Nanoengineering of cathode layers for solid oxide fuel cells to achieve superior power densities

A self-assembled composited cathode coated with dual-exsolved core-shell FeNi@FeOx nanoparticles as efficient CO2 reduction electrocatalysts

Solid oxide electrolytic cells (SOECs) enable efficient electrochemical reduction of CO2 into CO, providing a sustainable solution for greenhouse gas mitigation. Nevertheless, the scarcity of stable and highly active cathode materials for the real application of SOECs is a serious challenge. Herein, a novel self-assembled composed cathode of Ni co-doped (Pr0.5Sr0.5)0.95Fe0.9Nb0.1O3-δ-Gd0.1Ce0.9O2-δ (PSFNNb-GDC) is proposed as an efficient CO2 electrolysis. The NiFe/FeOx nanoparticles with a core-shell structure are uniformly deposited onto the surface of the PSFNNb-GDC cathode. La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM)-based single cell with NiFe/FeOx@PSFNNb-GDC cathode achieve excellent performance (1.33 A cm-2 at 850 °C@1.6 V) and stability (800 °C@1.2 V) in long-term operation. The performance enhancement original from increased surface oxygen vacancies and in situ formed FeNi@FeOx core-shell nanoparticles. This research highlights the potential of rational structural design of SOECs cathode materials in advancing the field of CO2 utilization.

"Bifunctional Strontium-Iron Doped Neodymium Cobaltite: A Promising Electrocatalyst for Intermediate Temperature Solid Oxide Fuel Cells and CO2 Electrolyzer"

A novel intermediate temperature solid oxide fuel cell cathode, Nd₀.₆₇Sr₀.₃₃Co₀.₈Fe₀.₂O₃- δ (NSCF), synthesized via auto-combustion, exhibits exceptional mixed ionic-electronic conducting properties with a cubic perovskite structure. At 800 °C, NSCF demonstrates high electrical (1003 S cm-1) and ionic (1.676 × 10⁻2 S cm-1) conductivities, with activation energies of 0.0335 and 0.481 eV, respectively. Electronic analysis confirms its metallic nature, while the calculated oxygen migration energy (0.455 eV) correlates with experimental ionic conduction activation energy. The negative bulk oxygen vacancy formation energy (-38.70 kcal mol-1) indicates efficient oxygen reduction reaction and CO₂ electrolysis kinetics. Electrical conductivity relaxation shows non-debye behavior, with Dchem of 5 × 10⁻⁴ cm2 s-1 and Kex of 6.450 × 10⁻⁴ cm -1s at 800 °C. NSCF exhibits low interfacial polarization resistance (0.05 Ω cm2) and area-specific resistance (0.025 Ω cm2), further reducing to 0.014 Ω cm2 with an NSCF-GDC Gadolinium doped ceria interlayer. An anode-supported cell achieves peak power densities of 2.27, 1.52, and 0.86 W cm- 2 at 800, 750, and 700 °C, respectively. In SOEC mode, NSCF demonstrates excellent CO₂ reduction capability of constant current density of -1.1 A cm- 2 with stable 55-h performance, which establishes its potential both as IT-SOFC cathode and CO2 electrolysis catalysts.

Hybridizing Fabrications of Gd-CeO2 Thin Films Prepared by EPD and SILAR-A+ for Solid Electrolytes

