bluuebunny/crossref_metadata_2025 huggingface dataset:
Towards Totally Aqueous Membrane-Free Flow Batteries: Fundamentals and Challenges
Authors: Navalpotro Paula , Ibañez Santiago Enrique , Pedraza Eduardo , Marcilla Rebeca
Published: February 2024

The implementation of renewable energies (solar, wind, etc) is driven the development of new energy storage systems that can mitigate their inherent intermittency solving the mismatch between the energy demand and production. Among different systems, electrochemical energy storage devices stand out due to their efficiency, flexibility and modularity. Specifically, Redox Flow Batteries (RFB) are the unique type of battery able to decouple energy and power densities which makes them versatile and adaptable to different applications. Nevertheless, although they are commercially available, their implementation is limited by the high cost and issues associated with some components such as the vanadium-based electrolytes and Nafion ion-exchange membranes. In this regard, our approach to overcome these limitations is the development of a membrane-free flow battery based on immiscible/biphasic electrolytes with organic active species1,2. In this talk, we will present a totally aqueous membrane-free battery based on a sustainable and safe aqueous biphasic system with near neutral pH and highly soluble organic active species. The aqueous biphasic electrolytes allow a selective thermodynamic separation of the active species instead of using any membrane or physical barrier. Thanks to a new flow-cell design3, it becomes the first example of aqueous membrane-free flow battery (Figure 1). The results show high coulombic efficiency (94%), capacity utilization (98%), and stable long-term performance over 250 cycles4. The fundamental aspects and the last advances in this innovative concept will be discussed.

Figure 1 Schematic representation of the development of a membrane-free flow battery based on two aqueous biphasic electrolytes with organic active species.

References:

[1] Navalpotro, P.; Palma, J.; Anderson, M.; Marcilla, R.. Angew. Chemie - Int. Ed. 2017, 56 (41), 12460–12465.

[2] Navalpotro, P.; Trujillo, C.; Montes, I.; Neves, C. M. S. S.; Palma, J.; Freire, M. G.; Coutinho, J. A. P.; Marcilla, R.. Energy Storage Mater. 2020, 26, 400–407.

[3] Montes, I.; Marcilla, R.; Palma, J.; Ventosa, E.; Vera, M.; Sánchez Sanz, M.; Ibañez, S.E.. Redox flow Battery with immiscible electrolyte and flow through electrode, WO2021209585A1.

[4] Navalpotro, P.; Ibañez, S. E.; Pedraza, E.; Marcilla, R.. Energy Storage Mater. 2023, 56, 403-411.

Figure 1
Towards Semi-Solid Organic Redox Flow Batteries: Material Screening, Electrochemical Performance, and Reactor Design Optimization
Authors: Zaffaroni Riccardo , Alfonso Villanueva Angel , van der Willige Nolan , Brandt Nathanael , Brentjes Antoni , Dussi Simone , Tedesco Michele
Published: February 2024

As our society transitions to cleaner sources of energy, the need for stationary electricity storage becomes increasingly important. In this context, redox flow batteries (RFBs) have emerged as a promising solution to provide electricity storage at full scale, due to their high scalability and flexibility. However, despite the growing research interest, there is still a urgent need of novel batteries, which are able to operate at high energy densities while relying on sustainable, abundant, and cost-effective electrolytes.

In this work we report the development of novel semi-solid RFBs based on cost-effective and environmentally friendly organic materials. We have systematically screened different classes of organic molecules, to identify suitable redox couples that can operate under stable conditions (i.e., >5,000 cycles) in a wide pH range. Therefore, we have experimentally investigated the most promising redox couples in a 10-cm2 electrochemical cell, to understand the behavior of the systems under different carbon and active molecule loadings. Finally, we have simulated the performance of the battery under dynamic and steady-state conditions, aiming to quantify the influence of fluid dynamics and rheological properties of the carbon slurry on the electrochemical performance. Based on our simulations results, we have identified new reactor designs for the RFB, aiming to optimize both fluid dynamics and electrochemical performance of the battery. Such designs represent an important first step towards future upscaling strategies.
Study of the Properties of Iron/Iron Redox Flow Batteries
Authors: Challuri Sai Venkata Akhil Kumar , Noack Jens
Published: February 2024

New energy storage technologies are needed to offset the erratic power supply of renewable energy sources due to the rising global energy demand and the urgency of climate change action. Even if there are still concerns with operational parameters and efficiency, the Iron/Iron redox flow battery is a viable contender for large-scale energy storage. Iron is a highly affordable active material, making it possible to create inexpensive energy storage systems and possibly batteries with very low initial investment costs due to the positive electrode's moderate pH and relatively low voltage, maintaining minimal toxicity and aggression. Many challenges have been faced in the experiments on iron/iron redox flow batteries. For example, hydrogen formation and its impacts on the system must be minimized to ensure long-term use as an energy storage device. Iron hydroxides quickly form in response to elevated pH levels or contact with ambient oxygen, which restricts the battery's effectiveness.

