High-temperature fuel cells, as highly efficient and clean electrochemical energy conversion devices, represent a kind of key technology for achieving “dual carbon” energy strategies. Their core appeal lies in the broad fuel adaptability, high energy conversion efficiency and stable all-solid-state structure. Fuel cells can utilize not only hydrogen as fuel but also directly employ diverse fuels such as hydrocarbons (e.g., natural gas, methanol) and ammonia, demonstrating excellent application flexibility and energy compatibility. Compared to conventional internal combustion engine power generation, high-temperature fuel cells directly convert chemical energy into electricity through electrochemical reactions, achieving power generation efficiencies exceeding 60%. Furthermore, by utilizing waste heat from the reaction process for combined heat and power generation, overall energy utilization efficiency can be elevated to over 80%. However, commercialization of high-temperature fuel cell technology remains intrinsically tied to a core challenge—key component materials. Specifically, developing component materials capable of long-term stable operation under harsh conditions of high temperatures is currently the bottleneck that restricts advancement of high-temperature fuel cells. Breakthroughs in this area will lay cornerstone for development of high-temperature fuel cell technology in the future.

Conventional high-temperature fuel cells rely on classic material systems such as yttria-stabilized zirconia (YSZ) electrolytes, nickel-YSZ metal-ceramic anodes, and lanthanum-strontium-manganese (LSM) oxide cathodes. These materials exhibit outstanding electrochemical activity and ionic conductivity under high-temperature conditions, providing a crucial foundation for achieving efficient energy conversion. However, as operating temperatures are reduced to the medium-to-low range (400-700 ℃), the oxygen ion migration rate and electrode reaction kinetics of conventional material systems significantly decline, markedly deteriorating the electrochemical performance of the cells. To enable the operation of high-temperature fuel cells at lower temperatures while maintaining efficiency and stability, researchers are actively developing novel electrolyte materials with high ionic conductivity and highly catalytically active electrode materials. This advancement aims to promote the widespread application of high-temperature fuel cell technology within next-generation energy systems.

At the invitation of the editorial board of Journal of Inorganic Materials, I served as a guest editor to organize and compile this topical section on “Key Materials for High-temperature Fuel Cells”. Renowned domestic research groups from institutions including Harbin Institute of Technology, Xi’an Jiaotong University, Beijing Huairou Laboratory, and Wuhan Institute of Technology have dedicated themselves to analyzing the latest advances in fundamental research, preparation techniques, performance optimization, and mechanism studies concerning materials for high-temperature fuel cells.

This topical section is intended to provide researchers with a deeper understanding of high-temperature fuel cells, serving as a window into the latest developments within the field, and actively promoting advancement of materials for high-temperature fuel cells as well as progress in the discipline. I extend my heartfelt gratitude to all experts who contributed to this topical section amidst their busy schedules. It is through their diligent efforts and generous support that this publication has come to fruition.

Solid oxide cell (SOC) has attracted extensive attention in recent years due to its high-efficiency clean power generation capability in fuel cell (SOFC) mode and excellent hydrogen production and energy storage potential in electrolysis cell (SOEC) mode. Conventional SOC typically employs pore-forming agents such as graphite or carbon powder to fabricate porous electrode supports. This approach results in disordered pore distribution and complex pore structure, leading to high tortuosity factor. Particularly under conditions of dilute fuel or high current densities, these factors cause concentration polarization, limiting further performance improvements. To address these challenges, application of straight-pore structures has shown significant progress. The ordered pore channels in this structure enhance gas diffusion and transport, reduce concentration polarization, and improve the impregnation efficiency of electrode materials while increasing the utilization of active sites, thereby significantly boosting the electrochemical performance of SOC. This review systematically summarizes recent advancements in the preparation techniques for straight-pore structured SOC. It details the pore-forming mechanisms, process characteristics, and applications of key technologies (phase inversion, freeze-drying and alginate ion gelation) in both planar and tubular SOC configurations. Furthermore, it provides an in-depth analysis of how the straight-pore structure enhances performance in both SOFC mode (hydrogen and hydrocarbon fuel adaptability) and SOEC mode (conventional H₂O/CO₂ electrolysis and fuel-assisted electrolysis), elucidating the underlying mechanisms. Despite the great potential demonstrated by straight-pore structures in SOC, comprehensive reviews focusing on their fabrication techniques remain scarce. This paper aims to consolidate the latest progress in straight-pore SOC preparation technologies, analyze their technical advantages and existing challenges, and propose future research directions.

