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The development of multi-functional and highly mixed ionic-electronic conductive perovskite oxide-based electrodes is becoming an established trend for designing and developing SOFC/SOEC reversible cells. Ideally, the same material can be employed at both electrodes provided that structural stability, high conductivity and catalytic activity are preserved in different operational atmospheres. Here, controlled Fe substitution with a small extent (0.5 mol%) of platinum at the B-site of a lanthanum strontium ferrite is proposed as an effective method to enhance the original oxide properties as both air and fuel electrode for solid oxide cells. The effects of low Pt-doping on La 0.6 Sr 0.4 FeO 3-δ structure, morphology and electrocatalytic activity are investigated and discussed. La 0.6 Sr 0.4 Fe 0.995 Pt 0.005 O 3-δ (05P-LSF) is first tested as air electrode, displaying lower area specific resistance as compared to the Pt-free perovskite. 05P-LSF structural stability and conductivity are assessed in 100 % CO 2 and 50 % CO 2 –50 % CO environments. Symmetric devices are then tested as SOECs in 100 % CO 2 , obtaining a current density output of 1.08 A/cm2 at 1.5 V. Electrochemical impedance spectroscopy (EIS) with distribution of relaxation times analysis (DRT) are used to provide insights on the electrode operation. Pt nanoparticle exsolution at the fuel electrode is induced by voltage application. The device stability under applied voltage is assessed for over 120 h. SOFC/SOEC characterization in a 50 % CO 2 /50 % CO mixture at 850 °C is also provided, obtaining a maximum power density of 270 mW/cm2 in SOFC mode, and a current density of 0.91 A/cm2 at 1.5 V in SOEC mode. [ABSTRACT FROM AUTHOR]

Sustainable aviation fuel (SAF) production from captured carbon dioxide and green hydrogen, is referred to as the key to decarbonize the hard-to-abate aviation sector. Fischer-Tropsch is a mature and reliable pathway for hydrocarbon synthesis, with a wide spectrum of technological options and high plant efficiency extending to more than 80 % of e-kerosene selectivity. In this work, an Aspen Hysys model, coupled with different Matlab simulations for Fischer-Tropsch, Hydrocracker and SOEC, was set up to estimate efficiency and selectivity. The results show that global efficiency is mainly linked to the efficiency of the production of H 2. Energetic efficiency reaches 48.06 % using the already existing commercial electrolyte supported cell in a SOEC electrolyser, but it could increase to 65.74 % if cathode supported cell was considered. • An energy analysis of the Power-to-Liquid process has been performed. • The system reaches a global efficiency of 48.06 % and up to 38.71 % of Power-to-Kerosene efficiency. • It is possible to increase global efficiency up to 65.74 % and Power to kerosene efficiency to 53.60 %. [ABSTRACT FROM AUTHOR]

The mixture of H2 and CO, the so-called syngas, is the value-added product of H2O and CO2 co-electrolysis and the feedstock for the production of value-added chemicals (mainly through Fischer-Tropsch). The H2/CO ratio determines the process in which syngas will be utilized and the type of chemicals it will produce. In the present work, we investigate the effect of H2O/CO2 (steam/carbon dioxide, S/C) ratio of 0.5, 1 and 2 in the feed, on the electrochemical performance of an 8YSZ electrolyte-supported solid oxide cell and the H2/CO ratio in the outlet, under co-electrolysis at 900 °C. The B-site iron doped lanthanum strontium chromite La0.75Sr0.25Cr0.9Fe0.1O3-δ (LSCF) is used as fuel electrode material while as oxygen electrode the state-of-the art LSM perovskite is employed. LSCF is a mixed ionic-electronic conductor (MIEC) operating both under a reducing and oxidizing atmosphere. The cell is electrochemically characterized under co-electrolysis conditions both in the presence and absence of hydrogen in the feed of the steam and carbon dioxide mixtures. The results indicate that under the same concentration of hydrogen and different S/C ratios, the same electrochemical performance with a maximum current density of approximately 400 mA cm−2 is observed. However, increasing p(H2) in the feed results in higher OCV, smaller iV slope and Rp values. Furthermore, the maximum current density obtained from the cell does not seem to be affected by whether H2 is present or absent from the fuel electrode feed but has a significant effect on the H2/CO ratio in the analyzed outlet stream. Moreover, the H2/CO ratio seems to be identical under polarization at different current density values. Remarkably, the performance of the LSCF perovskite fuel electrode is not compromised by the exposure to oxidizing conditions, showcasing that this class of electrocatalysts retains their reactivity in oxidizing, reducing, and humid environments. [ABSTRACT FROM AUTHOR]

The application of solid oxide electrolysis cell in CO2 electroreduction is a hot research topic at present, but the development of low−cost catalysts with high catalytic activity has always been a challenge for this work. Herein, we use NiCu alloy nanoparticles to modify the perovskite LSCM electrode to build a metal–oxide active interface to obtain high catalytic performance. At 850 °C, 4.66 mL min−1 cm−2 CO productivity and 97.7% Faraday current efficiency were obtained. In addition, the current remained stable during the 100 h long−term test, indicating that the active interface has the dual effect of improving catalytic performance and maintaining cell durability. [ABSTRACT FROM AUTHOR]

