With the growing penetration of intermittent and fluctuating renewable energy sources, global and domestic energy systems are changing rapidly and traditional power grids are facing dramatic challenges. Under this scenario, the role of electricity should be reconsidered: it can not only directly meet the power demand of end users but also be converted into and stored as chemical energy. In this perspective, two routes of realizing this role transition of electricity are discussed, which are the electrified fuel conversion and the electrified fuel synthesis. Electricity can facilitate the traditional conversion of carbon-based fuels (e. g., the fuel reforming and gasification processes) by both electrified heating and electrochemical enhancement of reaction kinetics. For the fuel synthesis, the H2O and CO2 electrolysis, the direct and indirect electrochemical synthesis of both carbonaceous fuels and ammonia are highlighted for enabling diverse fuel options in the future. Finally, the importance of electricity in fuel separation and compression is also emphasized to achieve efficient interconnection between different energy networks.

The investigation of the reaction mechanism in solid oxide cells can establish a theoretical basis for improving the electrode structure, optimizing operational conditions, and enhancing cell performance. The conventional approach to mechanism research involves generating the cell's performance curve through experiments or constructing a basic reaction model, which is intricate and susceptible to human error. In this study, we introduce a novel mechanism identification method based on machine learning. This model can extract kinetic details from electrochemical impedance spectra with high precision and categorize the four hydrogen oxidation mechanisms accurately. The outcomes demonstrate that utilizing advanced artificial intelligence tools can simplify complex traditional electrochemical analyses into automated black-box models, offering a promising solution to liberate researchers from expensive and laborious experiments.

Solid Oxide Fuel Cells (SOFCs) represent one of the most promising technologies for clean and efficient energy conversion due to their high efficiency and fuel flexibility [1]. However, carbon deposition, which can occur due to the reaction of hydrocarbons in the fuel within the anode, leads to significant reduction of durability. Understanding the mechanisms of carbon-induced degradation is critical for improving the long-term stability and performance of SOFCs. Currently, some studies have conducted experimental tests on the microstructure of anode under carbon deposition [2,3] or simulated the deformation of electrode materials under long-term operation [4-7], but there is still a lack of microstructure simulation considering carbon deposition reaction kinetics. In this study, we employed a phase-field modeling (PFM) approach to investigate the carbon evolution in the nickel-based anode and combined it with a one-dimensional transient elementary reaction kinetic model. The PFM model incorporates a set of coupled partial differential equations, which describe the growth and diffusion of carbon species in the anode material. The PFM model accounts for the interactions between the carbon and Ni-YSZ crystal grains, using a free energy functional that includes the bulk free energy and gradient energy. The time evolution of the system is governed by the time-dependent Ginzburg-Landau equation and Cahn-Hilliard equations. The kinetic model incorporates the coupling effect of heterogeneous elementary chemical and electrochemical reactions, the electrode microstructure and the charge and mass transport processes. The carbon deposition source term is calculated by the heterogeneous elementary chemical reactions using methane and water as fuels. Then to ensure the accuracy and reliability, the model is validated by experimental I-V curves. After validation, the size and distribution of carbon, the porosity of the anode, and the three phase boundary area can be analyzed under different temperatures and fuel compositions. This study provides valuable insights into the mechanisms of carbon-induced degradation in SOFCs and offers a predictive tool for optimizing operating conditions to enhance the long-term stability of SOFCs. References: [1] Faro M L, Antonucci V, Antonucci P L, et al. Fuel flexibility: A key challenge for SOFC technology[J]. Fuel, 2012, 102: 554-559. [2] Sciazko A, Komatsu Y, Nakamura A, et al. 3D microstructures of solid oxide fuel cell Ni-YSZ anodes with carbon deposition[J]. Chemical Engineering Journal, 2023, 460: 141680. [3] Wang R, Wang T, Ma Y, et al. Control of carbon deposition over methane-fueled SOFCs through tuning the O/C ratio at the anode/electrolyte interface[J]. Journal of Power Sources, 2022, 544: 231854. [4] Li Q, Liang L, Gerdes K, et al. Phase-field modeling of three-phase electrode microstructures in solid oxide fuel cells[J]. Applied Physics Letters, 2012, 101(3). [5] Vijay P, Tadé M O, Shao Z. Model based evaluation of the electrochemical reaction sites in solid oxide fuel cell electrodes[J]. International Journal of Hydrogen Energy, 2019, 44(16): 8439-8459. [6] Wang Y, Wu C, Du Q, et al. Morphology and performance evolution of anode microstructure in solid oxide fuel cell: A model-based quantitative analysis[J]. Applications in Energy and Combustion Science, 2021, 5: 100016. [7] Jiao Z, Shikazono N. Prediction of nickel morphological evolution in composite solid oxide fuel cell anode using modified phase field model[J]. Journal of The Electrochemical Society, 2018, 165(2): F55.

