Solid Oxide Electrolysis Research Articles

Local temperature difference control of high temperature solid oxide electrolytic cell based on temperature observer

–High-temperature Solid Oxide Electrolysis Cell (SOEC) may generate excessive local temperature differences during transient operation, which can affect its electrochemical performance and thermal safety. Therefore, this study develops a localized temperature difference control strategy based on a temperature observer, which can avoid a series of issues such as sealing failure caused by the installation of thermocouples. Firstly, a discrete thermoelectric coupling model was developed, dividing SOEC along the flow direction into five nodes. This model was rigorously validated and refined using actual sensor data, including voltage and outlet temperature. Subsequently, a temperature observer for the SOEC's local temperature distribution was designed using a NARX neural network. Finally, an adaptive PID algorithm-based local temperature difference controller was developed, employing the local temperature data provided by the observer as the controlled variable. The effectiveness of the controller was verified under conditions such as excessive electrolysis current and air leakage. The test results show that the response time of the open-loop NARX observer is only 2 seconds, with the observation error controlled within 0.09K, providing a stable and reliable control variable for the local temperature difference controller. The local temperature difference control strategy effectively ensures that all thermal safety indicators remain within the specified range, demonstrating higher safety and reliability compared to traditional inlet and outlet temperature difference control methods.

Recent advances in high temperature solid oxide electrolysis cell for hydrogen production

ABSTRACT When renewable energy sources are coupled with high-temperature solid oxide electrolysis cells (SOECs) that produce hydrogen, it seems like future energy sustainability is within reach. The ability to electrolyze water to make hydrogen and then reverse the process to generate electricity in a single solid oxide cell (SOC) device is particularly attractive for renewable energy sources such as solar and wind power. The development of efficient, long-lasting, and economically viable SOEC technologies is hindered by the performance of critical materials, the stability and dependability of electrode and electrolyte materials under reversible electrolysis and fuel cell operating modes, and fuel cell operation modes. Due of their immaturity, SOEC pose both opportunities and challenges to the growing community of material scientists and system engineers studying electrochemical energy conversion and storage.

Integration of a solid oxide electrolysis system with solar thermal and electrical energy: A testing campaign for operation and control strategy definition

AbstractThe EU project PROMETEO has the scope of testing a 25 kW solid oxide electrolysis system integrated with a concentrated solar power plant via thermal energy storage in a relevant environment. Given the plant layout and the hydrogen demand characteristics, this work aims to identify how to operate the system effectively when renewable electricity is unavailable and how to modulate the load during hydrogen generation, thus defining the system's operation modes and control strategy. A 5 kWe stack has been tested at the FBK facility. The hot standby tests show that feeding a reducing gas at the negative electrode and air at the positive electrode, without polarizing the stack, effectively keeps the stack hot at 750°C and prevents degradation. Conversely, the electric protection approach leads to significant stack degradation (15% voltage drop in 200 h for one cluster). Regarding modulation of hydrogen generation, with low steam flowrates, the stack current and the flow rate of produced hydrogen mainly depend on the steam flow rate, while it is not affected by the stack temperature; conversely, with high steam flowrates, the current depends only on the stack temperature (from 25 A at 670°C to 65 A at 760°C). Based on the results, two hot standby modes and two load control strategies to be implemented and tested in the PROMETEO prototype are proposed.

Atomically Dispersed Ru Species Induced by Strong Metal-Support Interaction for Electrochemical Methane Reforming.

During the high-temperature oxygen evolution reaction for CO2 electrolysis in solid oxide electrolysis cells (SOECs), the key elementary process of O2- transfer is restricted by the high anodic oxygen pressure thermodynamically, thus requiring a high external voltage [open-circuit voltage (OCV)] to drive the electrolysis reaction. Herein, electrochemical CH4 reforming is introduced to the SOEC anode, which remarkably lowers the anodic oxygen pressure and OCV, finally reducing the energy demand from 3.12 to 0.11 kW h per cubic meter of CO. Meanwhile, atomically dispersed Ru species is anchored on the anode surface due to the strong metal-support interaction, which exhibits superior CH4 reforming activity (90% of CO selectivity) and stability (300 h) to the infiltrated Ru nanoparticles and doped Ru species in the bulk lattice at 600 °C. This work proposes an efficient strategy to boost the SOEC performance thermodynamically and produce value-added chemicals at both the cathode and anode of SOEC simultaneously.

