Solid Oxide Electrolysis Research Articles

BaZr0.1Ce0.7Y0.1Yb0.1O3-δ particles embedded PrBa0.5Sr0.5Co1.5Fe0.5O5+δ hollow nanofibers with 3D fast transmission path as oxygen electrode for proton-conducting solid oxide electrolysis cell

To address the challenge of low-temperature catalytic activity of oxygen electrodes, a high-activity triplex ionic conductor material, PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF), is prepared using electrospinning. The preparation PBSCF and BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (BZCYYb) nanofibers composite electrodes are used with different composite methods to improve the catalytic activity and the proton transport pathway within the electrode. The results show that PBSCF@BZCYYb prepared by PBSCF and BZCYYb pre-mixed one-step electrospinning has high porosity and 3D interwoven continuous transmission path, exhibiting minimal polarization impedance on symmetric cells. The electrolysis cell with PBSCF@BZCYYb|BZCYYb|NiO-BZCYYb (active layer) |NiO-BZCYYb (support layer) structure shows electrolysis current densities of 775.4 mA cm−2 under 1.3 V at 650 °C with 20%H2O+80%Air atmosphere. Additionally, during the constant voltage electrolysis, the cell shows acceptable stability in 60 h at 650 °C, considered to be a promising oxygen electrode material in this work.

Performance analysis of combining solid oxide electrolysis cell hydrogen production and marine hydrogen compressed natural gas engine system

Natural gas holds promise as an alternative energy source for ships, and its combustion blended with hydrogen can achieve better beneficial of energy saving and emission reduction. Nevertheless, the current challenges in hydrogen, characterized by its high cost and difficulties in storage and transportation, hinder its application in maritime technology. To address the issue, this study proposes a system that integrates a marine hydrogen compressed natural gas (HCNG) engine, a supercritical carbon dioxide Brayton cycle (SCBC), and a solid oxide electrolysis cell (SOEC). In this system, SCBC is capable of recovering waste heat for electricity generation, while SOEC serves as an energy storage device to adjust engine load and enhance fuel economy. The generated hydrogen can be utilized as a source of hydrogen in HCNG fuel, thereby improving engine performance and reducing pollutant emissions. Various system numerical simulation schemes with different engine hydrogen volume fractions were studied. The results show that the electrical efficiency of SOEC is improved by 17.86% by heating the feed stream with engine exhaust gas. In addition, the hydrogen fraction in which SOEC can act as a complete hydrogen source ranges from 30% to 40%. The results of the sensitivity analysis show that the cycle efficiency reaches a peak of 31.5% at a compressor outlet pressure of 16 MPa, while the efficiency of the whole system reaches a maximum of 50.8% at 21 MPa. The optimal operating temperature for the SOEC falls within the range of 650–700 °C for the 30, 40 HCNG schemes, and between 750 and 800 °C for the 50, 60 HCNG schemes.

Enhancing Electrochemical Efficiency of Solid Oxide Electrolysis Cells for Carbon Dioxide Reduction Through Nickel‐Doped Titanate‐Based Cathode with Doped Ceria Electrolyte

AbstractSolid oxide electrolysis cell (SOEC) is a potential technology for converting the principal greenhouse gas, carbon dioxide (CO2), into carbon monoxide (CO) by employing renewable energy. SOECs have great potential, including high‐energy efficiency, fast electrode kinetics, and competitive cost; however, this technology still has challenges in developing highly active, robust CO2 cathode electrocatalysts. In this work, we report the Ni‐doped lanthanum strontium calcium titanate (La0.20Sr0.25Ca0.45Ni0.05Ti0.95O3−δ) cathode for application as the cathode of CO2 electrolysis with gadolinia‐doped ceria (Gd0.1Ce0.9O1.95) electrolyte in SOEC. The exsolution of Ni nanoparticles is achieved by a simple in situ growth method at 800 °C. The Ni doping in LSCT significantly improved the electrochemical activity of the catalyst by increasing oxygen vacancies, and the Ni metallic nanoparticles can afford much more active sites for CO2 reduction. The CO2 electrolysis mechanism is studied by the distribution of relaxation time analysis of impedance spectroscopy. Ni‐LSCT renders a higher activity for electrolysis of CO2 with an exceptionally high reduction current density of 3.89 A cm−2 at 2.5 V potential applied and 800 °C temperature with GDC (Gd0.1Ce0.9O1.95) electrolyte. Ni doping is a crucial factor in controlling the electrochemical performance and catalytic activity in SOEC and GDC electrolytes, which is further helped by the high ionic conductivity.