Solid oxide fuel cells (SOFCs) have attracted considerable attention owing to their high efficiency and fuel flexibility. However, the consequent reduction in service life and an increase in failure mechanisms, such as degradation caused by sulfur impurities in the fuel, have hindered the development of SOFCs on an industrial scale. Electrochemical impedance spectroscopy (EIS) can be used to obtain a rough overview of the fuel cell performance but requires specialized data processing for unambiguous identification. In contrast, the total harmonic distortion analysis (THDA) approach provides additional higher-order response signals and offers considerable potential in diagnosing sulfur poisoning of SOFC anodes. Consequently, we explored the test parameters for THDA applications in diagnosing sulfur poisoning in SOFC anodes. The results showed that the THD values significantly increased after sulfur poisoning of the anode in the 0.01-30 Hz range. Furthermore, long-term monitoring at 1, 10, and 20 Hz confirmed the reliability of THD for diagnosing the mechanism of sulfur poisoning in SOFC anodes. This work provides a diagnostic basis for SOFC sulfur poisoning and is expected to promote research on advanced diagnostic techniques and sulfur poisoning mechanisms.

Protonic ceramic fuel cells (PCFCs) are promising electrochemical energy conversion devices that operate at intermediate temperatures. However, the leakage current resulting from the nonnegligible electronic conductivity in the electrolyte significantly impacts the energy efficiency of PCFC. Therefore, understanding the characteristics of the leakage current is crucial for the optimization of PCFC. In this study, we develop a twodimensional multi-physics coupling model of a tubular protonic ceramic fuel cell considering leakage current. The multi-ion transport process in the electrolyte is solved by the Nernst-Planck equation. Based on this model, we investigate the effects of cell heat generation and inlet oxygen concentration on the leakage current and cell efficiency. We analyze the impact mechanism of multi-physics coupling on the leakage current. We study the axial temperature and leakage current distribution of the cell, and we reduce the nonuniformity of the temperature and leakage current through thermal management method.

Protonic ceramic fuel cells (PCFC) is an electrochemical conversion device with excellent kinetic performance at intermediate temperatures(673-923K) [1][2]. The tubular PCFC is a configuration known for its high structural strength and resistance to thermal shock, making it suitable for portable and mobile applications [3]. Currently, some simulation studies have been conducted on planar PCFC single cells and stacks [4][5]. However, research on tubular PCFC stacks is still lacking and has not been widely reported. A three-dimensional physical model plays an important role in the design and optimization of PCFC stacks [3]. Therefore, this study develops a 4-cell in parallel three-dimensional PCFC stack model. Unlike traditional oxygen ion conductor solid oxide fuel cells, PCFC electrolytes are typically perovskite materials [6], such as BZY and BCZYYb, where three types of charged defects are formed inside the electrolyte (OH O • ,O O • , V O •• ) [7]. In this case, the charge conservation of a single ion is no longer sufficient to describe the charge transport inside the electrolyte. Thus, this study solves the multi-ion transport process within the electrolyte based on the chemical equilibrium of gases and defects, as well as the Nernst-Planck equation. Using this model, the distribution of physical quantities within the stack was studied, as well as the effects of inlet temperature and humidity on the electrochemical performance and current efficiency of the stack. To validate the accuracy of the model, we fabricated a 4-cell in parallel PCFC stack, as shown in Fig. 1(a). The composition, geometric structure, and fabrication process of the PCFC single cells used can be referenced from our previous work [8][9]. The discharge performance of the stack was experimentally tested at three different temperatures, as shown in Fig. 1(b). The geometric structure of the three-dimensional multi-physics coupling PCFC stack model is shown in Fig. 1(c), which includes the gas distribution chamber, the cell body, and the cathode chamber. Fig. 2(a) shows the surface flux density distribution of O-site polarons for two cells at different positions. The cell near the air inlet exhibits a gradually increasing flux density of O-site polarons along the air flow direction, while the cell near the air outlet shows the opposite trend. Fig. 2(b) presents the total flux of O-site polarons in the PCFC stack at different temperatures. It can be observed that as the temperature increases, the total flux of O-site polarons increases, with the total flux at 650°C being an order of magnitude higher than that at 550°C. Fig. 2(d) shows the total flux of O-site polarons at different inlet water vapor concentrations on the air side. As the water vapor concentration increases, the total flux of O-site polarons decreases. This study built a PCFC stack model that considers the coupling of multiple physical and chemical processes. The multi-ion transport process inside the electrolyte is calculated by Nernst-Planck equation. Using this model, the temperature distribution, component distribution, and multi-ion transport inside the electrolyte of the PCFC stack can be obtained. Studies show that regions with high oxygen concentration and high temperature enhance the transport of O-site polarons, increasing the local leakage current density; lower inlet temperatures can suppress the transport of O-site polarons, thereby reducing leakage current; Increasing the inlet water vapor concentration on the air side can promote the hydration reaction, thereby inhibiting the generation of O-site polarons and improving current efficiency. This study will provide a reference for future experimental and simulation research on PCFC stacks. References [1]Cao J, Ji Y, Shao Z. Perovskites for protonic ceramic fuel cells: a review. Energy Environ Sci 2022;15:22-2232. [2] Kim J, Sengodan S, Kim S, Kwon O, Bu Y, Kim G. Proton conducting oxides: A review of materials and applications for renewable energy conversion and storage. Renewable and Sustainable Energy Reviews 2019;109:606-618. [3] Kee RJ, Ricote S, Zhu H, Braun RJ, Carins G, Persky JE. Perspectives on Technical Challenges and Scaling Considerations for Tubular Protonic-Ceramic Electrolysis Cells and Stacks. J Electrochem Soc 2022;169:54525. [4] Li Z, Wang C, Bello IT, Yu N, Chen X, Xuan J, et al. A comprehensive 3D modelling exploration of a protonic ceramic electrolysis cell stack with metal foam. J Power Sources 2024;606:234581. [5] Li Q, Sun X, Shen L, Li G. Three-dimensional multiphysics coupling numerical simulation of a proton conductor solid oxide fuel cell based on multi-defect transport. Phys Chem Chem Phys 2023;25:7154-7169. [6] Wang N, Tang C, Du L, Zhu R, Xing L, Song Z, et al. Advanced Cathode Materials for Protonic Ceramic Fuel Cells: Recent Progress and Future Perspectives. Adv Energy Mater 2022;12. [7] Zhu H, Ricote S, Duan C, O Hayre RP, Kee RJ. Defect Chemistry and Transport within Dense BaCe0.7Zr0.1Y0.1Yb0.1O3−δ (BCZYYb) Proton-Conducting Membranes. J Electrochem Soc 2018;165:F845. [8] Huang X, Shi J, Liu Z, Wang Y, Ye X, Shi Y. Numerical study on current leakage of a tubular protonic ceramic fuel cell. J Power Sources 2025;631:236241. [9] Miao X, Feng J, Dai Z, Zhu X, Wen J, Zhang L, et al. A Regenerative Coking‐resistant CO2 Hydrogenation Reactor using a Protonic Ceramic Electrolysis Cell with Thin and Robust Fuel Electrode. Adv Energy Mater 2024;14. Figure 1

