Solid Oxide Research Articles

Role of charge-compensation process on the structural, microstructure and electrical properties of pure and Nb-doped Sr2SnO4

This article explores the charge compensation method by synthesising Sr2SnO4, Sr2Sn0.99Nb0.01O4, and Sr1.995Sn0.99Nb0.01O4. The synthesis of a monophasic, tetragonal sample was achieved using a typical ceramic approach and high-temperature heat treatment. The XRD followed by Rietveld refinement, confirmed the crystallization of material under the space group I4/mmm. The crystallite sizes for all samples determined to be less than 50 nm, while the micro-strain falls within the range of (1.78–2.93) × 10–3. The microstructure exhibits a cuboidal shape for all samples, and the grain size is observed to decrease with the addition of Nb. The dielectric characteristics of the samples indicate the existence of Maxwell-Wagner and Orientational polarization in the sample. The sample Sr2Sn0.99Nb0.01O4 demonstrates a greater conductivity value compared to Sr1.995Sn0.99Nb0.01O4. This is attributed to the presence of excess electrons that compensate for the overall charge, as opposed to Sr1.995Sn0.99Nb0.01O4 where the extra charge is compensated by a cationic vacancy VSr″. The time-temperature-superposition principle (TTSP) is applicable to all compositions and indicates that similar sources are responsible for both conduction and relaxation processes. The dielectric permittivity and dissipation factor are found to be in the range of 150 to 175 and 0.2 to 0.5, respectively. This suggests that they have potential for future use in millimeter-wave communication with dielectric resonator antennas (DRAs). Due to the presence of oxygen ions and the ability to conduct both ions and electrons, at temperatures above 400 °C, it is a suitable choice for electrode materials in the application of intermediate temperature solid oxide fuel cell (IT-SOFCs). Exploring the manipulation of defects using electrical and ionic charge compensation methods shows potential for enhancing materials in semiconductor technology.

Effect of Sintering Temperature on the Residual Stress of SrO-MgO-SiO2 Glass-Ceramic Sealant for Solid Oxide Fuel Cells

Effect of Sintering Temperature on the Residual Stress of SrO-MgO-SiO2 Glass-Ceramic Sealant for Solid Oxide Fuel Cells

3D printing of reversible solid oxide cell stacks for efficient hydrogen production and power generation

Renewable hydrogen offers a promising pathway to address the challenge of large-scale chemical energy storage in the transition to a decarbonized future. The most efficient devices to convert renewable electricity into hydrogen, and vice versa, are reversible solid oxide cells (SOC-s). Despite recent advances in materials performance and durability, conventional ceramic manufacturing technologies strongly limit the huge potential of SOC-s, imposing severe geometrical restrictions that penalize the overall system efficiency. Here we capture the benefits of using previously unexplored complex-shapes by scaling 3D-printed reversible solid oxide cells with improved mechanical properties, higher performance, and embedded functionality. Stacks made of 45 cm2-3D-printed electrolyte-supported solid oxide cells combined with ultrathin flat metallic interconnects were successfully fabricated and operated in fuel cell (SOFC) and electrolysis (SOEC) modes delivering up to 85 L/h of hydrogen production while presenting less than 5 % degradation after more than 500 h of operation. The advances presented here demonstrate the viability of upscaling the process of solid-oxide-cell 3D printing and brings advantageous stack designs aimed for a cost-competitive and customizable hydrogen technologies deployment. In particular, the enhancement by design achieved here provides innovative SOC stacks with volumetric and gravimetric power densities that are three and four times higher, respectively, than their planar counterparts using the same set of materials.

A Review on Solid Oxide Fuel Cell Technology: An Efficient Energy Conversion System

The increasing global dependence on fossil fuels for energy has prompted researchers to explore alternative power generation sources that offer higher efficiency, cost-effectiveness, and low environmental impact. Developed countries have been making continuous efforts to reduce their reliance on depleting fossil fuel sources to curb carbon emissions. As a result, hydrogen has gained significant attention among researchers as a potential future fuel that meets all the necessary criteria. Many countries aiming for a hydrogen economy have invested in research on fuel cells. Among various fuel cells, the solid oxide fuel cell (SOFC) has emerged as a commercially viable power source at a small scale. This paper provides an extensive review of the components, materials, design, operation, and integration strategies of SOFCs with existing thermal-based power plants. The performance and prospects of various SOFCs in standalone and hybrid modes are summarized, along with the limitations. Additionally, the research and commercialization efforts that can enhance the potential applications of SOFCs as a sustainable and reliable system in the long term are outlined.