RETRACTED: Engineering a high-performance W-doped Sr0.9Fe0.67Ti0.3Co0.03O3-δ hydrogen electrode for Solid Oxide Electrolysis Cells (SOECs)

Traditionally, Ni-based cermet fuel electrodes have been extensively utilized in Solid Oxide Electrolysis Cells (SOECs) for their excellent conductivity and catalytic properties. However, the development of alternative materials has gained attraction due to concerns over Ni's susceptibility to carbon deposition and long-term stability issues. To overcome this issue, we designed Sr0.9Fe0.67Ti0.30Co0.07O3-δ (SFTC) and W-doped SFTC (SFTCW) via the sol-gel method and thoroughly characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TG-DSC), and electrochemical tests. The results reveal that the incorporation of W enhances the stability of the electrode material under both oxidizing and reducing conditions, with no impurity phases detected. Furthermore, W doping promotes the precipitation of Co–Fe alloy, preserves the original structure, and facilitates the creation of oxygen vacancies within the material. In a reducing atmosphere containing 40 % H2O, SFTCW demonstrates superior electrolysis performance at an electrolysis voltage of 1.8 V, exhibiting a remarkable improvement of approx. 35 % compared to the SFTC sample. During a 100 h long-term stability test, the current density of SFTCW increased from -240 mA cm–2 to -270 mA cm–2, attributed to the enhanced hydrogen oxidation activity and increased reactive sites resulting from W doping, thereby enhancing its long-term stability. This work provides a feasible scheme for the selection and construction of hydrogen electrodes for electrolytic water.

Efficient H2O/CO2 co-electrolysis with NixCu1-x alloy nanocatalysts modified perovskite-type titanate cathodes

Syngas, a mixture of H2 and CO with adjustable compositional ratios, can be directly produced via H2O/CO2 co-electrolysis in solid oxide electrolysis cells (SOECs). In this study, We have developed a strategy to enhance the catalytic activity of titanate perovskite cathodes by constructing active metal-oxide interfaces through the in-situ growth of NixCu1-x alloy nanocatalysts (x = 0, 0.25, 0.5, 0.75 and 1) on LST matrix. The evenly distribution of NixCu1-x alloy nanoparticles (∼30 nm) on the LST substrate has been confirmed through a serious of characterization techniques, including XRD, XPS, SEM and TEM. Specifically, the LSTNi0.75Cu0.25 cathode demonstrated an optimal synergistic effect, achieving high efficiency in the co-electrolysis of H2O/CO2 to syngas. Under an applied voltage of 1.6 V at 800 °C, the syngas production rate reaches 5.43H2 and 3.48 CO ml min−1 cm−2 with ∼96 % Faradaic efficiency. Furthermore, the composition of the produced syngas can be finely tuned in a broad range from 0.8 to 3.5 b y simply adjusting the inlet gas composition (H2O/CO2 ratio) and the operating temperature. The LSTNi0.75Cu0.25 cathode, when subjected to continuous H2O/CO2 co-electrolysis for 100 h, exhibited remarkable stability, attributing to the robust and active nature of the metal-oxide interfaces.

Thermodynamic analysis of a solid oxide electrolysis cell system in thermoneutral mode integrated with industrial waste heat for hydrogen production