Component analysis of a 25-cell stack following 6.7 kh of high temperature electrolysis

The demonstration of relevant lifetimes for solid oxide electrolysis stacks is an underlying necessity to the rapidly industrializing technology. Following a 6.7 kh test of a 25-cell stack, post-mortem analyses of cells, seals, and interconnects were carried out to assess their long-term stability.Micrographs of cells aged in nominal conditions highlighted Ni depletion in the functional layer, SZO interlayer growth, and the presence of a Sr-rich secondary phase. The microstructure of glass-ceramic seals remained for the most part stable following operation. In addition, in spite of a thin design and the absence of coating, interconnects showed remarkable stability, with limited chromia growth and Cr depletion. Notably, no Cr poisoning could be detected in the cell functional layer.In view of the results, the loss of tightness of the H2 compartment, due to initial defects or caused by failures, is seen as the most immediate threat to this stack long-term operation.

Extracting Quantitative Insights from electrochemical impedance spectra using Statistical Methods

Statistical analysis of electrochemical impedance spec- troscopy data provides a systematic way of detecting changes in electrochemical energy systems. Applying concepts of divergence measures directly on electrochemical impedance spectroscopy data, one can reliably detect and quantify statistically significant changes. The results is a set of high- lighted frequency bands where the measured impedance characteristics differ statistically significantly from a ref- erence curve. The approach is evaluated on a solid-oxide electrolyser cell operated under different conditions and proves to be sensitive to even the smallest changes. The complete numerical implementation and corresponding experimental data are available as supplementary material at https://portal.ijs.si/nextcloud/s/xTa2cmtfxXn2jSz

Electrochemical Performances of a Solid Oxide Electrolysis Short Stack Under Multiple Steady-State and Cycling Operating Conditions

Solid oxide electrolysis cells (SOECs) are increasingly utilized in hydrogen production from renewable energy sources, yet high degradation rates and unclear degradation mechanisms remain significant barriers to their large-scale application. Consequently, endurance testing of stacks under various operating conditions and studying the degradation mechanisms associated with these conditions is imperative. However, due to the generally poor performance consistency among stacks, multi-condition data from numerous stacks lack reliability. In this experimental study, having established a specific SOEC stack’s performance and optimal conditions, durability tests under varied conditions, including various current densities, current operation modes (cyclic or constant current), fuel utilization rates, and temperature cycles were conducted. Electrochemical analysis tools like electrochemical impedance spectroscopy and distribution of relaxation time were employed to analyze the causes of voltage fluctuations under high current densities. The results confirmed that the SOEC stack could handle current cycling at low current densities and constant-current electrolysis at high current densities and withstand at least two temperature cycles.

Technical evaluation and life-cycle assessment of solid oxide co-electrolysis integration in biomass-to-liquid processes for sustainable aviation fuel production

Building upon prior research, this paper integrates solid oxide electrolysis (SOEL) into a Biomass-to-Liquid (BtL) process, facilitating the production of sustainable aviation fuel (SAF) through gasification, co-electrolysis, and Fischer-Tropsch synthesis. Two different integration concepts are developed: An inline integration resulting in a directly electrified-Biomass-to-Liquid (eBtL) process and a parallel integration for a Power-and-Biomass-to-Liquid (PBtL) process. To maximize process efficiency, the SOEL is operated under endothermic conditions with heat supply from syngas cooling after gasification. The developed processes allow for an increase in carbon efficiency up to about 61% to 94%. The electrolysis power required corresponds to electrification ratios of 0.32 to 0.83MWel/MWth. Compared to the conventional H2 addition in PBtL processes, electricity demand can be reduced by 13% to 29% when using co-electrolysis instead of water electrolysis. The resulting increase in energy yield and energy efficiency is because up to 17% of the SOEL’s energy demand can be substituted with heat in the electrified BtL processes. A life cycle analysis shows the absolute requirement to operate the process with renewable electricity to reduce indirect greenhouse gas emissions. A critical evaluation of the technological feasibility indicates further development requirements for the SOEL and the gasification heat recovery technology to enable the integration approach.