Ni migration on porous yttria-stabilized zirconia and yttria-micropatterned fuel electrodes in solid oxide fuel cells

This study investigates the mechanism of Ni migration and methods for preventing Ni migration by utilizing ceramic obstacles that can block or slow Ni movement during solid oxide fuel cell (SOFC) operation. A patterned thin-Ni model anode on mirror-polished yttria-stabilized zirconia (YSZ) substrate exhibited dynamic movement during operation, as reported previously. In this study, we attempt to elucidate the mechanism of Ni migration that occurs only on the surface of solid-state Ni by blocking or slowing this movement using porous patterns of different materials. Porous micropatterns of 100 % YSZ and 80 wt% yttria (Y2O3) + YSZ composites were fabricated on a YSZ electrolyte, and velocity changes and blocking of Ni were observed. The porous YSZ structure changed the velocity of the Ni. In contrast, no Ni migration occurred in the Y2O3/YSZ composite porous structure, despite migration occurring in the neighboring smooth YSZ area in the same cell. The Ni-migrated areas were separated by the Y2O3/YSZ porous area, indicating that Ni migration was not caused by microscale differences in temperature or supplied gas diffusion, and Ni moved only on the cell surface, not via Ni-containing gases because temperatures and gases cannot form micropatterns.

Study of high temperature mechanical properties and damage behavior of Ni-YSZ anode/SrO–MgO–SiO2 glass-ceramic sealant/430 s.s. interconnect system in solid oxide fuel cells (SOFC)

In the sealing system of Ni-YSZ anode/SrO–MgO–SiO2 glass-ceramic sealant/430 s s. interconnect, the phase transformation and mechanical properties of interfaces are studied after operating 0 h, 100 h, and 1800 h at 750 °C. The results show that the interface fracture appears in the glass/anode and glass/interconnect interfaces after operating at 1800 h. The interface mechanical parameters within different operation times are collected to investigate the effects of crystallization, penetration, and high temperature mechanical properties on the interlayer stress and structure damage. The Sr2MgSi2O7 crystal phase increases the glass modulus from 104.5 GPa to 129.8 GPa with a runtime from 0 h to 1800 h. The modulus of the Ni-YSZ interface also increases from 82.4 GPa to 128.3 GPa with the glass penetration process. The 430 s s. modulus is reduced by 13 % at 750 °C after 1800 h to reach 191.1 GPa. The established anode/glass/interconnect interlayer stress model accurately calculates the compressive stress at the glass/anode side interface and glass/interconnect side interface, with values reaching −755.2 MPa and −587.1 MPa, respectively. The crystallization zone of the SrO–MgO–SiO2 glass-side interface near Ni-YSZ and 430 s s. become the stress damage sensitive zones and break under interlayer stress.

In Situ Self‐Assembled Active and Stable Ir@MnOx/La0.7Sr0.3Cr0.9Ir0.1O3‐δ Interfaces for CO2 Electrolysis

Solid oxide electrolysis cells are prospective approaches for CO2 utilization but face significant challenges due to the sluggish reaction kinetics and poor stability of the fuel electrodes. Herein, we strategically addressed the long‐standing trade‐off phenomenon between enhanced exsolution and improved structural stability via topotactic ion exchange. The surface dynamic reconstruction of the MnOx/La0.7Sr0.3Cr0.9Ir0.1O3‐δ (LSCIr) catalyst was visualized at the atomic scale. Compared with the Ir@LSCIr interface, the in situ self‐assembled Ir@MnOx/LSCIr interface exhibited greater CO2 activation and easily removable carbonate intermediates, thus reached a 42% improvement in CO2 electrolysis performance at 1.6 V. Furthermore, an improved CO2 electrolysis stability was achieved due to the uniformly wrapped MnOx shell of the Ir@MnOx/LSCIr cathode. Our approach enables a detailed understanding of the dynamic microstructure evolution at active interfaces and provides a roadmap for the rational design and evaluation of efficient metal/oxide catalysts for CO2 electrolysis.