For each series, various iron/iron redox flow batteries were assembled, and their functional properties were studied as a sustainability factor. The functional properties of the battery, such as an increase in electrolyte volume, an increase in charge/discharge times, the addition of a break time between charge/discharge cycles, varied charge cut-off voltages, varied discharge cut-off voltages and IU charge/discharge were investigated. It was also possible to complete more than 50 cycles with 8 hours of charging time and calculate and compare efficiencies and other performance values. The 8 hours of charge/discharge parameter proved to be the most suitable for conducting long-term cycling experiments because of the increased CE and EE trendline over 25 cycles. The 60 minutes rest time recorded a delay of charge voltage with a maximum of 35 minutes starting from the third cycle because of the blockage of the membrane and polarization effects. An optimized battery achieved up to 62% energy efficiency at 25 mA/cm2 with 4 hours of charging time and 8.01 Ah maximum theoretical capacity.

Figure 1
Strategies to Stabilize the Sodium metal anode for High-energy Room-temperature Sodium-Sulfur Batteries
Authors: Kumar Vipin
Published: February 2024

Room temperature sodium-sulfur batteries possess higher specific energy and improved inherent safety compared to their high-temperature analogs used in stationary grid storage. The viability of room temperature sodium batteries depends critically on the mechanical and ionic transport properties of the solid electrolyte interphase. Solid electrolyte interphases address a number of concomitant challenges, including large volume change, low ionic conductivity, rapid dendrite growth, and high chemical reactivity, which limit the viability of sodium anodes. In this presentation, novel strategies to stabilize the sodium metal anode are discussed that enable a high-rate cycling of sodium anodes. A solid-vapor growth approach is developed to fabricate a variety of artificial interphases directly on the surface of the sodium metal anode. As a result, the metal anode could be cycled for over 600 cycles at relatively higher currents. A room-temperature sodium-sulfur cell comprising modified sodium metal anode and sulfur cathode could be cycled for over 500 cycles with minimal capacity decay per cycle.
(Invited) Data-Driven Design for Energy Materials
Authors: Persson Kristin A.
Published: February 2024

Fueled by our abilities to compute materials properties and characteristics orders of magnitude faster than they can be measured and recent advancements in harnessing literature data, we are entering the era of the fourth paradigm of science: data-driven materials design. The Materials Project uses supercomputing together with state-of-the-art quantum mechanical theory to compute the properties of inorganic materials, design novel materials and offer the data for free to the community together with online analysis and design algorithms. Specifically relevant to the Energy Materials Network effort, the Project produces and disseminates materials properties relevant for a broad range of energy materials, interfacial reaction predictions, and Pourbaix diagrams to assess corrosion. We will in this talk survey the existing capabilities, current and ongoing developments and highlight design of novel materials for photocatalysis; from ab initio prediction to synthesis and characterization. Specifically, we identify bottlenecks in the design process and our efforts to accelerate it. Finally, we recognize that the highest impact from the Materials Project comes from its rapidly growing user community, currently counting over 400,000 registered users, and their use of our resources.
(Invited) Multiscale Simulations of Materials Degradation in Hydrogen Production and Storage Applications
Authors: Wood Brandon C.
Published: February 2024

Most hydrogen production and storage technologies rely on controlled chemical or electrochemical reactions occurring at complex interfaces. However, under actual operating conditions, competing mechanisms of chemistry, transport, and phase evolution can activate other processes that compete with or deactivate the desired processes. In certain cases, such mechanisms can lead to critical degradation of materials and their performance. In this talk, I will discuss how multiscale, multiphysics materials modeling from atomistic to continuum scales is being applied to understand fundamentals of degradation in materials relevant to hydrogen technology. Topics will include modeling of competing reaction pathways for hydrogen-rich chemicals, secondary phase formation in high-temperature hydrogen environments, impeded transport pathways in metals for hydrogen storage, and corrosion and oxidation of secondary components and contacts. In each case, I will show how HPC-accelerated models are being integrated across scales and interfaced with microscopy and spectroscopy, as well as modern data science approaches, to gain new physicochemical understanding and guide efforts towards improvement. Examples will be drawn from current efforts within the DOE HydroGEN, HyMARC, and H2NEW hydrogen production and storage multi-laboratory consortia, as well as closely related activities within the Corrosion Science Strategic Initiative at Lawrence Livermore National Laboratory. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
(Invited) Importance of Accelerated Stress Tests in Accelerated Discovery of Energy Materials
Authors: Mukundan Rangachary
Published: February 2024

Accelerated Stress Tests (ASTs) are critical to the rapid discovery and deployment of new stable materials in electrochemical energy conversion technologies. The widespread use of validated ASTs can spur materials development efforts that address the key shortcomings of today’s materials. An excellent example of the use of ASTs has been in polymer electrolyte membrane fuel cells (PEMFCs). This talk will describe the various ASTs that have been utilized to evaluate oxygen reduction reaction (ORR) catalysts, catalyst supports and membranes in fuel cells. As better materials get developed, the ASTs have evolved over time to provide quick feedback on the degradation rates of these materials. Finally, the ASTs can also provide insights into the tradeoffs between cost, performance and durability of these electrochemical systems. Results from the Million Mile Fuel Cell Truck Consortium (M2FCT) will be presented with particular emphasis on heavy duty application of fuel cells. This talk will also address the ASTs that are currently under development for polymer electrolyte membrane water electrolyzers (PEMWEs). The Department of Energy (DOE) has recently set performance and durability targets for PEMWEs. The Hydrogen from Next generation Electrolyzers of Water (H2NEW) consortium is currently engaged in developing ASTs for PEMWEs and these results will be presented and discussed. By providing these two specific examples, the importance of ASTs in materials discovery will be highlighted.