To study the synergy between the transition metals for enhancing the electrochemical and chemical activity, a series of SOECs were modified with a small amount of Co ions, namely 1.8, 3.6, and 5.4 wt% in the reduced state. The addition of βCD into the precursor solution allowed for extremely fine dispersion of Co species across the Ni-YSZ cermet structure. The sample containing 3.6 wt% Co reached an outstanding over 2.5-times-higher concentration of CH 4 in the outlet stream. At the same time, the Co greatly enhanced the electrochemical efficiency of water and CO 2 co-electrolysis. Full characterization involving STXM imaging allowed for better understanding of the synergy between the Ni and Co host metal and made it possible to find the causes of the increased activity. It revealed the complexity of the substructures formed within the electrode. A novel discovery was described regarding the NiCo 2 O 4 spinel structure subjected to the O 2 -TPO measurements. Despite the applied oxidizing atmosphere, the catalyst evolved oxygen at elevated temperatures in a reversible manner. The performance tests indicated the roles of both rWGS and direct electrolysis of CO 2 in the electroreduction process. The addition of Co did not influence the prolonged degradation of the cell. [Display omitted] • Novel SOEC for co-electrolysis and methanation was fabricated. • Addition of Co into Ni-YSZ electrode ensured higher activity. • The change of Ni valence in the electrode has crucial influence on the activity. • Novel discovery on the Ni–Co spinel was made while TPO studies. [ABSTRACT FROM AUTHOR]

• A 3-D SOEC co-electrolysis model was built based on experimental observations. • The model is applicable across a wide range of operating conditions. • Different reaction mechanism and carbon deposition risk were demonstrated. • Critical operating conditions important for practical operation were brought out. Solid Oxide Electrolysis Cell (SOEC) has attracted considerable attention for its potential scalability and high energy conversion efficiency. It is capable of electrolyzing both H 2 O and CO 2 simultaneously, generating syngas that can be further synthesized into carbon-based fuels, which are good energy carriers for long-term energy storage. However, despite its promise, the understanding of the reaction mechanism crucial for extending cell longevity remains incomplete, and concerns persist regarding carbon deposition during co-electrolysis. A dual approach, combining experiments and Multiphysics simulations was adopted to explore the reaction mechanism and carbon deposition risk across a wide range of operating conditions on industrial-size cells. Both experimental observations and simulation results indicate that CO 2 electrolysis and carbon deposition are significantly influenced by the inlet water content and flow rates at the fuel electrode. Increasing the inlet H 2 O concentration and fuel electrode flow rates lead to CO 2 electrolysis occurring at higher current densities. Also, carbon deposition, which was found at the interface of fuel electrode and electrolyte, can be mitigated by controlling the conversion rate relative to the inlet H 2 O content and by increasing the flow rate at the fuel electrode. Additionally, the current density distribution of H 2 O electrolysis and CO 2 electrolysis across the cell were also investigated. The obtained insights hold significance for the practical operation of SOEC co-electrolysis. [ABSTRACT FROM AUTHOR]

• The La-doped perovskite air electrode exhibited superior polarization resistance for oxygen evolution reaction compared to pristine SrEu 2 Fe 2 O 7. • La substitution enhances the oxygen vacancy conduction performance and optimises the carrier transport pathway. • The La-doped air electrode resulted in an increased stability performance and excellent electrolytic current density at the same time. Ruddlesden–Popper (R-P) oxides (A n+1 B n O 3n+1) are potential air electrodes for solid oxide electrolysis cells (SOECs) because of their good electrochemical performance. Among them, SrEu 2 Fe 2 O 7-δ (SEF) with n = 2 has received extensive attention because of its special structure and promising ionic–electronic conductivity. However, the SEF material is prone to degradation at high temperatures (600 °C–800 °C), and its long-term stability is easily affected. In this study, R-P oxide Sr 1-x La x Eu 2 Fe 2 O 7-δ (SLEFx; x = 0, 0.05, 0.1) was successfully synthesized using the sol–gel method. XRD results showed that La-doped SEF displayed good chemical and thermal compatibility with the gadolinia-doped ceria electrolyte. The SLEF0.05 electrode exhibited a polarization resistance of 0.075 Ω cm2 at 800 °C, which was 88.2 % lower than that of SEF. The half-cell based on the SLEF0.05 air electrode exhibited improved performance under the long-term stability test at a current density of − 0.5 A cm−2 for over 110 h at 800 °C, indicating excellent stability. Moreover, an electrolysis current density as high as 0.712 A cm−2 at 1.5 V was obtained for the full cell with the SLEF0.05 air electrode, which was 45.8 % higher than the SEF electrode when the temperature and feed gas were 800 °C and 50 % CO 2 –50 % CO, respectively. The XPS and cell testing results confirmed that La with high valance and small radius promoted the formation of oxygen vacancies and effectively enhanced the electrochemical performance and structural stability of the SEF material. Therefore, the R-P oxide SLEF0.05 is a promising air electrode material for SOECs. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive investigation into the electrochemical reduction of LSCF perovskite during electrolysis, aiming to understand the exsolution of metal nanoparticles. The exsolution of metal nanoparticles from perovskite electrodes can significantly enhance their electrochemical performance in electrolysis. By applying cathodic polarization to the perovskite oxide electrode, the exsolution process was shown to be electrochemically induced within a few minutes. Additionally, a user-designed X-ray absorption spectroscopy operando cell was employed to analyze the edge energy change of the B-site atoms during electrolysis. The electrochemical reduction of perovskite and the subsequent exsolution of the B-site metal nanoparticles were investigated by scanning the cell voltage, providing an understanding of the electrochemical behavior during electrolysis. The electrochemical switching point, characterized by a decrease in the incremental area-specific resistance, was identified. This study offers valuable insights into the electrochemical exsolution process of metal nanoparticles from perovskite oxide electrodes. [Display omitted] • Cathodic polarization induced exsolution of metal nanoparticles from perovskites. • Operando XANES analysis unveiled reduction of oxidation state on B-site atoms. • Electrochemical exsolution was evident during H 2 O and CO 2 electrolysis. • Electrochemical switching point was determined by a decrease in incremental ASR. • In-situ electrochemical exsolution lowered R P during H 2 O and CO 2 electrolysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni-Co alloy nanoparticles were induced to grow on layered perovskite. • The cell renders 1.53A cm−2 at 2.0 V and 850 °C for CO 2 electrolysis. • Faradic efficiencies of the SOEC are higher than 90 % above 1.6 V. • No degradation was observed in a stability test for 32 h. It has never been more important to develop new technologies that can reduce CO 2 emissions or convert them into useful chemical products. As solid-state electrochemical devices, solid oxide electrolysis cell (SOEC) is capable of converting CO 2 efficiently and selectively into CO or, when combined with water electrolysis, producing syngas (CO and H 2). Herein, we demonstrate a novel layered perovskite oxide, reduced (La 4 Sr 4) 0.9 Ti 7.2 Ni 0.4 Co 0.4 O 26 (LSTNC-r), decorated by exsolved Ni-Co alloy nanoparticles for high-efficiency CO 2 electrolysis. The cell renders a higher activity for electrolysis of CO 2 with a current density of 1.53 A cm−2 @2.0 V and 850 °C. Faradic efficiency measurement and stability test suggest that LSTNC-r are promising fuel electrodes for high-efficient CO 2 electrolysis. [ABSTRACT FROM AUTHOR]