Driven by global energy transition and carbon neutrality goals, proton-conducting solid oxide fuel cells (P-SOFCs) have become a research hotspot in clean energy technology due to their advantages of efficient medium-to-low temperature power generation (400-600 ℃), excellent fuel compatibility, and high energy conversion efficiency. This review analyzes the development prospects of hydrogen-containing fuel P-SOFCs. Addressing key technological bottlenecks, this review focuses on three core dimensions including material design, reaction mechanisms, and characterization techniques to summarize research progress and technical challenges in hydrocarbon-fueled and ammonia-fueled P-SOFC systems. For hydrocarbon-fueled P-SOFCs, the carbon deposition issue is thoroughly examined. Their formation mechanisms, characterization methods and influencing factors on carbon deposition are discussed in depth. Advanced improvement strategies are highlighted, including modification of reforming catalysts, optimization of proton-conducting electrolytes, and novel design of electrodes. Regarding direct ammonia fuel cells (DAFCs), challenges related to insufficient anode durability are addressed. Critical influencing factors are identified as catalyst activity, support types, nitridation corrosion mechanisms, hydrogen partial pressure, ammonia flow rate, and anode microstructure. Based on cutting-edge research, novel improvement strategies, such as anode modification, optimization of anode catalytic layers and innovative cell structure designs, are summarized. This review outlines future development directions to advance the commercialization of hydrogen-containing fuel P-SOFCs.

High-temperature hydrogen fuel cell, commonly referred to as solid oxide fuel cell (SOFC), is regarded as an effective energy conversion device for achieving the "dual carbon" goals due to its advantages such as high energy conversion efficiency, strong fuel flexibility, environmental friendliness, and all-solid-state structure. To address the issues of high cost, volatility, high thermal expansion coefficient, and easy reaction with electrolyte of traditional cobalt-based cathodes, a cobalt-free composite cathode (O-SSF-SDC), consisting of 75% (in mass) perovskite oxide Sm_0.6Sr_0.4FeO_3-δ (SSF) and 25% (in mass) fluorite structure Ce_0.8Sm_0.2O_1.9 (SDC), was prepared by one-pot synthesis method for SOFC application. The morphological results and element mapping images demonstrated that the O-SSF-SDC composite cathode exhibited uniform particle size, which provided more active reaction sites for the oxygen reduction reaction in the cathode. The symmetrical cell with O-SSF-SDC cathode showed a relatively low electrode polarization resistance of 0.175 Ω·cm² at 700 ℃ in air, while the maximum output power density of the single cell equipped with O-SSF-SDC cathode reached 609.6 mW·cm^-2 when exposing the anode and cathode to 3% H₂O wet H₂ and ambient air, respectively, demonstrating comparable electrochemical performance to traditional cobalt-based cathodes. This work can provide reference for the development of efficient high-temperature hydrogen fuel cells.

Two-dimensional CoPS₃ electrocatalyst for water splitting suffers from scarcity of in-plane metal active sites, resulting in slow kinetics for oxygen evolution reaction (OER) at anode, thereby limiting overall efficiency of hydrogen production via water splitting. To address this issue, this study proposes a new strategy to enhance the catalytic activity through synergistic effects of quantum confinements and edge chemical modification. Initially, two typical CoPS₃ quantum dots (CoPS₃-QDs) structures with high edge-site densities were constructed. Through binding and bond energy calculations, structure of thermodynamically stable CoPS₃-QDs1 was identified, with its edge Co2 site exhibiting the best OER activity among other edge sites (Gibbs free energy change for the rate-determining step, ΔG at 1.68 eV). Subsequently, oxygen modification was introduced at Co2 site of the CoPS₃-QDs1 and its neighboring sulfur atoms, obtaining five O-CoPS₃-QDs models. Theoretical calculations revealed that the M4 model (with O modification at the S3 site) had an overpotential (η^OER) of only 0.32 V, which was 29% lower than that of the unmodified system but significantly better than that of the noble metal catalyst RuO₂ reported in the literature. Partial density of states analysis further revealed that O modification optimized charge redistribution around the Co sites, enabling moderate adsorptions of oxygen intermediates (*OH, *O, *OOH). This study elucidates the crucial role of edge-site modification of quantum dots in regulating electronic structure and reaction kinetics, providing a theoretical basis for designing efficient and low-cost OER electrocatalysts.

Ammonia (NH₃) has been considered as a hydrogen storage material due to high hydrogen storage density and ease of liquefaction, thus hydrogen (H₂) production by ammonia decomposition is an ideal method for hydrogen preparation. However, traditional ammonia decomposition technologies face challenges such as high operating temperatures, low efficiency at moderate temperatures, and difficulties in hydrogen purification. In this study, proton ceramic membrane reactor (PCMR) with symmetric structure of porous electrode Ni-BZCY/BZCY/Ni-BZCY (BZCY: BaZr_0.1Ce_0.7Y_0.2O_3-δ) was prepared by co-pressing method. At 600 ℃, PCMR exhibited polarization resistances (R_p) of 0.11 and 0.23 Ω·cm² in H₂ and NH₃ atmospheres, respectively, with corresponding current densities of 1.87 and 1.56 A·cm^-2 at an applied voltage of 0.8 V. Even at 300 ℃ and 0.8 V, the current densities in H₂ and NH₃ remained at 0.16 and 0.06 A·cm^-2, respectively. The NH₃ conversion efficiency of PCMR reached 80% at 600 ℃, improving by 8% compared to bare catalyst material. Even at 350 ℃, an additional improvement of 0.3% can still be attained, and the NH₃ conversion efficiency of about 1% was demonstrated even at 300 ℃. This study provides a novel approach to low-temperature ammonia decomposition for hydrogen production.