Acknowledgement:

This work was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE). Funding is through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos and Hydrogen from Next generation of Electrolyzers of Water (H2NEW) consortia, technology manager Dave Peterson.

REFERENCES:

https://www.energy.gov/eere/fuelcells/technical-targets-proton-exchange-membrane-electrolysis
(Invited) A Practical Approach to Model Development and Validation for High Performance SOFC and SOEC Systems
Authors: Ramanan Ram
Published: February 2024

Bloom Energy’s mission is to power our planet with resilient, sustainable, and predictable energy. Bloom’s flexible, future-proof technology generates lower-carbon energy today, while laying the foundation for a net-zero tomorrow. As an early employee of the company, I helped create the framework, organizational structure, hired the teams and set the culture of leading product development and innovation through state-of-the-art modeling and data sciences. This framework has resulted in rapid innovation, Design for Manufacturing, Design for Reliability and Cost Reduction initiatives.

The methodology used for rapid innovation and development of high-performance SOFC and SOEC systems is based on a combination of state-of-the-art modeling and data sciences. We use a variety of modeling tools to simulate the performance of our systems and to identify potential areas for improvement. We also use data from our test cells and from customer sites to optimize our designs.

We have achieved significant success with this methodology. We have developed SOFC and SOEC systems that are among the most efficient and reliable in the world. We have also reduced the cost of our systems by nearly a factor of five since we started the company.

In conclusion, we have developed a successful methodology for rapid innovation and development of high-performance SOFC and SOEC systems. This methodology has resulted in significant improvements in the performance and cost of our systems. We are confident that this methodology will continue to enable us to develop innovative and cost-effective energy solutions in the future.
(Invited) Hydrogen Consortium: Technical Progress on Renewable Hydrogen Production R&D
Authors: Dinh Huyen N
Published: February 2024

HydroGEN Energy Materials Network (EMN) is an U.S. Department of Energy (DOE) EERE Hydrogen and Fuel Cell Technologies Office (HFTO)-funded consortium that aims to accelerate the discovery and development of advanced water splitting materials (AWSM) for clean, low-cost hydrogen production. This is in line with the H2@Scale initiative, with the goal to meet U.S. DOE’s Hydrogen Shot production cost target of $1/kg H2 within 1 decade (1 1 1). Materials innovations are key to enhancing performance, durability, and cost of hydrogen generation technologies. Large scale, low cost hydrogen from diverse domestic resources can enable an economically competitive and environmentally beneficial future energy system across multiple sectors.

HydroGEN is focused on low technology readiness level AWS technologies, including low- (alkaline exchanged membrane electrolysis) and high-temperature electrolysis (proton-conducting solid oxide electrolysis), photoelectrochecmical (PEC) and solar thermochemical (STCH) water splitting. This presentation will provide an overview of the HydroGEN EMN and technical highlights of a few lab-led and FOA-awarded R&D projects. HydroGEN continues to grow its community of industry, university, and national laboratories, forming a national innovation ecosystem focused on renewable hydrogen production.
(Invited) Crosscutting Materials and Molecular Catalysts in Hybrid Photoelectrodes for Liquid Solar Fuel Production
Authors: Meyer Gerald J
Published: February 2024

The Solar Hub entitled the
C

enter for Hybrid Approaches in Solar Energy to Liquid Fuels, or CHASE, is advancing the quest for liquid fuels from water, nitrogen, and/or carbon dioxide feedstocks with sunlight as the only energy source. To realize this quest, CHASE utilizes hybrid photoelectrodes based on molecular catalysts integrated with visible light absorbing semiconductors with controlled microenvironments to achieve liquid solar fuel production. These crosscutting materials serve as hybrid photoelectrodes in photoelectrochemical cells. This presentation will focus on recent advances on photocatalysis at hybrid Si interfaces with particular attention to the individual electron transfer and proton coupled electron transfer step(s) relevant to water oxidation and carbon dioxide reduction catalysis. The impact of CHASE findings on solar energy conversion and the quest for liquid solar fuels will be discussed.
(Invited) Ammonia Electrolysis from Fundamentals to Scale up
Authors: Alvarez Pugliese Christian E , Gecgel Ozhan , Botte Gerardine G
Published: February 2024

Dr. Botte’s research group has been studying the ammonia electrolysis process, for the production of nitrogen and hydrogen from ammonia and ammonia waste streams, from fundamentals in materials for electrocatalysis including computational work, mathematical modeling, optimization studies and microkinetic models combined with hydrodynamic analysis, simulation on parallel plates flow cells to system integration and scale-up in a skid with a stack of 6000 cm2 electrolysis cell, the biggest reported in the literature. In this presentation, we will discuss how the integration of the components have been critical for the evolution of the technology. In addition, results from the most recent prototype of this technology, installed in a wastewater treatment plant in line with a clinocliptolite ion exchange system that capture the ammonia from wastewater and concentrated it prior to the inlet of the electrolyzer, will be discussed. The electrochemical process operates in a polarity pulse mode that allows NH3 conversions above 80% with specific energy consumption of 5.7 kWh kg−1 of NH3-N without considering the energy that can be obtained from the H2.
(Invited) Ionic Transport and Structure of Battery Electrolytes, Electrodes and Interfaces: New NMR, Diffraction and Optical Microscopy Approaches
Authors: Grey Clare P.
Published: February 2024

