412 results found
Chen X, Liu X, Ouyang M, et al., 2019, Multi-metal 4D printing with a desktop electrochemical 3D printer, Scientific Reports, Vol: 9, ISSN: 2045-2322
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.
Chen X, Liu X, Ouyang M, et al., 2019, Electrospun composite nanofibre supercapacitors enhanced with electrochemically 3D printed current collectors, Journal of Energy Storage, Vol: 26, Pages: 100993-100993, ISSN: 2352-152X
Carbonised electrospun nanofibres are attractive for supercapacitors due to their relatively high surface area, facile production routes and flexibility. With the addition of materials such as manganese oxide (MnO), the specific capacitance of the carbon nanofibres can be further improved through fast surface redox reactions, however this can reduce the electrical conductivity. In this work, electrochemical 3D printing is used as a novel means of improving electrical conductivity and the current collector-electrode interfacial resistance through the deposition of highly controlled layers of copper. Neat carbonised electrospun electrodes made with a 30 wt% manganese acetylacetonate (MnACAC) and polyacrylonitrile precursor solution have a hydrophobic nature preventing an even copper deposition. However, with an ethanol treatment, the nanofibre films can be made hydrophilic which enhances the copper deposition morphology to enable the formation of a percolating conductive network through the electrode. This has the impact of increasing electrode electronic conductivity by 360% from 10 S/m to 46 S/m and increasing specific capacitance 110% from 99 F/g to 208 F/g at 5 mV/s through increased utilisation of the pseudocapacitive active material. This novel approach thus provides a new route for performance enhancement of electrochemical devices using 3D printing, which opens new design possibilities.
Chakrabarti B, Yufit V, Kavei A, et al., 2019, Charge/discharge and cycling performance of flexible carbon paper electrodes in a regenerative hydrogen/vanadium fuel cell, International Journal of Hydrogen Energy, Vol: 44, Pages: 30093-30107, ISSN: 0360-3199
© 2019 Hydrogen Energy Publications LLC The regenerative hydrogen/vanadium fuel cell (RHVFC) is investigated with Freudenberg carbon paper electrodes (CPs). Along with thermal treatment, the Freudenberg CPs are also treated with reduced graphene oxide (rGO) using electrophoretic deposition at 300 V. The rGO modified CP results in 25% higher power density than its untreated counterpart under the same operating conditions. In comparison to the first preliminary study, the power density reported herein is more than four times higher. Additionally, the Freudenberg CPs modified with heat treatment followed by rGO deposition facing the membrane (rGOHTFM) provide the best electrolyte discharge utilization (UE) of 99%, followed by untreated (98%) and heat treated samples (97%) at 50 mA cm−2. The rGOHTFM also record high charge and discharge energy efficiencies (ηE) of 93% at the same current density, which is slightly higher than untreated CPs (ηE = 91%). Cycling the system 10 times also results in higher ηE and UE for rGOHTFM CP (ηE = 92% and UE = 99% on average) in comparison to untreated electrodes (ηE = 86% and UE = 97% on average). In comparison the widely investigated SGL 10AA CP has lower efficiencies and utilization as expected (ηE = 74% and UE = 83% on average).
Pino-Munoz CA, Chakrabarti BK, Yufit V, et al., 2019, Characterization of a Regenerative Hydrogen-Vanadium Fuel Cell Using an Experimentally Validated Unit Cell Model, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, Vol: 166, Pages: A3511-A3524, ISSN: 0013-4651
Chen J, Wang X, Boldrin P, et al., 2019, Hierarchical dual-porosity nanoscale nickel cermet electrode with high performance and stability, Nanoscale, Vol: 11, Pages: 17746-17758, ISSN: 2040-3364
Nano-structured metal-ceramic materials have attracted attention to improve performance in energy conversion applications. However, they have poor long-term stability at elevated temperatures due to coarsening of the metal nanoparticles. In this work we show that this can be mitigated by a novel design of the nano-structure of Ni cermet fuel electrodes for solid oxide cells. The strategy is to create a dual porosity microstructure, without the use of fugitive pore-formers, with micron-size pores to facilitate gas transport and nanoscale pores to control nano-particle coarsening. This has been achieved using a continuous hydrothermal synthesis and two-stage heat treatments to produce electrodes with micron size agglomerates of nano-structured porous Ni-Yttria-Stabilised-Zirconia (YSZ). This unique hierarchical microstructure combines enhanced electrochemical reaction in the high activity (triple phase boundary density 11 μm-2) nanoscale regions with faster gas diffusion in the micron-sized pores. The electrodes are aged at 800 °C in humidified 5% H2-N2 for up to 600 h. The electrochemical reaction resistance is initially 0.17 Ω cm2 but later reaches a steady long-term value of 0.15 Ω cm2. 3-D reconstruction of the electrodes after 10 h and 100 h of ageing reveals an increase in YSZ network connectivity and TPB percolation. This improvement is well-correlated to the 3-D tomography parameters using a physical model adapted from mixed conducting SOC air electrodes, which is also supported, for the first time, by numerical simulations of the microstructural evolution. These also reveal that in the long term, nickel coarsening is inhibited by the nanoscale entanglement of Ni and YSZ in the hierarchical microstructure.
