Imperial College London

Professor Nigel Brandon OBE FREng

Faculty of Engineering

Dean of the Faculty of Engineering
 
 
 
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Contact

 

+44 (0)20 7594 8600n.brandon Website

 
 
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Location

 

2.06Faculty BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

412 results found

Gadoue S, Chen K-W, Mitcheson P, Yufit V, Brandon Net al., 2018, Electrochemical Impedance Spectroscopy State of Charge Measurement for Batteries using Power Converter Modulation, 9th International Renewable Energy Congress (IREC), Publisher: IEEE, ISSN: 2378-3435

Conference paper

Chen X, Liu X, Childs P, Brandon N, Wu Bet al., 2018, Design and fabrication of a low cost desktop electrochemical 3D printer, Pro-AM Conference in 2014, Pages: 395-400, ISSN: 2424-8967

Copyright © 2018 by Nanyang Technological University. Additive manufacturing (AM) (3D printing) is the process of creating 3D objects from digital models through the layer by layer deposition of materials. Electrochemical additive manufacturing (ECAM) is a relatively new technique which can create metallic components based depositing adherent layers of metal ions onto the surface of conductive substrate. In this paper, the design considerations for a meniscus confined ECAM approach is presented which demonstrates superior print speeds to equivalent works. This is achieved through the increase of the meniscus diameter to 400 \im which was achieved through the integration of a porous sponge into the print head to balance the hydraulic head of the electrolyte. Other piston based methods of controlling the electrolyte meniscus are discussed.

Conference paper

Speirs JF, balcombe P, johnson E, martin J, brandon N, hawkes Aet al., 2018, A Greener Gas Grid: What Are the Options?, Energy Policy, Vol: 118, Pages: 291-297, ISSN: 0301-4215

There is an ongoing debate over future decarbonisation of gas networks using biomethane, and increasingly hydrogen, in gas network infrastructure. Some emerging research presents gas network decarbonisation options as a tractable alternative to ‘all-electric’ scenarios that use electric appliances to deliver the traditional gas services such as heating and cooking. However, there is some uncertainty as to the technical feasibility, cost and carbon emissions of gas network decarbonisation options. In response to this debate the Sustainable Gas Institute at Imperial College London has conducted a rigorous systematic review of the evidence surrounding gas network decarbonisation options. The study focuses on the technologies used to generate biomethane and hydrogen, and examines the technical potentials, economic costs and emissions associated with the full supply chains involved. The following summarises the main findings of this research. The report concludes that there are a number of options that could significantly decarbonise the gas network, and doing so would provide energy system flexibility utilising existing assets. However, these options will be more expensive than the existing gas system, and the GHG intensity of these options may vary significantly. In addition, more research is required, particularly in relation to the capabilities of existing pipework to transport hydrogen safely.

Journal article

Liu X, Naylor Marlow M, Cooper S, Song B, Chen X, Brandon N, Wu Bet al., 2018, Flexible all-fiber electrospun supercapacitor, Journal of Power Sources, Vol: 384, Pages: 264-269, ISSN: 0378-7753

We present an all-fiber flexible supercapacitor with composite nanofiber electrodes made via electrospinning and an electrospun separator. With the addition of manganese acetylacetonate (MnACAC) to polyacrylonitrile (PAN) as a precursor for the electrospinning process and subsequent heat treatment, the performance of pure PAN supercapacitors was improved from 90 F.g-1 to 200 F.g-1 (2.5 mV.s-1) with possible mass loadings of MnACAC demonstrated as high as 40 wt%. X-ray diffraction measurements showed that after thermal treatment, the MnACAC was converted to MnO, meanwile, the thermal decomposition of MnACAC increased the graphitic degree of the carbonised PAN. Scanning electron microscopy and image processing showed that static electrospinning of pure PAN and PAN-Mn resulted in fiber diameters of 460 nm and 480 nm respectively after carbonisation. Further analysis showed that the fiber orientation exhibited a slight bias which was amplified with the addition of MnACAC. Use of focused ion beam scanning electron microscopy tomography also showed that MnO particles were evenly distributed through the fiber at low MnACAC concentrations, while at a 40 wt% loading the MnO particles were also visible on the surface. Comparison of the electrospun separators showed improved performance relative to a commercial Celgard separator (200 F.g-1 vs 141 F.g-1).