This talk will discuss the development and use of new characterisation methods to understand function over different time and lengthscales, to improve materials function and battery performance. We show how electrode material function can be studied with NMR to measure transport, X-ray diffraction to measure phase segregation within the bulk, optical measurements to explore processes at the particle level, and continuum modelling to tie transport with particle level observations. In the examples discussed, NMR measurements provide hopping frequencies and diffusion coefficients and operando diffraction measurements provide evidence for solid solution vs two phase behaviour as a function of cycling. New optical measurements then allow phase transformation and phase fronts to be visualized directly. The processes that underpin the formation and movement of various phase fronts can then be explored via simulations. Applications to both anode cathode materials will be described. Finally new approaches to investigate the structures of pristine and degraded electrolyte will be discussed.
(Invited) Novel Strategies in the Design of the Oxygen Evolving Catalysts for Water Electrolysis
Authors: Krtil Petr , Nebel Roman , Sharma Lalita
Published: February 2024

Hydrogen producing electrolytic water splitting is one of the most important electrochemical technologies supporting the de-fossilization of the society and enabling integration of renewable energy sources into electric grid. The water electrolysis in fact combines two electrocatalytic reactions – a two electron hydrogen evolution and four electron oxygen evolution, which in most cases represents the kinetically limiting process determining the efficiency of the green hydrogen production. Given the harsh conditions at which the oxygen evolution is driven in water electrolysers a design of practical oxygen evolving catalysts needs to reflect not only the intrinsic activity, but also stability and feasibility. To reflect these additional factors a specific challenges connected with the pH at which the intended water electrolysis ought to operate need to be included into catalyst design. The development of the anode materials for alkaline water electrolyzers faces less restrictions given reasonable stability of the non-noble transition metal oxides/oxihydroxides at operando conditions. The development of novel anode materials for polymer electrolyte water electrolyzers is far more challenging due the low stability of transition metals at OER potentials in acid media which restricts the available catalysts to those based on scarce Ru, or Mn.

The presented paper will describe two approaches attempting development of novel OER catalysts for acid media. The first approach aims at following the high entropy concept pioneered theoretically by Svane and Rossmeisl [1]. The synergetic effects encountered in high entropy oxides will be demonstrated on mixed Ru-Ir pyrochlores stabilized by lanthanides prepared by spray freeze freeze drying technique. While the high entropy oxides are highly active in OER the need to explore noble metal oxides may still represent a stumbling block in large scale deployment. This restriction may be removed by targeted activation of wide band semiconducting oxides by simultaneous n- and p- co-doping [2]. The co-doping strategy alters the electronic structure of the host oxide generating a pseudo-band in the materials band gap facilitating an electrocatalytic activity (in dark). The concept predicts that a wide band semiconductors based on , e.g. Ti, may be activated into a active OER catalysts potentially compensating a lower intrinsic activity with low price. The potential of the approach will be demonstrated on two systems – co-doped anatase polymorph of TiO2 and on co-doped cubic titanate based perovskites.

References:

K. Svane, J. Rossmeisl, Angew. Chem., 134 (2022), 4923-4925

T. Kutlusoy, S. Divanis, R. Pittkowski, R. Marina, A. M. Frandsen, K. Minhova-Macounova, R. Nebel, D. Zhao, S. F. L. Mertens, H. Hoster, P. Krtil, J. Rossmeisl, Chem. Sci., 2022,13, 13879-13892
(Invited) Development of Sustainable Electrocatalysts for Anion Exchange Membrane Fuel Cells and Electrolyzers
Authors: Miller Hamish Andrew , Bartoli Francesco , Pagliaro Maria Vincenza , Bellini Marco , Peruzzolo Tailor , Evangelisti Claudio , Castello Carolina , Poggini Lorenzo , Vizza Francesco
Published: February 2024

The electrocatalytic hydrogen oxidation (HOR) and evolution (HER) reactions under alkaline conditions are kinetically slow processes even when Pt group metals are employed. This presentation discusses our strategies to improve the activity of non platinum catalysts. For example, to improve the alkaline HOR activity of transition metal nanoparticles we look at engineering strong interactions with metal oxides incorporated with carbon-based catalyst supports.(1,2) Another strategy involves utilizing novel carbon materials such as onion like carbon (OLC). We have shown that the combination of CeO2 and OLC in Pd–CeO2/OLC induces surface defects and modifies the electronic structure of the Pd-OLC interface, significantly improving electrical conductivity due to enhanced charge redistribution. Such results were corroborated by density functional theory (DFT) calculations.(3) Using this strategy, peak power densities of up to 2 W cm-2 have been achieved when Pd-CeO2 is incorporated in AEMFCs.(4) Regarding the alkaline HER, mixed phase Ni-Mo and MoO3-x materials are known to have enhanced alkaline hydrogen evolution reaction (HER) activity. Here we describe the optimization of the preparation of an active HER catalyst composed of MoO2 surface nanorod arrays on nickel foam (see Figure). Large circular cathode electrodes (Area 80 cm2) were prepared and tested in a three cell stack AEM electrolyser.(5)

M. V. Pagliaro, C. L. Wen, B. Sa, B. Y. Liu, M. Bellini, F. Bartoli, S. Sahoo, R. K. Singh, S. P. Alpay, H. A. Miller and D. R. Dekel, ACS Catal., 10894 (2022).