Wang Y, Banerjee A, Wehrle L, et al., 2019, Performance analysis of a reversible solid oxide cell system based on multi-scale hierarchical solid oxide cell modelling, ENERGY CONVERSION AND MANAGEMENT, Vol: 196, Pages: 484-496, ISSN: 0196-8904
Lombardo AG, Simon BA, Taiwo O, et al., 2019, A pore network model of porous electrodes in electrochemical devices, JOURNAL OF ENERGY STORAGE, Vol: 24, ISSN: 2352-152X
Boldrin P, Brandon NP, 2019, Progress and outlook for solid oxide fuel cells for transportation applications, Nature Catalysis, Vol: 2, Pages: 571-577, ISSN: 2520-1158
With their high temperatures and brittle ceramic components, solid oxide fuel cells (SOFCs) might not seem the obvious fit for a power source for transportation applications. However, over recent years, advances in materials and cell design have begun to mitigate these issues, leading to the advantages of SOFCs such as fuel flexibility and high efficiency being exploited in vehicles. Here, we review these advances, look at the vehicles that SOFCs have already been used in, discuss the areas that need improvement for full commercial breakthrough and the ways in which catalysis can assist with these. In particular, we identify lifetime and degradation, fuel flexibility, efficiency and power density as key aspects for SOFCs’ improvement. Expertise from the catalysis landscape, ranging from surface science and computational materials design, to improvements in reforming catalysts and reformer design, are instrumental to this goal.
Chen J, Ouyang M, Boldrin P, et al., 2019, Fabrication and Characterisation of Nanoscale Ni-CGO Electrode from Nano-Composite Powders, ECS Transactions, Vol: 91, Pages: 1799-1805, ISSN: 1938-6737
Anderson K, Brandon N, Techno-economic analysis of thermoelectrics for waste heat recovery, ENERGY SOURCES PART B-ECONOMICS PLANNING AND POLICY, Vol: 14, Pages: 147-157, ISSN: 1556-7249
Ouyang M, Boldrin P, Maher R, 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
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, CO2, NO2 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
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
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 yttriastabilized zirconia (YSZ), hereafter called 2D cells, is studied by coupling in-situ environmentalscanning 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. Thismicrostructural 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.
Liu X, Taiwo O, Yin C, et al., 2019, Aligned lonogel electrolytes for high‐temperature supercapacitors, Advanced Science, Vol: 6, Pages: 1-7, ISSN: 2198-3844
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.
Song W, Liu X, Wu B, et al., 2019, Sn@C evolution from yolk-shell to core-shell in carbon nanofibers with suppressed degradation of lithium storage, Energy Storage Materials, Vol: 18, Pages: 229-237, ISSN: 2405-8297
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.
