Prof. Dr. Electo Eduardo Silva Lora
(Univ. Federal de Itajubá, Brazil)
Biomass as an energy source: today and in 2050. Is there enough land for biofuels?. Global land availability and biomass potentials in different scenarios. Biomass gasification as an hydrogen source: world and countries potentials. Green hydrogen for biofuels yield enhancing. General scheme of the Biomass-to-hydrogen process (BTH). The synthesis gas reforming and shift processes. Types of gasifiers and fluids most suitable for hydrogen production: Indirect heated gasifiers, steam and supercritical water. Negative carbon emissions of hydrogen production through gasification – the HyBECCS concept . Other biological routes to obtain hydrogen: biogas, etanol and microbial hydrogen. Technological maturity-TRL of biohydrogen routes. Economic viability of hydrogen obtained through biomass gasification. Hydrogen costs comparisons. Life Cycle Analysis of the BTH process. Case studies.
Prof. Stefania Specchia
POLITECNICO DI TORINO, Dept. of Applied Science and Technology, Torino, Italy
Fuel cells are clean and efficient energy devices able to harvest electric energy from the chemical reaction of a fuel and oxygen without any byproduct. Up to now the most widely used electrocatalysts for the cathodic oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFC) make use of platinum or other noble metals to favor this sluggish reaction, but they face problems, such as expensive price, scarcity and geopolitical concerns correlated with the location of the main producers. Great efforts are being made in the design and development of low cost and stable ORR electrocatalysts not containing platinum group metals (PGM) but still retaining a good activity in alkaline or acidic environment.
In the last decades the usage of transition metals electrocatalysts such as Fe-N-C have been proposed. They can reach electrocatalytic activities similar to those of PGM exploiting a process of heteroatom doping (mainly nitrogen-doped catalyst), although the mechanism of reaction and active centers are still object of debate. The study of N-doped porous carbon materials has become an interesting topic because of their low cost, non-toxicity and renewability, displaying a promising performance as ORR electrocatalysts. A specific niche is being taken by biomass-derived materials, especially from waste, that have been considered for supercapacitors, metal-air battery, and fuel cells applications. The already low cost of PGM-free materials is even lowered if the starting precursors are a common and abundant waste. Moreover, this pathway of valorizing waste into valuable resources and products fits very well in the view of circular economy.
Recently reported biomass derived materials with good activity were obtained from coconuts shells, eggplants, soy beans, or other biomass sources, but they are only the tip of the iceberg, as a multitude of materials have been synthesized, sometimes with more provocative value than real scientific interest. Purpose of this study is the engineering of the biomass carbon structure and incorporation of iron active sites in the material with ball milling method. The starting biomass material, pyrolyzed spent tea leaves and coffee grounds, presents a macro-porous structure. Hence, the porous network is increased by activation with CO2 or urea in order to artificially create and tune the pores. Tea and coffee are very common wastes commonly used by many families as a drink for breakfast or afternoon break. This implies that there is abundance of spent product that normally is thrown away without being recycled or reutilized. Thus, waste biomass could find a second life as a carbon source to be a precursor for ORR electrocatalysts.
The best results have been obtained by ball milling of activated biochar and Fe(II) phthalocyanine. The biochar used as a carbon support was produced from pyrolysis of waste tea leaves at 1500 °C in argon atmosphere, then activated with CO2 or urea. FE-SEM, HR-TEM, XPS, and Raman analyses were performed to investigate the morphology and the physicochemical properties of the electrocatalysts. The ORR activity and methanol tolerance of the Fe-N-C electrocatalysts were tested in rotating ring disk electrode (RRDE), showing promising results in terms of mass activity, onset and half-wave potential in an alkaline environment. Two different short potential cycling protocols demonstrated the high stability of these Fe-N-C electrocatalysts, especially when compared with a 20 wt. % commercial Pt/C electrocatalyst.
Prof. Elena Pastor
Instituto Universitario de Materiales y Nanotecnología (IMN)Departamento de QuímicaUniversidad de La Laguna
The development of noble metal-free catalysts with high activity for reactions in electrolyzers appears as the best option to reduce the cost of high purity H2 production. Transition metal carbides (TMCs) emerge as an alternative to noble metals for this application. In addition, ionic liquids (ILs) have generated interest in electrochemical applications due to their electrical and mechanical properties. Here, recent results for the hydrogen evolution reaction (HER) at metal carbides and composite materials containing TMCs and alkyl pyridinium hexafluorophosphate are discussed. The activity towards the HER was deeply studied by differential electrochemical mass spectrometry (DEMS) following the ionic current for m/z = 2 for an accurate calculation of Tafel slopes. Thus, mechanism studies were achieved as the new method for finding the rate-determining step allows discriminating contributions to reduction currents other than hydrogen production (e.g., surface oxide reduction currents). Finally, also results with other noble metal-free catalysts (as graphene-based materials) for the HER are described.