Thin films of gadolinium-doped ceria (GDC) nanoparticles were fabricated as electrolytes for low-temperature solid oxide fuel cells (SOFCs) by combining electrophoretic deposition (EPD) and the successive ionic layer adsorption and reaction-air spray plus (SILAR-A+) method. The Ce1-xGdxO2-x/2 solid solution was synthesized using hydrothermal (HY) and solid-state (SS) procedures to produce high-quality GDC nanoparticles suitable for EPD fabrication. The crystalline structure, cell parameters, and phases of the GDC products were analyzed using X-ray diffraction. Variations in oxygen vacancy concentrations in the GDC samples were achieved through the two synthetic methods. The ionic conductivities of pressed pellets from the HY, SS, and commercial G0.2DC samples, measured at 150 °C, were 0.6 × 10-6, 2.6 × 10-6, and 2.9 × 10-6 S/cm, respectively. These values were determined using electrochemical impedance spectroscopy (EIS) with a simplified equivalent circuit method. The morphologies of G0.2DC thin films prepared via EPD and SILAR-A+ processes were characterized, with particular attention to surface cracking. Crack-free GDC thin films, approximately 730-1200 nm thick, were successfully fabricated on conductive substrates through the hybridization of EPD and SILAR-A+, followed by hydrothermal annealing. EIS and ionic conductivity (1.39 × 10-9 S/cm) measurements of the G0.2DC thin films with thicknesses of 733 nm were performed at 300 °C.

Strain-Enhanced Low-Temperature High Ionic Conductivity in Perovskite Nanopillar-Array Films

Solid oxide ionic conductors with high ionic conductivity are highly desired for oxide-based electrochemical and energy devices, such as solid oxide fuel cells. However, achieving high ionic conductivity at low temperatures, particularly for practical out-of-plane transport applications, remains a challenge. In this study, leveraging the emergent interphase strain methodology, we achieve an exceptional low-temperature out-of-plane ionic conductivity in Na0.5Bi0.5TiO3 (NBT)-MgO nanopillar-array films. This ionic conductivity (0.003 S cm-1 at 400 °C) is over one order of magnitude higher than that of the pure NBT films and surpasses all conventional intermediate-temperature ionic conductors. Combining atomic-scale electron microscopy studies and first-principles calculations, we attribute this enhanced conductivity to the well-defined periodic alignment of NBT and MgO nanopillars, where the interphase tensile strain reaches as large as +2%. This strain expands the c-lattice and weakens the oxygen bonding, reducing oxygen vacancy formation and migration energy. Moreover, the interphase strain greatly enhances the stability of NBT up to 600 °C, well above the bulk transition temperature of 320 °C. On this basis, we clarify the oxygen migration path and establish an unambiguous strain-structure-ionic conductivity relationship. Our results demonstrate new possibilities for designing applicable high-performance ionic conductors through strain engineering.

A Self-Assembled Multiphasic Thin Film as an Oxygen Electrode for Enhanced Durability in Reversible Solid Oxide Cells

The implementation of nanocomposite materials as electrode layers represents a potential turning point for next-generation of solid oxide cells in order to reduce the use of critical raw materials. However, the substitution of bulk electrode materials by thin films is still under debate especially due to the uncertainty about their performance and stability under operando conditions, which restricts their use in real applications. In this work, we propose a multiphase nanocomposite characterized by a highly disordered microstructure and high cationic intermixing as a result from thin-film self-assembly of a perovskite-based mixed ionic-electronic conductor (lanthanum strontium cobaltite) and a fluorite-based pure ionic conductor (samarium-doped ceria) as an oxygen electrode for reversible solid oxide cells. Electrochemical characterization shows remarkable oxygen reduction reaction (fuel cell mode) and oxygen evolution activity (electrolysis mode) in comparison with state-of-the-art bulk electrodes, combined with outstanding long-term stability at operational temperatures of 700 °C. The disordered nanostructure was implemented as a standalone oxygen electrode on commercial anode-supported cells, resulting in high electrical output in fuel cell and electrolysis mode for active layer thicknesses of only 200 nm (>95% decrease in critical raw materials with respect to conventional cathodes). The cell was operated for over 300 h in fuel cell mode displaying excellent stability. Our findings unlock the hidden potential of advanced thin-film technologies for obtaining high-performance disordered electrodes based on nanocomposite self-assembly combining long durability and minimized use of critical raw materials.