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
Yufit V, Tariq F, Biton M, et al., 2019, Operando visualisation and multi-scale tomography studies of dendrite formation and dissolution in zinc batteries, Joule, Vol: 3, Pages: 485-502, ISSN: 2542-4351
Alternative battery technologies are required to meet growing energy demands and address the limitations of present technologies. As such, it is necessary to look beyond lithium-ion batteries. Zinc batteries enable high power density while being sourced from ubiquitous and cost-effective materials. This paper presents, for the first time known to the authors, multi-length scale tomography studies of failure mechanisms in zinc batteries with and without commercial microporous separators. In both cases, dendrites were grown, dissolved, and regrown, critically resulting in different morphology of dendritic layer formed on both the electrode and the separator. The growth of dendrites and their volume-specific areas were quantified using tomography and radiography data in unprecedented resolution. High-resolution ex situ analysis was employed to characterize single dendrites and dendritic deposits inside the separator. The findings provide unique insights into mechanisms of metal-battery failure effected by growing dendrites.
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.
Stevenson GR, Boldrin P, Brandon NP, 2019, Liquid-based synthesis of nickel- And lanthanum- co-doped strontium titanates for use as anodes in all-ceramic solid oxide fuel cell anodes, Pages: 1761-1770, ISSN: 1938-6737
© The Electrochemical Society. Nickel- lanthanum- co-doped compositions of strontium titanate have been synthesized and characterized by a scaleable liquid-based synthesis that may offer an alternative to conventional solid-state synthesis. La0.52Sr0.28Ti0.94Ni0.06O3 is synthesized from soluble precursors followed by calcination in air. The materials can be made phase pure at temperatures as low as 1250°C, as highlighted by X-ray diffraction, and nickel exsolves in hydrogen in the same way as solid-state-synthesized materials. The particle size can be varied by calcination temperature and ball milling between 2 µm and 20 µm. The material is then measured electrochemically by electrochemical impedance spectroscopy and 4-point DC conductivity. A reduction in particle size from 20 µm to 9 µm results in a large improvement in impedance response measured.
Ouyang M, Bertei A, Cooper SJ, et al., 2019, Design of fibre Ni/CGO anode and model interpretation, ECS Transactions, Vol: 91, Pages: 1721-1739, ISSN: 1938-6737
© The Electrochemical Society. A new structure of Ni/gadolinium-doped ceria (CGO) is prepared by a highly tuneable and facile combination of electrospinning and tape-casting method. The structure consists of a network made by continuous Ni fibres and filled in with CGO matrices. When used as the anode of solid oxide fuel cell (SOFC), though it has a lower triple phase boundary (TPB) density, it exhibits better performance compared with impregnated and cermet Ni/CGO with higher nickel loading. An algorithm is developed to determine the ceria-pore double phase boundary (DPB) density with different distance from nickel phase. Using the results, the relative electrochemical reaction rate on DPB and TPB of three different electrodes are calculated and proves that fibre-matrices structure has the morphology advantage of efficiently making use of all ceria-pore DPB. The relative contribution of DPB and TPB in anode reaction of SOFC is quantified in the first time and the importance of DPB is further stressed. This work provides new inspirations in material design of SOFC/SOEC and develops a novel strategy to evaluate the performance of electrodes quantitatively.
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
© 2018 Elsevier Ltd Global decarbonisation scenarios include Carbon Capture and Storage (CCS) as a key technology to reduce carbon dioxide (CO2) emissions from the power and industrial sectors. However, few large scale CCS plants are operating worldwide. This mismatch between expectations and reality is caused by a series of barriers which are preventing this technology from being adopted more widely. The goal of this paper is to identify and review the barriers to CCS development, with a focus on recent cost estimates, and to assess the potential of CCS to enable access to fossil fuels without causing dangerous levels of climate change. The result of the review shows that no CCS barriers are exclusively technical, with CCS cost being the most significant hurdle in the short to medium term. In the long term, CCS is found to be very cost effective when compared with other mitigation options. Cost estimates exhibit a high range, which depends on process type, separation technology, CO2transport technique and storage site. CCS potential has been quantified by comparing the amount of fossil fuels that could be used globally with and without CCS. In modelled energy system transition pathways that limit global warming to less than 2 °C, scenarios without CCS result in 26% of fossil fuel reserves being consumed by 2050, against 37% being consumed when CCS is available. However, by 2100, the scenarios without CCS have only consumed slightly more fossil fuel reserves (33%), whereas scenarios with CCS available end up consuming 65% of reserves. It was also shown that the residual emissions from CCS facilities is the key factor limiting long term uptake, rather than cost. Overall, the results show that worldwide CCS adoption will be critical if fossil fuel reserves are to continue to be substantively accessed whilst still meeting climate targets.
