Electrode Scaffold Research Articles

Improving lithium deposition in porous electrodes: Phase field simulation

The development of structured lithium metal anodes is a key area of focus in the field of lithium battery research, which can significantly improve the energy density, cycle life and safety of lithium metal batteries. In this study, an electrochemical phase field model is used to construct the total free energy of the electrochemical system in conjunction with the effect of the porous electrode scaffold. It investigates the anisotropy of the diffusion coefficient of lithium ions in the electrolyte and the effect of the gradient size of the porous electrode scaffolds on the lithium deposition within the pores. Our numerical results show that increasing the diffusion coefficient of lithium ions in the x-direction cannot improve the lithium deposition within the pores. Instead, it leads to the appearance of lithium dendrites in the top layer of the porous electrode. Appropriately increasing the diffusion coefficient of lithium ions in the y-direction can significantly increase the lithium deposition capacity within the pores. However, excessive increases can lead to a reversal of the lithium deposition capacity within the pores. In addition, adopting the gradient size of the porous electrode scaffold in the y-direction can effectively alleviate the phenomenon that lithium metal is preferentially deposited at the top of the scaffold. These findings provide new ideas for the future design of structured lithium metal anode batteries.

Three‐dimensional‐printed Ni‐based scaffold design accelerates bubble escape for ampere‐level alkaline hydrogen evolution reaction

AbstractAlkaline hydrogen evolution reaction (HER) for scalable hydrogen production largely hinges on addressing the sluggish bubble‐involved kinetics on the traditional Ni‐based electrode, especially for ampere‐level current densities and beyond. Herein, 3D‐printed Ni‐based sulfide (3DPNS) electrodes with varying scaffolds are designed and fabricated. In situ observations at microscopic levels demonstrate that the bubble escape velocity increases with the number of hole sides (HS) in the scaffolds. Subsequently, we conduct multiphysics field simulations to illustrate that as the hole shapes transition from square, pentagon, and hexagon to circle, where a noticeable reduction in the bubble‐attached HS length and the pressure balance time around the bubbles results in a decrease in bubble size and an acceleration in the rate of bubble escape. Ultimately, the 3DPNS electrode with circular hole configurations exhibits the most favorable HER performance with an overpotential of 297 mV at the current density of up to 1000 mA cm−2 for 120 h. The present study highlights a scalable and effective electrode scaffold design that promotes low‐cost and low‐energy green hydrogen production through the ampere‐level alkaline HER.

Stretchable and biodegradable plant-based redox-diffusion batteries.

The redox-diffusion (RD) battery concept introduces an environmentally friendly solution for stretchable batteries in autonomous wearable electronics. By utilising plant-based redox-active biomolecules and cellulose fibers for the electrode scaffold, separator membrane, and current collector, along with a biodegradable elastomer encapsulation, the battery design overcomes the reliance on unsustainable transition metal-based active materials and non-biodegradable elastomers used in existing stretchable batteries. Importantly, it addresses the drawback of limited attainable battery capacity, where increasing the active material loading often leads to thicker and stiffer electrodes with poor mechanical properties. The concept decouples the active material loading from the mechanical structure of the electrode, enabling high mass loadings, while retaining a skin-like young's modulus and stretchability. A stretchable ion-selective membrane facilitates the RD process, allowing two separate redox couples, while preventing crossovers. This results in a high-capacity battery cell that is both electrochemically and mechanically stable, engineered from sustainable plant-based materials. Notably, the battery components are biodegradable at the end of their life, addressing concerns of e-waste and resource depletion.

Modification of Fuel Electrode Microstructure for Protonic Ceramic Cells by the Infiltration of Various Metal Nanoparticles

Proton ceramic cells (PCCs) are promising eco-energy electrochemical energy conversion systems. Proton conducting perovskite oxide electrolytes of PCCs have high ion conductivity at intermediate and low temperatures because of their low activation energy. Most of electrode infiltration studies for fuel electrode supported PCCs were carried out on a thin air electrode layer rather than a thick fuel electrode. In the present study, various metallic nanoparticles (such as Ni, Pd and Pt) were infiltrated in fuel electrode scaffolds to increase the thriple phase boundary (TPB, electrode-electrolyte-gas phase). The fabricated fuel electrode supported PCC consisted of Ni-BaCe0.7Zr0.1Y0.1Yb0.1O3-ẟ cermet fuel electrode, BaCe0.7Zr0.1Y0.1Yb0.1O3-ẟ (BCZYYb) electrolyte, and BCZYYb-La0.6Sr0.4Co0.2Fe0.8O3-ẟ composite air electrode. SEM analysis results revealed that metallic nanoparticles can be infiltrated up to the fuel electrode functional layer and their distribution was uniform through the layer. The PCC with metal nanoparticle infiltrated fuel electrode exhibited higher power density and lower polarization resistance than that with bare fuel electrode. This study shows the electrochemical performance of fuel electrode supported PCCs can be further improved by the facile infiltration method.