In this study, a widely applicable hydrogen production system based on solid oxide electrolysis cells (SOEC) is proposed for industrial waste heat recovery. When the thermoneutral mode is employed to maintain the isothermal state of SOEC, the performances of a single SOEC and the system are comprehensively analyzed respectively. The results show that an increase in SOEC temperature leads to a rise in current density, power, hydrogen production, and inlet steam flow rate. Conversely, as the steam conversion rate rises, these parameter values decrease. A set of 3D performance maps are provided to illustrate parameter variations. The thermoneutral data of SOEC can be utilized in various systems, not limited to the proposed one.Increasing the steam conversion rate improves energy efficiency and energy consumption performance of the system, but decreases the inlet steam flow rate and production capacity. A temperature rise improves the inlet steam flow rate and production capacity but has a slight effect on energy efficiency and energy consumption performance. When the inlet steam flow rate is 50 kg/h and the temperature is 800 °C, the system achieves a maximum hydrogen production of 2.473 kmol/h. The proportion of waste heat supply to total energy consumption fluctuates between 15.5 % and 20.6 % across the operation conditions. It shows great potential for hydrogen production utilizing industrial waste heat. Meanwhile, the stack consumes almost all of the electrical energy.

Harnessing the electrocatalytic potential of in-situ exsolution of Ni nanoparticles on lanthanum and calcium co-doped strontium titanate for CO2 reduction in solid oxide electrolysis cells

The exsolution phenomenon of metal nanoparticles from a perovskite oxide involves the creation of oxygen vacancies, contributing to improved catalytic activity for CO2 reduction. In this context, a B-site Ni-doped and A-site La, Ca co-doped strontium titanate, denoted as La0.20Sr0.25Ca0.45Ni0.05Ti0.95O3-δ (Ni-LSCT), is synthesized with the aim of serving as a highly efficient cathode in conjunction with LSM as the anode and YSZ as the electrolyte for CO2 reduction via solid oxide electrolysis process. The incorporation of 5 mol% Ni doping at the B-site of the perovskite is successfully achieved, leading to the subsequent release of highly dispersed nanoparticles upon exposure to a reducing environment. YSZ-electrolyte-supported SOECs featuring the Ni-LSCT cathode demonstrate a notable current density of 0.93 A/cm2 at an applied voltage of 2.5 V at 800 °C in pure CO2. Moreover, at the same temperature, the reduction current density measures 1.21 A/cm2 when the Ni-LSCT serves as the cathode in a 70/30 molar ratio (CO2/H2) environment and 1.73 A/cm2 with a 50/50 molar ratio of the feed gas, both at an applied voltage of 2.5 V. This suggests an enhanced CO2 reduction performance in a reducing atmosphere. The introduction of Ni doping into LSCT enhances the electrochemical activity of the cathode by augmenting oxygen vacancies, while the presence of Ni nanoparticles on the cathode surface intensifies the active sites. Collectively, this innovative electrocatalyst configuration presents promising prospects for CO2 electrolysis within the SOEC framework.

Green ammonia production using current and emerging electrolysis technologies

This study investigates utilizing hydrogen produced via water electrolysis to produce green ammonia. Routes are benchmarked based on employing either alkaline electrolysis (AEC) or solid oxide electrolysis (SOEC). Both existing and possible improvements are modeled for the AEC and SOEC technologies coupled with the Haber-Bosch process to synthesize ammonia. The cost of green ammonia is estimated considering the cost of electrolyzers for both today and future projections and are compared with that of "fossil" ammonia synthesized from natural gas. Threshold CO2 taxes required to achieve cost parity between green and "fossil" ammonia are determined based on the price of natural gas and the levelized cost of electricity. It is found that whereas the green ammonia produced from a system based on AEC is cheaper today, SOEC shows to be more cost-effective, when basing the comparison on the projected future cost of the electrolyzers. Green ammonia from an SOEC-based plant is estimated to have accost of 495 €/t by 2050 with an assumed electricity price of 30 €/MWh. In the SOEC-based ammonia plants, approximately 57 % and 31 % of the steam needed for the electrolyzers can be generated through heat integration between the electrolyzer and Haber-Bosch process, for low-pressure and high-pressure electrolyzers, respectively. A good fraction of the heat can also be covered by the intercoolers of the compressors. With the projected cost for SOEC, reducing the levelized cost of electricity from 60 to 10 €/MWh would decrease the cost of green ammonia from 690 to 340 €/t by 2050.

