Progress and prospects of reversible solid oxide fuel cell materials

Enhancing surface activity and durability in triple conducting electrode for protonic ceramic electrochemical cells

With the material system operating at lower temperatures, protonic ceramic electrochemical cells (PCECs) can offer high energy efficiency and reliable performance for both power generation and hydrogen production, making them a promising technology for reversible energy cycling. However, PCEC faces technical challenges, particularly regarding electrode activity and durability under high current density operations. To address these challenges, we introduce a nano-architecture oxygen electrode characterized by high porosity and triple conductivity, designed to enhance catalytic activity and interfacial stability through a self-assembly approach, while maintaining scalability. Electrochemical cells incorporating this advanced electrode demonstrate robust performance, achieving a peak power density of 1.50 W cm⁻2 at 600 °C in fuel cell mode and a current density of 5.04 A cm-2 at 1.60 V in electrolysis mode, with enhanced stability on transient operations and thermal cycles. The underlying mechanisms are closely related to the improved surface activity and mass transfer due to the dual features of the electrode structure. Additionally, the enhanced interfacial bonding between the oxygen electrode and electrolyte contributes to increased durability and thermomechanical integrity. This study underscores the critical importance of optimizing electrode microstructure to achieve a balance between surface activity and durability.

Life Cycle Economic and Environmental Assessment for Emerging Heavy-Duty Truck Powertrain Technologies in China: A Comparative Study of Battery Electric, Fuel Cell Electric, and Hydrogen Combustion Engine Trucks

Amid ambitious net-zero goals and growing demands for freight logistics, addressing the climate challenges posed by the heavy-duty truck (HDT) sector is an urgent and pivotal task. This study develops an integrated HDT model by incorporating vehicle dynamic simulation and life cycle analysis to quantify energy consumption, greenhouse gas (GHG) emissions, and total cost of ownership associated with three emerging powertrain technologies in various truck use scenarios in China, including battery electric, fuel cell electric, and hydrogen combustion engine trucks. The results reveal varying levels of economic suitability for these powertrain alternatives depending on required driving ranges and duty cycles: the battery electric for regional-haul applications, the hydrogen fuel cell for longer-haul and low-load driving conditions, and the hydrogen combustion engine to meet high power requirements. The GHG mitigation potential of these technologies, on the other hand, critically hinges on energy sources. All three powertrains could achieve over 55% GHG emission reductions if the power sector and hydrogen supply are substantially decarbonized by 2035. The analysis underscores the necessity for a broad policy approach on a life cycle basis to incorporate all powertrain technologies and all energy sources in a complementary manner for facilitating a low-carbon road freight future.

Closing the Loop: Solid Oxide Fuel and Electrolysis Cells Materials for a Net-Zero Economy

Solid oxide fuel cells (SOFCs) and solid oxide electrolyzer cells (SOECs) represent a promising clean energy solution. In the case of SOFCs, they offer efficiency and minimal to zero CO2 emissions when used to convert chemical energy into electricity. When SOFC systems are operated in regenerative mode for water electrolysis, the SOFCs become solid oxide electrolyzer cells (SOECs). The problem with these systems is the supply and availability of raw materials for SOFC and SOEC components. This raises significant economic challenges and has an impact on the price and scalability of these technologies. Recycling the materials that make up these systems can alleviate these economic challenges by reducing dependence on the supply of raw materials and reducing overall costs. From this point of view, this work is a perspective analysis and examines the current research on the recycling of SOFC and SOEC materials, highlighting the potential paths towards a circular economy. The existing literature on different approaches to recycling the key materials for components of SOFCs and SOECs is important. Mechanical separation techniques to isolate these components, along with potential strategies like chemical leaching or hydrometallurgical and material characterization, to ensure the quality of recycled materials for reuse in new SOFCs and SOECs are important as well. By evaluating the efficiency of various methods and the quality of recovered materials, this study aims to provide valuable insights for advancing sustainable and economically viable SOFC and SOEC technologies within a net-zero economic framework.