Interface engineering is an effective strategy to develop fuel electrode materials with excellent catalytic activity of CO₂ for solid oxide electrolysis cell. In this study, La_0.3Sr_0.6Ti_1-xNi_xO_3-δ/Ce_0.9Gd_0.1O_2-δ (LSTN_x/GDC) composite fibers were directly prepared by electrospinning technology, by which novel fiber-based fuel electrodes were constructed with LSTN_x as electronic channel skeleton, GDC as embedded ion channel and in-situ Ni as exsolution nanoparticles. Effect of B-site Ni-doping on the morphology, structure and CO₂ catalytic activity of the fiber-based fuel electrode was studied. The results of SEM observation reveal that the LSTN_x/GDC composite fibers with uniform diameter (100-150 nm) and without obvious particle agglomeration or fracture gap are successfully prepared when the Ni-doping coefficient (x) is 0.15 or 0.20. More in-situ B-site nickel nanoparticles (sizes between 20 and 30 nm) could be exsolved from the prepared fuel electrode under reducing atmosphere. The relaxation time distribution analysis confirms that in-situ exsolution of B-site nickel metal nanoparticles can not only provide more active sites, but also form rich heterointerfaces with composite fiber, accelerating the interfacial charge transfer, significantly increasing the adsorption and enhancing the catalytic ability of CO₂. Electrolytic current density of the single cell (with the doping coefficient of 0.20 at 850 ℃, CO₂ : H₂ at 5 : 5 (in volume) under 1.5 V) increases to 0.799 A·cm^-2 while polarization impedance decreases to 0.171 Ω·cm², presenting excellent stability without significant current fluctuation up to 70 h.

Carbon support is an important component of Pt/C catalyst commonly used in the membrane electrodes of proton exchange membrane fuel cells, and ionomer is one of the key components that make up the catalytic layer. However, the influence of support characteristics on coverage of ionomer and oxygen reduction performance for Pt/C catalysts is still unknown. Here, six different types of representative commercial carbon supports (VC, KB1, KB2, BP, SJR, and AB) were focused. The microstructure and surface chemical properties of the carbon supports and the Pt/C catalysts prepared with and without addition of ionomer were investigated using various characterization methods. The oxygen reduction reaction (ORR) performance of various Pt/C catalysts was tested to explore the electrocatalytic structure-activity relationship of representative carbon supports for Pt catalysts. As revealed, carbon supports with large specific surface areas and rich pore structures, such as KB1, KB2 and BP, contribute to more uniform distribution of Pt particles. Presence of oxygen-containing functional groups on solid carbon supports with strong hydrophilicity, such as VC and SJR, contributes to dispersion of Pt particles. Meanwhile, carbon supports with abundant mesopores in the range of 2-8 nm (KB1 and KB2) are beneficial for improving location of Pt within pores of carbon particles, while those with high specific surface area and full of micropores (BP) and those with medium or low specific surface area (VC, SJR, and AB) have the most Pt nano-particles distributed on the outer surface of the carbon particles. By combining changes in specific surface area and pore structure of various Pt/C samples before and after addition of ionomer, the coverage of ionomer was calculated, and a distribution model of ionomer on different catalyst particles was proposed. On the solid carbon supported catalysts, a certain amount of ionomer basically covers entire outer surface of carbon particles. For the BP supported catalyst which is dominated by micropores, ionomer can block the micropores, resulting in a significant decrease in specific surface area and pore volume. For the mesoporous carbon supported catalysts, the same amount of ionomer is hard to block all micropores and mesopores, leading to lower coverage. Furthermore, ORR activity of Pt/C catalyst mainly depends on the Pt nano-particle size, and the Pt nano-particles located in the pores inside of the carbon particles can be protected from the poisoning of ionomer. Therefore, Pt catalysts supported on the carbon supports of KB series exhibit excellent performance for the ORR kinetics occurring in liquid-phase.