In situ exsolved CoFe alloy nanoparticles for stable anodic methane reforming in solid oxide electrolysis cells

In situ exsolved CoFe alloy nanoparticles for stable anodic methane reforming in solid oxide electrolysis cells

Boosting carbon utilization efficiency for sustainable methanol production from biomass: Techno-economic and environmental analysis

Concerns about depleted fossil fuels and the climate crisis have intensified the interest in producing biomass-derived methanol. However, the traditional biomass-to-methanol (BTM) process suffers from low carbon conversion ability and serious CO2 emissions caused by the water–gas-shift (WGS) unit. In this study, three novel BTM processes coupled with solid oxide electrolysis, methane pyrolysis, and methane chemical looping technologies are proposed to eliminate WGS unit, and the systematic heat integration is considered to achieve energy cascade utilization. Meanwhile, process performances are comprehensively evaluated to compare the technical, economic, and environmental attractiveness of three novel BTM processes. It is found that compared with the original BTM process, three novel processes significantly improve carbon efficiency by 22%. Meanwhile, CO2 emissions are reduced by 60%. Moreover, the application of methane chemical looping technology is more economical, and the associated net production cost decreases by more than 30%. Additionally, the BTM process coupled with solid oxide electrolysis is more environmentally friendly, whereas the process with methane pyrolysis technology is more exergy-efficient. Overall, the integrated processes have significant application prospects for carbon conversion and mitigation ability as well as economic attractiveness.

Solid Oxide Electrolysis Cell-Based Syngas Production and Tailoring: A Comparative Assessment of Coelectrolysis, Separate Steam, CO2 Electrolysis, and Steam Electrolysis

Solid Oxide Electrolysis Cell-Based Syngas Production and Tailoring: A Comparative Assessment of Coelectrolysis, Separate Steam, CO₂ Electrolysis, and Steam Electrolysis

Collective Synergistic Catalysis of Electrochemical CO2 Reduction on Nonstoichiometric Double Perovskites

AbstractPerovskite oxides show great promise as an alternative catalyst to the conventional nickel cermets for CO2 reduction reactions (CO2RR) in solid oxide electrolysis cells (SOECs) owing to their advantages of redox stability and coking resistance. Nevertheless, practical applications of these oxides are prevented largely by their poor CO2RR activities. Herein, a novel donor and acceptor co‐doped nonstoichiometric double perovskite, La0.3Sr1.55Fe1.5Ni0.1Mo0.4O6−δ (LSFNM), is developed with in situ exsolved FeNi3 nanoparticles to efficiently catalyze CO2RR in SOECs. Pure CO2 electrolysis over the impregnated FeNi3@LSFNM catalysts is evaluated on two types of SOECs—one with thin (ZrO2)0.89(Sc2O3)0.1(CeO2)0.01 (SSZ) electrolytes supported on 430L alloys and the other with thin La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) electrolytes supported on impregnated SmBa0.5Sr0.5Co2O5+δ (SBSCO)@LSGM anodes, producing unprecedently high current densities of 2.84 A cm−2 for the former and 3.07 A cm−2 for the latter at 1.5 V and 800 °C. Experimental analysis and density‐functional theory (DFT) calculations reveal collective synergistic catalysis of oxygen vacancies (), the doping Ni2+ ions and FeNi3 nanoparticles via the cooperative ‐O(CO2), and Ni(II)–C(sp) and Ni(0)–O(CO2) interactions in LSFNM, not only facilitating CO2 chemisorption on oxygen vacancies but also destabilizing and dissociating surface carbonates in the vicinity of FeNi3 spontaneously into CO.

The Case of Renewable Methane by and with Green Hydrogen as the Storage and Transport Medium for Intermittent Wind and Solar PV Energy

Long-duration energy storage is the key challenge facing renewable energy transition in the future of well over 50% and up to 75% of primary energy supply with intermittent solar and wind electricity, while up to 25% would come from biomass, which requires traditional type storage. To this end, chemical energy storage at grid scale in the form of fuel appears to be the ideal option for wind and solar power. Renewable hydrogen is a much-considered fuel along with ammonia. However, these fuels are not only difficult to transport over long distances, but they would also require totally new and prohibitively expensive infrastructure. On the other hand, the existing natural gas pipeline infrastructure in developed economies can not only transmit a mixture of methane with up to 20% hydrogen without modification, but it also has more than adequate long-duration storage capacity. This is confirmed by analyzing the energy economies of the USA and Germany, both possessing well-developed natural gas transmission and storage systems. It is envisioned that renewable methane will be produced via well-established biological and/or chemical processes reacting green hydrogen with carbon dioxide, the latter to be separated ideally from biogas generated via the biological conversion of biomass to biomethane. At the point of utilization of the methane to generate power and a variety of chemicals, the released carbon dioxide would be also sequestered. An essentially net zero carbon energy system would be then become operational. The current conversion efficiency of power to hydrogen/methane to power on the order of 40% would limit the penetration of wind and solar power. Conversion efficiencies of over 75% can be attained with the on-going commercialization of solid oxide electrolysis and fuel cells for up to 75% penetration of intermittent renewable power. The proposed hydrogen/methane system would then be widely adopted because it is practical, affordable, and sustainable.