(Keynote) Reversible CO2 Reduction Electrocatalysis in Solar-Powered Chemistry

Semi-artificial photosynthesis interfaces biological catalysts with synthetic materials such as electrodes or light absorbers to overcome limitations in natural and artificial photosynthesis. The benefit of using biocatalysts in electrocatalytic CO2 reduction is their electrochemical reversibility that enables their operation at very low overpotentials with high selectivity. This presentation will summarise my research group’s progress in integrating the CO2 reducing enzyme formate dehydrogenase into bespoke hierarchical 3D electrode scaffolds and the exploitation in solar-powered catalysis. I will present the electrochemical features and characterisation of the biocatalyst-material interface and provide my team's understanding of the electrochemical properties of the immobilised formate dehydrogenase. This insight allows the wiring of the biocatalyst into electrocatalytic schemes, photoelectrochemical devices and photocatalytic systems for unique CO2 utilisation reactions. The fundamental insights gained by integrating isolated formate dehydrogenase in electrodes will be presented and the case be made that this enzyme allows opening a solar-to-chemical conversion space that is currently not accessible with purly synthetic or biological catalysts (see uploaded Image as example).Recent publications: (1) Lam et al., Angew. Chem. Int. Ed., 2023, in print. (2) Bhattacharjee et al., Nat. Synth., 2023, 2, 182-92. (3) Badiani et al., J. Am. Chem. Soc., 2022, 144, 14207-16. (4) Cobb et al., Nat. Chem., 2022, 14, 417-24. (5) Edwardes Moore et al., Proc. Natl. Acad. Sci. USA, 2022, 119, e2114097199. (6) Anton Garcia et al., Nat. Synth. 2022, 1, 77-86.Reviews: (1) Fang et al., Chem. Soc. Rev., 2020, 49, 4926–52. (2) Zhang & Reisner, Nature Rev. Chem., 2020, 4, 6–21. (3) Kornienko et al., Acc. Chem. Res., 2019, 52, 1439–44. (4) Kornienko et al., Nature Nanotech., 2018, 13, 890–99

MoS2 Nanoflakes based Kilohertz Electrochemical Capacitors

AbstractAn ultra‐fast electrochemical capacitor (EC) designed for efficient ripple current smoothing was fabricated using vertically oriented MoS2 (VOM) nanoflakes deposited on freestanding carbonized cellulose (CC) sheets as electrodes. The daily used cellulose tissue sheets were transformed into electrode scaffolds through a rapid pyrolysis process within a preheated furnace, on which VOM nanoflakes were formed in a conventional hydrothermal process. With these ~10 μm thick VOM‐CC electrodes, ultrafast ECs with tunable frequency response and specific capacitance density were fabricated. The ECs with a cell‐level areal capacitance density of 0.8 mF/cm2 at 120 Hz were demonstrated for ripple current filtering from 60 Hz to 60 kHz. At a lower frequency response level, EC cell with a large capacitance density of 4.8 mF/cm2 was also demonstrated. With the facile and easily scaled up process to producing the nanostructured electrode, the miniaturized VOM‐CC based ECs have the potential to substitute the bulky aluminum electrolytic capacitors for current smoothing and pulse power applications.

Investigating Mass Transfer Relationships in Stereolithography 3D Printed Electrodes for Redox Flow Batteries

AbstractPorous electrodes govern the electrochemical performance and pumping requirements in redox flow batteries, yet conventional carbon‐fiber‐based porous electrodes have not been tailored to sustain the requirements of liquid‐phase electrochemistry. 3D printing is an effective approach to manufacturing deterministic architectures, enabling the tuning of electrochemical performance and pressure drop. In this work, model grid structures are manufactured with stereolithography 3D printing followed by carbonization and tested as flow battery electrode materials. Microscopy, tomography, spectroscopy, fluid dynamics, and electrochemical diagnostics are employed to investigate the resulting electrode properties, mass transport, and pressure drop of ordered lattice structures. The influence of the printing direction, pillar geometry, and flow field type on the cell performance is investigated and mass transfer vs. electrode structure correlations are elucidated. It is found that the printing direction impacts the electrode performance through a change in morphology, resulting in enhanced performance for diagonally printed electrodes. Furthermore, mass transfer rates within the electrode are improved by helical or triangular pillar shapes or by using interdigitated flow field designs. This study shows the potential of stereolithography 3D printing to manufacture customized electrode scaffolds, which could enable multiscale structures with superior electrochemical performance and low pumping losses.