Proton-conducting solid oxide fuel cells (H⁺-SOFC) have gained great attention due to weak temperature dependence and high energy conversion efficiency. However, how to improve their proton conductivity still remains an open problem. In this work, a fluorination strategy based on the BaZr_0.1Ce_0.7Y_0.1Yb_0.1O₃ (BZCYYb) electrolyte was proposed to improve the proton conductivity. It is found that the conductivity (σ) of the fluorinated BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_2.9F_0.1 (BZCYYbF) is 4.59×10^-3-2.14×10^-2 S/cm at 450-800 ℃ in dry H₂, higher than that of the primitive BZCYYb electrolyte (σ=3.99×10^-3-1.86×10^-2 S/cm). The electrolyte fluorination significantly reduces anode polarization resistance for hydrogen oxidation reaction from 2.50 Ω·cm² to 1.94 Ω·cm², and total resistance of the single cell with 300-μm-thick electrolyte supporting from 1.54 Ω·cm² to 1.47 Ω·cm². Therefore, the BZCYYbF single cell shows much higher maximum power density (172 mW·cm^-2) than the BZCYYb single cell (144 mW·cm^-2) at 700 ℃. This result is attributed to the fact that the electrolyte fluorination not only improves the proton conduction capacity but also enhances the rates of H₂ diffusion and adsorption/dissociation on the anode sides. In conclusion, the fluorination of BZCYYb electrolyte can significantly improve its proton conductivity and thereby contribute to superior electrochemical performance of H⁺-SOFC.

Solid oxide fuel cells (SOFCs) are a kind of highly efficient and clean power generation devices whose cathode performance is critically important for the commercial application of the entire cell. Cation segregation on the surface of cathodes significantly affects the performance and operational stability. The double perovskite oxide PrBa_0.8Ca_0.2Co₂O_5+δ (PBCC), a highly active cathode, still suffers from serious surface segregation and insufficient Cr-tolerance ability. In order to improve the stability of cathode, an A-site medium-entropy double perovskite oxide Pr_0.6La_0.1Nd_0.1Sm_0.1Gd_0.1Ba_0.8Ca_0.2Co₂O_5+δ (ME-PBCC) derived from PBCC was prepared, and its segregation behavior in Cr-containing atmosphere was systematically investigated. Compared with traditional PBCC cathode, segregation of BaCrO₄ and Co₃O₄ on the surface of ME-PBCC is significantly suppressed, which is attributed to its higher configurational entropy. Electrical conductivity relaxation (ECR) and electrochemical impedance spectroscopy (EIS) results indicate that electrochemical stability of the ME-PBCC cathode has been significantly improved. Among the improvements, after Cr deposition for 48 h, the oxygen surface exchange coefficient k_chem of the medium-entropy cathode decreases from 4.4×10^-4 cm·s^-1 to 1.8×10^-4 cm·s^-1, with the reduction of k_chem significantly lower than that of PBCC (which decreases from 7.3×10^-4 cm·s^-1 to 1.2×10^-4 cm·s^-1). Furthermore, the EIS results after treatment in Cr-containing air at 700 ℃ for 48 h show that the polarization resistance (R_p) of ME-PBCC is only 0.07 Ω·cm², which is lower than 0.11 Ω·cm² of PBCC, confirming that the medium-entropy cathode has significantly improved operational stability and Cr resistance. This study demonstrates that ME-PBCC is a promising cathode material for SOFCs.

Traditional metal-supported solid oxide fuel cells (MS-SOFCs) typically utilize yttria stabilized zirconia (YSZ) as the electrolyte with operating temperature of about 800 ℃. In order to enable MS-SOFC to serve at low temperature, this study used gadolinium doped ceria (GDC), which exhibits higher conductivity at lower temperature, as the electrolyte to facilitate the practical application of MS-SOFC. Tape casting was employed to fabricate thin-film anodes (NiO-GDC) and electrolytes (GDC), while ultrasonic spraying was used to prepare the cathode material La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ(LSCF)-GDC. The resulting components were assembled onto a metal support to construct an MS-SOFC with a thin-film GDC electrolyte, and its electrochemical performance was evaluated. At 650 ℃, the total impedance of the cell was 0.50 Ω·cm², with Ohmic impedance of 0.23 Ω·cm² and polarization impedance of 0.27 Ω·cm², and the maximum power density was 336 mW/cm². The cell was operated at 550 ℃ under a constant voltage of 0.5 V for 100 h without significant degradation. Its electrolyte and anode, which were prepared by warm isostatic pressing and co-sintering, were tightly bonded. After long-term operation, no delamination between layers of the cell was observed, indicating that structural stability ensured the long-term stability of the MS-SOFC. MS-SOFCs in this study prepared via a process route combining tape casting, warm isostatic pressing, and direct assembly, displayed excellent electrochemical performance and long-term stability, providing a new approach for industrial production of low-temperature SOFCs.