Journal article

Mazur CM, Offer G, Contestabile MSM, Brandon Net al., 2018, Comparing the effects of vehicle automation, policy making and changed user preferences on the uptake of electric cars and emissions from transport, Sustainability, Vol: 10, ISSN: 2071-1050

Switching energy demand for transport from liquid fuels to electricity is the most promising way to significantly improve air quality and reduce transport emissions. Previous studies have shown this is possible, that by 2035 the economics of alternative powertrain and energy vectors will have converged. However, they don’t address if the transition is likely or plausible. Using the UK as a case study, we present a systems dynamics model based study informed by transition theory and explore the effects of technology progress, policy making, user preferences and; for the first time, automated vehicles on this transition. We are not trying to predict the future, but to highlight what is necessary in order for different scenarios to become more or less likely. Worryingly we show that current policies with the expected technology progress and expectations of vehicle buyers are insufficient to reach global targets. Faster technology progress, strong financial incentives or a change in vehicle buyer expectations are crucial, but still insufficient. In contrast the biggest switch to alternatively fuelled vehicles could be achieved by the introduction of automated vehicles. The implications will affect policy makers, automotive manufactures, technology developers and broader society.

Journal article

Hack J, Heenan TMM, Iacoviello F, Mansor N, Meyer Q, Shearing P, Brandon N, Brett DJLet al., 2018, A structure and durability comparison of membrane electrode assembly fabrication methods: self-assembled versus hot-pressed, Journal of The Electrochemical Society, Vol: 165, Pages: F3045-F3052, ISSN: 1945-7111

The most common means of fabricating membrane electrode assemblies (MEAs) for polymer electrolyte fuel cells (PEFCs) involves a hot-press step. The conditions used to perform the hot-press impacts the performance and durability of the fuel cell. However, the hot-press process is not essential for achieving operational MEAs and some practitioners dispense with the hot-press stage altogether by using a self-assembled approach. By performing the integration of the components in-situ during fuel cell assembly, there is the potential to lower the cost and time of manufacture. This study investigates the electrochemical performance and mechanical microstructure of MEAs that were either hot-pressed or self-assembled (non-hot-pressed) and compared at beginning-of-test (BOT) and end-of-test (EOT), following accelerated stress testing. Hot-pressed and self-assembled MEAs were found to show negligible difference in their performance and almost identical performance degradation. X-ray computed tomography (X-ray CT) showed distinct differences in the microstructure of the electrodes. In addition to a crack network in the catalyst layer, the self-assembled samples exhibit indentations that were not present in the hot-pressed sample. It was concluded that in-situ assembly of MEAs could be a suitable means of fabricating PEFC MEAs.

Journal article

Wang X, Chen Z, Atkinson A, Brandon Net al., 2018, Numerical study of solid oxide fuel cell contacting mechanics, Fuel Cells, Vol: 18, Pages: 42-50, ISSN: 1615-6846

Assembly of a planar solid oxide fuel cell (SOFC) or solid electrolyzer (SOE) stack involves the lamination of cells and interconnect plates under an applied load. In most designs a pattern of ribs on the interconnector makes contact with a porous ceramic current collector layer on the air side. These localized contacts are regions of increased stress on the cells and can cause damage if the stresses become too large. In this paper the mechanical response of an anode-supported cell to localized loads from interconnector ribs is simulated. The simulations show that the critical stress for initiating and propagating a crack in the electrolyte (∼300MPa for a 10 μm thick electrolyte) is reached when the interconnector displacement reaches 20 μm (after touching the cathode) with reduced support, or 30 μm when in an oxidized state. The difference is due to the lower stiffness of the reduced support. The residual compressive stress in the electrolyte layer has a major protective effect for the electrolyte. It is concluded that fracture is very unlikely for a geometrically perfect contact, but if the contact is non-uniform due to manufacturing variability in the contact plate or cell, local displacements >∼20 μm can be dangerous. The simulations are used in an example of contacting geometry optimization.

