399 results found
Ouyang M, Boldrin P, Maher RC, et al., 2019, A mechanistic study of the interactions between methane and nickel supported on doped ceria, Applied Catalysis B: Environmental, Vol: 248, Pages: 332-340, ISSN: 0926-3373
© 2019 Elsevier B.V. A novel combined method using modified methane pulses and in-situ Raman spectroscopy together with mass spectrometry is applied to impregnated Ni/gadolinium-doped ceria (CGO). The partial oxidation of methane is deduced to proceed via a Mars-van-Krevelen type mechanism composed of initial methane decomposition together with carbon oxidation by oxygen from CGO. The critical role of the ceria surface and the bulk oxygen in the reaction is defined in detail. Oxygen is a necessary reactant in the reaction, as well as inhibiting carbon deposition. Oxygen spill-over is the driving force for the carbon oxidation and the ceria surface oxygen is resupplied by bulk oxygen after depletion. Bulk migration of oxygen to the surface is the rate-determining step. We also demonstrate that the ceria oxygen stoichiometry significantly affects the type of reaction and the rate of reaction between methane and Ni/CGO: The total oxidation of methane happens only when the oxygen stoichiometry is high while the oxygen spill-over rate decreases with decreasing oxygen stoichiometry, which reduces the rate of carbon elimination and results in reduction in the rate of methane oxidation. This work lays out a comprehensive evaluation methodology and provides important insights for future design of methane oxidation catalysts for solid oxide fuel cells, and more widely for methane reforming with different oxidants (steam, CO 2 , NO 2 etc).
Crow DJG, Balcombe P, Brandon N, et al., 2019, Assessing the impact of future greenhouse gas emissions from natural gas production, Science of the Total Environment, Vol: 668, Pages: 1242-1258, ISSN: 0048-9697
© 2019 Greenhouse gases (GHGs) produced by the extraction of natural gas are an important contributor to lifecycle emissions and account for a significant fraction of anthropogenic methane emissions in the USA. The timing as well as the magnitude of these emissions matters, as the short term climate warming impact of methane is up to 120 times that of CO 2 . This study uses estimates of CO 2 and methane emissions associated with different upstream operations to build a deterministic model of GHG emissions from conventional and unconventional gas fields as a function of time. By combining these emissions with a dynamic, techno-economic model of gas supply we assess their potential impact on the value of different types of project and identify stranded resources in various carbon price scenarios. We focus in particular on the effects of different emission metrics for methane, using the global warming potential (GWP) and the global temperature potential (GTP), with both fixed 20-year and 100-year CO 2 -equivalent values and in a time-dependent way based on a target year for climate stabilisation. We report a strong time dependence of emissions over the lifecycle of a typical field, and find that bringing forward the stabilisation year dramatically increases the importance of the methane contribution to these emissions. Using a commercial database of the remaining reserves of individual projects, we use our model to quantify future emissions resulting from the extraction of current US non-associated reserves. A carbon price of at least 400 USD/tonne CO 2 is effective in reducing cumulative GHGs by 30–60%, indicating that decarbonising the upstream component of the natural gas supply chain is achievable using carbon prices similar to those needed to decarbonise the energy system as a whole. Surprisingly, for large carbon prices, the choice of emission metric does not have a significant impact on cumulative emissions.
Song B, Bertei A, Wang X, et al., 2019, Unveiling the mechanisms of solid-state dewetting in Solid Oxide Cells with novel 2D electrodes, Journal of Power Sources, Vol: 420, Pages: 124-133, ISSN: 0378-7753
© 2019 The Authors During the operation of Solid Oxide Cell (SOC) fuel electrodes, the mobility of nickel can lead to significant changes in electrode morphology, with accompanying degradation in electrochemical performance. In this work, the dewetting of nickel films supported on yttria-stabilized zirconia (YSZ), hereafter called 2D cells, is studied by coupling in-situ environmental scanning electron microscopy (E-SEM), image analysis, cellular automata simulation and electrochemical impedance spectroscopy (EIS). Analysis of experimental E-SEM images shows that Ni dewetting causes an increase in active triple phase boundary (aTPB) length up to a maximum, after which a sharp decrease in aTPB occurs due to Ni de-percolation. This microstructural evolution is consistent with the EIS response, which shows a minimum in polarization resistance followed by a rapid electrochemical degradation. These results reveal that neither evaporation-condensation nor surface diffusion of Ni are the main mechanisms of dewetting at 560–800 °C. Rather, the energy barrier for pore nucleation within the dense Ni film appears to be the most important factor. This sheds light on the relevant mechanisms and interfaces that must be controlled to reduce the electrochemical degradation of SOC electrodes induced by Ni dewetting.