Techno-economic performance analysis of biomass-to-methanol with solid oxide electrolyzer for sustainable bio-methanol production

The analysis of the technical and economic performance of an integrated biomass to methanol and solid oxide electrolysis process (BtM-SOEC) is studied to find more sustainable process of bio-methanol production. The oil palm empty fruit branch (EFB) which is abundant in Thailand is used as biomass feedstock. Modeling of the BtM-SOEC is done using Aspen Plus. For technical aspects, the production rate of oxygen and hydrogen from the SOEC can be enhanced through an appropriate adjustment of the number of cells and cell temperature. The BtM-SOEC offers higher methanol yield and overall efficiency, while consumes less energy than the conventional biomass to methanol process (BtM). The maximum methanol production rate of 0.4995 kmol h-1 derived from BtM-SOEC is achieved at a number of cells of 325 cells and a cell temperature of 700 oC, at this condition the overall efficiency is 64.79 %. The economic assessment indicates that the conventional BtM and BtM-SOEC are still not economically feasible. However, the conventional BtM is more economically feasible than the BtM-SOEC. The methanol cost of BtM-SOEC can turn out to be economically feasible when renewable electricity cost and SOEC cost decrease substantially. The methanol cost of the BtM-SOEC (620 USD ton-1) can be competitive to that of the BtM (703 USD ton-1) when the cost of input renewable electricity decreases by 80%. Consequently, this research highlights the potential of BtM-SOEC from agricultural residues for sustainable bio-methanol production in the future market condition that the cost of renewable electricity tends to continuously decrease with the technology development and increased technology adoption and the carbon policy tends to be tightened to relieve global warming.

Electrosynthesizing high-value fuels from CO2 in solid oxide electrolysis cells: Fundamentals, advances, and perspectives

Electrosynthesizing high-value fuels from CO2 in solid oxide electrolysis cells: Fundamentals, advances, and perspectives

Fluorine-doped perovskite cathodes with boosted electrocatalytic activity for CO2 electrolysis

Global energy demands that have traditionally been satisfied by the use of fossil fuels have led to substantial emissions of CO2, an important greenhouse gas. Solid oxide electrolysis cells (SOECs) offer a practical approach for transforming CO2 into valuable fuels. Accordingly, creating stable electrocatalysts and perovskite cathodes capable of efficiently converting CO2 is a primary aim for the further development of SOECs. Although reconstructing active sites during CO2 electrolysis is significantly challenging, it is also constrained by our lack of understanding of this process. Herein, we introduce an innovative strategy that involves co-doping with Cu and F to better facilitate the exsolution reaction, which resulted in the formation of an advanced cathode composed of Cu-Fe alloy nanoparticles embedded in a fluorine-doped Sr2Fe1.5Mo0.5O6−δ (SFM) ceramic matrix. The in-situ electrochemical reconstruction of the SFM cathode through co-doping not only improves mass-transfer efficiency during CO2 electrolysis but also enhances the catalytic activity and durability of the ceramic cathode. A SOEC assembled with this material as a symmetrical electrode delivered 4.99 mL min−1 cm−2 of CO at 850 °C and an applied voltage of 1.8 V, which is 168 % higher than that of a pure SFM electrode. In addition, no carbon deposits were observed at the end of the reaction. The co-doping strategy delivered enhanced performance without degradation over 100 h of high-temperature operation, which suggests that it is a reliable cathode material for CO2 electrolysis. This study introduced an innovative method for improving the SOEC-electrode microstructure and developing efficient electrocatalysts for CO2 electrolysis.