Journal article

Few SPM, Schmidt O, Offer GJ, Brandon N, Nelson J, Gambhir Aet al., 2018, Prospective improvements in cost and cycle life of off-grid lithium-ion battery packs: An analysis informed by expert elicitations, Energy Policy, Vol: 114, Pages: 578-590, ISSN: 0301-4215

This paper presents probabilistic estimates of the 2020 and 2030 cost and cycle life of lithium-ion battery (LiB) packs for off-grid stationary electricity storage made by leading battery experts from academia and industry, and insights on the role of public research and development (R&D) funding and other drivers in determining these. By 2020, experts expect developments to arise chiefly through engineering, manufacturing and incremental chemistry changes, and expect additional R&D funding to have little impact on cost. By 2030, experts indicate that more fundamental chemistry changes are possible, particularly under higher R&D funding scenarios, but are not inevitable. Experts suggest that significant improvements in cycle life (eg. doubling or greater) are more achievable than in cost, particularly by 2020, and that R&D could play a greater role in driving these. Experts expressed some concern, but had relatively little knowledge, of the environmental impact of LiBs. Analysis is conducted of the implications of prospective LiB improvements for the competitiveness of solar photovoltaic + LiB systems for off-grid electrification.

Journal article

Bertei A, Ruiz-Trejo E, Clematis D, Carpanese MP, Barbucci A, Nicolella C, Brandon Net al., 2018, A perspective on the role of the three-phase boundary in solid oxide fuel cell electrodes, Bulgarian Chemical Communications, Vol: 50, Pages: 31-38, ISSN: 0861-9808

© 2018 Bulgarian Academy of Sciences, Union of Chemists in Bulgaria. Within composite electrodes for solid oxide fuel cells (SOFCs), electrochemical reactions take place in the proximity of the so-called three-phase boundary (TPB), the contact perimeter where the electron-conducting, the ionconducting and the porous phases meet. Strictly speaking, the TPB is a line and efforts have been made to increase its length per unit of electrode volume in order to reduce the activation losses. In this communication, by integrating physically-based modelling, 3D tomography and electrochemical impedance spectroscopy (EIS), a renovated perspective on electrocatalysis in SOFCs is offered, showing that the electrochemical reactions take place within an extended region around the geometrical TPB line. Such an extended region is in the order of 4 nm in Ni/Sc0.2Zr0.9O 2 .1 (Ni/ScSZ) anodes while approaches hundreds of nanometres in La0.8Sr0.2MnO 3 -x/Y0.16Zr0.92O 2 .08 (LSM/YSZ) cathodes. These findings have significant implications for preventing the degradation of nanostructured anodes, which is due to the coarsening of the fractal roughness of Ni nanoparticles, as well as for the optimisation of composite cathodes, indicating that the adsorption and surface diffusion of oxygen limit the rate of the oxygen reduction reaction (ORR). In both anodes and cathodes, the results point out that the surface properties of the materials are key in determining the performance and lifetime of SOFC electrodes.

Journal article

Munoz CAP, Dewage HH, Yufit V, Brandon NPet al., 2017, A unit cell model of a regenerative hydrogen-vanadium fuel cell, Journal of The Electrochemical Society, Vol: 164, Pages: F1717-F1732, ISSN: 1945-7111