This paper studies the Solid Oxide Electrolyzer Cell as a promising system in the sustainable development for the hydrogen economy and energy systems as a robust system. The Solid Oxide Electrolyzer Cell converts the steam and carbon-dioxide directly to functional fuels through consumption of the additional electrical power of green power sources or off-peak network powers. The present paper evaluates the static efficiency of the SOEC under four various gas mixtures. Modeling of this system is performed using Elman neural network (ENN) and modified particle swarm optimization (MPSO) algorithm. The MPSO algorithm is utilized to determine the optimal values for ENN adjustable parameters. It's known from the empirical results that the steam and carbon-dioxide concentrations can affect the SOEC efficiency. The operational potential and volume share of the hydrogen, carbon dioxide and steam are considered as the system inputs, and efficiency (current) is remarked as its output. The correlation factors of the achieved model are greater than 0.999, and its MSE (mean squared error) is lower than 0.017. It reveals that the forecasted values are almost equal to the empirical data. Subsequently, the efficiency of the SOEC is studied using the achieved model of the MPSO-based ENN in various feedstock concentrations. Thus, this dataset that is used for ENN model can be desirable for different applications of fast-modeling in a standalone group. It as well can be useful for cost, computing-time, and computing burden reduction in a model construction in the efficiency analyzing and system-level designing processes. • The static model of a SOEC is identified in this paper. • Elman neural network is applied in this paper as a novel method in the modeling process. • MPSO algorithm is used to increase the accuracy of the obtained model. • Static efficiency of the SOEC is evaluated for various gas mixtures. • The obtained results demonstrated the high precision of the proposed model. [ABSTRACT FROM AUTHOR]

Abstract As a promising renewable energy storage device, the solid oxide electrolysis cell (SOEC) attracts wide attention in the world. In this study, the effect of operating pressure on the co-electrolysis of water and carbon dioxide in SOEC is investigated by a three-dimensional model, in which the reversible water gas shift reaction and direct internal reforming reaction are considered. After comparison with experimental data, the influence of operating pressure on the polarization loss, electrolysis reaction rate, chemical reaction rate and thermal-neutral voltage is also studied in detail. The results show that the cell voltage increases below 8 atm and then decreases with the operating pressure. In addition, the effects of thermal insulation boundary condition, gas flow configuration and gas utilization rate under different operating pressures are also discussed. It is found that the reverse direct internal reforming reaction is activated under the operating pressure higher than 3 atm. Moreover, compared to co-flow arrangement, counter-flow arrangement is more helpful to cell performance improvement at high current densities. Highlights • A 3D SOEC model is developed to study pressure effect. • Electrolysis voltage is reduced under operating pressure above 8 atm. • The TNV rises to 1.358 V first and then drops to 1.276 V with increasing pressure. • The cell performance can be improved by counter flow arrangement. • The effect of gas utilizations on pressurized SOEC voltage is slight. [ABSTRACT FROM AUTHOR]

The advantages of double-layer electrode are available in the literature about single electrolysis of H 2 O and CO 2 using solid oxide electrolysis cell (SOEC). However, for the co-electrolysis of CO 2 and H 2 O, the influence of the structural parameters of the double-layer electrode on the co-electrolysis performance has been still unclear. In this study, a multi-scale model describing the co-electrolysis process of CO 2 and H 2 O in SOEC is adopted. After model validation, a comparison of the performance of SOEC between a single-layer cathode and a double-layer cathode is conducted with different inlet flow rates. Moreover, parametric analyses are performed to investigate the effects of the thickness and porosity of cathode diffusion layer (CDL) and the internal composition of cathode function layer (CFL). The results show that when the CDL porosity increases from 0.45 to 0.65, the conversion ratio of H 2 and CO increase by 10.17 % and 10.24 %, respectively. The optimal thickness of CDL (200 μm) for enhancing the durability of the cell and the preferable internal composition of CFL for improving the co-electrolysis performance are found within the scope of this study. This numerical analysis can provide guidance for the design of the double-layer cathode and the optimization of the co-electrolysis performance. [Display omitted] • A multi-scale model is applied for describing co-electrolysis process of CO 2 and H 2 O in SOEC. • The co-electrolysis performance with a single-layer and a double-layer cathode is compared. • The effects of porosity of cathode diffusion layer and internal composition of cathode function layer are discussed. • This numerical analysis can provide guidance for the design of cathode-supported SOEC. [ABSTRACT FROM AUTHOR]

