Abstract: This paper describes the developments under a European Space Agency (ESA) activity for the development of a high-pressure steam electrolyser system for exploration surface missions. The base case scenario considered is a hydrogen and oxygen production unit for lunar missions, where water for the electrolyser is generated from ice-bearing consolidated regolith.

Abstract: Onsite production of oxygen and hydrogen is an essential contribution to any manned mission to the Moon or to Mars. In both environments there are elements consisting of bound oxygen, such as water ice-bearing consolidated regolith on the moon and carbon dioxide on Mars. These resources can be used to generate oxygen gas through electrolysis, together with energy carriers, namely hydrogen and CO, as by-products. Solid Oxide Electrolysis (SOE) technology possesses the highest potential for this application, due to the high operation temperature ranging from, 650°C to 900°C. Therefore, it can split each or both H 2 O and CO 2 , into H 2 , CO and O 2 without compromising the integrity of the electrodes by poisoning, while the process can be further integrated with other thermal processes, such as the reduction of mineral oxide to provide overall very high system efficiencies. The solid oxide cell (SOC) technology is also fully reversible (i.e., the cell works both as electrolyser and as fuel cell) and can be used for unitised reversible fuel cell systems (URFCS) for energy storage and generation. This paper describes the developments under a European Space Agency (ESA) activity for the development of a high-pressure steam electrolyser system for exploration surface missions. The base case scenario considered is a hydrogen and oxygen production unit for lunar missions, where water for the electrolyser is generated from ice-bearing consolidated regolith. The development of the electrolyte supported cells was based in an all-ceramic approach. Specifically, electrolyte (8YSZ, 3YSZ, 6Sc1CeSZ and 10Sc1CeSZ) supported cells were fabricated comprising substituted lanthanum chromite La 0.75 Sr 0.25 Cr 0.9 Fe 0.1 O 3 (LSCrF), as fuel electrode, and (La 0.80 Sr 0.20 ) 0.95 MnO 3-x (LSM) or (La 0.60 Sr 0.40 ) 0.95 Co 0.20 Fe 0.80 O 3-x (LSCoF), as oxygen electrodes. The electrochemical characterization and performance assessment in button cells (with an electrode footprint of ~0.8 cm 2 ) was conducted for (i) steam electrolysis and (ii) reversible cell operation (fuel cell and electrolysis modes). All cells exhibited stable performance within the whole range of potentials, thus revealing the fact that Solid Oxide technology is in principle reversible and versatile in functionalities. Regarding steam electrolysis, the effect of hydrogen co-fed was investigated. The lack of reducing agent (H 2 ) in the fuel side results in a non-trivial evolution of the current-potential curve, as the Nernst potential is not fixed and the production of a substantial concentration of hydrogen is required for the IV curve to follow the typical linear relation. However, within the linear IV region the performance of the cells is similar in presence or in absence of hydrogen, exhibiting ~2 A/cm 2 at 1.5 V. Following these key developments, a high-pressure short stack is designed and constructed, comprising five (5) cells with an active area of 42 cm 2 . The stack is enclosed in a hot box consisting of the mechanical and thermal environment for the stack. To operate at pressure up to 10 bars, the hot box is placed inside a stainless-steel chamber made of standard piping elements. The hot box is complemented with all necessary balance of plant (steam generator, water system, gas storage) to realise a complete a steam electrolysis system which will be validated in operation against a load profile representing energy storage in Lunar environment for 3 lunar days (~2,126 h). Figure 1