The performance of solid oxide fuel cell (SOFC) is mainly constrained by the cathode's oxygen reduction reaction (ORR), which is crucial for overall cell efficiency. In this study, La_0.25M_0.75FeO_3-δ (M=Ca, Sr, Ba, abbreviated as LCF, LSF, LBF) perovskite cathodes were synthesized based on tolerance factors and structural design, and effects of Ba, Sr, and Ca doping on electrochemical performance was examined. Different alkaline earth elements have a significant effect on the crystal structure. LBF is Pm-3m cubic phase, LSF is R-3c rhombohedral phase, and LCF is a composite phase of P21ma orthogonal and Pcmn rhombohedral. Difference of crystal structure also leads to various thermal expansion coefficient (TEC) and electrical conductivity. LCF possesses the smallest TEC (1.38×10^-5 K^-1), while LSF possesses the highest conductivity, which reaches 404.4 S·cm^-1 at 550 ℃. All three Fe-based cathodes exhibit excellent stability in air and CO₂ atmospheres, as well as chemical compatibility with electrolytes. In addition, different alkaline earth elements also affect catalytic activity of the material. LSF and LBF have low area specific resistance (ASR). At 800 ℃, their ASR are only 0.022 and 0.027 Ω·cm², which are better than the 0.351 Ω·cm² of LCF. The higher oxygen reduction activity is attributed to its crystal structure, oxygen adsorption and dissociation ability. In view of the advantages and disadvantages of Ba²⁺, Sr²⁺ and Ca²⁺ in cathode performance, medium/high-entropy design can be effectively introduced in A-site in the future to give full play to their respective advantages to obtain SOFC cathode with excellent comprehensive performance.

Solid oxide fuel cells (SOFCs) are highly efficient energy conversion devices. However, the sulfur poison, which deteriorates traditional Ni-based anodes, restricts commercialization of the technology. Here, layered perovskite oxide NaYTiO₄ was prepared using solid-state method and modified by partial substitution with different valence ions. Properties of NaYTiO₄ before and after doping were systematically studied. Ni was doped into the perovskite layer and contributed to forming NaYTi_0.95Ni_0.05O₄, which regulated growth characteristics of the crystal and in-situ exsoluted in reduction conditions. Two-dimensional distribution of alkali metals and polar structures in the material provides advantages, including excellent chemical water absorption capacity and good sulfur-resistance. With an increased chemisorbed oxygen species of 64.5%, Ni-doped material becomes more outstanding. SOFC with NaYTi_0.95Ni_0.05O₄ as composite anode showed superior electrocatalytic activity. The peak power density reached 183.8 mW·cm^-2 at 800 ℃ with H₂ as fuel. Furthermore, the power density increased by 25.2% with an addition of 0.1% H₂S in H₂. The modified cell could work stably even at 700 ℃, a more toxic condition, for 40 h without significant poisoning effect. These results indicate that the modified layered perovskite oxides are excellent sulfur-resistance anodes.

As classical cathode materials of solid oxide fuel cell (SOFC), Fe-based perovskite materials are favored for their affordable price, low thermal expansion coefficient and high stability. In this study, B-site high-entropy perovskite oxide La_0.7Sr_0.3(FeNiCo)_0.8Mo_0.1Ti_0.1O_3-δ (LSFNCMT) was prepared by the citric acid-nitrate combustion method. Due to the faster oxygen surface exchange rate of the high-entropy material, the LSFNCMT cathode shows excellent oxygen reduction reaction (ORR) activity with a polarization impedance (R_p) of 0.11 Ω·cm² at 800 ℃, which is much lower than that of the La_0.7Sr_0.3FeO_3-δ (LSF) cathode (0.31 Ω·cm²). Furthermore, the high-entropy material exhibits superior stability due to incorporation of highly acidic Ni, Co, and Mo cations as well as Ti cation with more negative average bonding energy (ABE) of metal-oxygen. In the 22 h-stability test of the symmetric cell with LSFNCMT cathode in the Cr-containing atmosphere, R_p only increases from 1.07 Ω·cm² to 2.98 Ω·cm², while R_p of the LSF cathode increases from 2.62 Ω·cm² to 7.90 Ω·cm² under the same conditions, indicating better Cr-resistance of LSFNCMT due to the high-entropy strategy. The fact that the maximum power density (MPD) of the single cell with LSFNCMT cathode at 800 ℃ is 1105.26 mW·cm^-2, significantly higher than that of LSF cathode (830.74 mW·cm^-2), and R_p at 800 ℃ is 0.24 Ω·cm², lower than that of LSF cathode (0.36 Ω·cm²), confirming excellent toxicity resistance of the high-entropy cathode. This study shows that B-position high entropy is an effective way to improve the catalytic activity and chromium resistance of cathode materials.