Abstract This article presents the experimental results of a novel Power-to-Gas (PtG) concept combining a pressurized high-temperature steam electrolysis (SOEC) and a CO 2 -methanation module in stand-alone and thermally integrated operation. For the electrolyser, steam conversion and energy demands at pressures up to 15 bar were examined. In terms of the methanation module, cooling performance, steam production and product gas quality were of main interest. Additionally, temperature profiles inside the fixed beds were gathered by a multipoint thermocouple at pressures up to 30 bar and load modulations from 20 to 100%. With less than 2 vol% H 2 and over 97 vol% CH 4 in the finally produced synthetic natural gas (SNG), it can be directly injected into the existing German natural gas grid without further gas cleaning and without capacity limitations. The achieved overall PtG efficiency of 76% is significantly higher than state of the art plants and has the potential to reach 80% in industrial scale. Highlights • Integration of pressurized high-temperature steam electrolysis and CO 2 -methanation • Diluted fixed bed methanation reactor for improved temperature control • Produced substitute natural gas is fully compatible with existing natural gas grid. • Efficiency of coupled modules is 76% with potential to 80% at industrial scale. • Technical feasibility of novel Power-to-Gas concept successfully proven [ABSTRACT FROM AUTHOR]

Experiments have been performed in pressurized co-electrolysis mode at 800 °C on a typical Ni-YSZ//YSZ//CGO-LSCF cell. The polarization curves and the composition of the produced syngas have been measured at 1 bar and 10 bar. It has been found that the cell performances are improved under pressure at 1.3 V. The gas analyses have revealed that the methane formation is only activated under polarization and pressure. These experimental results have been used to validate a model which encompasses a chemical and electrochemical description of the co-electrolyser combined with a mass transport module. It has been found that the model is able to predict accurately the polarization curves as well as the syngas compositions at the cell outlet. Once validated, the model has been used to analyze the operating mechanisms in pressurized co-electrolysis. The impact of pressure on the mass transfer, the electrochemical and chemical reactions has been discussed. The close interaction between the electrochemical and chemical reactions for the internal production of CH 4 has been specifically highlighted. Finally, operating maps have been computed at 10 bar from 700 °C to 800 °C. These simulations have shown that formation of CH 4 in the co-electrolyser remains limited at 700 °C. [ABSTRACT FROM AUTHOR]

Improving the catalytic activity of perovskite electrodes by loading metal nanoparticles through interface engineering is one of the research hotspots in the field of CO 2 electrolysis in solid oxide electrolytic cell (SOEC). The challenge is to improve the stability and carbon resistance of the metal-oxide interface while reducing time costs and improving scalability. We used applied voltage-driven reduction and non-stoichiometric doping to make Fe nanoparticles uniformly and firmly anchored on the surface of Sr 2 Fe 1.5+x Mo 0.5 O 6-δ (SF 1.5+x M, x = 0, 0.025, 0.05, 0.075, 0.1) within 180 s, optimized the distribution of Fe nanoparticles on the surface of SF 1.5+x M, and thus constructed a metal-oxide interface with high activity and high stability, effectively preventing the sintering and carbon deposition of metal particles. When the electrode composition is SF 1.575 M, the CO yield is 4.0 mL·min-1·cm-2, while the polarization impedance is 0.155 Ω·cm-2, at 850 °C, 1.6 V. It can be said that voltage-driven reduction is an effective and efficient method applied to interface engineering. • Metal-oxide interface can improve the performance of SOEC electrolytic CO 2. • Voltage-driven reduction is short in time, simple in operation and high in safety. • Metal-oxide interface increases non-sintering and anti-carbon deposition. [ABSTRACT FROM AUTHOR]

Despite the considerable efforts to develop innovative electrode materials, nickel/yttria-stabilized zirconia (Ni/YSZ) electrodes are still employed in nearly all commercial and industrial solid oxide cell units. This is because Ni/YSZ cermets have good electrocatalytic activity in both electrolysis and fuel cell modes, while they are cost-effective as compared to alternative electrodes under development at the lab scale. Infiltration of nanoparticles has immersed as a promising concept to enhance the performance and robustness of conventional Ni/YSZ. Herein, we apply a relatively simple procedure to infiltrate Ni/YSZ electrodes with hexane solution containing prefabricated Ni-doped CeO 2 nanoparticles. Cells with modified Ni/YSZ electrodes show a great improvement in the electrocatalytic activity and stability towards direct CO 2 reduction as compared to unmodified cathodes. Besides, a single infiltration step is sufficient to achieve the optimum cell performance, streamlining the preparation process. More importantly, we show that this strategy can be equally efficient to fully reactivate previously degraded Ni/YSZ electrodes and restore their electrochemical performance at levels even higher than the initial ones. In addition, due to the high viscosity of the hexane solution, Ni-doped CeO 2 nanoparticles access the entire electrode volume all the way close to the YSZ interface, while it penetrates the micro cracks between Ni and YSZ particles. In this way the electrocatalytic reaction zone is recovered, and the degraded Ni/YSZ electrode is reactivated. Physicochemical, microstructural and electrochemical characterization of the cells evinces several effects that contribute to the performance improvement of Ni/YSZ after infiltration, such as the enhanced surface reducibility of Ni and the amelioration of charge transfer processes within the electrode. The simplicity of the proposed infiltration method and the significant promotion in CO 2 electroreduction activity, advocate it as a cost-efficient strategy to improve or regenerate conventional Ni/YSZ electrodes without significantly altering the already well-established fabrication process. [Display omitted] • Infiltration of NiYSZ with NiCeO x NPs increases CO 2 electroreduction current up to 3-times. • Degraded NiYSZ electrodes are reactivated after one-step impregnation with NiCeO x NPs. • NiCeO x NPs enhance Ni reducibility and improves charge transfer of NiYSZ electrode. • A promising strategy to promote or re-activate direct CO 2 electrolysis on conventional NiYSZ electrodes. [ABSTRACT FROM AUTHOR]