In this study, a time dependent model for a regenerative hydrogen-vanadium fuel cell is introduced. This lumped isothermal model is based on mass conservation and electrochemical kinetics, and it simulates the cell working potential considering the major ohmic resistances, a complete Butler–Volmer kinetics for the cathode overpotential and a Tafel–Volmer kinetics near mass-transport free conditions for the anode overpotential. Comparison of model simulations against experimental data was performed by using a 25 cm2 lab scale prototype operated in galvanostatic mode at different current density values (50−600Am−2). A complete Nernst equation derived from thermodynamic principles was fitted to open circuit potential data, enabling a global activity coefficient to be estimated. The model prediction of the cell potential of one single charge-discharge cycle at a current density of 400Am−2 was used to calibrate the model and a model validation was carried out against six additional data sets, which showed a reasonably good agreement between the model simulation of the cell potential and the experimental data with a Root Mean Square Error (RMSE) in the range of 0.3–6.1% and 1.3–8.8% for charge and discharge, respectively. The results for the evolution of species concentrations in the cathode and anode are presented for one data set. The proposed model permits study of the key factors that limit the performance of the system and is capable of converging to a meaningful solution relatively fast (s–min).

Journal article

Song B, Ruiz Trejo E, Bertei A, Brandon Net al., 2017, Quantification of the degradation of Ni-YSZ anodes upon redoxcycling, Journal of Power Sources, Vol: 374, Pages: 61-68, ISSN: 0378-7753

Ni-YSZ anodes for Solid Oxide Fuel Cells are vulnerable to microstructural damage during redox cycling leading to a decrease in the electrochemical performance. This study quantifies the microstructural changes as a function of redox cycles at 800 °C and associates it to the deterioration of the mechanical properties and polarisation resistance. A physically-based model is used to estimate the triple-phase boundary (TPB) length from impedance spectra, and satisfactorily matches the TPB length quantified by FIB-SEM tomography: within 20 redox cycles, the TPB density decreases from 4.63 μm−2 to 1.06 μm−2. Although the polarisation resistance increases by an order of magnitude after 20 cycles, after each re-reduction the electrode polarisation improves consistently due to the transient generation of Ni nanoparticles around the TPBs. Nonetheless, the long-term degradation overshadows this transient improvement due to the nickel agglomeration. In addition, FIB-SEM tomography reveals fractures along YSZ grain boundaries, Ni-YSZ detachment and increased porosity in the composite that lead to irreversible mechanical damage: the elastic modulus diminishes from 36.4 GPa to 20.2 GPa and the hardness from 0.40 GPa to 0.15 GPa. These results suggest that microstructural, mechanical and electrochemical properties are strongly interdependent in determining the degradation caused by redox cycling.

Journal article

Balcombe P, Brandon NP, Hawkes AD, 2017, Characterising the distribution of methane and carbon dioxide emissions from the natural gas supply chain, Journal of Cleaner Production, Vol: 172, Pages: 2019-2032, ISSN: 0959-6526

Methane and CO2 emissions from the natural gas supply chain have been shown to vary widely butthere is little understanding about the distribution of emissions across supply chain routes,processes, regions and operational practises. This study defines the distribution of total methaneand CO2 emissions from the natural gas supply chain, identifying the contribution from each stageand quantifying the effect of key parameters on emissions. The study uses recent high-resolutionemissions measurements with estimates of parameter distributions to build a probabilistic emissionsmodel for a variety of technological supply chain scenarios. The distribution of emissions resemblesa log-log-logistic distribution for most supply chain scenarios, indicating an extremely heavy tailedskew: median estimates which represent typical facilities are modest at 18 – 24 g CO2 eq./ MJ HHV,but mean estimates which account for the heavy tail are 22 – 107 g CO2 eq./ MJ HHV. To place thesevalues into context, emissions associated with natural gas combustion (e.g. for heat) areapproximately 55 g CO2/ MJ HHV. Thus, some supply chain scenarios are major contributors to totalgreenhouse gas emissions from natural gas. For methane-only emissions, median estimates are 0.8 –2.2% of total methane production, with mean emissions of 1.6 - 5.5%. The heavy tail distribution isthe signature of the disproportionately large emitting equipment known as super-emitters, whichappear at all stages of the supply chain. The study analyses the impact of different technologicaloptions and identifies a set of best technological option (BTO) scenarios. This suggests thatemissions-minimising technology can reduce supply chain emissions significantly, with this studyestimating median emissions of 0.9% of production. However, even with the emissions-minimisingtechnologies, evidence suggests that the influence of the super-emitters remains. Therefore,emissions-minimising technology is only part of the soluti