In Situ Self-Assembled Active and Stable Ir@MnOx/La0.7Sr0.3Cr0.9Ir0.1O3-δ Interfaces for CO2 Electrolysis.

Solid oxide electrolysis cells are prospective approaches for CO2 utilization but face significant challenges due to the sluggish reaction kinetics and poor stability of the fuel electrodes. Herein, we strategically addressed the long-standing trade-off phenomenon between enhanced exsolution and improved structural stability via topotactic ion exchange. The surface dynamic reconstruction of the MnOx/La0.7Sr0.3Cr0.9Ir0.1O3-δ (LSCIr) catalyst was visualized at the atomic scale. Compared with the Ir@LSCIr interface, the in situ self-assembled Ir@MnOx/LSCIr interface exhibited greater CO2 activation and easily removable carbonate intermediates, thus reached a 42% improvement in CO2 electrolysis performance at 1.6 V. Furthermore, an improved CO2 electrolysis stability was achieved due to the uniformly wrapped MnOx shell of the Ir@MnOx/LSCIr cathode. Our approach enables a detailed understanding of the dynamic microstructure evolution at active interfaces and provides a roadmap for the rational design and evaluation of efficient metal/oxide catalysts for CO2 electrolysis.

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

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

On the Possibility of Improving the Oxidation Resistance of High-Chromium Ferritic Stainless Steel Using Reactive Element Oxide Nanoparticles

AbstractHigh-chromium ferritic steels are current the only viable candidates for cheap interconnect materials for application in high-temperature solid oxide fuel and electrolyzer cells (HT-SOFCs/SOECs). The durability and operating characteristics of interconnects manufactured using these materials may be improved significantly by applying a protective-conducting MoCo2O4 coating and depositing an intermediate layer consisting of nanoparticles of Gd2O3—a reactive element oxide—on the surface of the steel substrate. The study demonstrated that the conditions of the thermal treatment of this layered system determine the efficacy of the applied modification with the reactive element. The persistence of this effect was tested over 7000 hours of quasi-isothermal oxidation in air at 800 °C.

Two-Step Conversion of Metal and Metal Oxide Precursor Films to 2D Transition Metal Dichalcogenides and Heterostructures.

The widely studied class of two-dimensional (2D) materialsknown as transition metal dichalcogenides (TMDs) are now well-poised to be employed in real-world applications ranging from electronic logic and memory devices to gas and biological sensors. Several scalable thin film synthesis techniques have demonstrated nanoscale control of TMD material thickness, morphology, structure, and chemistry and correlated these properties with high-performing, application-specific device metrics. In this review, the particularly versatile two-step conversion (2SC) method of TMD film synthesis is highlighted. The 2SC technique relies on deposition of a solid metal or metal oxide precursor material, followed by a reaction with a chalcogen vapor at an elevated temperature, converting the precursor film to a crystalline TMD. Herein, the variables at each step of the 2SC process including the impact of the precursor film material and deposition technique, the influence of gas composition and temperature during conversion, as well as other factors controlling high-quality 2D TMD synthesis are considered. The specific advantages of the 2SC approach including deposition on diverse substrates, low-temperature processing, orientation control, and heterostructure synthesis, among others, are featured. Finally, emergent opportunities that take advantage of the 2SC approach are discussed to include next-generation electronics, sensing, and optoelectronic devices, as well as catalysis for energy-related applications.

Optimization and comparative evaluation of novel marine engines integrated with fuel cells using sustainable fuel choices

Large ships are more utilized than ever before to facilitate transporting heavy goods and oils overseas. However, they rely on fossil fuels and cause severe environmental impacts. Utilizing alternative fuels and implementing new engine designs are considered promising methods to reduce greenhouse gas emissions and improve engine performance. This paper compares three developed, hybridized marine engines operated using five fuel blends of hydrogen, methanol, dimethyl ether, ethanol, and methane. In addition, the paper presents a multi-objective particle swarm optimization to increase the engine power and its exergetic efficiency and reduce the cost and environmental impact. A marine engine (SRC-GT-SOFC) containing a steam Rankine cycle, a gas turbine, and a solid oxide fuel cell is considered to weigh less and perform better. It is found that the optimized SRC-GT-SOFC engine power is increased by about 10 %, corresponding to 16269 kW with an increased exergetic efficiency of 70.6 %, respectively. Its specific fuel and product exergetic costs are found to be 12 $/GJ and 15.67 $/GJ, and its specific fuel and product environmental impacts are 7.4 Pt/GJ and 9.3 Pt/GJ, respectively. This results in a significant reduction in the relative cost difference and the relative environmental impact difference of the optimized SRC-GT-SOFC of 30 % and 25.4 %, respectively.