M. V. Pagliaro, M. Bellini, F. Bartoli, J. Filippi, A. Marchionni, C. Castello, W. Oberhauser, L. Poggini, B. Cortigiani, L. Capozzoli, A. Lavacchi, H. A. Miller and F. Vizza, Inorg. Chim. Acta, 543 (2022).

J. Ogada, A. K. Ipadeola, P. V. Mwonga, A. B. Haruna, F. Nichols, S. W. Chen, H. A. Miller, M. V. Pagliaro, F. Vizza, J. R. Varcoe, D. M. Meira, D. M. Wamwangi and K. I. Ozoemena, ACS Catal., 12, 10938 (2022).

H. A. Miller, M. Bellini, D. R. Dekel, and F. Vizza, Electrochemistry Communications, 135, 107219 (2022).

F. Bartoli, L. Capozzoli, T. Peruzzolo, M. Marelli, C. Evangelisti, k. Bouzek, J. Hnat, G. Serrano, L. Poggini, K. Stojanovski, V. Briega-Martos, S. Cherevko, H. A. Miller and F. Vizza, J. Mater. Chem. A, 11, 5789 (2023).

Figure 1
(Invited) In Situ Photoelectron Spectroscopy Reveals the Chemical Nature of Semiconductor Surface States
Authors: Favaro Marco
Published: February 2024

The accessible photovoltage of semiconducting photoabsorbers is typically 0.5-1 V below the theoretically achievable values predicted by the Shockley-Queisser limit [1]. Although the reason for this is still not well understood, surface and interface states within the photoabsorbers energy band gap may play a crucial role as they generally induce Fermi level pinning [2]. Within the PEC community, two key elements have been identified for the maximization of the photovoltage in photoelectrodes for water splitting: (i) the passivation of surface defects which is needed to avoid Fermi level pinning, and (ii) the increase of the minority carrier concentration at the interface to improve contact selectivity and optimize carrier extraction [3,4].

To understand the role of surface defects on Fermi level pinning, detailed information on the chemical nature and electronic properties of surface states is needed. Such information is usually obtained with UHV surface science techniques such as XPS, but the photoelectrode surface under UHV conditions has little, if any, relevance to the electrified surface when immersed in the electrolyte. Moreover, recent studies have shown that semiconductor surfaces are not static, but undergo extensive structural and chemical transformations during PEC device operation [5,6]. In this talk, we will show our recent development of state-of-the-art techniques to study the structure and dynamics of semiconductor/water interfaces under practically relevant conditions [7]. The chemical nature of the electronic states for selected semiconductors prepared at the Institute for Solar Fuels has been explored using synchrotron-based resonant, ambient pressure soft and hard X-ray photoelectron spectroscopy (AP-XPS and AP-HAXPES) [6,8-11], and with in situ/operando Raman and photoluminescence spectroscopy. In particular, we will show that it is possible to study photon-induced chemical changes at solid/liquid interfaces using AP-XPS and AP-HAXPES [6,8].

We will conclude this contribution by discussing about future perspectives and technical implementations for multimodal in situ/operando investigations of photoelectrocatalytic processes.

[1] M.T. Mayer. Curr. Opin. Electrochem. 2017, 2, 104.

[2] A. J. Bard et al. J. Am. Chem. Soc. 1980, 102, 3671.

[3] A.G. Scheuermann et al., Nat. Mater. 2016, 15, 99.

[4] M. Schleuning et al., Sustainable Energy Fuels, 2022, 6, 3701.

[5] F.M. Toma et al., Nat.
Commun. 2016, 7, 12012.

[6] M. Favaro et al., J. Phys. Chem. B 2018, 122, 801.

[7] M. Favaro et al., Surf. Sci. 2021, 713, 121903.

[8] M. Favaro et al., J. Phys. D: Appl. Phys. 2021, 54, 164001.

[9] M. Favaro et al., J. Phys. Chem.
C 2019, 123, 8347.

[10] W. Wang et al., J. Am. Chem. Soc. 2022, 144, 17173.

[11] P. Schnell et al., Sol. RRL 2023, 2201104.
(Invited) Challenges with Ceria Diffusion Barrier Layer
Authors: Elangovan S , Hafen Tyler , Rane Taylor , Pike Jenna , Escobar Julian , Marina Olga A
Published: February 2024

Sr-doped perovskite has been the most commonly used oxygen electrode material for solid oxide cells due to their high conductivity and catalytic activity for oxygen reduction and oxygen evolution reactions. Direct contact of the electrode material with the doped zirconia electrolyte leads to formation of resistive Sr- and La-zirconate phases during cell fabrication and long-term operation leads to performance loss. A doped ceria barrier layer is applied between the electrolyte and the oxygen electrode to avoid the reactions that form the resistive phase. The ceria layer is applied using a variety of processes and screen printing is the preferred method as the oxygen electrode also uses the same fabrication option. The barrier layer is sintered at high temperature to target a thin, dense layer. The barrier layer sintering temperature needs to balance good resulting density without any reaction with the electrolyte. The ceria-zirconia solid solution is more resistive than the end members. Thus, it is accepted to limit the sintering temperature which results in a porous barrier layer.

