The development of efficient and stable intermediate-temperature solid oxide fuel cells (SOFCs) necessitates high-performance cathode materials that are cobalt-free, cost-effective, and compatible with proton-conducting electrolytes. While Sr2Fe2O6 (SFO)-based ferrites offer a promising cobalt-free alternative, their electrochemical performance requires further enhancement to compete with state-of-the-art cathodes. This study proposes and validates a multi-element doping strategy as a superior approach to tailor the properties of SFO. The specific oxide Sr2Fe1.5Mo0.125Sn0.125Sc0.125Zr0.125O6 (SFO-ZSSM) is designed, synthesized via a solid-state reaction method, and systematically evaluated as a cathode for proton-conducting SOFCs (H-SOFCs). Its performance is benchmarked against a series of SFO cathodes modified with single dopants (Mo, Sn, Sc, Zr). Structural characterization confirms the successful formation of a phase-pure perovskite structure with homogeneous elemental distribution. Electrical conductivity relaxation (ECR) measurements reveal that SFO-ZSSM exhibits dramatically enhanced oxygen and proton transport kinetics compared to all singly-doped counterparts, demonstrating a significant synergistic effect. Consequently, fuel cells employing the SFO-ZSSM cathode deliver exceptional peak power densities of 1580, 1137, and 854 mW cm-2 at 700, 650, and 600 °C, respectively, significantly outperforming cells with single-doped cathodes. Electrochemical impedance spectroscopy further corroborates its superior catalytic activity, showing the lowest polarization resistance. Moreover, the SFO-ZSSM cell demonstrates excellent operational stability over 100 hours, attributed to its robust microstructure and Ba-free composition.
Effect of Decreasing Cobalt Content on the Electrochemical Properties and Structural Stability of Li_(1-x)Ni_(y)Co_(z)Al_(0.05)O_(2) Type Cathode Materials
Critical to the development of improved solid oxide fuel cell (SOFC) technology are novel compounds with high oxygen reduction reaction (ORR) catalytic activity and robust stability under cathode operating conditions. Approximately 2145 distinct perovskite compositions are screened for potential use as high activity, stable SOFC cathodes, and it is verified that the screening methodology qualitatively reproduces the experimental activity, stability, and conduction properties of well-studied cathode materials. The calculated oxygen p-band center is used as a first principle-based descriptor of …
Crystal structure, cobalt and iron speciation and oxygen non-stoichiometry of La0.6Sr0.4Co1-yFeyO3-d nanorods for IT-SOFC cathodes
Pontificia Universidad Javeriana（波哥大耶稣会天主教大学）；Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica（康塞普西翁原子中心，国家原子能委员会）；Instituto de Nanociencia y Nanotecnología (INN), CNEA-CONICET（纳米科学与技术研究所，国家原子能委员会-国家科学研究和技术研究委员会）；CONICET / Laboratorio de Cristalografía Aplicada, Escuela de Ciencia y Tecnología, Universidad Nacional de Gral. San Martín（国家科学研究和技术研究委员会/应用晶体学实验室，科学与科技学院，圣马丁国立大学）；CNPEM, Laboratório Nacional de Luz Síncrotron（巴西纳米技术国家研究中心，同步光国家实验室）；Instituto de Física, Universidade de São Paulo（物理研究所，圣保罗大学）
A simple method has been used to synthesize nanostructured La0.5Ba0.5CoO3 (LBCO) powders, by confining chemical precursors into the pores of polycarbonate filters. The proposed method allows us to obtain powders formed by crystallites of different sizes, it is scalable and does not involve the use of sophisticated deposition techniques. The area specific polarization resistance of symmetrical cells was studied to analyze the electrochemical behavior of the LBCO nanostructures as cathodes for Solid-Oxide Fuel Cells. We show that the performance is improved by reducing the size of the crystallit…
Using a dual plasma process to produce cobalt--polypyrrole catalysts for the oxygen reduction reaction in fuel cells -- part II: analysing the chemical structure of the films
La0.6Sr0.4Fe0.8Mn0.2O3 (LSFM) compound is synthesized by Sol-gel method and evaluated as a cathode material for the intermediate temperature solid oxide fuel cell (IT-SOFC). X-ray diffraction (XRD) indicates that the LSFM has a Rhombohedral structure with R-3c space group symmetry. The XRD patterns reveal very small amount of impurity phase in the LSFM and Y2O3-Stabilized ZrO2 (YSZ) mixture powders sintered at 600, 700 and 800 C for a week. The maximum electrical conductivity of LSFM is about 35.35 S.cm-1 at 783 C in the air. The oxygen chemical diffusion coefficients, DChem, are increased fro…
