432 results found
Liu X, Qian X, Tang W, et al., 2021, Designer uniform Li plating/stripping through lithium–cobalt alloying hierarchical scaffolds for scalable high-performance lithium-metal anodes, Journal of Energy Chemistry, Vol: 52, Pages: 385-392, ISSN: 2095-4956
Lithium metal anodes are of great interest for advanced high-energy density batteries such as lithium-air, lithium-sulfur and solid-state batteries, due to their low electrode potential and ultra-high theoretical capacity. There are, however, several challenges limiting their practical applications, which include low coulombic efficiency, the uncontrollable growth of dendrites and poor rate capability. Here, a rational design of 3D structured lithium metal anodes comprising of in-situ growth of cobalt-decorated nitrogen-doped carbon nanotubes on continuous carbon nanofibers is demonstrated via electrospinning. The porous and free-standing scaffold can enhance the tolerance to stresses resulting from the intrinsic volume change during Li plating/stripping, delivering a significant boost in both charge/discharge rates and stable cycling performance. A binary Co-Li alloying phase was generated at the initial discharge process, creating more active sites for the Li nucleation and uniform deposition. Characterization and density functional theory calculations show that the conductive and uniformly distributed cobalt-decorated carbon nanotubes with hierarchical structure can effectively reduce the local current density and more easily absorb Li atoms, leading to more uniform Li nucleation during plating. The current work presents an advance on scalable and cost-effective strategies for novel electrode materials with 3D hierarchical microstructures and mechanical flexibility for lithium metal anodes.
Strbac G, Pudjianto D, Aunedi M, et al., 2020, Role and value of flexibility in facilitating cost-effective energy system decarbonisation, Progress in Energy, Vol: 2, Pages: 042001-042001
Loh A, Li X, Taiwo OO, et al., 2020, Development of Ni–Fe based ternary metal hydroxides as highly efficient oxygen evolution catalysts in AEM water electrolysis for hydrogen production, International Journal of Hydrogen Energy, Vol: 45, Pages: 24232-24247, ISSN: 0360-3199
© 2020 Hydrogen Energy Publications LLC A number of mixed metal hydroxide oxygen evolution reaction (OER) catalysts i.e. Ni–Fe, Ni–Co, Ni–Cr, Ni–Mo, Ni–Fe–Co, Ni–Fe–Mo and Ni–Fe–Cr were prepared by cathodic electrodeposition and characterised by SEM, TEM, EDS, XPS and micro X-CT. The compositions of selected catalysts were optimised to give lower OER overpotentials in alkaline media. Further optimisation of Ni–Fe based ternary metal hydroxide catalysts such as Ni–Fe–Co and Ni–Fe–Mo was carried out, showing improved performance at high current densities up to 1 A cm−2 in 1 M NaOH, 333 K. The influence of electrodeposition parameters such as current density, pH, electrodeposition time and temperature on the electrocatalytic performance of ternary Ni–Fe–Co metal hydroxide was further investigated and optimised. The durability of the optimised catalyst was tested at a current density of 0.5 A cm−2 in an anion exchange membrane (AEM) water electrolyser cell at 4 M NaOH, 333 K, demonstrating stable performance over 3.5 h.
Liu X, Ouyang M, Orzech M, et al., 2020, In-situ fabrication of carbon-metal fabrics as freestanding electrodes for high-performance flexible energy storage devices, Energy Storage Materials, Vol: 30, Pages: 329-336, ISSN: 2405-8297
Hierarchical 1D carbon structures are attractive due to their mechanical, chemical and electrochemical properties however the synthesis of these materials can be costly and complicated. Here, through the combination of inexpensive acetylacetonate salts of Ni, Co and Fe with a solution of polyacrylonitrile (PAN), self-assembling carbon-metal fabrics (CMFs) containing unique 1D hierarchical structures can be created via easy and low-cost heat treatment without the need for costly catalyst deposition nor a dangerous hydrocarbon atmosphere. Microscopic and spectroscopic measurements show that the CMFs form through the decomposition and exsolution of metal nanoparticle domains which then catalyze the formation of carbon nanotubes through the decomposition by-products of the PAN. These weakly bound nanoparticles form structures similar to trichomes found in plants, with a combination of base-growth, tip-growth and peapod-like structures, where the metal domain exhibits a core(graphitic)-shell(disorder) carbon coating where the thickness is in-line with the metal-carbon binding energy. These CMFs were used as a cathode in a flexible zinc-air battery which exhibited superior performance to pure electrospun carbon fibers, with their metallic nanoparticle domains acting as bifunctional catalysts. This work therefore unlocks a potentially new category of composite metal-carbon fiber based structures for energy storage applications and beyond.