Hydrogen production via solid oxide electrolysis: Balancing environmental issues and material criticality

Hydrogen production via solid oxide electrolysis: Balancing environmental issues and material criticality

Applications of Ferric Oxide in Water Splitting by Electrolysis: A Comprehensive Review.

In water electrolysis, the use of an efficient catalyst derived from earth-abundant materials which is cost-effective and stable is essential for the economic sustainability of hydrogen production. A wide range of catalytic materials have been reported upon so far, among which Fe2O3 stands out as one of the most credible candidates in terms of cost and abundance. However, Fe2O3 faces several limitations due to its poor charge transfer properties and catalytic ability; thus, significant modifications are essential for its effective utilization. Considering the future of water electrolysis, this review provides a detailed summary of Fe2O3 materials employed in electrolytic applications with a focus on critically assessing the key electrode modifications that are essential for the materials' utilization as efficient electrocatalysts. With this in mind, Fe2O3 was implemented in a heterojunction/composite, doped, carbon supported, crystal facet tuned system, as well as in metal organic framework (MOF) systems. Furthermore, Fe2O3 was utilized in alkaline, seawater, anion exchange membrane, and solid oxide electrolysis systems. Recently, magnetic field-assisted water electrolysis has also been explored. This comprehensive review highlights the fact that the applicability of Fe2O3 in electrolysis is limited, and hence, intense and strategically focused research is vital for converting Fe2O3 into a commercially viable, cost-effective, and efficient catalyst material.

Exploring the Potential of Cold Sintering for Proton-Conducting Ceramics: A Review.

Proton-conducting ceramic materials have emerged as effective candidates for improving the performance of solid oxide cells (SOCs) and electrolyzers (SOEs) at intermediate temperatures. BaCeO3 and BaZrO3 perovskites doped with rare-earth elements such as Y2O3 (BCZY) are well known for their high proton conductivity, low operating temperature, and chemical stability, which lead to SOCs' improved performance. However, the high sintering temperature and extended processing time needed to obtain dense BCZY-type electrolytes (typically > 1350 °C) to be used as SOC electrolytes can cause severe barium evaporation, altering the stoichiometry of the system and consequently reducing the performance of the final device. The cold sintering process (CSP) is a novel sintering technique that allows a drastic reduction in the sintering temperature needed to obtain dense ceramics. Using the CSP, materials can be sintered in a short time using an appropriate amount of a liquid phase at temperatures < 300 °C under a few hundred MPa of uniaxial pressure. For these reasons, cold sintering is considered one of the most promising ways to obtain ceramic proton conductors in mild conditions. This review aims to collect novel insights into the application of the CSP with a focus on BCZY-type materials, highlighting the opportunities and challenges and giving a vision of future trends and perspectives.

High-Temperature Electrolysis with Superheated Steam Provided by Volumetric-Type Steam Generator

High-temperature steam is essential for operating solid oxide electrolysis cells (SOEC). This paper demonstrated a new type of high-temperature solar steam generator that uses ceramic foam as a porous absorber. Water is sprayed into the porous absorber as microdroplets by using a nozzle. Experiments show that the solar steam generator is capable of generating superheated steam beyond 800 oC. The peak thermal efficiency in the steady state can reach 60.92% under a mass flow rate of 2.359 kg/h corresponding to an outlet temperature of 877.3 oC. The superheated steam will be supplied to a SOEC system to generate hydrogen. Thus, a comprehensive model is developed in this paper to research the performance of the solar SOEC system under fluctuated solar irradiation

Thermosiphon Cooling System for a Methanation Reactor: An Experimental Assessment

Abstract Operating the cooling system of a methanation reactor using an open-loop two-phase thermosiphon with evaporating water as the cooling liquid is an effective way to ensure safe operation as it does not rely on a recirculating pump. The aim of the reactor design is to co-generate methane and steam, the latter to be used in a solid-oxide electrolyzer to produce H2 to be injected in the reactor. The passive operation was analyzed to ensure a similar level of stability in the steam production compared to the active operation (i.e., with a pump). A total of 98% of the measured steam produced in passive cooling were within ±9.82% of the individual means, comparing well to ±9.5% for the active cooling operation.