In this study, response surface methodology (RSM) and the non-dominated sorting genetic algorithm-II (NSGA-II) are used to optimize the structure and inlet airflow rates of a microtubular solid oxide fuel cell (SOFC) stack. A multi-physics model of a rectangle eight-tube microtubular SOFC stack is developed with consideration of the charge/mass/momentum/heat transfer processes. RSM is used to develop the polynomial equations of the volumetric power density and the maximum temperature gradient in the stack using structural parameters and exceed air ratios. Because the temperature gradient is above the safe value, a stack with heat pipes is simulated to optimize the temperature distribution, and the polynomial equations are built. Then these equations are calculated using the NSGA-II to produce the Pareto front, which reveals the optimal results achieving both the maximum volumetric power and the lowest maximum temperature gradient. In this study, the optimization achieves a volumetric power density of 120.9 mW/cm(3) with a maximum temperature gradient <20 K/cm, demonstrating the feasibility of RSM and the NSGA-II approach in the optimization of the SOFC stack configuration.

A solid oxide fuel cell (SOFC) system model can be used to predict the influence of various parameters such as fuel inlet flow and voltage on the system output performance. This article focuses on a typical UAV (Unmanned Aerial Vehicle) SOFC power system and develops a system model that couples the SOFC surrogate model with other BOP (Balance of Plant) models. The SOFC surrogate model is trained using BP (Back Propagation) neural network on a dataset calculated from a multiphysics SOFC model. Based on this model, the effects of system operating conditions on key system performance are studied. The results demonstrate that fast prediction of the SOFC system performance can be realized.

Predicting the internal distributions of key parameters is critical for the development of solid oxide fuel cells but is complicated and time-consuming. In this study, a framework for fast parameter distribution prediction based on proper orthogonal decomposition (POD) and an artificial neural network (ANN) is proposed and applied to a tubular 20-cell segmented-in-series solid oxide fuel cell. The characteristics of the POD mode for temperature, hydrogen and potential distributions are analyzed, and the variation in the coefficient with respect to the operating parameters is investigated. The predicted distributions under 20 random operating conditions are compared with those simulated from the multi-physics model. The calculation time is reduced from 14 h to 24 min to 160 ms. The distributions predicted by the POD-ANN model have good agreement with the results simulated by the multi-physics model, both globally and locally.