Performance Degradation of a Double-Perovskite PrBaCo2O5+δ Cathode Operating under a CO2/H2O-Containing Atmosphere

The electrochemical activity and stability of the PBCO electrode are investigated under the annealing processes in an atmosphere containing CO2/H2O for solid oxide fuel cells (SOFCs). The electrochemical impedance spectrum results unequivocally confirm the significant deterioration in PBCO cathode performance upon annealing under ambient air conditions, particularly when exposed to CO2/H2O atmospheres. Microstructure and surface chemical state analyses reveal the segregation of BaO on the PBCO surface, and the formation of insulating BaCO3 degraded the electrochemical performance. CO2 and H2O exhibit a significant induced effect on the segregation of Ba in PBCO to the surfaces, thereby causing a rapid decline in electrode performance. Additionally, the analysis of volume relaxation reveals that the presence of oxygen in the electrode environment can also influence the deposition process occurring on the surface of the electrode. However, this phenomenon is not observed in N2. This study emphasizes the impact of various gases present in the working atmosphere on surface-separated BaO, which consequently plays a pivotal role in the activity and long-term stability of PBCO electrodes.

Enhancing the Electrochemical Performance in Symmetrical Solid Oxide Cells through Nanoengineered Redox-Stable Electrodes with Exsolved Nanoparticles

Symmetrical solid oxide cells (SSOCs) have recently gained significant attention for their potential in energy conversion due to their simplified cell configuration, cost-effectiveness, and excellent reversibility. However, previous research efforts have mainly focused on improving the electrode performance of perovskite-type electrodes through different doping strategies, neglecting microstructural optimization. This work presents novel approaches for the nanostructural tailoring of (La0.8Sr0.2)0.95Fe1-xTixO3-δ (LSFTx, x = 0.2 and 0.4) electrodes using a single-step spray-pyrolysis deposition process. By incorporating these electrodes into a Ce0.9Gd0.1O1.95 (CGO) porous backbone or employing a nanocomposite architecture with nanoscale particle size, we achieved significant improvements in the polarization resistance (Rp) compared with traditional screen-printed electrodes. To further boost the fuel oxidation performance, a Ni-doping strategy, coupled with meticulous microstructural optimization, was implemented. The exsolution of Ni nanoparticles under reducing conditions resulted in remarkable Rp values as low as 0.34 and 0.11 Ω cm2 in air and wet H2 at 700 °C, respectively. Moreover, an electrolyte-supported cell with symmetrical electrodes demonstrated a stable maximum power density of 617 mW cm-2 at 800 °C. These findings highlight the importance of combining electrode composition optimization with advanced morphology control in the design of highly efficient and durable SSOCs.

Research Progress in Enzyme Biofuel Cells Modified Using Nanomaterials and Their Implementation as Self-Powered Sensors

Enzyme biofuel cells (EBFCs) can convert chemical or biochemical energy in fuel into electrical energy, and therefore have received widespread attention. EBFCs have advantages that traditional fuel cells cannot match, such as a wide range of fuel sources, environmental friendliness, and mild reaction conditions. At present, research on EBFCs mainly focuses on two aspects: one is the use of nanomaterials with excellent properties to construct high-performance EBFCs, and the other is self-powered sensors based on EBFCs. This article reviews the applied nanomaterials based on the working principle of EBFCs, analyzes the design ideas of self-powered sensors based on enzyme biofuel cells, and looks forward to their future research directions and application prospects. This article also points out the key properties of nanomaterials in EBFCs, such as electronic conductivity, biocompatibility, and catalytic activity. And the research on EBFCs is classified according to different research goals, such as improving battery efficiency, expanding the fuel range, and achieving self-powered sensors.