Marc A. Rosen
Faculty of Engineering and Applied ScienceOntario Tech UniversityOshawa, Ontario, Canada
Hydrogen demand as an energy currency is anticipated to rise significantly in the future, with the emergence of a hydrogen economy. Hydrogen production is a key component of a hydrogen economy. Several production processes are commercially available, while others are under development including thermochemical water decomposition, which has numerous advantages over other hydrogen production processes. Recent advances in hydrogen production by thermochemical water decomposition are reviewed here. Hydrogen production from non-fossil energy sources such as nuclear and solar is emphasized, as are efforts to lower the temperatures required in thermochemical cycles so as to expand the range of potential heat supplies. Limiting efficiencies are explained and the need to apply exergy analysis is illustrated. The copper-chlorine thermochemical cycle is considered as a case study. It is concluded that developments of improved processes for hydrogen production via thermochemical water decomposition are likely to continue, thermochemical hydrogen production using such non-fossil energy will likely become commercial, and improved efficiencies are expected to be obtained with advanced methodologies like exergy analysis. Although numerous advances have been made on sulphur-iodine cycles, the copper-chlorine cycle has significant potential due to its requirement for process heat at lower temperatures than most other thermochemical processes.
Dr. Valeria Molinero
University of Utah, USA
Anion exchange membranes (AEMs) are an attractive alternative to proton exchange membranes in fuel cell applications because they can operate with nonprecious metal electrodes. However, widespread adoption of AEMs has been hampered by their insufficient ionic conductivity and chemical degradation. Much of the growing body of research on AEMs focuses on designing new polymer chemistries and architectures that would increase their conductivity, while controlling the swelling of the membrane due to water uptake. It is, however, challenging to assess the separate effects of water content and polymer architecture on the phase segregation and molecular transport of the ions and water in the membrane because changes in the chemistry of the polymer also impact the equilibrium water uptake. In this presentation we show that molecular simulations provide a versatile tool to disentangle these effects and elucidate the role of polymer chemistry and architecture on the water uptake, nanostructure, conductivity, electro-osmotic drag, and mechanisms of mobility of ions and water in ion exchange membranes.
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Dr. Esteban Franceschini
Instituto de Investigaciones en Fisicoquímica de Córdoba
Undoubtedly, the need to decarbonize energy production to mitigate climate change is what is currently driving the development of technologies leading to the hydrogen economy. It is estimated that the market for green hydrogen, produced with minimal carbon dioxide (CO2) emissions, will reach 530 million tons by 2050, with a $300 billion export market and job creation.To meet long-term hydrogen demand in the European Union, estimated at 2,250 TWh/a, recent studies confirm that at least 1,000 TWh/a of hydrogen will have to be imported into Europe, at a cost of just under $5/kg if favourable wind and solar resources are taken into account.This requires, among other things, increasing the efficiency of electrolyzers for hydrogen production. Conventional alkaline electrolyzers, although they are a mature technology (TRL 9), have a much longer lifetime than PEMs and can still be improved to increase their efficiency and thus reduce the cost of the hydrogen produced.This requires the use of materials with high efficiency and durability that can be scaled up and transferred to industry, such as nickel-based composites (Ni/TiO2, Ni/Nb2O5, Ni/WO3, etc.), but also computational optimizations of the design of electrochemical cells (internal fluidics, electric field, thermal balance, etc.), peripheral devices (gas separators, electrolyte circuit, heat exchangers, etc.), the replacement of inputs by others of lower cost (such as the replacement of ultrapure water) and their experimental validation in medium and high power prototypes.This work presents local advances in the development, scaling and transfer to industry of materials for conventional alkaline electrolyzers, design and modelling of electrolyzers and their application to industrial prototypes.
Dr. Sara Pérez-Rodríguez
Instituto de Carboquímica (CSIC), Zaragoza, Spain.
The sharp increase in the global lithium market due to the expansion of batteries and other energy storage devices demands the development of new sustainable and inexpensive technologies for lithium production. The largest lithium reserves are found in brines, which are highly concentrated salt solutions containing dissolved lithium in a high excess of other co-cations (such as sodium, potassium, and magnesium). Lithium-ion battery materials can be beneficially used for the selective sequestration of lithium from brines and their subsequent release in a recovery solution resulting in a pure lithium salt. The selective capture/release of lithium ions by the battery material can be driven by electricity or redox agents. Here, an overview of lithium recovery from brines is discussed. Moreover, some examples of the chemical and electrochemical approaches for lithium recovery using a common battery host material, LiFePO4, are given.
