Low-temperature Solid Oxide Fuel Cells Research Articles

Porous microsphere LiNi0.8Co0.15Al0.05O2 electrode modified by Na2CO3: Enhanced performance of low temperature solid oxide fuel cells

LiNi0.8Co0.15Al0.05O2 (NCAL) has been extensively adopted as symmetric electrode for low temperature solid oxide fuel cells (SOFCs) based on oxide semiconductor electrolytes. However, the performance of NCAL electrode depend on material source, morphology and operating conditions. In this study, commercial microsphere NCAL is successfully modified with Na2CO3 by a wet chemical method. The crystal structure, surface morphology, elemental analysis, surface chemistry and electrochemical properties of NCAL modified by Na2CO3 (NCALN) are characterized by various techniques. When Na2CO3 content in NCALN is 5 wt.% and 10 wt.%, the CeO2 electrolyte SOFCs with NCALN symmetric electrode show significantly superior performance to that with NCAL symmetric electrode. The optimal heterostructure electrode NCALN5 exhibits a peak power density of 805 mW·cm-2 and a polarization resistance of 0.237 Ω·cm2 at 550°C, which is 17% higher and 21% lower than those of NCAL electrode. Compared with NCAL electrode, NCALN5 electrode enhances the catalytic activities to both hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) but contributes more to ORR than HOR, especially at low temperatures. These results clearly demonstrate NCALN heterostructure composites are promising electrode materials for low temperature SOFCs.

Alternative Strategy for Development of Dielectric Calcium Copper Titanate-Based Electrolytes for Low-Temperature Solid Oxide Fuel Cells

HighlightsDielectric CaCu3Ti4O12 (CCTO) was used as electrolyte in low-temperature solid oxide fuel cells for the first time.A new heterostructure electrolyte was designed based on CCTO and Ni0.8Co0.15Al0.05LiO2−δ (NCAL). Promising ionic conductivity and high fuel cell performance were achievedCCTO–NCAL realized an electrolyte function due to its good dielectric property and a heterojunction effect.

Exploring novel nanostructural architecture of doubly doped ceria (Ce0.85Sr0.075Sm0.075O2-δ) and barium cerate (BaCeO3) as electrolytes for low-temperature solid oxide fuel cells

This study presents the development of a composite electrolyte for use in low-temperature (300–500 °C) Solid oxide Fuel Cells, focusing on a novel nanostructural design. The electrolyte comprises co-doped ceria (Ce0.85Sr0.075Sm0.075O2-δ, DCO) and barium cerate (BaCeO3, BCO), integrated into a unique nanostructural architecture. Initially, the constituent phases of the composite DCO and BCO are synthesized using a soft-chemical route separately, followed by their integration through liquid mixing technique in various compositions (90:10, 80:20, 70:30, 60:40, 50:50) of DCO:BCO in weight ratio. The composite structure is confirmed by X-ray diffraction, and refined the structural data by Rietveld refinement indicating a structural agreement with cubic and fluorite phases of DCO and BCO, respectively. Scanning Electron microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX) reveal a uniform distribution of two phases with fine size distribution below 50 nm. Transmission Electron microscopy (TEM) images illustrate the core-shell-like integration of the two phases. High-resolution TEM images indicate that the core consists of the DCO phase, while the shell is composed of the BCO phase. The microstructure of sintered pellets exhibits gas-tight densification, with grains dominated by the DCO phase and BCO phase dispersed along grain boundaries. The ionic conductivity of composite systems is extracted from Electrochemical impedance spectroscopy (EIS) studies, showing that DCO-BCO-40 exhibits the highest conductivity 1.132 × 10−3 Scm−1 @400 °C, which is higher than pristine DCO (0.34 × 10−4 Scm−1 @400 °C). Single cells fabricated using DCO-BCO-40 electrolytes deliver a power output of 280 mW cm−2 whereas pristine DCO showed 279 mW @500 °C. This study exhibits the potential of the core-shell-like nanostructural architecture of electrolytes in advancing Low-temperature solid oxide Fuel cell (LT-SOFC) technology and facilitating the transition toward sustainable energy systems.