Hack J, Rasha L, Cullen PL, et al., 2020, Use of X-ray computed tomography for understanding localised, along -the -channel degradation of polymer electrolyte fuel cells, ELECTROCHIMICA ACTA, Vol: 352, ISSN: 0013-4686
Speirs J, Jalil-Vega F, Cooper J, et al., 2020, The flexibility of gas - what is it worth?, White Paper 5: The Flexibility of gas – what is it worth?, London, UK, Publisher: Sustainable Gas Institute, Imperial College London, 5
What is the evidence on the flexibility value that gas vectors and gas networks can provide to support the future energy system?There is an increasing debate regarding the use of gas networks in providing support for the decarbonisation of energy systems.The perceived value of gas “vectors” – encompassing natural gas, hydrogen and biomethane – is that they may provide flexibility, helping to support daily and seasonal variation in energy demand, and increasingly intermittent electricity supply as renewable electricity generation increases as a proportion of the electricity mix.Arguments in support of gas suggest that electricity systems will find it difficult to maintain flexibility on their own, whilst also reducing greenhouse gas emissions and increasing production to meet new demand for heating and transport. Gas, on the other hand, is expected to provide flexibility at relatively low cost, and may be produced and used with relatively low greenhouse gas emissions.White Paper 5 investigates the evidence surrounding the flexibility provided by gas and gas networks and the cost of, and value provided by gas to the future energy system.
Chakrabarti B, Rubio-Garcia J, Kalamaras E, et al., 2020, Evaluation of a non-aqueous vanadium redox flow battery using a deep eutectic solvent and graphene-modified carbon electrodes via electrophoretic deposition, Batteries, Vol: 6, Pages: 1-20, ISSN: 2313-0105
Common issues aqueous-based vanadium redox flow batteries (VRFBs) face include low cell voltage due to water electrolysis side reactions and highly corrosive and environmentally unfriendly electrolytes (3 to 5 M sulfuric acid). Therefore, this investigation looks into the comparison of a highly conductive ionic liquid with a well-studied deep eutectic solvent (DES) as electrolytes for non-aqueous VRFBs. The latter solvent gives 50% higher efficiency and capacity utilization than the former. These figures of merit increase by 10% when nitrogen-doped graphene (N-G)-modified carbon papers, via a one-step binder-free electrophoretic deposition process, are used as electrodes. X-ray computed tomography confirms the enhancement of electrochemical surface area of the carbon electrodes due to N-G while electrochemical impedance spectra show the effect of its higher conductivity on improving RFB performance. Finally, potential strategies for the scaling-up of DES-based VRFBs using a simple economical model are also briefly discussed. From this study, it is deduced that more investigations on applying DESs as non-aqueous electrolytes to replace the commonly used acetonitrile may be a positive step forward because DESs are not only cheaper but also safer to handle, far less toxic, non-flammable, and less volatile than acetonitrile.
Xing X, Lin J, Brandon N, et al., 2020, Time-Varying Model Predictive Control of a Reversible-SOC Energy-Storage Plant Based on the Linear Parameter-Varying Method, IEEE TRANSACTIONS ON SUSTAINABLE ENERGY, Vol: 11, Pages: 1589-1600, ISSN: 1949-3029
Gayon-Lombardo A, Lukas M, Brandon N, et al., 2020, Pores for thought: Generative adversarial networks for stochastic reconstruction of 3D multi-phase electrode microstructures with periodic boundaries, npj Computational Materials, Vol: 6, Pages: 1-11, ISSN: 2057-3960
The generation of multiphase porous electrode microstructures is a critical step in the optimisation of electrochemical energy storage devices. This work implements a deep convolutional generative adversarial network (DC-GAN) for generating realistic n-phase microstructural data. The same network architecture is successfully applied to two very different three-phase microstructures: A lithium-ion battery cathode and a solid oxide fuel cell anode. A comparison between the real and synthetic data is performed in terms of the morphological properties (volume fraction, specific surface area, triple-phase boundary) and transport properties (relative diffusivity), as well as the two-point correlation function. The results show excellent agreement between datasets and they are also visually indistinguishable. By modifying the input to the generator, we show that it is possible to generate microstructure with periodic boundaries in all three directions. This has the potential to significantly reduce the simulated volume required to be considered “representative” and therefore massively reduce the computational cost of the electrochemical simulations necessary to predict the performance of a particular microstructure during optimisation.