Dr. Ernesto Julio Calvo
INQUIMAE- Facultad de Ciencia Exactas y Naturales, UBA. Buenos Aires, Argentina
The rechargeable lithium oxygen battery introduced by Abraham in 1996 exhibits very high energy density comparable to fossil fuels-. However, it suffers from capacity fading and the high charging overpotential due to parasitic reactions of the O2 reduction products with solvents and electrolyte. There is an extensive literature on this battery, and a consensus over the limitations due the oxygen chemistry; however, there is an ambiguous interpretation on the reactivity of the different oxygen reduction species towards solvent and electrolyte.The first electron transfer to oxygen in aprotic solvents containing lithium ions is the formation of the radical anion superoxide forming an ion pair with solvated Li+:or a second electron transfer to yield lithium peroxide, Li2O2.In the presence of lithium ions, superoxide radical anion undergoes disproportionation into Li2O2 insoluble in aprotic solvents and soluble O2, a fraction of which has been found to be the extremely reactive singlet oxygen (1O2 or 1Dg ) as well as triplet oxygen (3O2):where [Li+O2–]DMSO is a surface solvated superoxide ion pair.In this presentation we will discuss the use of operando spectroscopic studies of Raman and Fluorescence and electrochemical methods to detect the different oxygen reduction intermediates. Pressure evolution measurements during discharge and charge and galvanostatic charge-discharge cycles of Li-O2 batteries with limited capacity and full discharge will be presented. Recent experimental results with redox mediators to reduce the potential extremes and a physical quencher of singlet oxygen, such as sodium azide will be disclosed.We will present a critical discussion of the role of the very reactive singlet oxygen with a life time is 5.5 μs in DMSO based on the cycle life of batteries with 1O2 physical quencher and the combination with redox mediator to limit the extreme potentials.
Dr. Andrea Calderon
Instituto de Física Enrique Gaviola, Facultad de Matemática, Astronomía, Física y Computación, Universidad Nacional de Córdoba.
Lithium metal batteries (LMBs) and lithium-sulfur batteries (LSBs) are being considered strong candidate to replace lithium-ion batteries (LIBs) since their theoretical energy density is higher than the state-of-the-art LIBs. However, some issues need to be solved. During battery cycling the metallic lithium shows serious safety issues derived from dendrite formation, while sulfur is reduced to form electroactive polysulfides which are soluble in the electrolyte and produce the shuttle effect. These phenomena are responsible for a short life cycle of the battery. Replacement of liquid electrolytes with a polymer electrolyte has been recognized as an interesting approach to solve these problems because the possibility to design the properties from its composition, as well from inorganics additives. In this work we present results for a methacrylate-based polymer matrix with different inorganic additives as electrolyte in LMBs and LSBs.
Dr. Jose Zagal
Laboratorio de Electrocatalisis y Electronica Molecular, Faculty of Chemistry and Biology, University of Santiago de Chile
The identification of reactivity descriptors in electrocatalysis is very important as it allows the rapid structural identification of the best possible electrocatalysts for a given reaction. However, it is important to clarify that durability is also an important parameter in electrocatalysis and high reactivity does not necessarily mean high durability.A classical well-studied reactivity descriptor in electrocatalysis is the binding energy of key intermediates to the active sites. For example, this is well documented for the catalytic activity of metal electrodes for the oxygen reduction reaction (ORR) alloys and metal oxides and less studied for molecular catalysts. For many reactions, including ORR, the activity, expressed as a current density at constant potential, plotted versus the M-O2 binding energy has the shape of a volcano. This is well documented in several papers, especially by the group of NØrksov for metallic electrodes and can be applied to many electrochemical reactions. This has been recently extended to MN4 molecular catalysts, where MN4 stands for macrocyclic complexes like metal porphyrins, metal phthalocyanines, Cu phenanthrolines and in some case MNx pyrolyzed catalysts. In contrast to metallic electrodes that have an electronic band structure and having a high density of active sites, MN4 molecular catalysts have discrete energy levels and the active sites are discrete, usually the central metal, surrounded by an organic ligand with an MN4 central moiety. Essentially one of the key intermediates is the binding of the reacting O2 molecule to the active sites at the rate determining as a first step as: [MN4]ad + O2(aq) + e- ↔ [RMN4O2-]ad where MN4 is a surface confined macrocyclic complex or a pyrolyzed catalysts bearing a MN4 active moiety, embedded in a graphene or graphitic structure. As the ORR reaction involves the transfer of several electrons ( 2, 2+2 or 4 electrons), several adsorbed intermediates can be involved. If the controlling step is the first step, it is expected that for the binding step when DGad = 0 , hypothetically a maximum activity should be observed and under these conditions, the partial coverage of adsorbed intermediate should be = 0.5. On thermodynamic grounds this corresponds to a thermoneutral condition for the most active catalyst. In this work we have tested this hypothesis by studying ORR in alkaline media using several iron porphyrins and iron phthalocyanines as catalysts immobilized on graphite and carbon nanotubes.