Sustainability and affordability of Chinese-funded renewable energy project in sub-Saharan Africa: a hybridized solid oxide fuel cell, temperature sensors, and lithium-based solar system approach

Renewable energy projects are at the crux of all Chinese-funded investment in sub-Saharan Africa, which accounts for some 56% of all Chinese-led investments globally. However, the prevailing problem is that about 568 million people were still without electricity access in 2019 across urban and rural areas in sub-Saharan Africa, which does not commensurate with the United Nations Sustainable Development Goal (SDG7) of ensuring affordable and clean energy for all. Previous studies have assessed and improved the efficiency of integrated power generation systems often combined on three levels, power plant, solar panel, and fuel cells, and integrated into national grids or off-grid systems for a sustainable supply of power. This study has included a lithium-ion storage system as a key component in a hybridized renewable energy generation system for the first time that has proven to be efficient and investment worthy. The study also examines the operational parameters of Chinese-funded power plant projects in sub-Saharan Africa and their effectiveness in achieving SDG-7. The novelty of this study is evident in the proposed integrated multi-level hybrid technology model of solid oxide fuel cells, temperature point sensors, and lithium batteries powered by a solar system and embedded in thermal power plants as an alternative electrical energy system for domestic and industrial use in sub-Saharan Africa. Performance analysis of the proposed power generation model indicates its complementary capacity of generating additional energy output with thermodynamics energy and exergy efficiencies of 88.2% and 67.0% respectively. The outcome of this study draws the attention of Chinese investors, governments in sub-Saharan African countries, and top industry players to the following: to consider refocusing their energy sector policy initiatives and strategies towards exploring the lithium resource base in Africa, optimizing energy generation cost, recouping optimal profit from their renewable energy technology investments, and making electricity supply clean, sustainable, and affordable for use in sub-Saharan Africa.

Effect of Infiltration Ce0.8Sm0.2O1.9 Against Double Perovskite Performance LaBa0.5Sr0.5Co2O5+δ as IT-SOFC Cathode

Modifying the sample surface by infiltration technique using Ce0.8Sm0.2O1.9 (SDC) electrolyte has been done to increase the catalytic activity of the LaBa0.5Sr0.5Co2O5+δ (LBSC) cathode. The cathode powder structure was evaluated using X-ray diffraction (XRD) at room temperature, and the LBSC cathode microstructure was analyzed using scanning electron microscopy (SEM). The electrical conductivity of the LBSC cathode was tested using the four-probe DC method. Symmetrical cells were tested using a potentiostat Voltalab PGZ 301 and a digital source meter Keithley 2420. LBSC powder was discovered to have a tetragonal structure (space group: P4/mmm) with lattice parameters of a = 3.86253 Å, c = 7.73438 Å, and V = 115.338 Å. From the SEM image, the LBSC cathode has homogeneous, dense, and highly porous grains. The electrical conductivity showed metallic behavior, gradually decreasing from 167 S.cm-1 at 300℃ to 105 S.cm-1 at 800℃. A significant increase in current density (io) of 275% occurred at 800℃ from 154.10 mA.cm−2 (pure LBSC) to 577.86 mA.cm−2 (LBSC+0.5M SDC). The activation energy value (Ea) of symmetrical cells was determined using electrochemical impedance spectroscopy (EIS), low-field (LF), and high-field (HF) techniques. The activation energy of the LBSC+0.5 M SDC specimen was 47.9 kJ mol-1 or 79.4% lower than the activation energy of the LBSC cathode specimen without infiltration at atmospheric pressure of 0.03 atm. These results indicate that SDC infiltration of the LBSC cathode can reduce the activation energy of the significant. The cathode membrane adheres quite well to the electrolyte membrane, the cathode porosity varies in the range of 1–4 µm, and the grain size is 0.1–1.5 µm.