Modelling thermal dynamics in intermittent operation of a PEMEL for green hydrogen production

Green hydrogen plays a pivotal role in the imminent energy transition, addressing energy storage and electricity generation decarbonization. The European Commission’s hydrogen strategy underscores the goal to install at least 40 GW of green hydrogen electrolysers by 2023. Despite various electrolyser technologies, efficiency improvement and durability enhancement remain challenges, especially considering voltage intermittencies from renewable energy sources. This study emphasizes the impact of thermal gradients within electrolysers due to voltage interruptions, affecting membrane operation and causing premature wear. The study explores methods to minimize thermal gradients, revealing trade-offs between efficiency and durability. A lumped-parameter numerical model is developed and experimentally adjusted to simulate electrochemical and energy transport phenomena. Experimental and numerical results are compared, highlighting the need for a comprehensive thermal management code for effective electrolyser performance. The study addresses the importance of accurately modelling transient thermal responses for both proton exchange membrane electrolysis (PEMEL) and solid oxide electrolysis (SOEL) designs, providing insights for future advancements in thermal management strategies.

Electrochemical Analysis of an Electrolyte-Supported Solid Oxide Cell-Based MK35x Stack during Long-Term Electrolysis Operation

The currently ongoing scale-up of high-temperature solid oxide electrolysis (SOEL) requires an understanding of the underlying dominant degradation mechanisms to enable continuous progress in increasing stack durability. In the present study, the degradation behavior of SOEL stacks of the type “MK35x” with chromium-iron-yttrium (CFY) interconnects and electrolyte-supported cells (ESC) developed at Fraunhofer IKTS was investigated. For this purpose, the initial electrochemical performance of a 10-cell stack was characterized in various operating conditions in both fuel cell and electrolysis mode. Degradation was evaluated during galvanostatic steady-state steam electrolysis operation for more than 3000 h at an oxygen side outlet temperature of 816 °C and a current density of −0.6 A cm−2 and showed an average voltage evolution rate of −0.3%/kh demonstrating high stability. Initial and final characterization at the part load operating point at −0.39 A cm−2 and 800 °C led to the determination of a positive overall degradation rate of 0.4%/kh showing a considerable impact of the operating conditions on the degradation rate. By means of electrochemical impedance spectroscopy analysis it was shown that the stack’s ohmic resistance increased whereas the polarization resistance decreased most likely due to an enhancement in LSMM’/ScSZ oxygen electrode performance.

Microstructure of hydrogen electrode catalyst layer materials for solid oxide electrolysis cells

This research explores the synthesis of Ce0·6Mn0·3Fe0·1O2-δ (CMF) catalyst using the citric acid-EDTA method. CMF mixtures with various active carbon pore-forming amounts are achieved through controlled atmosphere sintering, revealing low permeability and high porosity. The permeability correlates with the microstructure. Results show poor porosity in unsintered carbon at 1250 °C. Increasing the amount of pore-forming powders does not enhance porosity. Sintering CMF and 9% active carbon at 1250 °C under Ar and then in air at 900 °C increases active carbon porosity, resulting in a mixture with a specific surface area of 2.11 m2 g−1 and porosity of 50.82%. This composition surpasses others in characteristics. Electrochemical assessment of solid oxide electrolysis cells (SOECs) indicates that Pt/SDC/CMF+9%AC (cell B) outperforms Pt/SDC/Pt (cell A), demonstrating potential for CMF oxide cathodes in steam electrolysis during SOEC operations with a current density of 847 mA cm−2 at 1.5 V.