A composite electrolyte, Zr doped BaCe 0.8 Y 0.2 O 3-δ (BaCe 0.5 Zr 0.3 Y 0.2 O 3-δ, BCZY) and binary carbonates [(Li,Na) 2 CO 3 ] (LNCO) was first applied to reduce CO 2 accompanied with steam electrolysis in solid oxide electrolysis cell (SOEC) at 600 °C, lower than which conventional SOEC composed by YSZ works in (usually above 800 °C). Electrolysis performances are improved due to sufficient steam feed at oxygen electrode side (30–110 ml/min). Steam electrolysis provides proton source for the reduction of CO 2 . Application of composite electrolyte promotes proton transport and directly leads to H 2 even CH 4 production. To a certain degree, carbon resistance guarantees the symmetric SOEC operation at a lower bias potential of 0.5 V (vs.OCV) applied. A redox-stable and carbon-tolerant LSCM as symmetric electrode with a hybrid-ion-conducting composite electrolyte realizes the fuel synthesis by CO 2 reduction in proton-type solid oxide electrolyzer. [ABSTRACT FROM AUTHOR]

Power-to-Substitute-Natural-Gas (SNG) processes are studied since they can offer solutions for renewable energy storage and transportation. In the present study, an original Power-to-SNG process combining high-temperature steam electrolysis and CO 2 methanation is economically assessed. This evaluation is based on experimental data describing the electrolyser performance and its degradation during long-term operation. These data are obtained on a commercial single cell. Tests are originally conducted by imposing voltage and steam conversion rate. The main conclusions of this experimental work are that two fields of current density evolution are evidenced in the tested conditions: a first transient one where the current density absolute value decreases very quickly, followed by a second field where the evolution of current density achieves a steady state. The influence of the operating point seems not significant once this state is achieved. The process assessed here has been developed in a previous work where a precise framework matching with a wide range of applications was defined. The design of the process main units and the calculation of matter and energy fluxes are based on this work. To go further, the economic assessment of this process is proposed. In this study, various scenarios of initial performance of the electrolyser are considered and integrate the performance degradation associated. The SNG production cost is estimated between 211 and 570 €/MWh HHV according to the scenario and the hypotheses considered. The two major items accounting for this high cost are the purchase cost of the electrolyser and its performance degradation. It also evidenced that none of the other items can be neglected. Through a sensitivity analysis, it is shown that an increase of plant annual availability and capacity makes the SNG production cost decrease. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cells remain at the forefront of research into electrochemical energy conversion technology. More recent interest has focused on operating in electrolyser mode to convert steam or carbon dioxide into hydrogen or carbon monoxide, respectively. The mechanism of these reactions is not fully understood, particularly when operated in co-electrolysis mode using both steam and CO 2 . This contribution reports the use of a thermal camera to directly observe changes in the cell temperature during operation, providing a remote, non-contact and highly sensitive method for monitoring an operational cell. [ABSTRACT FROM AUTHOR]

[Display omitted] • (PrBa) 0.95 Fe 1.6 Ni 0.2 Nb 0.2 O 5+δ as the cathode material of SOEC is reported first time. • In situ fabrication of highly active nanoalloy catalyst for CO 2 RR. • The abundant oxygen vacancies and active nanoalloy significantly improves the mass transfer process. • Good electrochemical performance and stability induced by efficient cathode reactions. The electroreduction of CO 2 through solid oxide electrolysis cells (SOEC) is considered as a promising technology for mitigating climate changes related to global warming. A SOEC system can effectively reduce polarization losses and best utilize process heat to electrolyze CO 2 to produce CO. However, this technology is hindered by the sluggish cathode kinetics, which is mainly due to the poor catalytic activity for the CO 2 reduction reaction. Herein, this work develops an A-site ordered layered perovskite oxide, (PrBa) 0.95 Fe 1.6 Ni 0.2 Nb 0.2 O 5+δ (PBFNN), as an efficient cathode catalyst for CO 2 -SOEC. FeNi 3 nanoparticles are in situ generated on the surface of perovskite substrate after reduction, the resulting active alloy-perovskite interfaces between FeNi 3 and PBFNN substrate can effectively promote the CO 2 reduction reaction (CO 2 RR). The nanoparticles and abundant oxygen vacancies of FeNi 3 -PBFNN significantly enhance CO 2 adsorption and activation, which is verified by the CO 2 -temperature programmed desorption measurement and density functional theory calculations. Distribution of relaxation time analysis and electrochemical performance characterization indicate that this interface engineering at nanoscale greatly improves the catalytic activity of the cathode for CO 2 RR. [ABSTRACT FROM AUTHOR]

Hydrogen, combined with fuel cell technology, is an option for reducing our reliance on hydrocarbon-based fuels. Solid oxide electrolyser cells (SOECs) have been studied as a possible technology to produce hydrogen from steam. As the current global energy mix is heavily reliant on hydrocarbon-based fuels, utilising existing technologies such as coal fired power plants, combined with SOECs in an integrated system, may enable a path towards reducing carbon dioxide emissions as well as creating a way of introducing 'cleaner' fuel, In this work, a steady state model of a SOEC was developed and used to assess the feasibility of using hot steam from a power plant as feed to a SOEC. The main objective was to study the ways of improving the SOEC efficiency. The most favourable feed for the SOEC was to extract steam prior to the intermediate pressure turbine, which showed SOEC efficiency improvement of 25% compared with conventional SOEC operation of heating water at 25 °C. The thermoneutral point of 4644 A m-2 was shown to be a guide for assessing design and operation options with heat integration possibilities after this point. For scenarios of 7% steam extraction and a purely H2 production plant, 250 MW (7500 kgh-1) and 290 MW (8700 kgh-1) H2 can be produced with SOECs sized at 43,300 and 50,100 m², respectively. [ABSTRACT FROM AUTHOR]