Li T, Lu X, Rabuni MF, et al., 2020, High-performance fuel cell designed for coking-resistance and efficient conversion of waste methane to electrical energy, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 13, Pages: 1879-1887, ISSN: 1754-5692
Jais AA, Ali SAM, Anwar M, et al., 2020, Performance of Ni/10Sc1CeSZ anode synthesized by glycine nitrate process assisted by microwave heating in a solid oxide fuel cell fueled with hydrogen or methane, JOURNAL OF SOLID STATE ELECTROCHEMISTRY, Vol: 24, Pages: 711-722, ISSN: 1432-8488
Tan R, Wang A, Malpass-Evans R, et al., 2020, Hydrophilic microporous membranes for selective ion separation and flow-battery energy storage, Nature Materials, Vol: 19, Pages: 195-202, ISSN: 1476-1122
Membranes with fast and selective ion transport are widely used for water purification and devices for energy conversion and storage including fuel cells, redox flow batteries and electrochemical reactors. However, it remains challenging to design cost-effective, easily processed ion-conductive membranes with well-defined pore architectures. Here, we report a new approach to designing membranes with narrow molecular-sized channels and hydrophilic functionality that enable fast transport of salt ions and high size-exclusion selectivity towards small organic molecules. These membranes, based on polymers of intrinsic microporosity containing Tröger’s base or amidoxime groups, demonstrate that exquisite control over subnanometre pore structure, the introduction of hydrophilic functional groups and thickness control all play important roles in achieving fast ion transport combined with high molecular selectivity. These membranes enable aqueous organic flow batteries with high energy efficiency and high capacity retention, suggesting their utility for a variety of energy-related devices and water purification processes.
Zhang D, Forner-Cuenca A, Taiwo OO, et al., 2020, Understanding the role of the porous electrode microstructure in redox flow battery performance using an experimentally validated 3D pore-scale lattice Boltzmann model, JOURNAL OF POWER SOURCES, Vol: 447, ISSN: 0378-7753
Hack J, Garcia-Salaberri PA, Kok MDR, et al., 2020, X-ray Micro-Computed Tomography of Polymer Electrolyte Fuel Cells: What is the Representative Elementary Area?, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, Vol: 167, ISSN: 0013-4651
Speirs J, Balcombe P, Blomerus P, et al., 2020, Natural gas fuel and greenhouse gas emissions in trucks and ships, Progress in Energy, Vol: 2, Pages: 012002-012002
Golbert J, Adjiman CS, Brandon NP, 2007, Micro-structural Modelling of SOFC Anodes, ECS Transactions, Vol: 7, Pages: 2041-2047
Brett, D J L, Aguiar P, et al., 2007, Operational experience of an IT-SOFC / battery hybrid system for automotive applications, Electrochem. Soc. Trans., Vol: 7, Pages: 113-122
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
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
A hydrogen-vanadium electrochemical system was characterized using extensive experimental tests at different current densities and flow rates of vanadium electrolyte. The maximum peak power density achieved was 2840 W m− 2 along with a limiting current density of over 4200 A m− 2. The cycling performance presented a stable coulombic efficiency over 51 cycles with a mean value of 99.8%, while the voltage efficiency decreased slowly over time from a value of 90.3% to 87.0%. The capacity loss was of 5.6 A s per cycle, which could be related to crossover of ionic species and liquid water. A unit cell model, previously proposed by the authors, was modified to include the effect of species crossover and used to predict the cell potential. Reasonable agreement between the model simulations and the experimental charge-discharge data was observed, with Normalized Root-Mean-Square Errors (NRMSEs) within the range of 0.8–5.3% and 2.9–19.0% for charge and discharge, respectively. Also, a good degree of accuracy was observed in the simulated trend of the polarization and power density, with NRMSEs of 3.1% and 1.0%, and 1.1% and 1.9%, for the operation at a flow rate of vanadium electrolyte of 100 and 50 mL min− 1, respectively, while the voltage efficiency during the cycling test were estimated within a Root-Mean-Square Error (RMSE) of 1.9%. A study of the effect of the component properties on the cell potential was carried out by means of a model sensitivity analysis. The cell potential was sensitive to the cathodic transfer coefficient and the cathode porosity, which are directly related to the cathodic overpotential through the Butler-Volmer equation and the cathodic ohmic overpotential. It was recognized that a kinetic study for the cathodic reaction is needed to obtain more reliable kinetic parameters at practical vanadium concentrations, as well as reliable microstructural parameters of carbon electrodes.
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, 2019, 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.
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