Semiconductor heterostructure LiCo0.5Al0.5O2-Ce0.8Sm0.2O2-δ electrolyte with enhanced ionic conductivity for low-temperature solid oxide fuel cells

Semiconductor heterostructure composite materials, exemplified by p-n junctions, have garnered substantial interest for their elevated ionic conductivity, crucial in solid oxide fuel cells (SOFCs). The inherent built-in electric field (BIEF) within these materials enhances ion transport while hindering electron flow, thereby mitigating the risk of short circuits. This research focuses on the electronic conduction properties of p-n junctions, specifically through the development of high-performance LiCo0.5Al0.5O2 (LCAO)-Ce0.8Sm0.2O2-δ (SDC) semiconductor heterojunction composite electrolytes for low-temperature solid oxide fuel cells (LT-SOFCs). Experimental results demonstrate a correlation between the electrolyte's performance and the LCAO to SDC weight ratio. The SOFC equipped with a 3LCAO-7SDC electrolyte achieved an open-circuit voltage (OCV) of 1.1 V and a maximum power density (MPD) of 1013 mW/cm2 at 550 °C, significantly outperforming other composite ratios and single-phase SDC electrolytes, which only reached 453 mW/cm2 under identical conditions. High-resolution transmission electron microscopy (HRTEM) revealed the presence of non-uniform interfaces within these composites. Energy band structure analyses confirm superior ionic conductivity and effective charge separation capabilities. This study introduces a novel p-n junction design for LT-SOFC electrolyte materials using LCAO-SDC, further advancing the exploration of p-n junctions in this application.

In situ reconstruction of proton conductive electrolyte from self-assembled perovskite oxide-based nanocomposite for low temperature ceramic fuel cells

In the development of low temperature solid oxide fuel cells (LT-SOFCs), also called ceramic fuel cells, the lack of highly conductive and the high manufacturing cost of dense electrolyte materials severely delay their wide development. In this work, we depart from the classic substitution approach to achieve sufficient ionic conduction (0.01 S cm−2 level at temperature ≥600 °C), a superionic conductive electrolyte material was obtained from a self-assembled hybrid oxide that was derived from the perovskite oxide precursor through alkali metal ion substitution. Moreover, the hybrid oxide was further in-situ reconstructed into a nanocomposite of oxide/carbonate-hydroxide under fuel cell condition. The nanocomposite possesses dominated proton conductivity as verified by the benefited hydration effect, versatile oxygen ionic blocking cell experiment, and concentration cell investigation. Specifically, an outstanding ionic conductivity of 0.185 S cm−1 and an excellent peak power density of 1012 mW cm−2 were demonstrated at 550 °C under an typical H2/air atmosphere. This research offers a rational design strategy to achieve low temperature, high-performance semiconductor-based functional composite electrolytes for efficient and sustainable energy conversion in SOFC technology.

Gd-doped ceria with extraordinary oxygen-ion conductivity for low temperature solid oxide fuel cells

Doped ceria has been extensively explored as an efficient electrolyte material for intermediate to low temperature solid oxide fuel cell. Among other ceria electrolytes, gadolinia doped ceria (GDC) is one of the most extensively studied electrolyte materials for low temperature SOFC applications. Here, co-precipitation method is employed to synthesize GDC nanoparticles with stoichiometric ratio of GdxCe1−xO2−δ (with 0 ≤\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\le$$\\end{document} x ≤\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\le$$\\end{document} 0.20). In this process, the molecular water of the precursors has been utilized during the co-precipitation to avoid possible agglomeration caused by hydrogen bonding. The cubic phase formation was examined using X-ray diffraction (XRD) and Raman profile ascribing absence of other phases. XRD along with Reitveld refinement confirm the presence of cubic phase of ceria and Raman profile confirms the oxygen vacancies due to the non-stoichiometry created in CeO2 lattice. The granularity of the sample was observed using field emission scanning electron microscopy (FESEM) with elemental mapping by EDS. It is observed from FESEM that the grains are compact in nature and the density observed was around 98% of the theoretical density. The electrochemical behavior was investigated using electrochemical impedance spectroscopy (EIS), which was taken between the temperature ranges of 350–700 °C. It is observed from the EIS study that ceria doped with 15 mol % Gd3+ (Gd0.15Ce0.85O2−δ) is having highest grain boundary ionic conductivity of about 0.104 S cm−1 at 700 °C with an activation energy of 0.81 eV. This work demonstrates the correlation between oxygen vacancy generation and the enhancement of ionic conductivity with Gd3+ doping in ceria.