Chen X, Liu X, Ouyang M, et al., 2019, Multi-metal 4D printing with a desktop electrochemical 3D printer., Sci Rep, Vol: 9
4D printing has the potential to create complex 3D geometries which are able to react to environmental stimuli opening new design possibilities. However, the vast majority of 4D printing approaches use polymer based materials, which limits the operational temperature. Here, we present a novel multi-metal electrochemical 3D printer which is able to fabricate bimetallic geometries and through the selective deposition of different metals, temperature responsive behaviour can thus be programmed into the printed structure. The concept is demonstrated through a meniscus confined electrochemical 3D printing approach with a multi-print head design with nickel and copper used as exemplar systems but this is transferable to other deposition solutions. Improvements in deposition speed (34% (Cu)-85% (Ni)) are demonstrated with an electrospun nanofibre nib compared to a sponge based approach as the medium for providing hydrostatic back pressure to balance surface tension in order to form a electrolyte meniscus stable. Scanning electron microscopy, X-ray computed tomography and energy dispersive X-ray spectroscopy shows that bimetallic structures with a tightly bound interface can be created, however convex cross sections are created due to uneven current density. Analysis of the thermo-mechanical properties of the printed strips shows that mechanical deformations can be generated in Cu-Ni strips at temperatures up to 300 °C which is due to the thermal expansion coefficient mismatch generating internal stresses in the printed structures. Electrical conductivity measurements show that the bimetallic structures have a conductivity between those of nanocrystalline copper (5.41 × 106 S.m-1) and nickel (8.2 × 105 S.m-1). The potential of this novel low-cost multi-metal 3D printing approach is demonstrated with the thermal actuation of an electrical circuit and a range of self-assembling structures.
Yufit V, Tariq F, Eastwood DS, et al., 2019, Operando Visualization and Multi-scale Tomography Studies of Dendrite Formation and Dissolution in Zinc Batteries, JOULE, Vol: 3, Pages: 485-502, ISSN: 2542-4351
Trudgeon DP, Qiu K, Li X, et al., 2019, Screening of effective electrolyte additives for zinc-based redox flow battery systems, JOURNAL OF POWER SOURCES, Vol: 412, Pages: 44-54, ISSN: 0378-7753
Speirs J, Balcombe P, Blomerus P, et al., 2019, Can natural gas reduce emissions from transport?: Heavy goods vehicles and shipping
Electrochemical energy storage is a key enabling technology for further integration of renewables sources. Redox flow batteries (RFBs) are promising candidates for such applications as a result of their durability, efficiency and fast response. However, deployment of existing RFBs is hindered by the relatively high cost of the (typically vanadium-based) electrolyte. Manganese is an earth-abundant and inexpensive element that is widely used in disposable alkaline batteries. However it has hitherto been little explored for RFBs due to the instability of Mn(III) leading to precipitation of MnO2 via a disproportionation reaction. Here we show that by combining the facile hydrogen negative electrode reaction with electrolytes that suppress Mn(III) disproportionation, it is possible to construct a hydrogen/manganese hybrid RFB with high round trip energy efficiency (82%), and high power and energy density (1410 mW cm−2, 33 Wh l−1), at an estimated 70% cost reduction compared to vanadium redox flow batteries.