Journal article

Jing R, Wang M, Wang W, Brandon N, Li N, Chen J, Zhao Yet al., 2017, Economic and environmental multi-optimal design and dispatch of solid oxide fuel cell based CCHP system, Energy Conversion and Management, Vol: 154, Pages: 365-379, ISSN: 0196-8904

Combined cooling, heating and power system (CCHP) is an efficient alternative for building energy supply. Meanwhile, the advantages of high energy efficiency and low emission for solid oxide fuel cells (SOFCs) make the technology a promising prime mover for CCHP systems. In this study, a SOFC based CCHP system design and operation optimization model has been developed using the Mixed Integer Non-linear Programming (MINLP) approach. The model provides two capacity sizing options of the fixed size (user specified), and the optimal sizing. In the fixed size option, four dispatch strategies are considered, namely baseload, day/night, full-load, and electrical load following. In the optimal sizing option, the installed capacity of devices and the dispatch strategy are both optimized. Moreover, multi-objective optimizations are also conducted to optimize two conflicting objectives simultaneously by the Ɛ-constraint method. The optimal results are displayed by Pareto frontiers and the most desired solutions have been identified and verified by two decision-making approaches of LINMAP and TOPSIS. To make the model applicable to real world operation, novel constraints including part-load efficiency, equipment on/off, and numbers of start constraints are applied. Finally, the proposed model is applied to a case study of a hospital in Shanghai, China considering state-of-the-art technical specifications, time-of-use energy pricing, and emission factors. The results indicate environmental advantages of SOFC based CCHP system. Moreover, the levelized cost of energy (LCOE) identified by the proposed optimal design and dispatch model would be 0.17 $/kWh, which is lower than the conventional energy system.

Journal article

Riveros M, Guo M, van dam, Bustos-Turu G, Brandon Net al., 2017, Carbon Arbitrage with Stationary Batteries in the City of London, 27th European Symposium on Computer Aided Process Engineering, Publisher: Elsevier, Pages: 529-534, ISSN: 1570-7946

Stationary batteries could facilitate provision of carbon arbitrage services in cities. Such services offer a smart solution to integrate low-carbon energy technology into grid electricity supply and help tackle climate change. In this paper the environmental implications and overall profitability of this approach are assessed. A modelling framework has been developed to design an energy storage system with optimal capacity to maximise carbon savings. The City of London was used as a case study to demonstrate model applicability and analyse the potential effect of intermittent renewable energy sources in the supply system. The total savings obtained for the carbon arbitrage service were economically valorised using carbon market prices. In addition, a critical profitability thresholds for carbon trading prices are identified. Results show that this approach could bring environmental benefits depending on the carbon intensity of the grid, but that high carbon trading prices are required before it is economically feasible.

Conference paper

Jing R, Wang M, Brandon N, Zhao Yet al., 2017, Multi-criteria evaluation of solid oxide fuel cell based combined cooling heating and power (SOFC-CCHP) applications for public buildings in China, Energy, Vol: 141, Pages: 273-289, ISSN: 0360-5442

This study aims to evaluate the feasibility of solid oxide fuel cell based combined cooling heating and power (SOFC-CCHP) applications in public buildings of China from different perspectives. Operations of the natural gas fueled SOFC-CCHP systems for 20 years’ have been simulated for five categories of public buildings in five locations of China. Parallel simulations of combustion based CCHP systems and conventional system have been conducted for comparison. By single criterion assessment, SOFC-CCHP systems demonstrate outstanding performance on energy efficiency as well as reducing carbon emission, air pollution and human health damage cost. The levelized cost of energy (LCOE) turns out to be competitive with commercial electricity price, but a long payback period (SPP) has also been identified. To further assess the overall performance of SOFC-CCHP systems, a multi-criteria assessment model has been developed by combining the gray relational analysis (GRA) approach and the entropy-weighting method. The result indicates that hospital, hotel, and supermarket achieve more benefits than office and school; warmer regions rank slightly higher than colder regions. In addition, sensitivity analysis has been performed on SPP and LCOE. Overall, this paper provides theoretical guidance and evaluation approach for SOFC-CCHP demonstrations in China.