High temperature steam electrolysis (HTSE) is one of the most promising ways for hydrogen mass production. If coupled to a CO2-free electricity and a low cost heat source, this process is liable to a high efficiency. High levels of performance and durability, in association with cost-effective stack and system components are the key points. To reach such goals, a low-weight stack has been designed, keeping the advantages of the high performing and robust stack previously validated in terms of performance, durability, and cyclability [1], but aiming at reducing the cost by the use of thin interconnects. This low-weight stack has demonstrated at the scale of a 3-cell stack a good performance of -1.0 A cm-2 at 1.3 V at 800 °C. Before performing the durability test, preliminary studies at the cell level have been carried out to highlight the effect of two major operating parameters that are the current density and the steam conversion (SC) ratio, those studies being carried out at one temperature, 800 °C. Based on these results, optimized operating parameters have been defined to perform the durability test on the stack, that is -0.5 A cm-2 and a SC ratio of 25%. Degradation rates around 3-4% 1,000 h-1 have been measured. The thermal cyclability of this stack has also been demonstrated with one thermal cycle. Therefore it can be concluded that these results make HTSE technology getting closer to the objectives of performance, durability, thermal cyclability, and cost. [ABSTRACT FROM AUTHOR]

Abstract: Parametric study of a power plant extension system based on solid-oxide electrolyzer cell (SOEC) system was conducted. Parameters involved in the analysis include temperature, amount of exhaust gas recirculation (EGR) and mole flux. Three limiting steps for reactant gases conversion were identified. An attempt has been made to explain the twin effects of EGR on the system performance. Increased performance of CO2 conversion at lower temperatures has been observed. Significant effects of mole flux and temperature on CO2 and H2O conversion have been confirmed. For the system configuration under study, 46.2% of electricity-to-syngas efficiency has been achieved. Maximum CO2 removal performance of ∼2.57 mol CO2/kWh was predicted at the temperature of 500 °C. Conversion ratio of 50–100% of CO2 is achievable depending on the operating conditions. Recommendations have been made for incorporating SOEC system into a power plant to mitigate CO2 and improve efficiency and flexibility of electricity production. [Copyright &y& Elsevier]

Abstract: Two Solid Oxide Electrolysis Cells (SOECs) with different oxygen electrodes have been tested in galvanostatic tests carried out at −1.5 Acm−2 and 800 °C converting 60% of a 50:50% mixture of H2O and CO2 (co-electrolysis). One of the cells had an LSM:YSZ oxygen electrode. The other had an CGO inter-diffusion barrier sandwiched between the YSZ electrolyte and an LSCF:CGO oxygen electrode. Impedance Spectroscopy was used during the tests to diagnose the change in electrochemical response of the different components of the SOECs. The results showed a significantly lower degradation rate for the cell with an LSCF:CGO oxygen electrode. This was attributed to three different effects: (1) The LSCF electrode was found to be more stable than its LSM:YSZ based counterpart. (2) The crack propagation in the YSZ electrolyte was less severe in the cell with an LSCF electrode. (3) The Ni:YSZ degradation was less severe in the cell with an LSCF electrode. We hypothesize further that (2) is an effect of the CGO inter-diffusion layer and that (3) is an indirect effect of (2). [Copyright &y& Elsevier]

Abstract: A composite of (La,Sr)(Cr,Mn)O3/(Gd,Ce)O2 (LSCM/GDC) was evaluated as a cathode in a high temperature solid oxide electrolysis cell (SOEC) used for steam electrolysis and/or steam-carbon dioxide co-electrolysis. When the steam feed rate was smaller than 30ml/min, the LSCM/GDC cathode is subject to large diffusion resistance from inadequate steam supply at steam concentration of 3–20%. Sigmoidal shaped I–V curves were thus observed for steam electrolysis, unlike when CO2 was present during reduction where smooth I–V characteristics were observed. With respect to steam-carbon dioxide co-electrolysis, the LSCM/GDC cathode showed lower performance than for CO2 electrolysis, due to insufficient steam content at a feed of 20% H2O–5% H2/Ar (10ml/min) and CO2/CO 70/30 (20ml/min) mixture. [Copyright &y& Elsevier]

Abstract: A solid oxide electrolysis cell model for syngas generation is developed using a button cell test system as a physical base. The model coherently bridges the multi transport processes of charge, mass, momentum, and energy with detailed surface chemistry. The model is validated using experimental polarization curves. Upon the validation, extensive simulations are performed to elucidate surface electrolysis processes. Results indicate that the electrolysis processes of CO2 and H2O are pretty much independent with each other in the H2 electrode (electrolysis cathode). The carbon coking effect is mainly determined by the content of CO2 in the H2 electrode. Increasing the applied cell voltage may improve syngas production, it also causes the enhancement of the surface coverage of C(s) and the deposition of carbon on the surface of Ni catalyst. High operating temperature may effectively improve adsorption/desorption rate and enhance surface electrolysis process as well as potentially mitigate carbon deposition on Ni surface. [Copyright &y& Elsevier]

Abstract: Electrolysis of steam and co-electrolysis of steam and carbon dioxide was studied in Solid Oxide Electrolysis Cell (SOEC) stacks composed of Ni/YSZ electrode supported SOECs. The results of this study show that long-term electrolysis is feasible without notable degradation in these SOEC stacks. The degradation of the electrolysis cells was found to be influenced by the adsorption of impurities from the applied inlet gases, whereas the application of chromium containing interconnect plates and glass sealings do not seem to influence the durability when operated at 850 °C. Cleaning the inlet gases to the Ni/YSZ electrode resulted in operation without long-term degradation, and may therefore be a solution for operating these Ni/YSZ based SOEC stacks without degradation. [Copyright &y& Elsevier]