OxEon stacks tested for several thousand hours were post-test analyzed at the Pacific Northwest National Laboratory using an array of electron microscopes, and Sr migration to the zirconia interface through pores and discontinuity in the barrier layer was confirmed. The use of Sr-free electrode composition between the barrier layer and the Sr-containing electrode layer did not prevent Sr migration to the electrolyte interface when discontinuities are present in the barrier layer.

In addition, the dopant in ceria, samaria in this case, also migrates into zirconia during long-term operation while as fabricated cells do not show migration of samaria.

Investigations are ongoing to improve the density of the barrier layer without deleterious interdiffusion during fabrication.
(Invited) Towards Developing a Highly Efficient and Durable Water Electrolyser with Low-Cost Cell Components
Authors: Gago Aldo Saul , Torrero Jorge , Morawietz Tobias , Garcia Daniel , Friedrich K. Andreas
Published: February 2024

Proton exchange membrane water electrolysis (PEMWE) is a promising technology for sustainable hydrogen production and decarbonization in the chemical industry. However, it is considered expensive due to the high cost of the stack components. Specifically, the titanium bipolar plates (BPPs) and porous transport layers (PTLs) are responsible for a large share of the cost. In prior work, the German Aerospace Center (DLR) addressed the cost issue by using stainless steel as a base material for manufacturing the BPPs of a PEMWE stack. In addition, a Nb/Ti macroporous layer (MPL) applied via plasma spraying enables the use of stainless steel PTL, which not only protects the PTL against corrosion but increases the cell performance significantly (Figure 1a) [1]. A significant cost reduction with stainless steel cell components can be achieved but the high amount of iridium (2-3 mgIr cm-2) in the anode is considered a critical issue for this technology. In this regard, an anode with 10-fold reduction of Ir has been developed recently using a reconstructed Sr2CaIrO6 catalyst, showing practically no degradation in a 1000 h durability test (Figure 1b) [2]. Therefore, a PEMWE with all low-cost components is possible. However, a complete removal of critical raw materials in PEMWE is a long-term development goal, which can be achieved with anion exchange membrane water electrolysis (AEMWE), as it does not require precious metals as catalysts. AEMWE combines the advantages of PEMWE and alkaline water electrolysis into the next generation of electrolysis technologies. The most recent developments by DLR in this field will also be presented.

Figure 1: a) Cell voltage (Ecell) vs. Current density (j) of a PEMWE with coated stainless steel BPPs and PTLs. The inset shows a cross section image of the catalyst coated membrane (CCM) after an accelerated stress test (AST) showing no Fe contamination; b) Ecell vs. Time of a PEMWE with Sr2CaIrO6 anode (0.2 mgIr cm-2). The insets show images of the electrode and catalyst at the end of the durability test (EoT).

References:

[1] S. Stiber, N. Sata, T. Morawietz, S.A. Ansar, T. Jahnke, J.K. Lee, A. Bazylak, A. Fallisch, A.S. Gago, K.A. Friedrich, A high-performance, durable and low-cost proton exchange membrane electrolyser with stainless steel components, Energy Environ Sci. 15 (2022) 109–122. https://doi.org/10.1039/d1ee02112e.

[2] J. Torrero, T. Morawietz, D.G. Sanchez, D. Galyamin, M. Retuerto, V. Martin-Diaconescu, S. Rojas, J.A. Alonso, A.S. Gago, and K.A. Friedrich, High Performance and Durable Anode with 10-fold reduction of Iridium loading for Proton Exchange Membrane Water Electrolysis, Adv Energy Mater. (2023), in press.

Figure 1
(Best Student Poster Award) Energy Harvesting from Carbon Dioxide Capture through an Ionic Liquid Based Supercapacitor
Authors: Molino Davide , Zaccagnini Pietro , Martellone Simone , Pedico Alessandro , Ferraro Giuseppe , Bocchini Sergio , Lamberti Andrea
Published: February 2024

Nowadays, Earth is undergoing effects of climate change due to the exponential increase of greenhouse gasses's emissions. The main component of greenhouse emissions is carbon dioxide (CO2), which is estimated responsible for about 60% of global warming generated by human activities, and its concentration is increased by 40% with respect to the concentration at the beginnings of industrial era. This increase is due to several factors such as the combustion of coal, oil and gas and the progressive deforestation: this last phenomenon generates a sort of bottleneck in the so called biogeochemical "carbon cycle". Deforestation causes the lack of one of the natural regulating sources of carbon dioxide concentration.

Scientific community set an increase of 2°C (with respect to the pre-industrial global temperature) as the threshold beyond which there is a much higher risk that dangerous and possibly catastrophic changes in the global environment will occur. At the moment the increase of the temperature has reached about +0,85°C thanks to greenhouse gasses. All technologies developed in CO2 capturing have to be intended in the reduction of global warming.