Journal article

Biton M, Tariq F, Yufit V, Chen Z, Brandon Net al., 2017, Integrating multi-length scale high resolution 3D imaging and modelling in the characterisation and identification of mechanical failure sites in electrochemical dendrites, Acta Materialia, Vol: 141, Pages: 39-46, ISSN: 1359-6454

The Zn-air battery system is attractive because of its potentially high power density, environmental compatibility and low-cost materials [1]. This paper is focused on understanding the degradation of Zn air batteries, in particular the evolution of Zn dendrites, one of the main degradation mechanisms. Complementary tomographic techniques allow the direct 3D imaging and characterisation of complex microstructures, including the observation and quantification of dendrite growth. Here we present results from 3D x-ray and FIB-SEM tomography of Zn dendrite formation in a zinc-air battery, down to resolutions of tens of nanometers, enabling analysis of complex micro-structures. This approach is shown to be effective in understanding how electrochemical dendrites grow, and demonstrates that tomography coupled with modelling can provide new insights into dendrite growth in electrochemical systems.

Journal article

Chen X, Liu X, Childs P, Brandon N, Wu Bet al., 2017, A low cost desktop electrochemical metal 3D printer, Advanced Materials Technologies, Vol: 2, ISSN: 2365-709X

Additive manufacturing (AM), or 3D printing as it is more commonly known, is the process of creating 3D objects from digital models through the sequential deposition of material in layers. Electrochemical 3D printing is a relatively new form of AM that creates metallic structures through electrochemical reduction of metal ions from solutions onto conductive substrates. The advantage of this process is that a wide range of materials and alloys can be deposited under ambient conditions without thermal damage and more importantly at low cost, as this does not require expensive laser optics or inert gas environments. Other advantages include the fact that this process can be both additive and subtractive through reversal of potential allowing for recycling of components through electrochemical dissolution. However, one main limitation of this technology is speed. Here, a novel electrochemical 3D printer design is proposed using a meniscus confinement approach which demonstrates deposition rates three orders of magnitude higher than equivalent systems due to improved mass transport characteristics afforded through a mechanical electrolyte entrainment mechanism. Printed copper structures exhibit a polycrystalline nature, with decreasing the grain size as the potential is increased resulting in a higher Vickers hardness and electronic resistivity.

Journal article

Brandon N, Hagen A, Dawson R, Bucheli Oet al., 2017, “Solid Oxide Fuel Cells, Electrolyzers and Reactors: From Development to Delivery – EFCF2016”, Fuel Cells, Vol: 17, Pages: 414-414, ISSN: 1615-6846

Journal article

Somalu MR, Muchtar A, Daud WRW, Brandon NPet al., 2017, Screen-printing inks for the fabrication of solid oxide fuel cell films: A review, RENEWABLE & SUSTAINABLE ENERGY REVIEWS, Vol: 75, Pages: 426-439, ISSN: 1364-0321

Journal article

Cooper SJ, Bertei A, Finegan DP, Brandon NPet al., 2017, Simulated impedance of diffusion in porous media, Electrochimica Acta, Vol: 251, Pages: 681-689, ISSN: 0013-4686

This paper describes the use of a frequency domain, finite-difference scheme to simulate the impedance spectra of diffusion in porous microstructures. Both open and closed systems are investigated for a range of ideal geometries, as well as some randomly generated synthetic volumes and tomographically derived microstructural data. In many cases, the spectra deviate significantly from the conventional Warburg-type elements typically used to represent diffusion in equivalent circuit analysis. A key finding is that certain microstructures show multiple peaks in the complex plane, which may be misinterpreted as separate electrochemical processes in real impedance data. This is relevant to battery electrode design as the techniques for nano-scale fabrication become more widespread. This simulation tool is provided as an open-source MatLab application and is freely available online as part of the TauFactor platform.