Budinis S, Krevor S, Mac Dowell N, et al., 2018, An assessment of CCS costs, barriers and potential, ENERGY STRATEGY REVIEWS, Vol: 22, Pages: 61-81, ISSN: 2211-467X
Balcombe P, Speirs JF, Brandon NP, et al., 2018, Methane emissions: choosing the right climate metric and time horizon, ENVIRONMENTAL SCIENCE-PROCESSES & IMPACTS, Vol: 20, Pages: 1323-1339, ISSN: 2050-7887
Crow DJG, Anderson K, Hawkes AD, et al., 2018, Impact of Drilling Costs on the US Gas Industry: Prospects for Automation, ENERGIES, Vol: 11, ISSN: 1996-1073
Zhang D, Cai Q, Taiwo OO, et al., 2018, The effect of wetting area in carbon paper electrode on the performance of vanadium redox flow batteries: A three-dimensional lattice Boltzmann study, ELECTROCHIMICA ACTA, Vol: 283, Pages: 1806-1819, ISSN: 0013-4686
Tariq F, Rubio-Garcia J, Yufit V, et al., 2018, Uncovering the mechanisms of electrolyte permeation in porous electrodes for redox flow batteries through real time in situ 3D imaging, SUSTAINABLE ENERGY & FUELS, Vol: 2, Pages: 2068-2080, ISSN: 2398-4902
Bertei A, Yufit V, Tariq F, et al., 2018, A novel approach for the quantification of inhomogeneous 3D current distribution in fuel cell electrodes, JOURNAL OF POWER SOURCES, Vol: 396, Pages: 246-256, ISSN: 0378-7753
Song B, Ruiz-Trejo E, Brandon NP, 2018, Enhanced mechanical stability of Ni-YSZ scaffold demonstrated by nanoindentation and Electrochemical Impedance Spectroscopy, JOURNAL OF POWER SOURCES, Vol: 395, Pages: 205-211, ISSN: 0378-7753
Balcombe P, Speirs J, Johnson E, et al., 2018, The carbon credentials of hydrogen gas networks and supply chains, RENEWABLE & SUSTAINABLE ENERGY REVIEWS, Vol: 91, Pages: 1077-1088, ISSN: 1364-0321
Mazur C, Offer GJ, Contestabile M, et 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
Few S, Schmidt O, Offer GJ, et 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
Chen Z, Wang X, Brandon N, et al., 2018, Numerical Study of Solid Oxide Fuel Cell Contacting Mechanics, FUEL CELLS, Vol: 18, Pages: 42-50, ISSN: 1615-6846
Balcombe P, Brandon NP, Hawkes AD, 2018, 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
Song B, Ruiz-Trejo E, Bertei A, et al., 2018, Quantification of the degradation of Ni-YSZ anodes upon redox cycling, JOURNAL OF POWER SOURCES, Vol: 374, Pages: 61-68, ISSN: 0378-7753
Hack J, Heenan TMM, Iacoviello F, et 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: 0013-4651
Chen X, Liu X, Childs P, et al., 2018, Design and fabrication of a low cost desktop electrochemical 3D printer, 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.
Bertei A, Ruiz-Trejo E, Clematis D, et 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.
Song W, Liu X, Wu B, et al., 2018, Sn@C evolution from yolk-shell to core-shell in carbon nanofibers with suppressed degradation of lithium storage, Energy Storage Materials
© 2018 Metallic Sn has high conductivity and high theoretical capacity for lithium storage but it suffers from severe volume change in lithiation/delithiation leading to capacity fade. Yolk-shell and core-shell Sn@C spheres interconnected by carbon nanofibers were synthesized by thermal vapor and thermal melting of electrospun nanofibers to improve the cycling stability. Sn particles in yolk-shell spheres undergo dynamic structure evolution during thermal melting to form core-shell spheres. The core-shell spheres linked along the carbon nanofibers show outstanding performance and are better than the yolk-shell system for lithium storage, with a high capacity retention of 91.8% after 1000 cycles at 1 A g -1 . The superior structure of core-shell spheres interconnected by carbon nanofibers has facile electron conductivity and short lithium ion diffusion pathways through the carbon nanofibers and shells, and re-develops Sn@C structures with Sn clusters embedded into carbon matrix during electrochemical cycling, enabling the high performance.
Liu X, Taiwo OO, Yin C, et al., 2018, Aligned Ionogel Electrolytes for High-Temperature Supercapacitors, Advanced Science
© 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Ionogels are a new class of promising materials for use in all-solid-state energy storage devices in which they can function as an integrated separator and electrolyte. However, their performance is limited by the presence of a crosslinking polymer, which is needed to improve the mechanical properties, but compromises their ionic conductivity. Here, directional freezing is used followed by a solvent replacement method to prepare aligned nanocomposite ionogels which exhibit enhanced ionic conductivity, good mechanical strength, and thermal stability simultaneously. The aligned ionogel based supercapacitor achieves a 29% higher specific capacitance (176 F g−1 at 25 °C and 1 A g−1) than an equivalent nonaligned form. Notably, this thermally stable aligned ionogel has a high ionic conductivity of 22.1 mS cm−1 and achieves a high specific capacitance of 167 F g−1 at 10 A g−1 and 200 °C. Furthermore, the diffusion simulations conducted on 3D reconstructed tomography images are employed to explain the improved conductivity in the relevant direction of the aligned structure compared to the nonaligned. This work demonstrates the synthesis, analysis, and use of aligned ionogels as supercapacitor separators and electrolytes, representing a promising direction for the development of wearable electronics coupled with image based process and simulations.
Gadoue S, Chen K-W, Mitcheson P, et 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
Jing R, Wang M, Wang W, et 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
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