different temperatures. The diffusion coefficient, D, of Fc and Cc+ is determined to lie between 8.28 × 10−10 to 6.65 × 10−9 cm2 s−1. These results show that both k0 and D increase with temperature in the studied DESs. In addition, better kinetic parameters for the DES with ethylene glycol as hydrogen bond donor means that this could be evaluated favorably as both solvents and electrolytes for redox flow cells.
Duboviks V, Lomberg M, Maher RC, et al., 2015, Carbon deposition behaviour in metal-infiltrated gadolinia doped ceria electrodes for simulated biogas upgrading in solid oxide electrolysis cells, Journal of Power Sources, Vol: 293, Pages: 912-921, ISSN: 1873-2755
One of the attractive applications for reversible Solid Oxide Cells (SOCs) is to convert CO2 into CO via high temperature electrolysis, which is particularly important for biogas upgrading. To improve biogas utility, the CO2 component can be converted into fuel via electrolysis. A significant issue for SOC operation on biogas is carbon-induced catalyst deactivation. Nickel is widely used in SOC electrodes for reasons of cost and performance, but it has a low tolerance to carbon deposition. Two different modes of carbon formation on Ni-based electrodes are proposed in the present work based on ex-situ Raman measurements which are in agreement with previous studies. While copper is known to be resistant towards carbon formation, two significant issues have prevented its application in SOC electrodes – namely its relatively low melting temperature, inhibiting high temperature sintering, and low catalytic activity for hydrogen oxidation. In this study, the electrodes were prepared through a low temperature metal infiltration technique. Since the metal infiltration technique avoids high sintering temperatures, Cu–Ce0.9Gd0.1O2−δ (Cu-CGO) electrodes were fabricated and tested as an alternative to Ni-CGO electrodes. We demonstrate that the performance of Cu-CGO electrodes is equivalent to Ni-CGO electrodes, whilst carbon formation is fully suppressed when operated on biogas mixture.
Parkes MA, Refson K, d'Avezac M, et al., 2015, Chemical descriptors of yttria-stabilized zirconia at low defect concentration: an ab initio study., Journal of Physical Chemistry A, Vol: 119, Pages: 6412-6420, ISSN: 1520-5215
Yttria-stabilized zirconia (YSZ) is an important oxide ion conductor with applications in solid oxide fuel cells (SOFCs) and oxygen sensing devices. Doping the cubic phase of zirconia (c-ZrO2) with yttria (Y2O3) is isoelectronic, as two Zr(4+) ions are replaced by two Y(3+) ions, plus a charge compensating oxygen vacancy (Ovac). Typical doping concentrations include 3, 8, 10, and 12 mol %. For these concentrations, and all below 40 mol %, no phase with long-range order has been observed in either X-ray or neutron diffraction experiments. The prediction of local defect structure and the interaction between defects is therefore of great interest. This has not been possible to date as the number of possible defect topologies is very large and to perform reliable total energy calculations for all of them would be prohibitively expensive. Previous theoretical studies have only considered a selection of representative structures. In this study, a comprehensive search for low-energy defect structures using a combined classical modeling and density functional theory approach is used to identify the low-energy isolated defect structures at the dilute limit, 3.2 mol %. Through analysis of energetics computed using the best available Born-Mayer-Huggins empirical potential model, a point charge model, DFT, and a local strain energy estimated in the harmonic approximation, the main chemical and physical descriptors that correlate to the low-energy DFT structures are discussed. It is found that the empirical potential model reproduces a general trend of increasing DFT energetics across a series of locally strain relaxed structures but is unreliable both in predicting some incorrect low-energy structures and in finding some metastable structures to be unstable. A better predictor of low-energy defect structures is found to be the total electrostatic energy of a simple point charge model calculated at the unrelaxed geometries of the defects. In addition, the strain relaxation energ
Teng F, Pudjianto D, Strbac G, et al., 2015, Potential value of energy storage in the UK electricity system, Proceedings of the ICE - Energy, Vol: 168, Pages: 107-117, ISSN: 1751-4223
This paper assesses the value of distributed energy storage and informs the business case for its multiple applications in the UK electricity system. In contrast to earlier studies that focus on the benefits of energy storage for system operation and development, this work analyses the value that it may deliver to the owner. For this purpose, three models are proposed and applied to analyse the benefit of energy storage with applications in energy and ancillary service markets, revenue maximisation in the context of feed-in tariffs and reduction of carbon dioxide emissions. A large set of studies is carried out to quantify the commercial and emissions benefits of energy storage for those applications. Sensitivity analysis across various scenarios is performed to understand the key drivers for the value of energy storage and how it is affected by energy storage parameters and other factors such as network constraints, prices of energy and ancillary services, and inherent energy system characteristics. A review of current and near-term storage technology costs and functionality is also presented.
Rhazaoui K, Cai Q, Kishimoto M, et al., 2015, Towards the 3D Modelling of the Effective Conductivity of Solid Oxide Fuel Cell Electrodes - Validation against experimental measurements and prediction of electrochemical performance, Electrochimica Acta, Vol: 168, Pages: 139-147, ISSN: 1873-3859
The effective conductivity of thick-film solid oxide fuel cell (SOFC) electrodes plays a key role in their performance. It determines the ability of the electrode to transport charge to/from reaction sites to the current collector and electrolyte. In this paper, the validity of the recently proposed 3D resistor network model for the prediction of effective conductivity, the ResNet model, is investigated by comparison to experimental data. The 3D microstructures of Ni/10ScSZ anodes are reconstructed using tomography through the focused ion beam and scanning electron microscopy (FIB-SEM) technique. This is used as geometric input to the ResNet model to predict the effective conductivities, which are then compared against the experimentally measured values on the same electrodes. Good agreement is observed, supporting the validity of the ResNet model for predicting the effective conductivity of SOFC electrodes. The ResNet model is then combined with the volume-of-fluid (VOF) method to integrate the description of the local conductivity (electronic and ionic) in the prediction of electrochemical performance. The results show that the electrochemical performance is in particular sensitive to the ionic conductivity of the electrode microstructure, highlighting the importance of an accurate description of the local ionic conductivity.
Hewa Dewage HARINI, wu BILLY, Tsoi ANTHONY, et al., 2015, A novel regenerative hydrogen cerium fuel cell for energy storage applications, Journal of Materials Chemistry A, Vol: 3, Pages: 9446-9450, ISSN: 2050-7496
A novel regenerative hydrogen cerium fuel cell is presented which has the potential to deliver both low cost and high performance. A 5 cm2 prototype is demonstrated, achieving 148 mW cm−2 when fully charged. Rate determining processes within the cell are identified.
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