Journal article

Speirs J, Balcombe P, Johnson E, Martin J, Brandon N, Hawkes Aet al., 2017, A Greener Gas Grid: What Are the Options?, A greener gas grid: what are the options?

Report

Chen J, Bertei A, Ruiz-Trejo E, Atkinson A, Brandon NPet al., 2017, Characterization of Degradation in Nickel Impregnated Scandia-Stabilize Zirconia Electrodes during Isothermal Annealing, Journal of The Electrochemical Society, Vol: 164, Pages: F935-F943, ISSN: 1945-7111

This study investigates the stability of nickel-impregnated scandia-stabilize zirconia composite electrodes during isothermal annealing at temperatures from 600 to 950°C in a humidified hydrogen atmosphere (3 vol % water vapor). Typically an initial rapid degradation of the electrode during the first 17 h of annealing is revealed by both an increase in polarization resistance and a fall in electronic conductivity. Secondary electron images show a shift in nickel particle size toward larger values after 50 h of annealing. The declining electrochemical performance is hence attributed to nickel coarsening at elevated temperatures. Nickel coarsening has two microstructural effects: breaking up nickel percolation; and reducing the density of triple phase boundaries. Their impact on electrode area specific resistance is explored using a physical model of electrode performance which relates the macroscopic electrochemical performance to measurable microstructural parameters.

Journal article

Ruiz-Trejo E, Bertei A, Maserati A, Boldrin P, Brandon NPet al., 2017, Oxygen Reduction, Transport and Separation in Low Silver Content Scandia-Stabilized Zirconia Composites, Journal of The Electrochemical Society, Vol: 164, Pages: F3045-F3054, ISSN: 1945-7111

Dense composites of silver and Sc-stabilized ZrO2 (Ag-ScSZ) are manufactured from ScSZ sub-micrometric particles coated with silver using Tollens’ reagent. A composite with 8.6 vol % of silver exhibits metallic conductivity of 186 S cm−1 and oxygen flux of 0.014 μmol cm−2 s−1 at 600°C for a 1-mm thick membrane when used as a pressure-driven separation membrane between air and argon. To gain insight into the role of oxygen transport in Ag and ScSZ, a dense non-percolating sample (Ag 4.7 vol%) is analyzed by impedance spectroscopy and the transport of oxygen through both phases is modelled. Oxygen transport takes place in both silver and ScSZ but it is still dominated by transport in the ionic conductor and therefore a large volume fraction of the ion conductor is beneficial for the separation. The oxygen transport in the silver clusters inside the composite is dominated by diffusion of neutral species and not by the charge transfer reaction at the interface between ScSZ and Ag, yet small silver particles on the surface improve the reduction of oxygen. Oxygen reduction is highly promoted by silver on the surface and there are no limitations of charge transfer at the interface between silver and ScSZ.

Journal article

Bertei A, Ruiz Trejo E, Kareh K, Yufit V, Wang X, Tariq F, Brandon Net al., 2017, The fractal nature of the three-phase boundary: A heuristic approach to the degradation of nanostructured solid oxide fuel cell anodes, Nano Energy, Vol: 38, Pages: 526-536, ISSN: 2211-2855

Nickel/zirconia-based nanostructured electrodes for solid oxide fuel cells suffer from poor stability even at intermediate temperature. This study quantifies the electrochemical and microstructural degradation of nanostructured electrodes by combining 3D tomography, electrochemical impedance spectroscopy (EIS) and mechanistic modeling. For the first time, the electrochemical degradation of nanostructured electrodes is quantified according to the fractal nature of the three-phase boundary (TPB). Using this hypothesis an excellent match between modeling and the electrochemical response is found. The origin of the degradation in microstructure and electrochemical performance can be found in the initial fractal roughness of the TPB at a length scale not detectable with state-of-the-art tomography at 30 nm resolution. This additionally implies that the hydrogen electro-oxidation takes place within 4 nm from the geometric TPB line, revealing that the electrochemical reaction zone cannot be regarded anymore as a one-dimensional line when dealing with nanoparticles.