Direct oxidative coupling of methane into ethylene in a catalyst-enhanced planar solid oxide fuel cell stack reactor

This study presents an efficient method to convert methane into valuable olefins using a Solid Oxide Fuel Cell (SOFC) membrane reactor. Methane, abundant in natural and shale gas, serves as a sustainable feedstock due to its favorable carbon-hydrogen ratio. The SOFC membrane reactor eliminates costly air separation units and safety risks associated with explosive methane-oxygen mixtures. A planar SOFC stack achieves over 30 % methane conversion, 40 % ethylene selectivity, and power generation capabilities. Optimization with mixed-conducting ceramics enhances electrical performance without compromising catalytic activity. The stack's scalability is demonstrated, with the 5-cell configuration surpassing the 2-cell setup. This innovative approach offers a sustainable solution to methane waste, producing high-value chemicals while reducing environmental impact.

Zn promoted GaZrOx ternary solid solution oxide combined with SAPO-34 effectively converts CO2 to light olefins with low CO selectivity.

We proposed a new strategy for CO2 hydrogenation to prepare light olefins by introducing Zn into GaZrOx to construct ZnGaZrOx ternary oxides, which was combined with SAPO-34 to prepare a high-performance ZnGaZrOx/SAPO-34 tandem catalyst for CO2 hydrogenation to light olefins. By optimizing the Zn doping content, the ratio and mode of the two-phase composite, and the process conditions, the 3.5%ZnGaZrOx/SAPO-34 tandem catalyst showed excellent catalytic performance and good high-temperature inhibition of the reverse water-gas shift (RWGS) reaction. The catalyst achieved 26.6% CO2 conversion, 82.1% C2=-C4= selectivity and 11.8% light olefins yield. The ZnGaZrOx formed by introducing an appropriate amount of Zn into GaZrOx significantly enhanced the spillover H2 effect and also induced the generation of abundant oxygen vacancies to effectively promote the activation of CO2. Importantly, the RWGS reaction was also significantly suppressed at high temperatures, with the CO selectivity being only 46.1% at 390°C.

Unravelling the La dopant induced physicochemical changes and the electrical behaviour on BaFeO3 under oxidising and reducing atmospheres

Electroceramic oxides like La-doped BaFeO3 garner greater interest owing to their tunability of mixed ionic conduction. However, reports on the effect of La on the microstructural changes, the type of conduction mechanism under different atmospheres and the negative charge transfer influenced by the Fe-O hybridization in Ba1−xLaxFeO3−δ are hardly available. Doping La induces cation vacancies and Fe reduction, creating nanorod decorated surface after the high-temperature treatment. Conductivity studies expose the rate-limiting steps for hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) as the ohmic resistances and Ba segregation effects. Among the samples studied, Ba0.9La0.1FeO3−δ performs better at 800 °C with an activation energy of ∼0.35 eV under both oxidizing and reducing atmospheres. Surface analysis after EIS reveals Fe and O with different oxidation states that enhance the total conductivity. The amount of hydroxyl species retained (23.66% for Ba0.9La0.1FeO3−δ ) and the ratio of the adsorbed to the lattice oxygen (15.33% for Ba0.9La0.1FeO3−δ ) gives insight on HOR and ORR activities. Also, computational studies validated the negative charge transfer mechanism of the samples under thermally assisted oxidation. The results indicate Ba0.9La0.1FeO3−δ as a tuneable electrode for solid oxide cells.