Synthesis and Ionic Conductivity of Lanthanum-based Ceria Ce1−xLaxO2−δ Electrolytes for Solid Oxide Fuel Cell Applications

In advanced low temperature solid oxide fuel cell (LT-SOFC) technology, we present a comprehensive study on the effects of lanthanum co-substitution in ceria electrolyte. Using a co-precipitation synthesis approach, we successfully incorporated trivalent La ions into the ceria matrix to improve its structural and functional properties. This study investigates La3+ doped CeO2 solid electrolytes (LDC) synthesis and characterization at varying concentrations (0.2, 0.3, 0.4, and 0.5). The materials were characterized using a suite of analytical techniques. X-ray diffraction (XRD) analysis revealed that all samples maintained a cubic fluorite-type structure with evident changes in peak intensity and broadening as La3+ ion concentration increased, indicative of induced lattice defects FT-IR spectra indicated minor modifications in the Ce-O bond vibrational modes. Optical studies demonstrated enhanced absorption in the UV region and a consistent band gap of 3.15 eV across all samples, underscoring the doping's influence on electronic transitions. Scanning electron microscopy (SEM) images highlighted increased grain sizes and improved interparticle connectivity, which is essential for material performance. X-ray fluorescence spectroscopy verified the existence of cerium and lanthanum, proving the successful addition of dopants. Raman spectroscopy also confirmed changes in the structure, indicating alterations in the characteristic vibrational frequencies and a decrease in their intensity as the dopant concentration increased. The conductivity of the material was tested at low temperatures ranging from 573 K to 873 K for use in Solid Oxide Fuel Cells, with the highest conductivity recorded at 0.21 mS/cm at 873 K.

Synthesis and characterization of cubic δ–phase stabilized Bi2O3 electrolytes by triple rare earth cation doping for intermediate temperatures SOFCs

Face–centered cubic–Bi2O3 (δ–phase), a high–ion conductor, is an essential solid electrolyte option, particularly for low–low–temperature SOFC applications. It is widely accepted that δ–Bi2O3 exhibits higher conductivity than the YSZ electrolytes typically utilized in HT–SOFC units. The present study investigates the structural, thermal, surface, and conductivity characteristics of the Bi2O3 electrolytes co–doped with Tb–Sm–Gd rare earth. The XRD data indicate that, except composition 20Tb20Sm20Gd, all compositions are stabilized with the cubic δ–phase at room temperature. The estimated lattice constants additionally suggest lattice contraction, confirming that the partial cation substitutes between host Bi3+ and rare earth cations are successful. The DTA curves do not have any endothermic or exothermic peaks, indicating a possible phase transition. Arrhenius plots prove that DC conductivity decreases as the dopant ratio increases, implying a drop in polarization power. The highest conductivity is found to be 0.131 S/cm for the composition 10Tb10Sm10Gd.

Scaffold Infiltrated Cathodes for Low-Temperature Solid Oxide Fuel Cells.

Lowering the operating temperature of solid oxide fuel cells (SOFCs) and electrolysis cells (SOECs) to reduce system cost and increase lifetime is the key to widely deploy this highly efficient energy technology, but the high cathode polarization losses at low temperatures limit overall cell performance. Here we demonstrate that by engineering a universal ceria-based scaffold with infiltrated nanoscale electrocatalysts, a low cathode polarization <0.25 Ω·cm2 with remarkably high performance 1 W/cm2 at 550 °C is achieved. The combination of low processing and operating temperature restrains the nanosized electrocatalysts, not only allowing fast oxygen transport but also providing an essential electronically connective network to facilitate electrochemical reactions without requiring the high-temperature processing of a separate cathode layer. Moreover, excellent SOFC durability was demonstrated for over 500 h. This work shows a promising pathway to reduce processing/system costs with all scalable ceramic processing techniques for the future development of low-temperature SOFCs and SOECs.