Flame synthesis of nanoparticles based on high flux electrostatic atomization burner

This study presents an innovative electrostatic spray flame synthesis (ESFS) reactor that combines the advantages of electrostatic spray and flame synthesis for precise spray control and efficient single-step continuous synthesis. To overcome the limitations of conventional ESFS systems, which often suffer from low atomized precursor flux, we successfully demonstrated a high-flux disk electrostatic atomizer coupled low-swirl flame reactor, achieving a precursor flux of up to 30 ml/h about 30 times higher than that of typical ESFS devices. The atomized precursor being rapidly carried away from the burner is undergoing high-temperature pyrolysis and particle formation through lifted premixed turbulent flames. The ESFS system provides extensive control over parameters such as flame temperature, equivalence ratio, residence time, initial droplet sizes, and precursor concentrations. For illustrative purposes, the ESFS system was utilized to synthesize silica nanoparticles, demonstrating the capability of synthesizing nanoparticles with various properties. By manipulating the collection position and height, the particle size has made a substantial leap from the nanoscale to the micrometer level. This remarkable achievement underscores the system's enormous potential for precise particle size regulation and one-step synthesis of complex structured thin films.

Smart Dual-Exsolved Self-Assembled Anode Enables Efficient and Robust Methane-Fueled Solid Oxide Fuel Cells

Perovskite oxides have emerged as alternative anode materials for hydrocarbon-fueled solid oxide fuel cells (SOFCs). Nevertheless, the sluggish kinetics for hydrocarbon conversion hinder their commercial applications. Herein, a novel dual-exsolved self-assembled anode for CH4 -fueled SOFCs is developed. The designed Ru@Ru-Sr2 Fe1.5 Mo0.5 O6-δ (SFM)/Ru-Gd0.1 Ce0.9 O2-δ (GDC) anode exhibits a unique hierarchical structure of nano-heterointerfaces exsolved on submicron skeletons. As a result, the Ru@Ru-SFM/Ru-GDC anode-based single cell achieves high peak power densities of 1.03 and 0.63 W cm-2 at 800 °C under humidified H2 and CH4 , surpassing most reported perovskite-based anodes. Moreover, this anode demonstrates negligible degradation over 200 h in humidified CH4 , indicating high resistance to carbon deposition. Density functional theory calculations reveal that the created metal-oxide heterointerfaces of Ru@Ru-SFM and Ru@Ru-GDC have higher intrinsic activities for CH4 conversion compared to pristine SFM. These findings highlight a viable design of the dual-exsolved self-assembled anode for efficient and robust hydrocarbon-fueled SOFCs.

Nanoengineering of electrodes via infiltration: an opportunity for developing large-area solid oxide fuel cells with high power density

Although nanoengineering of electrodes opens up the way to the development of solid oxide fuel cells (SOFCs) with improved performance, the practical implementation of such advances in cells suitable for widespread use remains a challenge. Here, the demonstration of large-area, commercially relevant SOFCs with two nanoengineered electrodes that display excellent performance is reported. The self-assembled nanocomposite La0.6Sr0.4CoO3-δ and Co3O4 is strategically designed and deposited into the well-interconnected Ce0.9Gd0.1O2-δ backbone as a cathode to enable an ultra-large electrochemically active region. The nanometer-scale Ce0.8Gd0.2O2-δ is deposited into a conventional Ni/yttria-stabilized zirconia (YSZ) anode to provide more active oxygen exchange kinetics and electronic conductivity compared to YSZ. The resulting nanoengineered cell with an effective size of 4 cm × 4 cm delivers a remarkable power output of 19.2 W per single cell at 0.6 V and 750 °C. These advancements have potential to facilitate the future development of high-performance SOFCs at a large scale by nanoengineering of electrodes and are expected to pave the way for the commercialization of this technology.