Thermodynamics of Formation and Disordering of YBaCo2O6-δ Double Perovskite as a Base for Novel Dense Ceramic Membrane Materials

Differential scanning calorimetry studies of the complex oxide YBaCo₂O_6-δ (YBC), combined with the literature data, allowed outlining the phase behavior of YBC depending on the oxygen content and temperature between 298 K and 773 K. The oxygen nonstoichiometry of single-phase tetragonal YBC was measured at different temperatures and oxygen partial pressures by both thermogravimetric and flow reactor methods. The defect structure of YBC was analyzed. As a result, the thermodynamic functions (∆Hi○, ∆Si○) of the defect reactions in YBC were determined. Experimental data on the oxygen content and those calculated based on the theoretical model were shown to be in good agreement. Standard enthalpies of formation at 298.15 K (∆Hf○) were obtained for YBC depending on its oxygen content using solution calorimetry. It was found that ∆Hf○ = f(6-δ) function is linear in the range of (6-δ) from 5.018 to 5.406 and that its slope is close to the value of the enthalpy of the quasichemical reaction describing oxygen exchange between the oxide and ambient atmosphere, which confirms the reliability of the suggested defect structure model.

Efficient Catalysts of Ethanol Steam Reforming Based on Perovskite-Fluorite Nanocomposites with Supported Ni: Effect of the Synthesis Methods on the Activity and Stability

Catalysts based on perovskite—fluorite nanocomposites with supported nickel 5%Ni/[Pr0.15Sm0.15Ce0.35Zr0.35O2 + LaMn0.9Ru0.1O3] were synthesized by three different methods. Structural and surface features of as-prepared samples were elucidated by N2 adsorption, XRD, HR TEM with EDX; reducibility and reactivity were estimated by H2-TPR, and catalytic properties were studied in ethanol steam reforming in the 500–700 °C temperature range. The best catalytic activity without coke accumulation was demonstrated for the 5%Ni/[Pr0.15Sm0.15Ce0.35Zr0.35O2+ LaMn0.9Ru0.1O3] catalyst with nanocomposite support obtained by a simple sequential polymeric preparation method. Highly dispersed particles of metallic nickel strongly fixed on the support after the reaction were shown by the HR-TEM and H2 –TPR data. The catalyst provides stable full conversion of ethanol and hydrogen yield above 60% at 600 °C for at least 6 h.

Nanofiber Composites as Highly Active and Robust Anodes for Direct-Hydrocarbon Solid Oxide Fuel Cells

Direct utilization of methane fuels in solid oxide fuel cells (SOFCs) is a key technology to realize the immediate inclusion of such high-efficiency fuel cells into the current electricity generation infrastructure. However, the broad commercialization of direct-methane fueled SOFCs is critically hindered by the inadequate electrode activity and their poor longevity, which primarily stems from the carbon build-up issues. To make the technology more competitive, a novel electrode structure that can dramatically improve the tolerance against coking is essential. Herein, we present highly active and robust core-shell nanofiber anodes, La_0.75Sr_0.25Cr_0.5Mn_0.5O₃@Sm_0.2Ce_0.8O_1.9 (LSCM@SDC), directly obtained with a single-nozzle electrospinning process through the use of two immiscible polymers. The intimate coverage of SDC on LSCM not only increases the active reaction sites but also promotes resistance toward carbon deposition and thermal aggregation. As such, the electrode polarization resistance obtained with LSCM@SDC NFs is among the lowest value ever reported with LSCM derivatives (∼0.11 Ω cm² in wet H₂ at 800 °C). The facile fabrication process of such complex heterostructures developed in this work is attractive for the design of not only SOFC electrodes but also other solid-state devices such as electrolysis cells, membrane reformers, and protonic cells.

Progress of selective catalytic reduction denitrification catalysts at wide temperature in carbon neutralization

With the looming goal of carbon neutrality and increasingly stringent environmental protection policies, gas purification in coal-fired power plants is becoming more and more intense. To achieve the NOx emission standard when coal-fired power plants are operating at full load, wide-temperature denitrification catalysts that can operate for a long time in the range of 260–420°C are worthy of study. This review focuses on the research progress and deactivation mechanism of selective catalytic reduction (SCR) denitration catalysts applied to a wide temperature range. With the increasing application of SCR catalysts, it also means that a large amount of spent catalysts is generated every year due to deactivation. Therefore, it is necessary to recycle the wide temperature SCR denitration catalyst. The challenges faced by wide-temperature SCR denitration catalysts are summarized by comparing their regeneration processes. Finally, its future development is prospected.