Enhancing the performance of the BaTiO3 electrolyte via A-site-deficiency engineering for low-temperature ceramic fuel cells (LT-CFCs)

The development of low-temperature solid oxide fuel cells (LT-SOFCs) is gaining abundant interest in semiconductor ionic materials (electrodes and electrolytes). Following this concept, an A-site deficiency technique is employed to unilaterally change BaTiO3 to regulate ionic conduction, further improving the electrolyte's performance. The electrolytes, namely BaTiO3, Ba0·95TiO3, and Ba0·90TiO3, have carefully been constructed and studied utilizing solid-state ball milling. The A-site deficiency in BaTiO3 resulted to improve the ionic conductivity and minimize activation energy. This can be attributed to the higher number of oxygen vacancies on the surface and at the interfaces. The enhanced morphology, direct visualization of lattice structures, and the existence of oxygen vacancies caused by A-site deficiency have been studied in detail. Out of all the prepared electrolytes, Ba0·90TiO3 shows an enhanced fuel cell performance of 625 mW/cm2. In comparison, the Ba0·95TiO3 achieved a reasonable fuel cell performance of 573 mW/cm2, and BaTiO3 achieved 548.40 mW/cm2 at a low temperature of 550 °C. Compensating for the lack of A-site ions is a successful approach to improve ion transportation in fuel cells without creating any leakage of electric current. This is achieved by modifying the arrangement of energy bands that control the movement of charge carriers. The results of this work demonstrate that A-site-deficiency engineering can be used to improve the electrolyte performance of LT-SOFCs, making it a promising method for advancing fuel cell technologies in the future.

Bridging the Gap between fundamentals and efficient devices: Advances in proton-conducting oxides for low-temperature solid oxide fuel cells

Low-temperature solid oxide fuel cells (LT-SOFCs) represent a cutting-edge solution in the domain of clean energy, poised to revolutionize electricity generation for both stationary and mobile applications. At the core of LT-SOFCs lies the proton-conducting solid oxide electrolyte, a subject of extensive exploration and advancement. This comprehensive review investigates the evolution of proton-conducting solid oxide electrolytes for LT-SOFCs, exploring the landscape from fundamental materials to diverse device architectures. The review meticulously examines three pivotal dimensions: 1) strategies for fine-tuning the properties and structures of ceramics and proton-conducting oxides, 2) advancements in techniques for protonic-conducting fuel cells (PCFCs), and 3) an exploration of the opportunities and challenges intrinsic to the progression of electrolyte-based PCFCs. By elucidating the advancements made in optimizing conductivity, chemical stability, sinterability, and electron-blocking characteristics of proton-conducting electrolytes, this review offers invaluable insights into the state-of-the-art for LT-SOFC technology. Furthermore, it casts a forward-looking perspective, envisioning the future trajectory of proton-conducting electrolyte research and its potential to reshape the landscape of LT-SOFC technology. By providing a comprehensive overview of past achievements and future prospects, this review serves as a valuable resource for researchers, engineers, and stakeholders, guiding them towards the realization of efficient and sustainable energy solutions.