The goal of the presented work is to develop a device able to cut down greenhouse emissions by reusing human produced carbon dioxide. This can be done exploiting the free energy released each time two solutions with different compositions are mixed. Even if this phenomenon holds true both for liquids and gases, in last decades it was deeply investigated for what concerns liquid sources (CapMix), while few technologies are available to harvest free energy coming from gas sources. The adopted structure is an electrical double layer super-capacitor based on ionic liquid electrolyte. Special attention should be paid to the choice of the electrolyte which should work both as an electrolyte and CO2 absorbing medium in a CapMix cell. Among the tested ionic liquids, the choice fell on an Imidazole based ionic liquid, which showed excellent absorption rates of gas, being able to capture 15.67% of CO2 over the total mass.

This work is a proof of concept of a novel not yet studied mechanism, which is able to work without any imposed external bias. When a CO2 gas stream is flushed through the supercapacitor, the gas strongly affects the electrode/IL interface and the IL physico-chemical properties, producing a change in the potential difference between the electrodes. In this way it is possible to convert the mixing energy into electrical energy.

Figure 1
(Invited) A Sustainable Future Fueled By Science: Recent Advances in Power-to-X Activities at Topsoe
Authors: Sala Elena Marzia , Ebbesen Sune Dalgaard , Blennow Peter Gustav , Padinjarethil Aiswarya Krishnakumar , Drasbæk Daniel Bovin , Heiredal-Clausen Thomas , Perin Giovanni , Rass-Hansen Jeppe , Dalby Kim N. , Tiruvalam Ramchandra , Hauch Anne
Published: February 2024

Topsoe aims at being recognized as the global leader in carbon emission reduction technologies by 2024, by developing a wide range of energy-efficient solutions to produce sustainable transportation fuels, such as ammonia, methanol, and hydrogen. With over 80 years of expertise in heterogeneous catalysis and its application to industrial chemical processes, Topsoe is now striving to develop strong Power-to-X solutions to fuel the transition towards a sustainable chemical industry and energy infrastructure. One of the key-technology that Topsoe has envisioned for such transition is the solid oxide electrolysis cell (SOEC) technology, well-recognized as the most energy-efficient amongst the electrolysis solutions. Here, Topsoe’s expertise in heterogeneous catalysis also plays a role in ensuring an effective downstream catalytic conversion of SOEC products (H2, CO, or syngas) into green fuels and chemicals. To tackle climate change at the pace that our times impose, Topsoe is committing to a goal of net-zero greenhouse gas emissions by 2040. To reach such an ambitious goal, a large industrial scale application of the SOEC technology is necessary. Accordingly, Topsoe has announced the construction of a SOEC manufacturing facility in Denmark to produce electrolysis stacks and modules with a capacity of 500 MW per year, planned to be operational in 20251.

In this presentation, Topsoe will provide an overview of its initiatives, lines of work and results in the field of SOECs, spanning from the thorough investigation of materials properties and electrode microstructure to the design and realization of a MW-sized electrolyzer plant. An extensive R&D effort is also directed towards increasing the lifetime of Topsoe’s fuel electrode-supported Ni/YSZ based cells, aiming at the development of robust and durable electrodes. The presentation will give examples of the analysis of electrode nano- and micro-structures by advanced characterization techniques, while illustrating the valuable role of impedance spectroscopy for the electrochemical characterization of the state-of-the-art cell performance. Finally, the presentation will also showcase results of stack testing applying Topsoe's stack technology for H2 production, as well as an update and outlook of Topsoe's efforts in upscaling its SOEC capacity.

P. Blennow, T. Heiredal-Clausen, J. Rass-Hansen, J. B. Hansen; M. Hultqvist, and P.-G. Moses, in Proceedings - 14th Europrean Solid Oxide Fuel and SOE Cell Forum, p. A0304 (2022)
(Digital Presentation) New Magnetron Sputtering Fabrication Process for Ba0.5Sr0.5Co0.8Fe0.2O3-
δ Miec Thin Film Membranes on Porous Support for Oxygen Permeation Applications
Authors: Mewafy Basma , Ravkina Olga , Wallis Jan , Wetegrove Marcel , Kircheisen Robert , Kriegel Ralf , Wartmann Jens , Kruth Angela
Published: February 2024