Porous Adsorption Materials for Carbon Dioxide Capture in Industrial Flue Gas

Due to the intensification of the greenhouse effect and the emphasis on the utilization of CO₂ resources, the enrichment and separation of CO₂ have become a current research focus in the environment and energy. Compared with other technologies, pressure swing adsorption has the advantages of low cost and high efficiency and has been widely used. The design and preparation of high-efficiency adsorbents is the core of the pressure swing adsorption technology. Therefore, high-performance porous CO₂ adsorption materials have attracted increasing attention. Porous adsorption materials with high specific surface area, high CO₂ adsorption capacity, low regeneration energy, good cycle performance, and moisture resistance have been focused on. This article summarizes the optimization of CO₂ adsorption by porous adsorption materials and then applies them to the field of CO₂ adsorption. The internal laws between the pore structure, surface chemistry, and CO₂ adsorption performance of porous adsorbent materials are discussed. Further development requirements and research focus on porous adsorbent materials for CO₂ treatment in industrial waste gas are prospected. The structural design of porous carbon adsorption materials is still the current research focus. With the requirements of applications and environmental conditions, the integrity, mechanical strength and water resistance of high-performance materials need to be met.

Structural, Interfacial, and Electrochemical Stability of La0.3Ca0.7Fe0.7Cr0.3O3-δ Electrode Material for Application as the Oxygen Electrode in Reversible Solid Oxide Cells

A detailed study aimed at understanding the structural, interfacial, and electrochemical performance stability of La0.3Ca0.7Fe0.7Cr0.3O3-δ (LCFCr) electrode material for application as the oxygen electrode in reversible solid oxide cells (RSOCs) is presented. Specifically, emphasis is placed on the stability of the LCFCr oxygen electrode during oxygen evolution (electrolysis mode), whereby many known electrode materials are known to fail due to delamination. The porous microstructure of the electrode was characterized by nanoscale X-ray microscopy (XRM) to reveal the percentage porosity, pore connectivity, average pore size, and electrochemical surface area, etc. Under polarization in a two-electrode symmetrical-cell configuration, while the working electrode was under anodic polarization, a very stable performance was observed at a cell potential of 0.2 V, although increasing the cell potential to 0.65 V caused significant performance degradation. This degradation was reversible when the cell was run at open circuit for 10 h. High-resolution transmission electron microscopy and wavelength dispersive spectroscopy revealed that the working electrode (LCFCr)/electrolyte (GDC) interface was structurally and chemically stable after hundreds of hours under polarization with no interdiffusion of the various species observed across the interface, hence rendering LCFCr a viable alternative for the oxygen electrode in RSOCs.

Triple Perovskite Nd1.5Ba1.5CoFeMnO9−δ-Sm0.2Ce0.8O1.9 Composite as Cathodes for the Intermediate Temperature Solid Oxide Fuel Cells

Triple perovskite has been recently developed for the intermediate temperature solid oxide fuel cell (IT-SOFC). The performance of Nd1.5Ba1.5CoFeMnO9−δ (NBCFM) cathodes for IT-SOFC is investigated in this work. The interfacial polarization resistance (RP) of NBCFM is 1.1273 Ω cm2~0.1587 Ω cm2 in the range of 700–800 °C, showing good electrochemical performance. The linear thermal expansion coefficient of NBCFM is 17.40 × 10−6 K−1 at 40–800 °C, which is significantly higher than that of the electrolyte. In order to further improve the electrochemical performance and reduce the thermal expansion coefficient (TEC) of NBCFM, Ce0.8Sm0.2O2−δ (SDC) is mixed with NBCFM to prepare an NBCFM-xSDC composite cathode (x = 0, 10, 20, 30, 40 wt.%). The thermal expansion coefficient decreases monotonically from 17.40 × 10−6 K−1 to 15.25 × 10−6 K−1. The surface oxygen exchange coefficient of NBCFM-xSDC at a given temperature increases from 10−4 to 10−3 cm s−1 over the po2 range from 0.01 to 0.09 atm, exhibiting fast surface exchange kinetics. The area specific resistance (ASR) of NBCFM-30%SDC is 0.06575 Ω cm2 at 800 °C, which is only 41% of the ASR value of NBCFM (0.15872 Ω cm2). The outstanding performance indicates the feasibility of NBCFM-30% SDC as an IT-SOFC cathode material. This study provides a promising strategy for designing high-performance composite cathodes for SOFCs based on triple perovskite structures.