Advances in low-temperature solid oxide fuel cells: An explanatory review

This review article explores recent advancements and potential advantages of low-temperature solid oxide fuel cells (LT-SOFCs), offering a comprehensive overview of critical developments in the field. It highlights the significance of utilizing oxygen ion conducting electrolytes such as La0.8Sr0.2Ga0.8Mg0.2O3–type (LSGM) perovskties and yttria-stabilized zirconia (YSZ) in LT-SOFCs, emphasizing their role in facilitating efficient oxygen transport at lower temperatures. Furthermore, the review discusses the importance of electrode tailoring at the nanoscale using techniques like sol-gel and pulsed laser deposition (PLD), which have been shown to enhance the oxygen reduction reaction (ORR) at the cathode, thereby improving overall cell performance. One of the key focal points of the review is the exploration of perovskite structures and their imperative characteristics in LT-SOFCs. Specifically, it elucidates how oxygen defects within perovskites contribute to the migration of oxygen ions, consequently augmenting electrical conductivity within the cell. This discussion underscores the significance of understanding the fundamental principles governing ion transport mechanisms in electrolyte materials, which is crucial for the development of next-generation LT-SOFCs with improved efficiency and performance. Moreover, the review highlights recent advancements in the fabrication of nanoscale electrolyte films, which have shown promising results in reducing series resistance and enhancing cell performance at lower temperatures. Techniques such as atomic layer deposition (ALD), and spark plasma sintering (SPS) are discussed in the context of fabricating these nanoscale membranes, underscoring their potential for revolutionizing LT-SOFC technology. Overall, this review consolidates recent research findings and technological advancements in the field of LT-SOFCs, shedding light on the novel approaches and strategies employed to overcome existing challenges and propel the development of more efficient and practical fuel cell systems. By synthesizing key insights and highlighting future research directions, this review serves as a valuable resource for researchers and engineers working towards the advancement of LT-SOFC technology.

Ni/GDC Fuel Electrode for Low-Temperature SOFC and its Aging Behavior Under Accelerated Stress

The microstructural integrity of Ni-based fuel electrodes is important for long-term solid oxide fuel cell (SOFC) operation. Degradation due to microstructural changes such as Ni-agglomeration, coarsening, and densification must be prevented by an appropriate microstructure. Here, the performance of four types of nickel-ceria-based fuel electrodes, which differ concerning layer sequence and manufacturing processes, was evaluated by electrochemical impedance spectroscopy at the nominal operating temperature of 600 °C. Electrodes produced through screen-printed GDC exhibited an acceptable polarization resistance (0.260 Ωcm2), whereas electrodes with an additional printed Ni/GDC layer demonstrated inferior performance (0.550 Ωcm2). Electrodes formed through infiltration of GDC into the printed GDC-layer displayed unreproducible performance values ranging from 0.16 to 1.20 Ωcm2 despite similar processing. Conversely, electrodes with an extra layer of GDC infiltrated into the Ni-backbone exhibited good performance (0.195 Ωcm2) and stability. Accelerated degradation tests under OCV at increased operating temperatures of 700 and 900 °C were performed on the sample based on a GDC infiltrated Ni-backbone that performed best among reproducible samples. The polarization resistance at 600 °C recorded at the beginning and the end of life increased by up to 100%. Microstructural analysis of the electrodes at different aging states revealed strong microstructural changes of fine-infiltrated GDC structures and Ni agglomeration at higher operating temperature.

Optimizing Bilayer Electrolyte Thickness Ratios for High-Performing Low-Temperature Solid Oxide Fuel Cells

Abstract Bilayer electrolytes for low-temperature solid oxide fuel cells (LT-SOFCs) offer the potential for higher power density by lowering the ohmic area specific resistance (ASR) and increasing the open circuit voltage (OCV) of mixed ionic/electronic conducting (MIEC) type electrolyte (e.g., GDC). However, optimizing the bilayer electrolyte thickness ratio is essential to achieve high power densities at low-temperatures (650-500℃). Herein we provide a systematic study of GDC/YCSB bilayer thickness ratios on anode-supported LT-SOFCs. In all cases the bilayer maximum power density (MPD) is higher than single-layer GDC based cells with reduced ohmic ASR values. Specifically, a high MPD of ~1 W/cm2 at 650℃ was achieved on a GDC(20 μm)/YCSB(12 μm) bilayer electrolyte based SOFC, which is 62% higher than single-layer GDC based SOFC (0.64 W/cm2) operating on humidified H2 as fuel. Such enhancement is due to the 9.3% improvement in OCV and 36% reduction in ohmic ASR values with the addition of the YCSB layer. The reduction in ohmic ASR of the bilayer electrolyte SOFCs is due to an increase of GDC electrical conductivity caused by the lower pO2 at the YCSB/GDC interface which must be considered in optimizing the thickness ratio of the bilayer electrolyte for achieving higher power density LT-SOFCs.