Laser nanostructured gold biosensor for proto-oncogene detection

The advancement of biosensor research has been a primary driving force in the continuing progress of modern medical science. While traditional nanofabrication methods have long been the foundation of biosensor research, recent years have seen a shift in the field of nanofabrication towards laser-based techniques. Here we report a gold-based biosensor, with a limit of detection (LoD) 3.18 µM, developed using environmentally friendly Laser Ablation Synthesis in Liquid (LASiS) and Confined Atmospheric Pulsed-laser (CAP) deposition techniques for the first time. The sensors were able detect a DNA fragment corresponding to the longest unpaired sequence of the c-Myc gene, indicating their potential for detecting such fragments in the ctDNA signature of various cancers. The LoD of the developed novel biosensor highlights its reliability and sensitivity as an analytical platform. The reproducibility of the sensor was examined via the production and testing of 200 sensors with the same fabrication methodology. This work offers a scalable, and green approach to fabricating viable biosensors capable of detecting clinically relevant oncogenic targets.

Elucidating the performance benefits enabled by YSZ/Ni-YSZ bilayer thin films in a porous anode-supported cell architecture

Increasing the performance and improving the stability of solid oxide cells are critical requirements for advancing this technology toward commercial applications. In this study, a systematic comparison of anode-supported cells utilizing thin films with those utilizing conventional screen-printed yttria-stabilized zirconia (YSZ) is performed. High-resolution secondary ion mass spectrometry (SIMS) imaging is used to visualize, for the first time, the extent of Ni diffusion into screen-printed microcrystalline YSZ electrolytes of approximately 2-3 μm thickness, due to the high temperature (typically >1300 °C) used in the conventional sintering process. As an alternative approach, dense YSZ thin films and Ni(O)-YSZ nanocomposite layers are prepared using pulsed laser deposition (PLD) at a relatively low temperature of 750 °C. YSZ thin films exhibit densely packed nanocrystalline grains and a remarkable suppression of Ni diffusion, which are further associated with some reduction in the ohmic resistance of the cell, especially in the low temperature regime. Moreover, the use of a Ni-YSZ nanocomposite layer resulted in improved contact at the YSZ/anode interface as well as a higher density of triple phase boundaries due to the nanoscale Ni and YSZ grains being homogeneously distributed throughout the structure. The cells utilizing the YSZ/Ni-YSZ bilayer thin films show excellent performance in fuel cell operation and good durability in short-term operation up to 65 hours. These results provide insights into ways to improve the electrochemical performance of SOCs by utilizing innovative thin film structures in conjunction with commercially viable porous anode-supported cells.

Tuning Cu-Content La1-xSrxNi1-yCuyO3-δ with Strontium Doping as Cobalt-Free Cathode Materials for High-Performance Anode-Supported IT-SOFCs

Cu-content La_1-xSr_xNi_1-yCu_yO_3-δ perovskites with A-site strontium doping have been tuned as cobalt-free cathode materials for high-performance anode-supported SOFCs, working at an intermediate-temperature range. All obtained oxides belong to the R-3c trigonal system, and phase transitions from the R-3c space group to a Pm-3m simple perovskite have been observed by HT-XRD studies. The substitution of lanthanum with strontium lowers the phase transition temperature, while increasing the thermal expansion coefficient (TEC) and oxygen non-stoichiometry δ of the studied materials. The thermal expansion is anisotropic, and TEC values are similar to commonly used solid electrolytes (e.g., 14.1 × 10^-6 K^-1 for La_0.95Sr_0.05Ni_0.5Cu_0.5O_3-δ). The oxygen content of investigated compounds has been determined as a function of temperature. All studied materials are chemically compatible with GDC-10 but react with LSGM and 8YSZ electrolytes. The anode-supported SOFC with a La_0.95Sr_0.05Ni_0.5Cu_0.5O_3-δ cathode presents an excellent power density of 445 mW·cm^-2 at 650 °C in humidified H₂. The results indicate that La_1-xSr_xNi_1-yCu_yO_3-δ perovskites with strontium doping at the A-site can be qualified as promising cathode candidates for anode-supported SOFCs, yielding promising electrochemical performance in the intermediate-temperature range.