Green ammonia production using current and emerging electrolysis technologies

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

A fully automated tool for constructing multiphysics model and performing simulations of kW-scale solid oxide cell stacks

Multiphysics simulations of solid oxide cell (SOC) require extensive experience and can be labor intensive. This paper reports the first successful implementation of automated multiphysics simulation process for industrial-scale planar SOC stacks. The automation is realized through Python based Ansys SpaceClaim scripting for building geometric model, Python based Ansys Workbench Meshing scripting for setting numerical grids, and Scheme based Ansys Fluent TUI commands for performing multiphysics simulations. The model building process allows for customized dimensions of all stack components and the corresponding edge grid counts. The automation of simulations streamlines all the computational steps in multiphysics modeling. The multiphysics model is shown to agree well with the experimental data. The automated tool is illustrated in a parametric analysis of SOC operations, illuminating the influences of size, shape and thermal boundary on the stack performance. The automation makes the simulations simple and efficient, invaluable for the SOC design and operation analysis.

Tuning the thermo-mechanical synergies effect of solid oxide fuel cells with negative thermal expansion NdMnO3 in La0.6Sr0.4Co0.2Fe0.8O3-δ-based symmetric electrode

Solid oxide fuel cells (SOFCs) are efficient and clean energy conversion devices, but one of the major challenges for their marketization is the instability of different component materials under high temperature operating conditions. The existence of a certain internal stress gradient between materials with different thermal expansion characteristics in the process of SOFCs from low temperature assembly to high temperature use is the main reason of this instability, leading to the inability of SOFCs to repeat start-stop and the rapid decay of long-term stability performance. To improve these problems, a creative concept of fuel cell interface overall regulation is proposed, simplifying the complex interface between different components of SOFCs into a unified and adjustable quasi-zero difference thermal expansion interface. The composite of high catalytic activity electrode material and high stability negative thermal expansion material is used for electrolyte support structure symmetrical cell, which makes the whole cell “sandwich” structure thermally and mechanically compatible. As a concept verification, the classic high catalytic performance electrode material La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF), Gd0.2Ce0.8O2-δ (GDC) and NdMnO3 (NM) negative thermal expansion material with high chemical stability and mechanical stability were composited in equal proportions to form LSCF@GDC&NM electrode as the symmetrical electrode. After equal proportion compositing, the thermal expansion curve of LSCF@GDC&NM material can highly coincide with the thermal expansion curve of GDC, making the single cell with LSCF@GDC&NM electrode can withstand 25 power thermal cycles without significant performance decay, achieving 442 mW cm−2 at 800 °C and maintaining stably for 140 h without any degradation. These results show that using negative thermal expansion material to regulate electrode strategy is expected to make a whole zero difference thermal fuel cell configuration.

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

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

Impregnated LSM-YSZ electrodes with RuO2/SDC nanocomposites for solid oxide cells

La0.8Sr0.2MnO3-δ-Y0.16Zr0.84O2-δ (LSM-YSZ) composites have been widely used as the oxygen electrodes in solid oxide cells (SOCs), however, their poor activities for oxygen reduction and evolution reactions result in relatively low cell performance. A common method to promote electrocatalytic activities of LSM-YSZ composites is to tailor the microstructure by impregnation. In this study, nanocomposite catalysts are developed by one-pot infiltration, where nano scale particles of RuO2 and Ce0.8Sm0.2O2-δ (SDC) are highly dispersed to achieve a uniform distribution with reduced particle sizes. Impedance measurements of symmetrical oxygen electrode cells reveal that modifying LSM-YSZ electrodes with SDC and RuO2/SDC can substantially promote their activities for oxygen reduction reactions (ORR). The measured polarization resistances at 750°C in air are 2.23, 0.24 and 0.14 Ω cm2 for the blank, SDC and RuO2/SDC modified LSM-YSZ electrodes, respectively. Compared to pure SDC, RuO2/SDC composites show higher ORR promotion, which can be correlated with their more surface oxygen vacancies. Solid oxide cells with thin YSZ electrolytes, RuO2/SDC impregnated LSM-YSZ oxygen electrode substrates and thin fuel electrodes of La0.3Sr1.55Fe1.5Ni0.1Mo0.4O6 achieve a peak power density of 0.7 W cm−2 at 750°C in the fuel cell mode and a steam electrolysis current density of 2.31 A cm−2 at 1.3 V and 800°C in the electrolysis mode.