Protonic Transport in Layered Perovskites BaLanInnO3n+1 (n = 1, 2) with Ruddlesden-Popper Structure

The work focused on the layered perovskite-related materials as the potential electrolytic components of such devices as proton conducting solid oxide fuel cells for the area of clean energy. The two-layered perovskite BaLa2In2O7 with the Ruddlesden–Popper structure was investigated as a protonic conductor for the first time. The role of increasing the amount of perovskite blocks in the layered structure on the ionic transport was investigated. It was shown that layered perovskites BaLanInnO3n+1 (n = 1, 2) demonstrate nearly pure protonic conductivity below 350 °C.

In-Situ Synthesis of Sm0.5Sr0.5Co0.5O3-δ@Sm0.2Ce0.8O1.9 Composite Oxygen Electrode for Electrolyte-Supported Reversible Solid Oxide Cells (RSOC)

Oxygen electrode has a crucial impact on the performance of reversible solid oxide cells (RSOC), especially in solid oxide electrolysis cell (SOEC) mode. Herein, Sm0.5Sr0.5Co0.5O3-δ@Sm0.2Ce0.8O1.9 (5SSC@5SDC) composite material has been fabricated by the in-situ synthesis method and applied as the oxygen electrode for RSOCs with scandium stabilized zirconia (SSZ) electrolyte. The phase structures, thermal expansion coefficients, and micromorphologies of 5SSC@5SDC have all been further analyzed and discussed. 5SSC@5SDC is composed of a skeleton with large SDC particles in the diameter range of 200~300 nm and many fine SSC nanoparticles coated on the skeleton. Thanks to the special microstructure of 5SSC@5SDC, the electrolyte-supported RSOC with SSC@SDC oxygen electrode shows a polarization resistance of only 0.69 Ω·cm2 and a peak power density of 0.49 W·cm−2 at 800 °C with hydrogen as the fuel in solid oxide fuel cell (SOFC) mode. In addition, the electrolysis current density of RSOC with SSC@SDC can reach 0.40 A·cm−2 at 1.30 V in SOEC model, being much higher than that with the SSC-SDC (SSC and SDC composite prepared by physical mixing). RSOC with 5SSC@5SDC shows an improved stability in SOEC model comparing with that with SSC-SDC. The improved performance indicates that 5SSC@5SDC prepared by the in-situ synthesis may be a promising candidate for RSOC oxygen electrode.

LaNi0.6Co0.4−xFexO3−δ as Air-Side Contact Material for La0.3Ca0.7Fe0.7Cr0.3O3−δ Reversible Solid Oxide Fuel Cell Electrodes

The goal of the current work was to identify an air-side-optimized contact material for La0.3Ca0.7Fe0.7Cr0.3O3−δ (LCFCr) electrodes and a Crofer22APU interconnect for use in reversible solid oxide fuel cells (RSOFCs). LaNi0.6Co0.4−xFexO3 (x = 0–0.3) perovskite-type oxides were investigated in this work. The partial substitution of Co by Fe decreased the thermal expansion coefficient values (TEC) closer to the values of the LCFCr and Crofer 22 APU interconnects. The oxides were synthesized using the glycine–nitrate method and were characterized using X-ray thermodiffraction and 4-probe DC electrical conductivity measurements. Based on the materials characterization results from the Fe-doped oxides investigated here, the LaNi0.6Co0.2Fe0.2O3−δ composition was selected as a good candidate for the contact material, as it exhibited an acceptable electrical conductivity value of 395 S·cm−1 at 800 °C in air and a TEC value of 14.98 × 10−6 K−1 (RT-900 °C).