Semiconductor ionic Cu doped CeO2 membrane fuel cells

Operation of low-temperature solid oxide fuel cells (LT-SOFCs) in the range of 300–500 °C has emerged as a promising technology and desired operational temperature for clean and efficient energy conversion. However, the lack of suitable electrolyte materials for these temperatures presents a significant challenge. In this article, a novel approach is proposed to address the hurdle of operational temperature by tailoring copper-doped cerium oxide, Cu0.1Ce0.9O2 as a semiconductor ionic membrane (SIM) to act as an electrolyte in a cell. The Cu0.1Ce0.9O2 formed a single-phase cubic fluorite structure. As a SIM, it shows enhanced ionic conductivity and reduced electrolyte/electrode polarizations, therefore achieved good fuel cell performance and electro-kinetics, reaching a power density of 515 mW/cm2 at 500 °C, with an ionic conductivity exceeding 0.1 S/cm. The detailed investigation shows dominant protonic conduction (H+) behavior in the Cu0.1Ce0.9O2 membrane. Interesting phenomenon of coupling effect elaborated through the distribution of relaxation time (DRT) analysis depicted to understand the romance of protons and electrons conduction mechanism. These advancements lead to Cu0.1Ce0.9O2 as a new type of SIM in LT-SOFCs, emphasizing the need for further research and development in this promising field to unlock the SIM and fuel cell potential.

Na0.6Co3O4- La/Pr co-Doped Ceria as Semiconductor-Ionic Heterostructure Material for Fuel Cell Application

Functional Sodium-doped cobalt oxide (Na0.6Co3O4, NCO) was incorporated to regulate and improve the electrochemical performance of La/Pr co-doped ceria (LCP) electrolytic materials with good operative stability, forming an p-n heterostructure electrolyte (LCP-NCO) for low-temperature solid oxide fuel cell (LTSOFC) application. LCP-NCO is a new potential semiconductor-ionic material, achieving a maximum power density of 1075 mW cm−2 along with a high open-circuit voltage of 1.061 V at 520 °C. Scanning electron microscopy combined with transmission electron microscopy unveiled the crystallographic microstructure of heterostructure interface between LCP and NCO. Raman spectra and Fourier transform infrared spectroscopy spectra were analyzed to distinguish the functional groups and the vibrational properties. Ultraviolet–visible absorption and ultraviolet photoelectron spectroscopy have determined the accurate band edge positions of LCP and NCO and p-n heterojunction nature. Built-in electric field in semiconductor heterostructure and more oxygen vacancies created through the variation of Co3+/Co2+ ratio in LCP-NCO during the fuel cell test, contributed to the enhanced ionic transport. Characteristic of competent conductivity of 0.26–0.42 S cm−1 at 400 °C–520 °C, and the improved cell duration, revealed that the LCP-NCO as a hybrid oxygen ion and protonic conductor would be a potential electrolyte for LTSOFC.

Enhancement of Performance and Sulfur Tolerance of Ceria-Based Fuel Electrodes in Low Temperature SOFC

The trend of operating the solid oxide fuel cell at significantly lower operation temperatures enables the application of electrodes with finer microstructure or even nanostructured electrodes with increased active surface and enhanced performance. To maintain the high performance in hydrocarbon fuels commonly impurified with sulfur compounds, a required sulfur tolerance has to be maintained. In this study we compare performance and H2S-poisoning of four ceria-based electrodes: conventional Ni/Ce0.9Gd0.1O2−δ cermets and sub-μm scaled Ce0.8Gd0.2O2−δ -electrodes with and without infiltrated nickel. Symmetrical cells were operated in a hydrogen/steam/nitrogen gas mixture with and without minor amounts of H2S at 600 °C. The performance is analyzed by electrochemical impedance spectroscopy. The distribution of relaxation times is applied to deconvolute the electrochemical processes followed by a complex nonlinear least square fit to quantify the loss processes and the impact of sulfur. Whereas two different Ni/Ce0.9Gd0.1O2−δ cermet electrodes exhibit polarization resistances at 600 °C without/with 0.1 ppm H2S of 2.89/5.56 Ωcm2 and 2.15/2.75 Ωcm2, the single phase Ce0.8Gd0.2O2−δ electrode reaches 0.98/2.37 Ωcm2. With an infiltration of Ni-nitrate forming nickel nanoparticles on the gadolinia-doped ceria-surfaces, the ASR could be drastically reduced to 0.32/0.37 Ωcm2.