Direct ethanol fuel cells (DEFC) have garnered significant attention due to their high energy conversion efficiency, low noise levels, and environmental friendliness. However, these fuel cells still face challenges such as high catalyst costs, poor stability, and low catalytic activity. In this study, graphene oxide (GO) was utilized as support, glycol as reducing agent, and hexahydrate chloroplatinic acid as precursor to introduce non-noble metal iron (Fe). By adjusting the molar ratio of Pt to Fe, a series of PtFeₓ/GO (x=1/6, 1/5, 1/4, 1/3, 1/2, 1) binary alloy catalysts were synthesized using microwave-assisted heating, and nanocrystals were in situ loaded on GO support. Fe with small atomic radii was incorporated into the lattice of Pt, resulting in reduction in spacing between adjacent atoms and lattice contraction, forming Pt-Fe alloy. Electrochemical performance tests demonstrated that the catalyst specifically at x=1/3 exhibited optimal catalytic activity with an electrocatalytic active area of 69.84 m²/g, an oxidation peak current density of 858.42 A/g, and a smaller Tafel slope. Its 1100 s steady stable current was 194.80 A/g, with CO oxidation peak potential of 0.554 V, activation energy of 18.37 kJ/mol, and current density retention rate of 80.48% after 800 cycles, all surpassing the performance of commercial Pt/C(JM). This study shows that incorporating the less expensive Fe can significantly enhance the catalytic activity and stability of Pt-based catalysts, providing important theoretical foundations for the design and potential applications of Pt-based catalyst materials.

PrBaFe₂O_5+δ (PBF) is one of the most promising cathode materials for intermediate-temperature solid oxide fuel cell (IT-SOFC). Although PBF possesses similar area specific resistance (ASR) to that of Co-based cathode materials, electronic conductivity of PBF is an order of magnitude lower. Up to now, various doping strategies have been reported to enhance the electrochemical performance of this material, but still leaving it an open issue. In this study, PBF and Pr_1+xBa_1−xFe₂O_5+δ (PBF_x, x=0.01, 0.02, and 0.04) materials were synthesized by replacing Ba in PBF with excessive Pr using a Sol-Gel method, and their electrochemical performances as IT-SOFC cathodes were evaluated. For x=0.01, excessive Pr enters the lattice interstitials of PBF. For x≥0.02, 0.01 (in molar) excessive Pr occupies interstitial sites, while the rest replaces Ba in PBF. Over the temperature range of 650-800 ℃, excessive Pr promotes the conductivity of PBF, and PBF_0.01 exhibits the highest conductivity of 109.21 S•cm^-1, improving by 76%, which is attributed to the reduction in electronic transport path length. Furthermore, the excessive Pr contributes to lattice stress and dislocation density, reducing oxygen reduction reaction (ORR) activity and slightly increasing ASR of the cathode. Compared to PBF device, the peak power density of the Ni-SDC|SDC|PBF_0.01 (SDC: Sm_0.2Ce_0.8O_2-δ) single cell increased by approximately 49%, indicating that excessive Pr can significantly improve the electrochemical performance of cathode materials.

Nowadays, we are facing increasingly serious energy and environmental problems, which urgently need more efficient chemical industry technologies to meet the requirements of low cost, high yield and sustainability. Developing efficient catalysts is of great significance for improving production efficiency, expanding economic benefits, optimizing energy structure, and ameliorating industrial structure. Single-atom catalysts (SACs), featuring unique properties arising from their single-atom dispersion on support surface, have demonstrated exceptional activity, selectivity and stability in energy catalysis, environmental catalysis and organic catalysis. Therefore, preparation methods and catalytic mechanisms of SACs have become a hot research topic on the international catalytic community. This review describes three strategies for preparing SACs: bottom-up synthesis, top-down synthesis and quantum dots cross-linking/self-assembly. Specifically, methods such as co-precipitation, immersion, atomic layer deposition, high-temperature atom thermal transfer, and high-temperature pyrolysis are presented in detail. These approaches precisely control the location and distribution of metal atoms, maximizing their utilization and catalytic efficiency. In addition, the challenges and development prospects faced by SACs related to stability, integrated control and industrial scalability are also summarized.

As one of the typical electrolyte materials for proton conducting solid oxide fuel cells, BaZr_0.1Ce_0.7Y_0.2O_3-δ (BZCY) possesses advantages such as high proton conductivity and stability. However, sintering activity of BZCY electrolyte is poor, usually requiring high sintering temperature for densification, which is inconducive to the preparation and application in cells. This study aimed to reduce the sintering temperature of BZCY electrolyte and explore the influence of sintering additives such as NiO, Fe₂O₃, ZnO, and CuO on the sintering characteristics of BZCY in detail. The results indicate that the oxides except Fe₂O₃ can effectively promote the grain growth of BZCY sintered body. Among them, the addition of CuO has the most significant promoting effect on the sintering process of BZCY. After adding 2% (in mass) CuO into BZCY (BZCY-2%CuO), even if the sintering temperature was reduced to 1250 ℃, the relative density of the sintered body still maintained higher than 98%. Additionally, the conductivity of BZCY-2%CuO was up to 2.7×10^-2 S·cm^-1 at 600 ℃ in wet H₂ atmosphere, which was nearly 5 times higher than that in wet air. More importantly, BZCY-2%CuO electrolyte exhibits negligible electronic conductivity under cell operating conditions while maintaining excellent stability.