Journal article

Chen YA, Ji L, Brandon N, Xie M, Scott K, Du W, Yang J, Wu Xet al., 2017, A study on the flow field design of lead flow batteries, 10th International Conference on Lead-Acid Batteries, LABAT 2017, Pages: 199-200

Conference paper

Xie M, Chen Y, Li X, Brandon N, Wu Xet al., 2017, Influences of surfactant additives on performances of lead acid flow batteries, 10th International Conference on Lead-Acid Batteries, LABAT 2017, Pages: 121-122

Conference paper

Brandon NP, Kurban Z, 2017, Clean energy and the hydrogen economy, Philosophical Transactions of the Royal Society A. Mathematical, Physical and Engineering Sciences, Vol: 375, ISSN: 1364-503X

In recent years, new-found interest in the hydrogeneconomy from both industry and academia hashelped to shed light on its potential. Hydrogencan enable an energy revolution by providing muchneeded flexibility in renewable energy systems. Asa clean energy carrier, hydrogen offers a rangeof benefits for simultaneously decarbonizing thetransport, residential, commercial and industrialsectors. Hydrogen is shown here to have synergieswith other low-carbon alternatives, and can enablea more cost-effective transition to de-carbonizedand cleaner energy systems. This paper presentsthe opportunities for the use of hydrogen in keysectors of the economy and identifies the benefitsand challenges within the hydrogen supply chain forpower-to-gas, power-to-power and gas-to-gas supplypathways. While industry players have alreadystarted the market introduction of hydrogen fuelcell systems, including fuel cell electric vehicles andmicro-combined heat and power devices, the use ofhydrogen at grid scale requires the challenges of cleanhydrogen production, bulk storage and distribution tobe resolved. Ultimately, greater government support,in partnership with industry and academia, is stillneeded to realize hydrogen’s potential across alleconomic sectors.

Journal article

Chen Z, Wang X, Brandon N, Atkinson Aet al., 2017, Spherical indentation of bilayer ceramic structures: dense layer on porous substrate, Journal of the European Ceramic Society, Vol: 37, Pages: 4763-4772, ISSN: 1873-619X

Spherical indentation of thin 8YSZ ceramic layers on porous substrates (NiO/Ni-8YSZ) was studied. Indentation-induced elastic and plastic deformation and damage of the bilayer was experimentally analysed. FE simulations of the indentation process were carried out using the Gurson model to account for densification of the porous substrates. The simulated load-depth responses were in excellent agreement with the measured ones. The resulting stress distributions showed that the damage to the YSZ initiates in a tensile region near the interface due to bending during loading at a failure stress of ∼2 GPa, which is consistent with pores of ∼1 μm size seen in the YSZ. Delamination occurs on unloading due to the elastic recovery of YSZ being greater than that of the substrates at a de-bonding stress of 120 MPa. Residual compressive stress in the YSZ inhibits crack opening displacements normal to the layer plane which is beneficial for application of these structures in SOFCs.

Journal article

Ouyang M, Boldrin P, Brandon NP, 2017, Methane Pulse Study on Nickel Impregnated Gadolinium Doped Ceria, 15th International Symposium on Solid Oxide Fuel Cells (SOFC), Publisher: ELECTROCHEMICAL SOC INC, Pages: 1353-1366, ISSN: 1938-5862

Conference paper

Cooper SJ, brandon NP, 2017, Solid Oxide Fuel Cell Lifetime and Reliability, Solid Oxide Fuel Cell Lifetime and Reliability Critical Challenges in Fuel Cells, Editors: Ruiz-Trejo, BOLDRIN, Publisher: Academic Press, Pages: 1-15, ISBN: 9780128097243

For its holistic approach, this book can be used both as an introduction to these issues and a reference resource for all involved in research and application of solid oxide fuel cells, especially those developing understanding in ...

Book chapter

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