Balcombe P, Speirs JF, Brandon NP, et al., 2018, Methane emissions: choosing the right climate metric and time horizon, Environmental Science: Processes and Impacts, Vol: 20, Pages: 1323-1339, ISSN: 2050-7895
Methane is a more potent greenhouse gas (GHG) than CO2, but it has a shorter atmospheric lifespan, thus its relative climate impact reduces significantly over time. Different GHGs are often conflated into a single metric to compare technologies and supply chains, such as the global warming potential (GWP). However, the use of GWP is criticised, regarding: (1) the need to select a timeframe; (2) its physical basis on radiative forcing; and (3) the fact that it measures the average forcing of a pulse over time rather than a sustained emission at a specific end-point in time. Many alternative metrics have been proposed which tackle different aspects of these limitations and this paper assesses them by their key attributes and limitations, with respect to methane emissions. A case study application of various metrics is produced and recommendations are made for the use of climate metrics for different categories of applications. Across metrics, CO2 equivalences for methane range from 4–199 gCO2eq./gCH4, although most estimates fall between 20 and 80 gCO2eq./gCH4. Therefore the selection of metric and time horizon for technology evaluations is likely to change the rank order of preference, as demonstrated herein with the use of natural gas as a shipping fuel versus alternatives. It is not advisable or conservative to use only a short time horizon, e.g. 20 years, which disregards the long-term impacts of CO2 emissions and is thus detrimental to achieving eventual climate stabilisation. Recommendations are made for the use of metrics in 3 categories of applications. Short-term emissions estimates of facilities or regions should be transparent and use a single metric and include the separated contribution from each GHG. Multi-year technology assessments should use both short and long term static metrics (e.g. GWP) to test robustness of results. Longer term energy assessments or decarbonisation pathways must use both short and long-term metrics and where this has a lar
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
Recent low gas prices have greatly increased pressure on drilling companies to reduce costs and increase efficiency. Field trials have shown that implementing automation can dramatically reduce drilling costs by reducing the time required to drill wells. This study uses the DYNamic upstreAm gAs MOdel (DYNAAMO), a new techno-economic, bottom-up model of natural gas supply, to quantitatively assess the economic impact of lower drilling costs on the US upstream gas industry. A sensitivity analysis of three key economic indicators is presented, with results quoted for the most common field types currently producing, including unconventional and offshore gas. While all operating environments show increased profitability from drilling automation, it is found that conventional onshore reserves can benefit to the greatest extent. For large gas fields, a 50% reduction in drilling costs is found to reduce initial project breakevens by up to 17 million USD per billion cubic metres (MUSD/BCM) and mid-plateau breakevens by up to 8 MUSD/BCM. In this same scenario, additional volumes of around 160 BCM of unconventional gas are shown to become commercial due to both the lower costs of additional production wells in mature fields and the viability of developing new resources held in smaller fields. The capital efficiency of onshore projects increases by 50%-100%, with initial project net present value (NPV) gains of up to 32%.
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
The vanadium redox flow battery (VRFB) has emerged as a promising technology for large-scale storage of intermittent power generated from renewable energy sources due to its advantages such as scalability, high energy efficiency and low cost. In the current study, a three-dimensional(3D) Lattice Boltzmann model is developed to simulate the transport mechanisms of electrolyte flow, species and charge in the vanadium redox flow battery at the micro pore scale. An electrochemical model using the Butler-Volmer equation is used to provide species and charge coupling at the surface of active electrode. The detailed structure of the carbon paper electrode is obtained using X-ray Computed Tomography(CT). The new model developed in the paper is able to predict the local concentration of different species, over-potential and current density profiles under charge/discharge conditions. The simulated capillary pressure as a function of electrolyte volume fraction for electrolyte wetting process in carbon paper electrode is presented. Different wet surface area of carbon paper electrode correspond to different electrolyte volume fraction in pore space of electrode. The model is then used to investigate the effect of wetting area in carbon paper electrode on the performance of vanadium redox flow battery. It is found that the electrochemical performance of positive half cell is reduced with air bubbles trapped inside the electrode.