Mixed ionic electronic conductor (MIEC) membranes provide a great route for introducing oxygen to combustion and reforming processes of new fuels such as green ammonia. Ba0.5Sr0.5Co0.8Fe0.2O3-
δ (BSCF) is known to be one of the most widely utilized perovskite material applied as oxygen transport membrane, as it possesses elevated oxygen permeability up to 7 ml(STP)·min-1·cm-2 at a temperature range of 850-900°C. Application of thin MIEC films of thicknesses of around 500 nm – 5 µm allow for reduction of Ohmic resistance for transport processes and sufficient oxygen permeation at lower temperatures as compared to bulk membranes, which is of great advantage with regard to materials stability and quality of sealing. However, fabrication techniques of thin MIEC membranes staunchly influence their phase purity. Crystallinity, microstructure and correlated oxygen diffusion properties as well as stability of membrane-substrate interfaces. Physical vapour deposition (PVD) such as magnetron sputtering (MS) is successfully applied to produce a dense and pinhole-free membrane with thicknesses ranging from 100 nm nanometer to a few micrometers. Challenges due to large size porosity of the ceramic substrate were addressed by tuning of the substrate porosity, ensuring formation of a continues layer and stability of the thin membranes. In this work, we report on the influence of the MS process parameters, as well as subsequent annealing techniques of both thermal annealing (TA) and line beam Laser annealing (LA) on the microstructure of a fabricated asymmetric membrane (AsM) consisting of BSCF thin membrane on a BSCF support wit tunable pore sizes. Oxygen permeability of the AsM was investigated at high temperatures (850-900 °C). For a substrate pore size of around 3 µm, BSCF membrane thicknesses of 1 to 5 µm could be applied for fabrication of AsM, resulting in a 2-fold increase of oxygen permeability ~5 ml.min-1.cm-2 at a temperature of 900 °C as compared to a bulk BSCF support of ~2 mm thickness, whereas comparable oxygen permeation is already reached at a temperature of 700°C by the thin membrane. Contrariwise, the one with high porosity (~10 µm) required the deposition of thicker layers, which obstruct the oxygen diffusion and inhibited the permeation. The results have optimised sputtering process parameters, supports porosity and TA&/SLA parameters, are key factors for producing thin film membrane exhibiting high oxygen flux and good stability.
Multi-Functional Alkaline Electrolysis Setup for Industrially Relevant Testing of Cell Components
Authors: Maide Martin , Prits Alise-Valentine , Mandati Sreekanth , Küngas Rainer
Published: February 2024

Alkaline electrolysis is an industrially mature and promising method for the production of green hydrogen at scale [1]. Alkaline electrolysers are typically characterized by low investment costs compared to other electrolysis technologies [2]. Despite being used for industrial applications for almost 100 years, the efficiency of alkaline systems can still be significantly improved. To this end, rigorous testing and optimisation of cell components is paramount.

Here, we report a multi-functional alkaline electrolysis setup, designed to facilitate testing of various cell components, including electrodes, diaphragms, and catalyst. The setup is a further development of the setup originally reported by Ju et al. [3]. Importantly, the setup allows cell components to be tested under industrially relevant conditions: temperatures up to 80°C, concentrated KOH, pressures of up to 30 barg. The setup features KOH recirculation, a drying column and gas analysers for estimating the purity of produced hydrogen and oxygen. The measurement setup further allows the use of different cell configurations, enabling comparative analysis and the identification of optimal combinations of cell components for specific use-cases. Example experimental results collected at various test conditions, including the EU harmonized test conditions for low-temperature electrolysis cells [4], are reported.

References:

Mueller-Langer, E. Tzimas, M. Kaltschmitt, S. Peteves, Int. J. Hydrogen En., 32, 3797–3810 (2007).

Buttler, H. Spliethoff, Renewable and Sustainable Energy Reviews, 82, 2440–2454 (2018).

Ju, M. V. F. Heinz, L. Pusterla, M. Hofer, B. Fumey, R. Castiglioni, M. Pagani, C. Battaglia, U. F. Vogt, ACS Sustainable Chem. Eng., 6 (4), 4829–4837 (2018).

Tsotridis, A. Pilenga, EU harmonised protocols for testing of low temperature water electrolysers, EUR 30752 EN, Publications Office of the European Union, Luxembourg (2021).

Figure 1
Exploring the Local Optoelectronic Properties of ALD Grown TiO2 Photoelectrode-Coatings with Atomic Force Microscopy Methods
Authors: Pourmahdavi Maryam , Raudsepp Ragle , Fengler Steffen , Kriegel Herman , Kollmann Jiri , Klassen Thomas , Schieda Mauricio , Toma Francesca Maria
Published: February 2024

Photoelectrochemical cells (PECs) hold great promise as an environmentally friendly method of converting sunlight into valuable fuels. However, the semiconductor components of PEC photoelectrodes are susceptible to corrosion under photoelectrochemical conditions.

In order to protect the surface of these semiconductors from degradation, a thin overlayer of Titanium dioxide (TiO2) is often applied by atomic layer deposition (ALD). In addition to their protecting function, the physicochemical properties of these thin films significantly affect the overall performance of the device. The local nano-scale optoelectronic characteristics, which considerably influence their macroscopic properties, have rarely been reported in the literature.

AFM methods constitute a powerful tool to investigate photo-induced charge separation, charge transport and recombination on photoelectrode surfaces with nanometer resolution.

In this context, we have employed Tunneling Conductive AFM (TUNA) and Kelvin Probe Force Microscopy (KPFM) in the dark and under illumination to investigate the surface of ALD-grown TiO2. The synthesis conditions determine the morphology, which has a strong impact on the local optoelectronic properties. TUNA measurements reveal higher photogenerated currents on the grain and facet boundaries, showing that these regions can be favorable conduction pathways. Based on KPFM experiments we can quantify the more efficient photo-induced charge separation on the crystalline TiO2 inclusions, which generate a significant surface photopotential (~450 mV) upon UV-illumination. Categorization of different regions of surface topography based on morphology allows us to analyze the evolution of surface potential over time and extract localized time constants for carrier dynamic processes on the films. This spatially resolved information provides valuable insight to guide the development of macroscopically stable and efficient photoelectrodes through the engineering of microstructure at the nano scale.