Dr. Ralf F. Ziesche
Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
Electrochemical storage systems, such as lithium batteries and fuel cells, have become an increasingly important pillar in a zero-carbon strategy for curbing climate change, with their potential to power multiscale stationary and mobile applications. Immense progress has been made in electrochemical storage technology during the past decades, but significant challenges remain and new development strategies are required to improve performance, fully exploit power density capacity, utilize sustainable resources, and lower production costs. Suitable characterization techniques are crucial for understanding, inter alia, 3D diffusion processes, formation of passivation layers or dendrites in batteries or visualize the water management in fuel cells. Studies of such phenomena typically utilize 2D or 3D imaging techniques, offering locally resolved information. Over the last decades neutron imaging has been steadily growing in many disciplines as a result of improvements to neutron detectors and imaging facilities, providing significantly higher spatial and temporal resolutions. The high sensitivity for light-Z elements, in particular hydrogen and lithium, makes neutron imaging to the perfect probe to study inter alia, changes of the media distribution and transport mechanisms in electrochemical components.A short introduction in neutron imaging will be provided with focus on the research of electrochemical devices. The advantages of neutron imaging will be discussed, whereby examples will provide a deeper insight into dynamic, multi-dimensional, complementary imaging and structural analysis. The main challenges for neutron imaging of electrochemical devices will be outlined and future developments of methods and their potential and significance for the electrochemical community will be discussed.
Dr. Clare Grey
University of Cambridge
Dr. Konrad Świerczek.
AGH University of Science and Technology, Faculty of Energy and Fuels. Krakow, Polonia.
Reversible Solid Oxide Cells (rSOC), able to either utilize chemical energy of the fuel and oxidizer to generate electricity and heat or to operate in the reversed mode, generating e.g. hydrogen with the usage of the surplus electrical energy, are of the special interest, especially regarding distributed energy generation. Numerous and strict requirements concerning transport, electrocatalytic and thermomechanical properties need to be fulfilled by the successful oxygen electrode material, and undoubtedly, perovskite-type and perovskite-related oxides are one of the best candidates, and in fact, the mostly studied. Known relationships between the electronic structure of the bulk and the surface-related catalytic behavior of the perovskite-type oxides enabled a rapid progress in development of the effectively-working electrode materials. However, high electrocatalytic activity in the oxygen reduction reaction (ORR) does not necessarily mean that the high efficiency of the oxygen evolution reaction (OER) can be also achieved in the reversed operation mode.In this work, several groups of mixed ionic-electronic conductors are discussed as candidate oxygen electrode materials for rSOCs, all showing the crystal structure beyond that of simple perovskites. Among them, the A-site layered RE(Ba,Sr)Co2-yMyO5+δ (RE: selected rare-earth cations; M: Mn, Fe, Cu, etc.) double perovskites, in which Co-rich materials are of interest, as they are known to exhibit very high mixed conductivity and high electrocatalytic activity. However, usage of carcinogenic and expensive cobalt is also linked with the high thermal expansion, as well insufficient stability in relation to several candidate solid electrolytes. As the alternative, the copper-based RE1-x(Ba,Sr)xCuO3-δ oxides, having either RE-(Ba,Sr) cation-ordered or cation-disordered sublattice, as well as the linked ordered or disordered oxygen sublattice defects are proposed and discussed in details. It is documented that the Cu-based complex perovskites may also exhibit attractive physicochemical properties in such application. Finally, the high entropy approach to develop efficient oxygen electrode materials is also presented, with an emphasis directed on the possible gains, which may arise from the presence of multiple cations at one or two cationic sublattices in the perovskite-type structure.
Prof. Dr. Alejandro A. Franco
Laboratoire de Réactivité et Chimie des Solides (LRCS), Université de Picardie Jules Verne, and ALISTORE-European Research Institute, Fédération de Recherche CNRS, Amiens & Institut Universitaire de France, Paris, France.