Tailoring the Stability of Ti-Doped Sr2Fe1.4TixMo0.6-xO6-δ Electrode Materials for Solid Oxide Fuel Cells

In this work, the stability of Sr₂(FeMo)O_6-δ-type perovskites was tailored by the substitution of Mo with Ti. Redox stable Sr₂Fe_1.4Ti_xMo_0.6-xO_6-δ (x = 0.1, 0.2 and 0.3) perovskites were successfully obtained and evaluated as potential electrode materials for SOFCs. The crystal structure as a function of temperature, microstructure, redox stability, and thermal expansion properties in reducing and oxidizing atmospheres, oxygen content change, and transport properties in air and reducing conditions, as well as chemical stability and compatibility towards typical electrolytes have been systematically studied. All Sr₂Fe_1.4Ti_xMo_0.6-xO_6-δ compounds exhibit a regular crystal structure with Pm-3m space group, showing excellent stability in oxidizing and reducing conditions. The increase of Ti-doping content in materials increases the thermal expansion coefficient (TEC), oxygen content change, and electrical conductivity in air, while it decreases the conductivity in reducing condition. All three materials are stable and compatible with studied electrolytes. Interestingly, redox stable Sr₂Fe_1.4Ti_0.1Mo_0.5O_6-δ, possessing 1 μm grain size, low TEC (15.3 × 10^-6 K^-1), large oxygen content change of 0.72 mol·mol^-1 between 30 and 900 °C, satisfactory conductivity of 4.1-7.3 S·cm^-1 in 5% H₂ at 600-800 °C, and good transport coefficients D and k, could be considered as a potential anode material for SOFCs, and are thus of great interest for further studies.

Nanostructured La0.75Sr0.25Cr0.5Mn0.5O3-Ce0.8Sm0.2O2 Heterointerfaces as All-Ceramic Functional Layers for Solid Oxide Fuel Cell Applications

The use of nanostructured interfaces and advanced functional materials opens up a new playground in the field of solid oxide fuel cells. In this work, we present two all-ceramic thin-film heterostructures based on samarium-doped ceria and lanthanum strontium chromite manganite as promising functional layers for electrode application. The films were fabricated by pulsed laser deposition as bilayers or self-assembled intermixed nanocomposites. The microstructural characterization confirmed the formation of dense, well-differentiated, phases and highlighted the presence of strong cation intermixing in the case of the nanocomposite. The electrochemical properties─solid/gas reactivity and in-plane conductivity─are strongly improved for both heterostructures with respect to the single-phase constituents under anodic conditions (up to fivefold decrease of area-specific resistance and 3 orders of magnitude increase of in-plane conductivity with respect to reference single-phase materials). A remarkable electrochemical activity was also observed for the nanocomposite under an oxidizing atmosphere, with no significant decrease in performance after 400 h of thermal aging. This work shows how the implementation of nanostructuring strategies not only can be used to tune the properties of functional films but also results in a synergistic enhancement of the electrochemical performance, surpassing the parent materials and opening the field for the fabrication of high-performance nanostructured functional layers for application in solid oxide fuel cells and symmetric systems.

Manipulating Electrocatalytic Activity of Perovskite Oxide Through Electrochemical Treatment

Perovskite oxides are widely used in electrochemical cells, profiting from their excellent accommodation of different elements and structure stability. Here, it is reported that when rapidly exceeding the electrochemical stability window of a perovskite oxide through electrochemical treatment, nanoparticles can dynamically exsolve from the perovskite lattice, yielding a nanoparticle decorated material (NDM) with fascinating particle population and distribution. It is reported that as compared to the NDM produced by chemical gas reduction, electrochemical treatment fabricated NDM shows much better electrochemical performance. At 900 °C, a peak power density (PPD) of 896 mW cm^-2 (more than tenfold enhancement) is obtained for a yttrium stabilized zirconia (YSZ) electrolyte-supported symmetrical cell with La_0.43 Ca_0.37 Ti_0.8 Co_0.1 Fe_0.1 O_{3- δ} (LCTCF) electrode after electrochemical treatment for several minutes, while it only reaches to 210 mW cm^-2 after chemical gas treatment for tens of hours using humidified hydrogen as fuel. The study establishes a new fairyland for tuning the performance of-but not limited to-the electrochemical cells.