Numerical study on improved mass and heat transfer performance in a solid oxide electrolysis cell with sine wave flow field

In this paper, the periodic variation of sine wave is used to promote the transport and diffusion process of reactive gases; and the relationship between the performance of a solid oxide electrolysis cell (SOEC) and the mass and heat transfer capabilities of its flow field is thoroughly examined. The impact of variations in the amplitude and frequency of the sine wave on the SOEC's electrolysis efficiency, its mass and heat transfer properties, and fluid flow dynamics are explored. The results indicate that longitudinal flow velocity of the gas in the sine wave flow channel is increased by 26.96–80.76% at a current density of 10000 A/m2, and this kind of flow channel exhibits superior gas transport performance. Moreover, the temperature-uniformity index and the maximum thermal stress of the positive-electrolyte-negative (PEN) structure are decreases by 18.93–22.67% and 20%, respectively. It indicates that this configuration is capable of reducing thermal stress and enhancing the uniformity of temperature distribution at high current-densities. Increasing the amplitude and frequency improves the comprehensive performance of the flow field. More specifically, frequency has a greater impact on flow field performance than amplitude.

Machine learning-assisted prediction and optimization of solid oxide electrolysis cell for green hydrogen production

The solid oxide electrolysis cell (SOEC) holds great promise to efficiently convert renewable energy into hydrogen. However, traditional modeling methods are limited to a specific or reported SOEC system. Therefore, four machine learning models are developed to predict the performance of SOEC processes of various types, operating parameters, and feed conditions. The impact of these features on the SOEC's outputs is explained by the Shapley additive explanations and partial dependency plot analyses. The preferred model is integrated with a genetic algorithm to determine the optimal values of each input feature. Results show the improved extreme gradient enhanced regression (XGBoost) algorithm is the core of the machine learning model of the process since it has the highest R2 (> 0.95) in the three outputs. The electrolytic cell descriptors have a greater impact on the system performance, contributing up to 54.5%. The effective area, voltage, and temperature are the three most influential factors in the SOEC system, contributing 21.6%, 16.6%, and 13.0% to its performance. High temperature, high pressure, and low effective area are the most favorable conditions for H2 production rate. After conducting multi-objective optimization, the optimal current intensity and hydrogen production rate were determined to be 1.61 A/cm2 and 1.174 L/(h·cm2).

Bimetallic Ni-Fe Supported by Gadolinium Doped Ceria (GDC) Catalyst for CO2 Methanation

CO2 conversion into fuels and high value-added chemical feedstocks, such as methane, has gained novel interest as a crucial process for further manufacturing multi-carbon products. Methane, CH4, becomes a promising alternative for environmental and energy supply issues. Nickel-based catalysts were found to be very active and selective for CH4 production. The use of promoter and support material to develop high activity, high selectivity, and durable catalysts for CO2 methanation at low temperature is a challenge. Gadolinium-Doped Ceria (GDC) has been known as material for Solid Oxide Fuel Cell (SOFC) and Solid Oxide Electrolysis Cell (SOEC) due to higher ionic conductivity and lower operating temperatures. However, few researches have been done regarding to CO2 methanation over GDC as catalyst support so far. In this present work, CO2 methanation was investigated over bimetallic Ni-Fe catalyst supported by GDC. The results showed that CH4 production rate by using Ni-Fe/GDC catalyst was higher than that of GDC at all reaction temperatures carried on. Ni-Fe/GDC showed remarkable CH4 production rate as of 17.73 mmol.gcat−1.h−1 at 280 °C. No catalytic activity was produced by GDC catalyst only. The highest CO2 conversion (46.50%) was observed at 280 °C, with almost 100% selectivity to CH4. The turnover frequency (TOF) value of Ni-Fe/GDC (4529.32 h−1) was the highest than that of Ni and common CO2 methanation catalyst, Ni/Al2O3 catalysts at 280 °C, further displaying the outstanding low-temperature catalytic activity. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Scientometric analysis of research trends on solid oxide electrolysis cells for green hydrogen and syngas production

Scientometric analysis of research trends on solid oxide electrolysis cells for green hydrogen and syngas production