This article reviews the development of cathode materials for secondary lithium ion batteries since its inception with the introduction of lithium cobalt oxide in early 1980s. The time has passed and numerous cathode materials are designed and developed to realize not only the enhanced capacity but also the power density simultaneously. However, there are numerous challenges such as the cyclic stability of cathode materials, their structural and thermal stability, higher operating voltage together with high ionic and electronic conductivity for efficient ion and charge transport during chargin…
Electrochemical devices such as solid oxide fuel cells (SOFC) may greatly benefit from the implementation of nanoengineered thin-film multifunctional layers providing, alongside enhanced electrochemical activity, improved mechanical, and long-term stability. In this study, an ultrathin (400 nm) bilayer of samarium-doped ceria and a self-assembled nanocomposite made of Sm0.2Ce0.8O1.9-La0.8Sr0.2MnO3-$δ$ was fabricated by pulsed laser deposition and is employed as a functional oxygen electrode in an anode-supported solid oxide fuel cell. Introducing the functional bilayer in the cell architecture…
Layered Li(Ni,Mn,Co,)O$_2$ (NMC) presents an intriguing ternary alloy design space for optimization as a cathode material in Li-ion batteries. Recently, the high cost and resource limitations of Co have added a new design constraint and high Ni-containing NMC alloys have gained enormous attention despite possible performance trade-offs. It is not fully understood if this material space is a disordered solid solution at room temperature and any arbitrary combination can be used or if there exist distinct transition metal orderings to which meta-stable solid solutions will decay during cycling a…
Hydrogen peroxide (H2O2) formation rates in a proton exchange membrane (PEM) fuel cell anode and cathode were estimated as a function of humidity and temperature by studying the oxygen reduction reaction (ORR) on a rotating ring disc electrode (RRDE). Fuel cell conditions were replicated by depositing a film of Pt/Vulcan XC-72 catalyst onto the disk and by varying the temperature, dissolved O2 concentration and the acidity levels in hydrochloric acid (HClO4). The HClO4 acidity was correlated to ionomer water activity and hence fuel cell humidity. The H2O2 formation rates showed a linear depend…
Micro-solid oxide fuel cells based on thin films have strong potential for use in portable power devices. However, devices based on silicon substrates typically involve thin-film metallic electrodes which are unstable at high temperatures. Devices based on bulk metal substrates overcome these limitations, though performance is hindered by the challenge of growing state-of-the-art epitaxial materials on metals. Here, we demonstrate for the first time the growth of epitaxial cathode materials on metal substrates (stainless steel) commercially supplied with epitaxial electrolyte layers (1.5 {um (…
Using a dual plasma process to produce cobalt--polypyrrole catalysts for the oxygen reduction reaction in fuel cells -- part I: characterisation of the catalytic activity and surface structure
介绍了一种新的双等离子体涂层工艺，用于制备燃料电池中氧还原反应的无铂催化剂。用各种方法分析由此产生的催化剂。通过循环伏安法、旋转环电极和旋转环盘电极进行电化学表征。由此获得的不同的催化剂的表面孔隙率的特征在于与氮气吸附技术和扫描电子显微镜用于确定膜的生长机制。它表明，催化活性化合物可以用这种双等离子体工艺生产。此外，催化活性可以通过改变等离子体工艺参数而显著变化。计算了生成的H $_2$ O $_2$的量，并表明2电子机理是主要的。等离子体涂覆机制不会显著改变所用碳载体的表面BET面积和孔径分布。此外，所产生的薄膜的扫描电子显微镜照片，并示出的柱状生长机制的偏好。通过使用不同的碳作为载体，它表明，有很强的依赖性的催化活性，这可能是有关的碳的化学性质。
Modern fuel cell technologies use Nafion as the material of choice for the proton exchange membrane (PEM) and as the binding material (ionomer), used to assemble the catalyst layers of the anode and cathode. These applications demand high proton conductivity as well as other requirements. For example, PEM is expected to block electrons, oxygen, and hydrogen from penetrating and diffusing while the anode/cathode ionomer should allow hydrogen/oxygen to move easily, so that they can reach the catalyst nanoparticles. Given some of the well-known limits of Nafion, such as low glass-transition tempe…
A one dimensional (1-D), isothermal model for a direct methanol fuel cell (DMFC) is presented. This model accounts for the kinetics of the multi-step methanol oxidation reaction at the anode. Diffusion and crossover of methanol are modeled and the mixed potential of the oxygen cathode due to methanol crossover is included. Kinetic and diffusional parameters are estimated by comparing the model to data from a 25 cm2 DMFC. This semi-analytical model can be solved rapidly so that it is suitable for inclusion in real-time system level DMFC simulations.