Solid oxide fuel cells (SOFCs) represent an advanced energy conversion technology capable of directly transforming chemical energy into electrical power at elevated temperatures. Characterized by exceptional energy conversion efficiency and minimal environmental impact, this technology has emerged as a promising candidate for future sustainable energy systems. However, when integrating high-performance microtubular SOFC (mT-SOFC) units into stack configurations, the collective output frequently underperforms relative to the sum of individual cell capacities. This performance discrepancy primarily stems from uneven fuel/air distribution within reactor assemblies, leading to localized cell overloading and subsequent stack degradation. Maintaining homogeneous reactant distribution thus constitutes a critical factor in optimizing stack longevity and operational efficiency. As power demand of the mTSOFC stack continues to grow, the structure of the stack becomes more complex, causing serious thermal stress gradient problems. A reasonable mass transfer channel is an effective solution to eliminate the high temperature region of the stack reduce the thermal stress. These are often difficult to observe and analyze in experiments, so how to design the flow field structure to optimize the performance of the stack has become a difficult point in the design and research of the stack. Therefore, it is of great scientific value to describe a model with a complete stack structure and a complete physics coupling. At present, researchers have widely reported a variety of SOFC stack and focus on planar SOFC configurations, with limited investigations on the mTSOFC stack model with complete physical field coupling. Chen [2] Explores the effects of different external airflow paths on the external gas and temperature distribution of cells by building large 3D multiphysics models consisting of 7×7 tubes. But only matters the physical fields of material transport and heat transfer. And the heat source is by assuming that a uniform electrochemical reaction occurs within the porous cathode functional layer, not an electrochemical reaction controlled by the concentration and temperature of the reaction gas. Lockett [3] proposed to use CFD software to predict and evaluate 20 microtubule stacks, also assuming the exothermic power of each cell, setting up heat transfer and substance transfer physics, and predicting the temperature distribution of a single cell. Pianko-Oprych [4] established a model of 48 anode-supported stacks to analyze the temperature distribution of the stacks and the resulting displacement and stress distributions, and to analyze the risk of damage to the stacks. The effects of electrochemistry are not involved. In this work, an accurate model was developed to predict the electrochemical reaction, mass transfer process, temperature distribution and thermal stress distribution of the mTSOFC stack by coupling multiple physics. The heat source comes from the heat released by the electrochemical reaction. A 10-tube stack with an external gas distributor was built to analyze the thermal stress distribution during stable operation, which can be mutually verified with the location where the stack is prone to fracture failure in the experimental test. The model predicts the current density distribution and internal gas distribution at different typical reaction temperatures. The effects of gas channel design on stack performance and thermal stress distribution were evaluated and analyzed. This work is based on the three-dimensional finite element model of the anode-supported tubular SOFC stack developed by our research group. Fig.1 is a schematic diagram of a 10-unit stack. It consists of two mullite anode gas distributor, a stack composed of 10 mTSOFC cells and a cathode flow channel. The total active area of the microtubular SOFC is about 107.3 cm 2 , and the power of a single cell can reach 5.5 W. The metal silver is used as the current collector to collect the current and connect the cell. Ten micro-tube SOFCs are connected in series and reinforced by high-temperature sealing ceramic glue. Mullite is used as a gas distributor and a cell fixing device at both ends, and two ceramic pipes are used as the inlet and outlet of the gas. On the side of the air electrode, the boundary reaction temperature is accurately controlled by a high-precision electric heating furnace. The furnace environment was replaced by a rectangular air domain. The model predicted the temperature distribution of a tubular SOFC stack under three gas flow modes (co-flow, counter-flow, and cross-flow. And three modes maintained identical hydrogen and air flow rates, with only the air inlet position varying), as shown in Figures 2(a)-(c). Under co-flow conditions, the stack reached a maximum temperature of 1170 K during steady-state 6V discharge at 973.15 K, while counter-flow mode exhibited a higher peak temperature of 1200 K. Cross-flow mode demonstrated the lowest maximum temperature of 1150 K. The elevated temperature in counter-flow mode arises from minimized temperature differential between air and cells when air reaches the rapid electrochemical reaction zone, leading to reduced heat dissipation. From thermal distribution perspective alone, cross-flow mode with its minimal temperature gradient appears most suitable for stack operation. Figure 2(d) illustrates the impact of gas flow modes on stack discharge power. Above 8V, performance differences were negligible, but became significant at 6V. Co-flow and counter-flow modes showed similar oxygen concentration distributions between cell rows, while cross-flow mode exhibited more uniform gas distribution. Figure 2(e) reveals maximum thermal stress (2.06 GPa) at cell-distributor connection points under cross-flow mode with extreme boundary conditions (zero thermal expansion coefficient assumed for gas distributor, fixed x-y axis constraints at cell interfaces). Notably, high-stress regions occurred at cell ends rather than maximum temperature zones. This stress concentration stems from two factors: significant temperature gradients and CTE mismatch between distributor materials and tubular cells. While thermal expansion along the Z-axis (longitudinal direction) was permitted, other directions remained constrained. These simulations align with experimental observations where fractures typically initiate at end regions. By building large 3D accurate models, the performance of 10-tube stacks is studied. Comparing the simulation results in the co-flow, counter-flow and cross-flow modes, it is concluded that the cross-flow mode has a higher power density, a more uniform gas distribution, and a smaller temperature range. Accordingly, in the cross-flow mode, it is found that the mismatch of the coefficient of thermal expansion between the anode of the gas distributor and the cell tube is the main reason for the huge stress of the stack. Second, the connector requires high yield strength to cope with multiple cold-restart stacks, resulting in poor contact with the electrodes. The results of the simulation can help to understand the operation of the stack and improve the service life of the stack. Figure 1 Figure 2