Abstract: Carbon dioxide electrolysis was studied in Ni/YSZ electrode supported Solid Oxide Electrolysis Cells (SOECs) consisting of a Ni-YSZ support, a Ni-YSZ electrode layer, a YSZ electrolyte, and a LSM-YSZ O2 electrode (YSZ=Yttria Stabilized Zirconia). The results of this study show that long term CO2 electrolysis is possible in SOECs with nickel electrodes.The passivation rate of the SOEC was between 0.22 and 0.44mVh−1 when operated in mixtures of CO2/CO=70/30 or CO2/CO=98/02 (industrial grade) at 850°C and current densities between −0.25 and −0.50Acm−2. The passivation rate was independent of the current density and irreversible when operated at conditions that would oxidise carbon. This clearly shows that the passivation was not caused by coke formation. On the other hand, the passivation was partly reversible when introducing hydrogen. The passivation may be a consequence of impurities in the gas stream, most likely sulphur, adsorbing on some specific nickel sites in the cathode of the SOEC. Activation can be carried out by hydrogen reacting with adsorbed sulphur to form the volatile compound H2S. Because adsorption of sulphur is site specific, only a part of the nickel sites were passivated and long-time operation of CO2 electrolysis in these Ni/YSZ electrode supported Solid Oxide Electrolysis Cells seems therefore feasible. [Copyright &y& Elsevier]

Electrolysis in solid oxide electrolysis cells is gaining significant attention as a possible pathway for CO 2 reduction and abatement. The main objective of this work is to demonstrate the potential of microkinetic models to represent the catalytic chemistry at the cathode (negative electrode in electrolysis) and its capability to predict the cell performance. An electrochemical model in terms of the CO, CO 2 and vacant site surface coverages is developed for the reduction of CO 2 on Pt/YSZ electrodes. The electrochemical model is coupled to a microkinetic model through the surface coverage terms and incorporated into a one-dimensional button cell model, which resolves the cell across its thickness. The model is then used to simulate experimentally measured i V characteristics, polarization losses and electrochemical efficiency. The discussion in the paper covers aspects of parameter fitting, uniqueness, possible reasons for the differences from the experimental results, and the sensitivity of model predictions to model parameters. It also presents features of cell operation which cannot be accessed using experimental techniques. [ABSTRACT FROM AUTHOR]

Surplus renewable electricity used to convert CO 2 into CO, the building block of liquid fuels, advances the energy transition by enabling large-scale, long-term energy storage and the synthesis of fuel for long-haul transportation. Among the various technologies developed, renewable electricity driven conversion of CO 2 by high-temperature electrolysis and by plasmolysis offer a tantalising potential. High-temperature electrolysis is characterized by high-yield and energy-efficiency and the direct separation of the CO 2 dissociation products CO and O 2. However, the difficulty to break the carbon-oxygen double bond poses challenging requirements on electrode materials. CO 2 plasmolysis on the other hand, offers a similar energy efficiency, does not employ scarce materials, is easy to upscale, but requires efficient gas separation and recuperation because the produced CO remains mixed with O 2 and residual CO 2. Here, we demonstrate that the coupling of the two processes leads to a renewable-electricity-driven route for producing CO from CO 2 , overcoming the main bottleneck of CO 2 plasmolysis. A simulated CO 2 plasmolysis gas mixture is supplied to a high-temperature electrolyser to separate the product gases electrochemically. Our results show that the product stream of the coupled-process contains 91% less oxygen and 138% more CO compared with the bare plasmolysis process. Apart from upgrading the produced gas mixture, this coupled approach benefits from material stability. Durability tests (~100 h) show better stability in coupled operation when compared with conventional CO 2 electrolysis. Synergy between plasmolysis and electrolysis opens up a novel route to efficient CO 2 conversion into valuable CO feedstock for the synthesis of long-chain hydrocarbons. • CO 2 conversion via coupled plasma-electrolysis process is demonstrated. • CO 2 plasmolysis gas mixture was upgraded by electrochemical oxygen separation. • Coupled-process outlet contains 91% less O 2 and 138% more CO vs bare plasmolysis. • Better stability was achieved in coupled operation vs conventional CO 2 electrolysis. • Synergy between plasmolysis and electrolysis opens up a novel CO 2 conversion route. [ABSTRACT FROM AUTHOR]

Keywords: CO 2 reduction; H 2 oxidation; oxygen vacancy; perovskites; SOEC; SOFC EN CO 2 reduction H 2 oxidation oxygen vacancy perovskites SOEC SOFC 1 1 1 12/27/21 20211223 NES 211223 B Perovskites b In article number 2102845, Xian-Zhu Fu and co-workers report that partial substitution of Mo by Fe in a perovskite of Sr SB 2 sb Fe SB 1+ I x i sb Mo SB 1- I x i sb O SB 6- sb shifts up the O I p i band energy closer to the Fermi level, which lowers O vacancy formation as well as the O migration barrier energy, significantly accelerating the catalytic reaction kinetics in H SB 2 sb oxidation and CO SB 2 sb reduction reactions. Unraveling the Enhanced Kinetics of Sr2Fe1+xMo1-xO6- Electrocatalysts for High-Performance Solid Oxide Cells (Adv. CO 2 reduction, H 2 oxidation, oxygen vacancy, perovskites, SOEC, SOFC. [Extracted from the article]