Lithium ion batteries (LIBs) are a very important technology for our societies. Their performance is strongly influenced by the mesostructure of their porous electrodes. This mesostructure results from a complex process encompassing multiple steps and numerous parameters. Its understanding and accelerated optimization is vital for the future of battery technology.
In this lecture I discuss a digital twin for accelerated optimization of the manufacturing process of LIBs we are developing within the context of the ARTISTIC project. Such digital twin is supported on a hybrid approach encompassing a physics-based multiscale modeling workflow, machine learning models and high throughput experimental characterizations. Different steps along the battery cells manufacturing process are simulated, such as the electrode slurry, coating, drying, calendering and electrolyte infiltration. The multiscale physical modeling workflow couples experimentally-validated Coarse Grained Molecular Dynamics, Discrete Element Method and Lattice Boltzmann simulations and it allows predicting the impact of the process parameters on the final electrode mesostructure in three dimensions. The predicted electrode mesostructures are injected in a continuum performance simulator capturing the influence of the pore networks and spatial location of carbon-binder within the electrodes on the solid electrolyte interphase formation (for anodes) and the electrochemical response (of anodes vs. lithium, cathodes vs. lithium and the full cells). Machine learning models are used to accelerate the physical models’ parameterization, to mimic their working principles and to unravel manufacturing parameters interdependencies from the physical models’ predictions and experimental data, and as a guideline for reverse engineering. The predictive capabilities of this digital twin, coupling physical models with machine learning models, are illustrated with results for different electrode formulations. Finally, the free online battery manufacturing simulation services offered by the project and our virtual reality technology supported on the project results to optimize battery electrodes are illustrated through several examples.
Dr. Serhiy CherevkoHead of Electrochemical Energy ConversionForschungszentrum Jülich GmbHHelmholtz-Institute Erlangen-Nürnberg for Renewable Energy
Durability and degradation are in the focus of modern electrocatalysis research. Before moving to real applications, e.g. fuel cells in transportation or water electrolyzers for production of green hydrogen, novel electrocatalytic materials must prove acceptable stability, but «how to assess the stability of electrocatalysts»? In the relatively mature proton exchange membrane fuel cell (PEMFC) research, stability is evaluated using various accelerated stress tests (ASTs). Unfortunately, even for the most studied Pt/C electrocatalysts, degradation processes like carbon corrosion and Pt dissolution that occur during common ASTs are not easily distinguishable. Moreover, advanced electrocatalysts such as different shape-controlled Pt alloy nanostructures, showing promising stability in ASTs performed in model aqueous systems, are often rendered useless when moved to real applications. Catalysts free of platinum-group-metals demonstrate different degradation extents if tested in oxygen or argon. Iridium oxides, the state of the art OER electrocatalysts, are prone to dissolution in aqueous media but much more stable in solid electrolyte based electrolyzers. These examples demonstrate the need for rethinking current approaches to test electrocatalyst stability. This talk highlights our recent results on using coupled electrochemical techniques and tuned gas diffusion electrode (GDE) with inductively coupled plasma mass spectrometry (ICP-MS) and membrane electrode assembly (MEA) cells to investigate dissolution of electrocatalysts, such as Pt/C for PEMFC, Fe-N-C for anion exchange membrane fuel cells (AEMFC), and Ir dissolution in aqueous and solid polymer electrolytes, in-operando at conditions closely resembling those in real devices. It is anticipated that the presented new findings will be useful for researchers dealing with both more fundamental understanding of noble metal electrocatalysts corrosion and engineers resolving more practical issues with electrocatalyst stability in fuel cells and electrolyzers.
Prof. Dr. K. Andreas FriedrichHead of Electrochemical Energy TechnologyGerman Aerospace Center (DLR)Institute for Technical Thermodynamics Electrochemical Energy TechnologyStuttgart, Germany
Hydrogen generation by electrolysis is expected to play an important role as a crosslinking technology between power generation on one hand and transport and industry on the other hand. When produced by water electrolysis from renewable energies – such as solar or wind – hydrogen can directly replace fossil fuels in transport and industry, thereby helping in the integration of renewable energies in other energy sectors. The relevant technologies are either the mature alkaline water electrolysis (AEL), the newer proton exchange membrane (PEMEL) water electrolysis, or the less-mature high-temperature solid oxide electrolysis (SOEL). The AEL has the benefit of using inexpensive materials and a superb durability record, whereas the PEMEL can excel with small footprint, high current densities and simplified system design. SOEL is not discussed here.An overview of recent developments in Europe and Germany regarding the use of electrolysis technology is provided. Furthermore, examples of research at DLR for integrating electrolyzers with renewables and for achieving cost reduction are given. Present activities, some highlights for low temperature technologies and the future research priorities are discussed.