Electrophoretic Deposition and Physicochemical Properties of Ni- and Fe-Doped Cu–Mn Spinel Coatings Enhanced with Ce0.9Y0.1O2 Nanoparticles on Fe16Cr Ferritic Stainless Steel Interconnects for SOEC Applications

Cu- and Mn-based spinel coatings are currently among the most promising materials for solid oxide electrolyzer cell (SOEC) interconnects due to their high electrical conductivity and ability to eliminate environmentally hazardous cobalt, which is included in the most widely used coatings. However, their properties are affected by the presence of the Cr2O3 scale and high-temperature corrosion, and to mitigate this they could be doped with elements such as Ni and Fe. In addition, the electrical properties of such steel/shell layered systems can be further improved using rare-earth element nanoparticles (Ce0.9Y0.1O2). In this work, low-chromium steel was modified using nanoparticles and/or spinel coatings and oxidized in air atmosphere at 800 °C for 2000 hours. The oxidized systems were then characterized using diffraction studies, microstructural observations and electrical measurements. Electrical studies in particular showed a significant reduction in area-specific resistance for steels modified using a combination of both nanoparticles and spinel coatings.

Optimal operation of CCHP system with duality operation strategy considering hydrogen trading and carbon capture

The combined cooling, heating, and power (CCHP) system, known for its outstanding compatibility performance, has been widely integrated with renewable energy sources such as hydrogen, wind, and photovoltaics, as well as decarbonization technologies in the energy field. However, the increased complexity of CCHP scheduling due to the high proportion of renewable energy sources and load fluctuations leads to negative returns if renewable energy sources are not scheduled reasonably and decarbonization technologies are not utilized. To address this challenge, this study introduced solid oxide electrolyzer cell (SOEC) and carbon capture system (CCS) into the CCHP system, and constructed a novel CCHP model considering hydrogen trading and decarbonization technologies. First, for the scheduling of SOEC and CCS, a game model was presented based on hydrogen sales and energy storage benefits. Second, a nudge and compel theory-based scheduling strategy and a duality operation strategy (DOS) considering sources-load fluctuation were proposed. Third, for the optimal energy scheduling problem of CCHP under new strategies and technologies, a novel multi-objective PID-based search algorithm with dynamic disturbance response was introduced. Finally, the proposed new strategies, methods, and models were verified through actual case studies on multiple typical days. The results revealed that, compared with the following electrical load strategy and following thermal load strategies, the DOS reduced costs by 3.03 % and 6.99 %, and emissions by 7.84 % and 1.39 %, respectively. The obtained outcomes contribute to the application and development of clean energy and decarbonization techniques.

Red mud enhanced biomass gasification to produce syngas: Mechanism, simulation and economic evaluation

Red mud (RM) has the potential to balance catalytic activity and recycling stability. To achieve the efficient utilization of RM, this study systematically explores the RM potential as the catalyst in biomass gasification through three aspects: catalytic experiment, simulation of biomass gasification coupled with solid oxide electrolysis cells for methanol and economic analysis. The catalytic experimental results indicate that RM has a positive effect on the biomass gasification, with a gas yield of 615.9 ml/gbiomass, representing an increment of 40.9 %. Fe2O3 and Al2O3 are the main catalytic components in RM. The simulation results on biomass gasification coupled with SOEC for methanol show that RM has increased the methanol yield to 381.83 kg/tonBiomass, with an increase of 23.9 %. The economic analysis indicates that the RM can reduce the methanol production cost, demonstrating a promising application prospect. This paper providing strong support for RM high-value synergistic utilization.

Diffusion nickel-cobalt coatings for protection of solid oxide electrolysis cells’ current collectors made of Crofer 22 APU steel

Diffusion nickel-cobalt coatings for protection of solid oxide electrolysis cells’ current collectors made of Crofer 22 APU steel