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: 369, Pages: 246-256, ISSN: 0378-7753
The electrode microstructural properties significantly influence the efficiency and durability of many electrochemical devices including solid oxide fuel cells. Despite the possibility of simulating the electrochemical phenomena within real three-dimensional microstructures, the potential of such 3D microstructural information has not yet been fully exploited. We introduce here a completely new methodology for the advanced characterization of inhomogeneous current distribution based on a statistical analysis of the current of each particle within the microstructure. We quantify the large variation in local current distributionand link it to the particle size dispersion, indicating how particle coarsening can trigger further degradation. We identify two classes of particles: those transferring more current than average, which show 10-40% more particle-particle contacts, and those producing more current than average, characterized by ~2.5 times larger three-phase boundary length per unit volume. These two classes of particles are mutually exclusive, which implies that up to the 30% of the electrode volume within the functional layer is underutilized. This fundamental insight goes well beyond the predictions of continuum modeling, allowing us to revisit the current standards regarding safe operating conditions and to suggest alternative strategies based on nanoparticle infiltration, template-assisted synthesis and additive manufacturing for designing more durable electrodes.
Song B, Ruiz-Trejo E, Brandon N, 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
The electrochemical performance of Ni-YSZ SOFC anodes can quickly degrade during redox cycling. Mechanical damage at interfaces significantly decreases the number of active triple phase boundaries. This study firstly focuses on the sintering temperature impact on YSZ scaffold mechanical properties. The YSZ scaffold sintered at 1200 °C exhibited 56% porosity, 28.3 GPa elastic modulus and 0.97 GPa hardness and was selected for further redox cycling study. The Ni infiltrated YSZ scaffold operated at 550 °C had an initial stabilized polarisation resistance equal to 0.62 Ω cm2 and only degraded to 2.85 Ω cm2 after 15 redox cycles. The active triple phase boundary density was evaluated by FIB-SEM tomography, and degraded from 28.54 μm−2 to 19.36 μm−2. The YSZ scaffold structure was robust after 15 redox cycles, as there was no observation of the framework fracturing in both SEM and FIB-SEM images, which indicated that the mechanical stability of YSZ scaffold improves the anode stability during redox cycling. Nonetheless, Ni agglomeration could not be prevented within Ni-YSZ scaffolds and this needs further consideration.
Balcombe P, Speirs J, Johnson E, et al., 2018, The carbon credentials of hydrogen gas networks and supply chains, Renewable and Sustainable Energy Reviews, Vol: 91, Pages: 1077-1088, ISSN: 1364-0321
Projections of decarbonisation pathways have typically involved reducing dependence on natural gas grids via greater electrification of heat using heat pumps or even electric heaters. However, many technical, economic and consumer barriers to electrification of heat persist. The gas network holds value in relation to flexibility of operation, requiring simpler control and enabling less expensive storage. There may be value in retaining and repurposing gas infrastructure where there are feasible routes to decarbonisation. This study quantifies and analyses the decarbonisation potential associated with the conversion of gas grids to deliver hydrogen, focusing on supply chains. Routes to produce hydrogen for gas grids are categorised as: reforming natural gas with (or without) carbon capture and storage (CCS); gasification of coal with (or without) CCS; gasification of biomass with (or without) CCS; electrolysis using low carbon electricity. The overall range of greenhouse gas emissions across routes is extremely large, from − 371 to 642 gCO 2 eq/kW h H2 . Therefore, when including supply chain emissions, hydrogen can have a range of carbon intensities and cannot be assumed to be low carbon. Emissions estimates for natural gas reforming with CCS lie in the range of 23–150 g/kW h H2 , with CCS typically reducing CO 2 emissions by 75%. Hydrogen from electrolysis ranges from 24 to 178 gCO 2 eq/kW h H2 for renewable electricity sources, where wind electricity results in the lowest CO 2 emissions. Solar PV electricity typically exhibits higher emissions and varies significantly by geographical region. The emissions from upstream supply chains is a major contributor to total emissions and varies considerably across different routes to hydrogen. Biomass gasification is characterised by very large negative emissions in the supply chain and very large positive emissions in the gasification process. Therefore, improvements in total emissions are large if even small i
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.