Pt₃Co catalyst is the most active catalyst for oxygen reduction reaction (ORR) in Pt based alloys, in which synthesis of Pt₃Co high-index facets (HIFs) is an effective strategy to improve its catalytic performance. However, HIFs possessing the highest ORR activity have not yet been clarified, and at present, there is a lack of a systematic study on the ORR of Pt₃Co HIFs. In this study, six different Pt₃Co HIFs were constructed, and their stability was proved through ab initio molecular dynamics (AIMD) calculations. Binding energies (BE) of *O, *OH and *OOH intermediates for the six Pt₃Co HIFs during ORR process were calculated by density functional theory (DFT), and d-band center (ε_d), Bader charge and coordination number (CN) were used to explain the different binding energies at terrace and edge sites. Relationship between CN of adsorbed atoms and ε_d was also analyzed. Overpotential (η) during ORR was analyzed through ORR free energy step diagram, and it revealed that the magnitude of η was mainly related to *OH binding energy (BE-*OH). The Pt₃Co(211) facet has the smallest η, which at the Pt₃Co(211) terrace site reaches 0.294 eV. Therefore, this work provides a sound theoretical basis for the development of high ORR activity HIFs catalysts.

Material property differences among components of solid oxide fuel cell (SOFC) lead to excessive stresses during cell fabrication and operation, among which functional gradient material electrodes have attracted attention for their ability to reduce residual and thermal stresses in SOFC. But so far, there is rare study on SOFC with functional gradient anode using numerical simulation of thermal stress. In this study, a multi-physics field coupling model of SOFC with complete structure was established by COMSOL Multiphysics 6.0. Based on multi-physics field coupling model and numerical simulation of the residual stresses and thermal stresses in SOFC, four different distribution curves were employed to characterize the component distribution of anode materials. The results show that the tensile stress of anode can be significantly reduced by using functional gradient material during fabrication at different temperatures, especially at room temperature. Compared with non-gradient distribution, the maximum tensile stress of the anode is reduced by 47.69% before reduction and 35.74% after reduction by using quadratic curve distribution. During the operation process, the heat generated by the electrochemical reaction and the convective heat transfer of gas leads to the temperature difference between inlet and outlet, resulting in significant stress concentration at inlet and outlet of the metal frame as well as at contact surface between rib and electrode. Functional gradient materials can significantly reduce the maximum stress on the anode, metal frame and electrolyte, which is particularly obvious when using quadratic curve distribution. Therefore, this research has potential theoretical significance and engineering value for designing and fabricating SOFCs.

Taking inspiration from the in-situ reduction technique employed for exsolved nano-metal as anodes in solid oxide fuel cells (SOFCs), this study utilized Sr₂V_0.1Co_0.9MoO₆, which was synthesized in an ambient air environment, with perovskites of other phases to co-fire with the electrolyte under atmospheric conditions for direct fabrication of a single cell. By this way, the procedure of subjecting the cell to harsh preparative conditions in a reducing/inert atmosphere to prevent its anodic oxidation can be circumvented. After preparation of the anode precursor on the electrolyte sheet, we adopted a simple process of in-situ reduction at 750 ℃ for 4 h on the fuel side to achieve formation of a pure phase Sr₂V_0.1Co_0.9MoO₆ (R-SVCMO) as anode. The results demonstrate a significant reduction in the activation energy of R-SVCMO, accompanied by an increase in conductivity from 2.7 to 21.6 S•cm^-1. Moreover, when employing R-SVCMO as anode in a single cell with H₂ and wet CH₄ as fuel gases, the maximum power density (P_max) at 850 ℃ can reach up to 862 and 514 mW·cm^-2, respectively, showcasing exceptional catalytic performance. The anodes before and after reduction exhibit average thermal expansion coefficient (TEC) of 1.15×10^-5 and 1.23×10^-5 K^-1, respectively, within the temperature range of 100-850 ℃, comparable to those observed in conventional SOFC electrolytes. Therefore, the reduction process does not induce any volumetric changes in the anode layer, significantly enhancing its structural stability. Meanwhile, degradation rate of only 0.13% is occurred. It is worth noting that this R-SVCMO synthesis method can result in remarkable long-term stability and high catalytic activity as an anode material. The obtained R-SVCMO can achieve a 60% catalytic efficiency for wet CH₄ and last for 1450 h. Based on this R-SVCMO, the single cell can maintain stability for 450 h at 0.7 V. In conclusion, this study demonstrates an effective way of employing an in-situ fuel reduction method to prepare a single cell with exceptional electrochemical performance and structural stability.