1. Introduction Compared to the low-temperature electrochemical conversion, solid oxide electrolysis cells (SOECs) exhibit significant advantages in both thermodynamics and kinetics (1). Additionally, SOECs employ an all-solid-state oxygen ion conductor system, enabling direct co-electrolysis of H 2 O/CO 2 . This system is characterized by low operating costs and tunable product outputs. Particularly in distributed energy systems with combined heat and power (CHP), the cascade utilization of energy can further enhance the overall energy efficiency of the system (2). Furthermore, utilizing surplus renewable electricity to electrochemically convert CO 2 /H 2 O emitted from fossil fuels into synthetic fuels holds the potential to simultaneously achieve resource utilization and fuel synthesis. Compared to experimental validation, mathematical modeling provides a more convenient and cost-effective approach for predicting the performance trends of SOEC co-electrolysis cells. However, as research progresses, it has become evident that conventional SOEC units struggle to meet the high power density requirements for large-scale applications. There is an urgent need to further integrate SOEC units into stacks. Given the intricate internal geometry of fuel cell stacks, a three-dimensional model is essential to accurately capture the spatial distribution of thermal, mass, electrical, and mechanical fields. However, due to the complexity and challenges inherent in 3D modeling, research on simulating SOEC co-electrolysis stacks remains relatively limited. Specially, we noticed that the cell configurations in constructed 3D models of stacks mainly focused on planar or flat-tube designs. The Hawkes group (3) was among the earliest to employ Fluent to construct a 3D co-electrolysis cell model, which they used to predict the performance of the co-electrolysis cell sub-model within a system-level model. On the other hand, Banerjee et al. (4) developed a multi-scale 3D model using a FORTRAN program. This model described the performance of a co-electrolysis SOEC stack designed to supply feedstock for Fischer-Tropsch reactors in commercial applications. In their model, they incorporated kinetic descriptions of thermocatalytic chemical reactions occurring on the Ni electrode. For the flow and chemical fields, they simplified the stack to a 2D model considering only axial and radial mass transport, while employing a 3D description for the thermal field. After calibration, the stack was capable of producing a H 2 :CO ratio of 2:1, meeting the requirements for subsequent Fischer-Tropsch synthesis. In addition to performance simulation, flow field design is another key objective of 3D modeling. Through flow field design, researchers can enhance heat and mass transfer within the stack, thereby optimizing the performance of co-electrolysis stacks. In a 3D model developed by Wang et al. (5) using Haberman software, they optimized the temperature distribution of the stack under different design schemes. The results showed that the new flow field design achieved a minimum temperature gradient of 3.81 K/cm, significantly lower than the 10 K/cm observed in traditional flow field designs. Du et al. (6) also investigated the impact of operating pressure on stack performance using a 3D model developed in the ANSYS/Fluent environment. They found that the operating voltage peaked at approximately 8 atm and decreased continuously with further increases in pressure. Furthermore, Wang et al. (7) studied the dynamic response characteristics of a co-electrolysis cell using a 3D model written in FORTRAN. They observed that changes in the excess air ratio and flow rate input led to significant variations in the internal temperature distribution of the stack. By adjusting these parameters, they successfully controlled the temperature gradient to within 2.3 K/cm. In contrast, there have been fewer reports on the construction of 3D models for tubular stacks, which exhibit better sealing performance and superior mechanical properties (8). Therefore, based on efficient current collection and connection techniques, we constructed a 10-cell SOEC co-electrolysis stack. Supported by experimental testing, a 3D model was developed to analyze the performance and efficiency of H 2 O/CO 2 co-electrolysis in the stack. The distribution characteristics of heat, mass, flow, and stress within the stack were obtained. Finally, the effects of different operating conditions on the H 2 O/CO 2 conversion rate, stack performance, and energy conversion efficiency were compared, thereby identifying optimization strategies for further improving the performance of the SOEC stack. 2. Experiment In previous studies, our group have developed an efficient current collection and connection method suitable for tubular solid oxide cells (SOCs) (9). In this work, a 10-cell SOEC stack was integrated, as shown in Figure 1. The tubular cell employs Ni-YSZ (yttria-stabilized zirconia) as the cathode, ScSZ (scandia-stabilized zirconia) as the electrolyte, and LSM(lanthanum strontium manganate)-ScSZ as the anode. The radial thicknesses of the cathode, electrolyte, and anode are 550 μm, 10 μm, and 25 μm, respectively. Furthermore, the effective current collection length is 140 mm, and the thickness of the current collection layer is 0.05 mm. Based on the structure of the 10-cell SOEC stack, we designed an experimental testing system. During the experiments, the inlet gas of fuel electrode flowed through a ceramic distributor, passed over the cathodes and collectors, and then exited the system. On the air electrode side, air was blown externally to prevent the accumulation of oxygen at the anode. In the experiments, we tested the electrochemical performance of the stack at different temperatures (650°C, 700°C, and 750°C) and different H 2 O/CO 2 ratios (1:1 and 2:1). The inlet flow rates for both the anode and cathode were fixed at 1000 sccm. The stack was achieved a 48.6W power output at 750℃ and 1.4V. 3. Model development The assumptions for constructing the three-dimensional multi-physics field coupling model are as follows: (1) Electrochemical reactions occur within porous electrodes, while thermochemical reactions only occur within porous cathodes. The active sites for electrochemical and thermochemical reactions are uniformly distributed in the electrode layer, and that the two conductive phases are continuous and uniform in each layer. (2) Ionic transport only occurs in porous cathodes, porous anodes, and current collectors, while electron transport occurs in porous cathodes, electrolyte layers, porous anodes, and current collectors. (3) The reaction gases for the cathode are selected as H 2 O/H 2 /CO 2 /Ar mixed gases as reaction materials, and the blowing gas for the cathode is selected as air. All gases are considered ideal gases. (4) In the gas flow channel, only bulk diffusion is considered, while in the