Structural and ionic conduction study of Sm–Pr co-doped ceria electrolyte materials for LT-SOFC applications

Samarium praseodymium (Sm–Pr) co-doped ceria was synthesized by the co-precipitation technique as an electrolyte for low-temperature solid oxide fuel cell (LT-SOFC) applications. The structural, morphological, compositional, and electrical characterization of the synthesized samples were evaluated via x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX) and impedance spectroscopy. The generation of a single-phase fluorite structure of co-doped ceria without any secondary phases has been verified by XRD analysis, exhibiting the successful incorporation of Sm and Pr ions into the ceria lattice. Vegard's law is utilized for Pr redox behavior explaining the variation in lattice constant values. SEM pictures show that the co-doped ceria powder has a homogeneous and well-dispersed microstructure, and has enhanced particle size. The impedance spectroscopy results indicate that Sm–Pr co-doped ceria has much higher ionic conductivity than single-doped ceria. The highest amount of ionic conductivity (σionic) for the composition Ce0.80Sm0.10Pr0.10O2−δ recorded as 2.12×10−2S/cm at 500°C, and 6.19×10−2S/cm at 750°C with the lowest activation energy Ea=0.48eV, which has been not reported earlier. Sm and Pr are chosen as dopants because of their capacity to generate oxygen vacancies and improve ceria's ionic conductivity. This study contributes to the enhancement in the ionic conductivity of co-doped ceria by co-precipitation technique and the temperature-dependent frequency exponent factor "s" is also explored to comprehend the conduction mechanism of the prepared samples.

In Situ Phase-Transformation Forming a Bicontinuous (Ni, Co, Ti, and Al)-Oxide/Li2CO3 Interpenetrating Network Electrolyte for Solid Oxide Fuel Cells.

Designing heterogeneous electrolytes with superior interface charge transfer is promising for low-temperature solid oxide fuel cells (LT-SOFCs). However, a rational construction with optimal interfaces to maximize ionic conduction remains a challenge. Here an in situ phase-transformation strategy is demonstrated to prepare a highly conductive heterogeneous electrolyte. A pristine LiNiO2-TiO2 nanocomposite precursor undergoes chemical reactions and phase-transformation upon heating and feeding H2, destroying the original phases, and forming new species, including an amorphous Li2CO3 scaffold within a (Ni, Co, Al, and Ti)-oxide (NCAT) matrix. It creates an intertwining and continuous network inside the electrolyte with plentiful interfaces. The in situ formed NCAT/Li2CO3 heterogeneous electrolyte displays superior ionic conductivity and impressive fuel cell performance. This work emphasizes the potential of rational heterogeneous structure design and interface engineering for LT-SOFC electrolyte through an in situ phase-transform approach. The generated interfaces enhance ion transport, presenting an opportunity for further optimizing electrolyte candidates, and lowering the operating temperatures of SOFCs.

Thermally Stable Silver Cathode Covered by Samaria-Doped Ceria for Low-Temperature Solid Oxide Fuel Cells.

Samaria-doped ceria (SDC) overlayers were deposited on Ag cathodes by sputtering. The SDC sputtering time was varied to investigate the properties of the Ag-SDC overlayer cathode-coated fuel cells depending on the thickness of the SDC overlayers. Among the fabricated fuel cells, Ag with a 10-nm-thick SDC overlayer (Ag-SDC10) cathode-coated fuel cell exhibited the highest peak power density of 6.587 mW/cm2 at 450 °C, showing higher performance than a pristine Pt-coated fuel cell. Moreover, electrochemical impedance spectroscopy revealed that the Ag-SDC10 cathode-coated fuel cell significantly mitigated polarization loss originating from enhanced oxygen reduction reaction kinetics compared to the pristine Ag-coated fuel cell.