High-entropy perovskites, architectured by s0/d0/d10 cations, as novel electrolytes for solid oxide fuel cells
WPI, International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University（九州大学）；Department of Automotive Science, Graduate School of Integrated Frontier Sciences, Kyushu University（九州大学）；Graduate School of Engineering, Kyushu University（九州大学）；Center for Energy System Design (CESD), International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University（九州大学）
Development of materials for electrochemical energy conversion requires a deep understanding of the factors governing chemical and physical rates at submicron length scales. Many workers have sought to develop chemically sensitive in situ or operando imaging techniques targeting these length scales. However, current methods focus on steady-state or stepwise response. To probe electrode processes both spatially and temporally, we have developed a frequency-resolved implementation of X-ray absorption imaging (FR-XAS) that can measure local electrochemical response in operando during a global sin…
Manganese oxide nano flakes onto simultaneously activated defective CNTs for the creation of CNTs-graphene supported oxygen reduction composite catalysts applied in air fuel cell
非贵金属氧化物与经济炭材料的合理组合是创造高性能空气电极材料的关键。在稀H $_2$ SO $_4$中，通过取消常规水热处理或添加表面活性剂模板剂，将商品化的碳纳米管（CNTs）与MnO $_4^-$反应，制备了CNTs负载的锰氧化物复合催化剂（CMnCs）。然后将CMnC组装成装备在金属空气燃料电池中的商用空气阴极。碳纳米管表现出结构上的缺陷。在合成过程中，外部CNT壁破裂成石墨烯纳米片，但仍保持部分附着于内部碳管。石墨烯平面的这种暴露表现出额外的氧还原反应性。在碳纳米管表面均匀生长了纳米级的氧化锰薄片（γ-MnOOH）。其沉积密度与KMnO $_4$对CNTs的添加量密切相关。在相同条件下，单独的CMnCs的ORR活性超过了原料CNT和合格的市场催化剂，并且在当前的生产工艺下，CMnCs添加的空气燃料电池能够在100 mA/cm $^2$下输出约15%以上的功率。
Wide proliferation of low temperature hydrogen fuel cell systems, a key part of the hydrogen economy, is hindered by degradation of the platinum cathode catalyst. Here, we provide a device level assessment of the molecular scale catalyst degradation phenomena, using advanced operando X-ray scattering tomography tailored for device-scale imaging. Each cell component, including the catalyst, carbon support, polymer electrolyte, and liquid water can be simultaneously mapped, allowing for deep correlative analysis. Chemical and thermal gradients formed inside the operating fuel cell produce highly…
Fuel cells recombine water from H2 and O2 thereby powering e.g. cars or houses with no direct carbon emission. In anion-exchange membrane fuel cells (AEMFCs), to reach high power densities, operating at high pH is an alternative to using large volumes of noble metals catalysts at the cathode, where the oxygen-reduction reaction occurs. However, the sluggish kinetics of the hydrogen-oxidation reaction (HOR) hinders upscaling despite promising catalysts. Here, we observe an unexpected ingress of B into Pd nano-catalysts synthesised by wet-chemistry, gain control over this B-doping, and report on…
A simple spin coating approach is introduced to fabricate Yttria-Stabilized Zirconia (YSZ) electrolyte layer on NiO-YSZ anode substrate for solid oxide fuel cell applications. Heating the substrate during the slurry spin coating process enhances the affected area through the layer and leads to optimize the compacting amount of coated electrolyte particles before sintering procedure. On top of this bilayer substrate, LCFN is deposited as an intermediate temperature solid oxide fuel cell cathode, in order to have suitable output performances at intermediate temperature ranges. Applying humidifie…
Proton-electron coupled catalyst for ionomer-free electrochemical energy conversion
University of California, Los Angeles（加州大学洛杉矶分校）；Georgia Institute of Technology（佐治亚理工学院）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；Max Planck Institute for Dynamics of Complex Technical Systems（马克斯·普朗克复杂技术系统动力学研究所）；California NanoSystems Institute（加州纳米系统研究所）；California Institute of Technology（加州理工学院）
Natural abundance, impressive chemical characteristics and economic feasibility have rekindled the appeal for rechargeable sodium (Na) batteries as a practical solution for the growing energy demand, environmental sustainability and energy independence. However, the scarcity of viable positive electrode materials remains a huge impediment to the actualization of this technology. In this paper, we explore honeycomb layered oxides adopting the composition Na$_2$Ni$_{2-x}$Co$_x$TeO$_6$ ($x = 0, 0.25$ and $0.50$) as feasible positive electrode (cathode) materials for rechargeable sodium batteries …