porous electrode, both bulk diffusion and Knudsen diffusion are considered. (5) The flow, diffusion, and heat transfer of the anode gas only occur within the specified cathode boundary, ignoring the radiation heat transfer effects of other parts. According to the model assumptions, in addition to setting symmetry conditions on the central boundary, the detailed settings of the other boundary conditions were as follows(10-14): Ionic charge balance : The transfer of ionic charges was continuous at the electrode/electrolyte interface and the collector/anode interface And ion charges cannot pass through other interfaces. Electronic charge balance: V cell,an and V cell,ca were specified on the anode of the nearest cell and the farthest collector respectively. Except for the interface at the collector layer/anode, all other boundaries were electron charge insulated. Mass balance: The mass fractions of inlet gas in the cathode and blowing gas in the anode were specified. Gas flux free conditions were set at the electrode/electrolyte interface boundaries and, as well as other boundaries. Momentum balance : The inlet velocities were specified at both the cathode and the anode, while the pressures were specified at the outlet of the gas channels. The other boundaries were set as non slip walls, and the gas velocities on them were zero. Energy balance: The inlet temperature of the gases at the cathode and anode were specified respectively. The outlet of the gas channels were defined as the convective heat flow boundary. The energy transfer processes between gases and solids were coupled at the cathode/cathode channel interface and the collector/anode channel interface, with the other boundaries being insulation layers. Stress balance: The cells were made of linear elastic material and other ceramic materials were considered as a rigid component. 4 . Results and discussion This model enabled us to obtain the thermal/mass/electrical/mechanical distribution characteristics in the stack. By analyzing the variations in the rates of electrochemical and thermochemical reactions inside, a competitive relationship among the two reduction pathways for CO 2 reduction has been discovered: at low voltages and towards the rear end of the flow, the thermochemical reaction became the primary pathway for CO production. Conversely, at the front end of the flow and under high voltage conditions, CO 2 tends to be reduced through electrochemical reactions. Additionally, we have observed the deformation caused by heat stress in the stack. The thermal stress was concentrated on area between the current collectors and the tubular cells. Due to the higher thermal expansion coefficient of the current collectors, they exhibited more pronounced deformation at high temperatures, which compressed the tubular cells, which led to a higher probability of fracture at this location. Furthermore, the impacts of different operating conditions on the H 2 O/CO 2 conversion rate, electrochemical performance, and energy conversion efficiency of the stack were analyzed. The results showed that the three common operating methods (increasing temperature, raising pressure, and enhancing inlet H 2 O/CO 2 ratio) can all effectively improve the electrochemical performance and H 2 O/CO 2 conversion rate. The analysis suggested that increasing temperature and pressure can kinetically enhance the electrolysis performance, and increasing the H 2 O/CO 2 ratio can more effectively utilize the reactive surface area and promote the reduction of CO 2 since the electrolysis performance of H 2 O is significantly stronger than that of CO 2 . In terms of energy conversion efficiency, both increasing pressure and the H 2 O/CO 2 ratio can enhance the syngas yield rate without altering the energy input, thus positively affecting the energy conversion efficiency. However, as the system required more heat for the heating process of the inlet gases when the temperature is increased, the energy conversion efficiency of the stack slightly decreases with rising temperature. Reference 1. Herranz J.,Pătru A.,Fabbri E., et al. Co-electrolysis of CO 2 and H 2 O: From electrode reactions to cell-level development[J]. Current O pinion in E lectrochemistry , 2020, 23: 89-95. 2. Min G., Park Y. J., Hong J. Thermodynamic analysis of a solid oxide co-electrolysis cell system for its optimal thermal integration with external heat supply[J]. Energy Conversion and Management , 2020, 225: 113381. 3. J.E. O’Brien, M.G. McKellar, C.M. Stoots, et al. Parametric study of large-scale production of syngas via high-temperature co-electrolysis[J]. International Journal of Hydrogen Energy , 2009, 234: 4216-4226. 4. A. Banerjee, Y. Wang, J. Diercks, et al, Hierarchical modeling of solid oxide cells and stacks producing syngas via H 2 O/CO 2 co-electrolysis for industrial applications[J]. Applied Energy , 2018, 203: 996-1013. 5. Y. Wang, Y. Du, M. Ni, et al, Three-dimensional modeling of flow field optimization for co-electrolysis solid oxide electrolysis cell[J]. Applied Thermal Engineering , 2020, 172: 114959. 6. Y. Du, Y. Qin, G. Zhang, et al.Modelling of effect of pressure on co-electrolysis of water and carbon dioxide in solid oxide electrolysis cell[J]. International Journal of Hydrog en Energy , 2019, 44: 3456-3469. 7. Wang, A. Banerjee, O. Deutschmann, Dynamic behavior and control strategy study of CO 2 /H 2 O co-electrolysis in solid oxide electrolysis cells[J]. Journal of Power Sources , 2019, 412: 255-264. 8. Y.Zheng, J.Wang, B. Yu, et al. A review of high temperature co-electrolysis of H 2 O and CO 2 to produce sustainable fuels using solid oxide electrolysis cells (SOECs): advanced materials and technology[J]. Chemical Society Reviews , 2017, 46: 1427-1463. 9. J. Shi, J. Fan, R. Zhang, et al. Experimental study on the long-term stability and thermal cycling endurance of micro-tubular solid oxide fuel cells and stacks using ammonia[C]. 3rd Symposium on Ammonia Energy, 2024, China, Shanghai. 10. Y. Shi,Cai, C. Li et al. Modeling of an anode-supported Ni-YSZ|Ni-ScSZ|ScSZ|LSM-ScSZ multiple layers SOFC cell[J]. Journal of Power Sources , 2007, 172: 235-252. 11. Y. Shi, Cai,C. Li, et al. A general approach for electrochemical impedance spectroscopy simulation using transient mechanisticSOFC model.[J] ECS Trans actions , 2007, 7: 1889-1899. 12. B. A. Haberman, B. Young. Three-dimensional simulation of chemically reactinggas flows in the porous support structure of an integrated-planar solid oxidefuel cell[J]. International Journal of Heat and Mass Transfer ，2004, 47: 3617-3629. 13. R. Krishna, J. A. Wesselingh. The Maxwell-Stefan approach to mass transfer[J]. Chemical Engineering Science , 1997, 52: 861-911. 14. T. Cui, G. Xiao, H. Yan, et al. Numerical simulation and analysis of the thermal stresses of a planar solid oxide electrolysis cell[J]. International Journal of Green Energy , 2023, 20(4): 432-444. Figure 1 Figure 2

The solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system is among the most efficient power generation technologies. However, the development of SOFCs has focused on lower operating temperatures, which is much lower than the turbine inlet temperature (TIT) of the advanced hundred-MW-class gas turbines (GTs) (＞1400oC), hindering their integration. Therefore, current large-scale GTs still primarily enhance power generation efficiency by increasing TIT, which approach has suffered from prominent marginal effects, leading to the bottleneck in efficiency enhancement. To address this, we propose a super-high-temperature SOFC operating at above 1200°C, which can be integrated with a commercial hundred-MW-class gas turbine to break the efficiency bottleneck. In our laboratory, a single tubular SOFC achieved a peak output power of 4.67 W at 1200°C, which is 5.5 times higher than that at 700°C. We simulated a hundred-MW-class hybrid system to demonstrate the necessity of the elevation of SOFCs temperature, analyzing it thermodynamically based on a T-s indicator diagram. When the SOFC operating temperature increases from 800°C to 1200°C, the temperature mismatch degree between the SOFC and the F-class gas turbine decreases significantly from 68.16% to 0%. This improvement is accompanied by an increase in fuel cell combustor (FCC) exergy efficiency from 76.52% to 85.93%, and an increase in system efficiency from 58.60% to 74.12%. Further elevating the SOFC operating temperature to approximately 1300°C could potentially yield a system efficiency of 80.31%. Considering these substantial thermodynamic advantages, we propose a new development route for SOFCs towards a super-high operating temperature of over 1200oC.