• A solid oxide electrolytic cell with (La 0.80 Sr 0.20) 0.95 MnO 3-δ (LSM) cathode for CO 2 electrolysis. • Reduced endothermic load and cell voltage using H 2 as the anode fuel. • No LSM catalyst oxidation in pure CO 2 and can operate without safe gas. • CO formation rate of 1.15 mL.min−1. cm−2 and 100 % faradaic efficiency obtained with an applied current of 150 mA.cm−2. • Stable performance observed during 10 h of cell operation at 850 °C. CO 2 conversion to CO via solid oxide electrolysis provides a potentially efficient method for converting CO 2 into an industrially relevant product. A solid oxide electrolysis cell with (La 0.80 Sr 0.20) 0.95 MnO 3-δ (LSM) as the CO 2 reduction cathode, yttrium stabilized zirconia (YSZ) as electrolyte, and nickel as the H 2 oxidation anode was operated 800 °C and 850 °C. Thermogravimetric analysis of the LSM material showed no catalyst oxidation at operating temperatures allowing for CO 2 electrolysis without reducing safe gas. In addition, no cathode material mass gain was observed in the presence of CO suggesting little to no carbon deposition occurred above 750 °C. The formation rates of CO for the cell reached 1.15 mL∙min−1∙ cm−2 for an applied current of 150 mA∙cm−2 achieving a faradaic efficiency of 100 %. Furthermore, the cell displayed good stability in the short-term CO 2 electrolysis test with a nominal voltage drop of 4 mV h−1 for 10 h at 850 °C. This study shows the feasibility of operating a solid oxide CO 2 electrolysis cell for CO production with H 2 at the anode to reduce endothermic process load. [ABSTRACT FROM AUTHOR]

A multi-scale model for CO 2 reduction at Ni/samarium-doped ceria (SDC) cathode in solid oxide electrolysis cell (SOEC) was developed for a cathode-supported button cell. Compared to the current multi-physics SOEC models, the present study considers the following two new features: 1) reaction kinetics obtained from Density Functional Theory (DFT), including the pre-exponential factors and activation energies for each elementary step; 2) an analysis on the three possible reaction mechanisms to describe the charge transfer steps. The present multi-scale model revealed insights into the charge transfer step and CO/CO 2 ratio effects. This study shows that the most likely charge transfer step is CO 2 (s)+Ni(s)+2e−↔ CO(s)+O(s)2- reaction. A sensitivity analysis shows that CO desorption is the rate-controlling step. The results also indicate that a temperature above 700 °C and an CO:CO 2 inlet ratio between 1:1–1:3 are needed to maintain low carbon deposition, low polarization resistance and high current density. • Most likely charge transfer step is identified as CO 2 (s)+(s)+2e−↔ CO(s)+O(s)2-. • Ni catalyst surface coverage is dominated by CO(s). • CO desorption is the rate-controlling step. • 700 °C or above and CO:CO 2 inlet ratio between 1:1–1:3 are suggested for operation. [ABSTRACT FROM AUTHOR]

Infiltration of nano-catalysts in ionic-conductive backbones is receiving increasing attention to fabricate highly performing electrodes for Solid Oxide Cells application. In particular, nanostructured, high surface area scaffolds based on ceria and infiltrated with functional perovskites have already proved their excellent catalytic activity as oxygen electrodes. A major challenge for this type of nanocomposites is keeping the enhanced performance when up-scaling to large area cells and during long term operation. In this work, Ce 0.8 Gd 0.2 O 1.9 -La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3- δ infiltrated mesoporous oxygen electrodes were fabricated and tested in state-of-the-art 25 cm2 area fuel electrode supported solid oxide electrolysis cells. Injected currents as high as 11.2 A (0.7 A cm−2) at 1.3 V were measured in co-electrolysis mode at 750 °C showing improved performances with respect to button cell counterparts. Stability tests at injected currents of 8 A (0.5 A cm−2) for more than 600 h yielded a degradation rate of 126 mV kh−1 mainly related to the metallic nickel depletion approaching the fuel electrode-electrolyte interface, proving the stability of the oxygen electrode under highly demanding operating conditions. The excellent results presented here anticipate the relevance of nanostructured infiltrated electrodes for the next generation of enhanced Solid Oxide Cells. • We tested large area SOCs with nanostructured oxygen electrode for co-electrolysis. • We proved the scalability of mesoporous electrodes from button to large area cells. • A durability test of 600 h was carried out with a detailed EIS characterization. • Loss of percolating Ni at the fuel electrode greatly contributes to degradation. [ABSTRACT FROM AUTHOR]

• (La 0.60 Sr 0.40) 0.95 Co 0.20 Fe 0.80 O 3-x -Gd 0.20 Ce 0.80 O 1.95 cathode for CO 2 electrolysis. • Protecting gas H 2 or CO is not required in feed stream. • Stable performance observed during 350 h of cell operation. • Electrochemical performance better than Ni-YSZ electrode for dry CO 2 electrolysis. High temperature solid oxide electrolysis cells (SOECs) have a tremendous potential to provide a practical pathway for onsite on demand production of high purity CO by recycling waste CO 2 at industry relevant production scale. CO is an important feedstock for production of numerous chemicals required for the pharmaceutical, food and plastics industry. Recently, SOECs are also being developed to produce renewable fuels and energy carriers to allow transport and storage of renewable energy. Despite promising pre-commercial demonstrations, some key technical challenges need to be addressed to make this technology economically feasible. These include lowering capital costs with low cost materials and cell designs, and improvements in the electrode performance and lifetime, the cathode. The conventional Nickel-YSZ cathode is found to be promising in terms of performance during initial operation; however, a continuous supply of valuable reducing gas is needed to prevent oxidation of Ni to NiO, and accelerated degradation has been observed due to Ni migration and deactivation. In the present study we have evaluated the performance of A-site deficient doped lanthanum ferrites ((La 0.60 Sr 0.40) 0.95 Co 0.20 Fe 0.80 O 3-x) - Gd 0.20 Ce 0.80 O 1.95) dual phase mixed ionic and electronic conducting cathode for CO 2 electrolysis in a symmetrical tubular cell without the addition of reductant or protective gas during the cell operation. A polarization resistance as low as 0.36 ohm-cm2 was observed at 1.2 V after 350 h of CO 2 electrolysis at 800 °C. The electrochemical performance of the electrode is also compared with state-of-the-art Ni-YSZ cathode using similar cells and experimental conditions. [ABSTRACT FROM AUTHOR]