Abstract: Polymer electrolyte membrane (PEM) water electrolyzers suffer mainly from slow kinetics regarding the oxygen evolution reaction (OER). Noble metal oxides, like IrO2 and RuO2, are generally more active for OER than metal electrodes, exhibiting low anodic overpotentials and high catalytic activity. However, issues like electrocatalyst stability under continuous operation and cost minimization through a reduction in the catalyst loading are of great importance to the research community. In this study, unsupported IrO2 of various particle sizes (different calcination temperatures) were evaluated for the OER and as anode electrodes for PEM water electrolyzers. The electrocatalysts were synthesized by the modified Adams method, and the effect of calcination temperature on the properties of IrO2 electrocatalysts is investigated. Physicochemical characterization was conducted using X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area measurement, high-resolution transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analyses. For the electrochemical performance of synthesized electrocatalysts in the OER, cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were conducted in a typical three-cell electrode configuration, using glassy carbon as the working electrode, which the synthesized electrocatalysts were cast on in a 0.5 M H2SO4 solution. The materials, as anode PEM water electrolysis electrodes, were further evaluated in a typical electrolytic cell using a Nafion®115 membrane as the electrolyte and Pt/C as the cathode electrocatalyst. The IrO2 electrocatalyst calcined at 400 °C shows high crystallinity with a 1.24 nm particle size, a high specific surface area (185 m2 g−1), and a high activity of 177 mA cm−2 at 1.8 V for PEM water electrolysis.

Abstract: A challenging barrier for the broad, successful implementation of SOFC/SOEC technologies, remains the long term stability by the effective control and minimization of degradation resulting from carbon built up. A class of Au-modified commercially available NiO/GDC and NiO/YSZ cermet powders has been developed and studied for their performance and tolerance to carbon deposition, employed as SOFC anodes for CH 4 steam reforming, as well as bi-functional electrodes in a Regenerative SOFC operating on the CO 2 cycle (SOEC: CO 2 electrolysis, SOFC: power generation through the electrochemical reaction of CO and oxygen). In-situ HT-XRD tests revealed that the presence of Au, in an optimum nominal loading of 3wt%, affects the Ni crystal phase and has a significant positive effect in inhibiting carbon deposition. Cell testing in the temperature range of 800-1000° under carbon forming conditions, showed promising stable performance of the modified electrodes.

Abstract: In a time, where first solid oxide based systems enter demonstration and commercial markets, the European NewSOC project focuses on next generations. It aims at significantly improving performance, durability, and cost competitiveness of solid oxide cells and stacks compared to state-of-the-art (SoA). In order to achieve these goals, NewSOC investigates twelve innovative concepts in the following areas: (i) structural optimization and innovative architectures based on SoA materials, (ii) alternative materials, which allow for overcoming inherent challenges of SoA, (iii) innovative manufacturing to reduce critical raw materials and reduction of environmental footprint at improved performance and lifetime. The NewSOC unifies competences of 16 strong research and industry players. First scientific highlights were achieved despite the challenging working conditions under the European wide Covid-19 restrictions in the first year of the project. The presentation will provide a selection of these highlights.