Solid oxide fuel cells (SOFCs) have attracted considerable attention as a promising technology for future energy development because of their high energy efficiency and wide range of available fuels. However, challenges such as long-term anode degradation caused by trace sulfur in carbonaceous fuels must be overcome before SOFCs can be used for large-scale industrial production. Extant reviews on sulfur poisoning of SOFC anodes have focused on summarizing the sulfur-resistant anode materials. This paper comprehensively reviews the mechanisms underlying sulfur poisoning, potential methods for anode regeneration after poisoning, and recent advances in mitigating sulfur poisoning. In particular, the effects of SOFC operating parameters on the mechanism of sulfur poisoning and the relationship between sulfur poisoning and carbon deposition are comprehensively evaluated. Adjusting the working conditions of the SOFC and optimizing the anode material are effective measures to alleviate the issue of sulfur poisoning. This review highlights the present issue of sulfur poisoning-related anode deterioration and provides a solid foundation for future problem solving. It will potentially provide a solid theoretical foundation for addressing the issue of degradation caused by sulfur poisoning.

[Objectives]A portable solid oxide fuel cell(SOFC)system includes a gas supply module,a fuel processing module,an SOFC power generation module,a thermal management module,an exhaust treatment module and a control module.There is a complex coupling relationship between the fuel processing module and the SOFC power generation module.Clarifying the coupling characteristics between them is crucial for improving system performance and operating time.[Methods]The effects of temperature,the carbon-to-oxygen ratio and other factors on the performance of catalytic partial oxidation(CPOx)of propane with Rh as catalyst were analyzed,and the coupling performance of CPOx and SOFC stack was further tested.[Results]With the increasing of fuel flow rate,the reforming efficiency first increases and then decreases.The most suitable flow rate is 100 or 150 mL/min.An increase in temperature can continuously improve the reforming efficiency,but the improvement in reforming efficiency at high temperatures caused by an increase in temperature gradually decreases.The optimal C/O ratio obtained from the experiment is 1.0.Under the optimal operating conditions,the output power of SOFC stack reaches 8.38 W.[Conclusions]Under the conditions of propane flow rate of 150 min-1,carbon and oxygen mole fraction ratio of 1.0,and operating temperature of 800℃,the coupling performance between SOFC stack and CPOx is the best,the portable propane power generation system can generate 150 W of power with a volume of 12 L.

Tubular segmented-in-series solid oxide fuel cells (SIS-SOFCs) offer the advantages of high voltage, low current, easy sealing, and high thermal shock resistance. Tubular SIS-SOFCs can be assembled into a highly integrated power-generation stack module to increase the volumetric power density. This study investigated the air flow characteristics of a kilowatt-class tubular SIS-SOFC stack with a 5 x 10-cell array, each containing 59 segments. A three-dimensional stack model that considers practical stack structures, coupled electrochemical reactions, and the mass/momentum/heat transfer processes was developed. The results show that a large flow nonuniformity existed in the conventional tubular stack design, which resulted in a severe temperature distribution. Local hot spots at the marginal positions and circumferential temperature difference were found to be non-negligible. To improve the flow uniformity, an air distributor with optimized diameters at different positions was designed, and manifold parameters were adjusted to balance the flow resistance. The maximum temperature was reduced by 35 K and temperature uniformity was significantly improved.

Solid oxide fuel cells (SOFCs) have witnessed significant advancements in recent years, emerging as potential alternatives to low-temperature fuel cells for mobile applications owing to their wide fuel flexibility and high efficiency. This paper offers a comprehensive assessment of the progress achieved thus far and the challenges faced in transitioning from stationary to mobility sectors. Three pivotal aspects are highlighted across different levels: enhancing fuel tolerance and flexibility at the anode level, achieving rapid start-up at the cell level, and realizing compact integration at the stack level. This review can lay a theoretical foundation for the development of SOFC systems tailored to unique requirements, such as high power density and rapid start-up, crucial for mobile applications. This review will facilitate commercial breakthroughs and advances in the mobility of SOFCs, which holds substantial strategic importance.