To solve the problem of large concentration polarization impedance of anode-supported direct carbon solid oxide fuel cell (DC-SOFC), tubular cone-shaped anode-supported segmented-in-series solid oxide fuel cell (SOFC) was prepared by an improved gel-casting method. By appropriately increasing content of the solvent, fluidity of the slurry and quality of the obtained product were improved. By increasing content of the pore-forming agent, the porosity of the anode was increased, reducing the diffusion resistance of gas. As-improved SOFC was fueled by hydrogen and operated at 800 ℃ with an open-circuit voltage of 1.05 V. The polarization impedance of the electrochemical impedance spectrum decreased while the maximum power density was 0.67 W•cm^-2 and the active area of the cathode was 2.2 cm². These SOFC electrochemical performances were significantly higher than that before improvement. Activated carbon loaded on the anode with 5% (in mass) K as catalyst was directedly used as the fuel of SOFCs. Using this anode-supported direct carbon, the DC-SOFC was prepared, showing an open circuit voltage of 1.030 V and a peak power density of 0.74 W•cm^-2 at 800 ℃. This DC-SOFC was discharged at a constant current of 400 mA, and its effective utilization rate of carbon fuel was 31% which was higher than that before improvement (17%). Four improved tubular cone-shaped single cells were connected in series to form a four-cell stack, showing a peak power of 8.0 W and a corresponding power density of 0.91 W•cm^-2 at 800 ℃, which was higher than that before improvement (4.1 W), exceeding the maximum of previous reported DC-SOFC, and displayed an effective utilization rate of 15% for carbon fuel.

Intermediate-temperature solid oxide fuel cells (IT-SOFCs), as the operating temperature decreases, require cathode materials with high catalytic activity. In this study, double perovskite Sr₂CoFeO_5+δ (SCF) was synthesized by Sol-Gel method, and effect of SCF cathode compounded with 20% (molar fraction) Sm₂O₃ doped CeO₂ (SDC) at different ratios on the electrode performance was elucidated. The SOFC single-cell performance was improved by optimized chemical expansion and area-specific resistance (ASR) from composite electrodes. Results show that, SCF cathode after annealing at 950 ℃ for 10 h exhibits good chemical compatibility with common electrolytes. For the composite of SCF and SDC at a mass ratio of 1 : 1, the average thermal expansion coefficient (TEC) can be significantly reduced from 2.44×10⁻⁵ K^-1 of pure SCF to 1.54×10⁻⁵ K^-1. ASR of SCF−xSDC (x=20, 30, 40, 50, x: mass percentage) composite cathodes are as low as 0.036, 0.034, 0.028 and 0.092 Ω·cm² at 800 ℃, respectively. The SCF−40SDC composite cathode displays the lowest ASR value among SCF−xSDC in the whole temperature range. Based on the 0.3 mm-thick La_0.9Sr_0.1Ga_0.8Mg_0.2O_3-δ (LSGM) electrolyte, the maximum power density of SOFC using SCF−40SDC (757 mW·cm⁻²) as a cathode is higher than that of pure SCF (684 mW·cm⁻²). These results demonstrate that the SCF−40SDC composite cathode is a promising candidate for application in IT-SOFCs.

In order to fulfil the requirement of low area specific resistance and highly stable cathode contact material in planar type solid oxide fuel cell (SOFC) stack assembling, this work investigated the electrical property evolution of LaNi_0.6Fe_0.4O₃ (LNF) with manipulated particle size and its effect on SOFC electrochemical performance. The optimized pre-treatment strategies of LNF were obtained with decreasing ASR, improving SOFC single cell performance and thermal cycling stability. Results show that, the dry-pressed LNF-2 and the high-temperature sintering-pre-treated LNF-3 possess smaller area specific resistances of 0.074 and 0.076 Ω·cm², respectively, more stable particle sizes with shorter conditioning state and faster transfer into steady state after applying 1 A/cm² current load at 750 ℃. Specifically, the single cell with LNF-2 shows improved peak power density of 0.94 W/cm² compared to 0.66 W/cm² of LNF without treatment at 750 ℃. However, it exhibits significant performance degradation during thermal cycling, decreasing by 20%. In contrast, the peak power density of LNF-3 single cell decreases by only 4% after 20 thermal cycles. This work is expected to provide guideline and valued reference for reliable SOFC stack assembling and stable operation.