Abstract: Solid oxide technologies (SOC: Solid oxide fuel cells SOFC & Solid oxide electrolysis SOE) are key enabling technologies for energy systems based on renewable sources and allow for a strong interlinking of sectors electricity, heat, and gas/fuels. SOC can emerge as key players in many concepts, such as fuel/gas to power and heat at small to large scale, energy storage through power to hydrogen/fuel, utilization and upgrading of biogas, balancing of intermittent electricity from renewable sources through load following and reversible operation, and central and decentral solutions for electricity and heat production. In a time, where first SOC systems enter demonstration and commercial markets, the NewSOC project focusses on next generations. It aims at significantly improving performance, durability, and cost competitiveness of solid oxide cells & stacks compared to state-of-the-art (SoA). In order to achieve these goals, NewSOC investigates twelve innovative concepts in the following areas: (i) structural optimization and innovative architectures based on SoA materials, (ii) alternative materials, which allow for overcoming inherent challenges of SoA, (iii) innovative manufacturing to reduce critical raw materials and reduction of environmental footprint at improved performance & lifetime. The NewSOC unifies competences of 16 strong research and industry players. First scientific highlights were achieved despite the challenging working conditions under the European wide covid-19 restrictions in the first year of the project. The presentation will provide a selection of these highlights. One focus area is the development of novel electrode materials, where high performance, impurity tolerance and stability are the primary targets. Nanostructured fuel electrodes based on doped SrTiO 3 perovskites such as LaSrFeNiTiO 3 are being developed as backbones. Subsequent, wet infiltration of Ni:GDC ensures high electro catalytic activity and ionic conductivity, while retaining the advantages of Ni-metal free fuel electrodes outlined above. Furthermore, a class of doped lanthanum chromites (La 0.75 Sr 0.25 Cr x M 1-x O 3-δ , M=Fe, Mn, Ni) is developed as Ni-metal free fuel electrodes, to overcome the challenges faced by the SoA Ni-cermets. The perovskite structured electrodes, combined with highly conductive electrolytes have high performance, low ASR and flexibility in various operating modes (SOEC, rSOC). The most attractive feature of this class of electro catalysts is that they retain their properties (oxidative state, conductivity) in reducing and oxidizing environments at SOC operating temperatures, even in absence of a reducing agent, i.e. H 2 . Another approach is to modify SoA electrodes. Commercial (SoA) Ni/GDC was modified with iron by deposition – precipitation (D.P.), leading to enhanced performance as functional SOE fuel electrode. The promoting effect depends on the wt.% Fe content, where D.P. of quite a small amount of iron, through the formation of a Ni-Fe alloy, caused a 3-fold enhancement compared to Ni/GDC. Interestingly, the 0.5-Fe-Ni/GDC electrode performed similarly well like the noble-metal modified 3Au-0.3Mo-Ni/GDC. Materials compositions and structuring go hand in hand for tailoring cell properties. Under this focus, novel air electrode architectures for SOFC & SOE applications based on Co- and Ni-free materials with the (La, Ca, Sr)FeO 3 perovskite class of materials are developed. The typically increased overpotential of Co- and Ni-free air electrodes is a challenge, which is tackled by introduction of a patterned porous barrier layer and addition of a composite layer at the electrode/electrolyte interface to enhance the triple phase boundary density between electrolyte and the Co-free air electrode. In another approach, the microstructure of SoA Ni/YSZ and LSCF/GDC electrodes was assessed to identify the best tradeoff between the cell performances, the durability and the robustness by a methodology coupling of manufacturing, characterization, and modeling. As a result, the performance of the LSCF/GDC composite electrode was improved, with different porosities, graded electrodes and composites. The role of the Ni/YSZ microstructure on the Ni migration during operation was investigated, with focus on finer and more homogeneous electrodes. Manufacturing and deposition methods contribute significantly to performance & lifetime, but also costs and environmental impact of SOC production. Thus, alternative approaches providing cells & stacks with required specifications are part of the NewSOC project. Progress on sputter deposited GDC buffer layers has been obtained in view of their implementation in the fabrication process of commercial Solid Oxide Fuel Cells.

Abstract: Solid Oxide Fuel Cells (SOFC) and Electrolyzers (SOEC) hold great potential for the security of energy sector, providing solutions for efficient power generation and production of hydrogen and synthesis gas. A challenging barrier for the successful implementation of SOFC and SOEC technologies, remains the long term stability under realistic operating conditions by the effective control and minimization of degradation due to carbon built up. The problem arise from the fact that the commonly used anode cermets, e.g. Ni-YSZ and Ni-GDC, are prone to carbon deposition onto nickel, as a result of the Boudouard reaction (CH 4 cracking, disproportionation of CO), leading to low activity and fast degradation. In this study, a class of Au-modified commercially available NiO/GDC and NiO/YSZ cermet powders has been developed and studied for their performance and tolerance to carbon deposition, operating as SOFC anodes for CH 4 steam reforming, as well as bi-functional electrodes in a Regenerative SOFC operating on the CO 2 cycle (SOEC mode: electrolysis of CO 2 , SOFC mode: electrochemical reaction of CO and oxygen for power generation). In- situ HT-XRD tests revealed that the presence of Au, in an optimum nominal loading of 3wt%, affects the Ni crystal phase and has a significant positive effect in inhibiting carbon deposition. The results from cell testing in the temperature range of 800-1000°C, showed promising, stable performance of electrodes under carbon forming conditions (e.g. H 2 O/CH 4 =0.25, CO or CO/CO 2 mixtures of 0.7/0.3). The work is supported by the FCHJU project T-CELL (298300).