A Highly Compressible, Elastic, and Air‐Dryable Metallic Aerogels via Magnetic Field‐Assisted Synthesis

AbstractMetallic aerogels emerge as a group of materials for various applications since they exhibit the merits of both metal and aerogel. However, their performance characteristics are largely depreciated by the poor compressibility, elasticity, and complicated preparation process. Herein, a highly compressible and air‐dryable nickel nanowire aerogel (NNWA) is prepared via a facile magnetic‐field‐assisted gelation strategy. Its unique anisotropic lamellar structure and abundant cold‐welded junctions of intertwined nanowires enable superior electric conductivity and compression fatigue resistance. Such a free‐standing NNWA featured with ultralow density (20 mg cm−3) can be directly used as electrode scaffolds for energy storage and electrocatalysis purposes even at high mass loading (e.g., 10 mg cm−2) and large current density (e.g., 1 A cm−2) with superior performance. This method represents a general strategy for producing metallic aerogels with excellent comprehensive performance and mass‐production capability, providing a versatile platform for advanced applications.

(Invited, Digital Presentation) Infiltrated Electrodes for High Temperature Energy Conversion, Electrolysis, and Chemical Synthesis

Solid oxide cell (SOC) infiltrated electrodes typically consist of a ceramic or cermet porous scaffold with the pore walls coated with catalyst particles. The pore size of the scaffold is 1 to 50 mm, whereas the catalyst particles are 10 to 300 nm. This scaffold provides a stable and durable mechanical structure, and the fine catalyst particles provide high surface area for electrochemical and heterogeneous reactions. The scaffold is sintered and bonded to the other layers of the complete cell. After this high temperature processing is finished, catalyst precursor solution is flooded into the scaffold and fired at moderate temperature to form the desired catalyst composition and phase. Because the scaffold is sintered in the absence of catalysts, re-optimization of the fabrication process, ink formulation, deposition process, and sintering protocol is not needed when a new catalyst is introduced to the cell design. Instead, a new precursor solution can be prepared from a stoichiometric mixture of metal salts, with minimal change in processing. This approach makes it straightforward to screen many catalyst compositions in a short period of time, and adapt an existing cell structure for a wide variety of applications.The Lawrence Berkeley National Laboratory metal-supported solid oxide cell (MS-SOC) design has a thin electrode scaffold of zirconia ceramic co-sintered on a thick porous stainless steel support layer. Both layers are coated with infiltrated catalysts. The catalyst precursor solution is an aqueous mixture of metal nitrate salts. After the solution is flooded into the pores of the scaffold, it is dried and heated in air to convert the nitrate salts to mixed metal oxides. The oxides can then be reduced to metals by firing in reducing atmosphere, if desired. The drying rate, heating rate, conversion temperature, and other processing parameters can have a dramatic impact on the catalyst particle morphology and ultimately on the performance and durability of the electrochemical device.Depending on the choice of catalyst composition, the MS-SOCs can be configured as fuel cells, electrolysis cells, or chemical conversion reactors. Several examples will be highlighted, including: fuel cell operation with hydrogen, ethanol, and natural gas; steam electrolysis for hydrogen production; and oxidative coupling of methane for valuable chemical synthesis. In each case, technical progress will be presented with a focus on catalyst development and device performance. Figure 1

Improved electrosorption performance using acid treated electrode scaffold in capacitive deionization

Capacitive deionization (CDI) is an emerging and environmentally friendly technology for water desalination with promising future. However, co-ion expulsion is a prevalent problem during CDI operation which subsequently reduces the electrosorption performance. To address this challenge, we employ acid treated polyurethane sponge (APS) as a scaffold to fabricate the electrodes and nitrogen-doped carbon derived from camphor soot (NCS) as an electrode material. The morphological studies of APS are executed by scanning electron microscopy showing the increase in oxygen content. The contact angle measurement shows the improvement in wettability of APS. The electrochemical analysis of ordinary camphor soot and NCS are performed by cyclic voltammetry and galvanostatic charge-discharge confirming the significant enhancement in the specific capacitance with the nitrogen doping. Moreover, acid treated sponge (APS-NCS) exhibits significantly higher electrosorption capacity than ordinary sponge (OPS-NCS) owing to the mitigation of co-ion expulsion effect. Further, APS-NCS displays better cyclic stability over twenty adsorption-desorption cycles retaining 66.1% of the initial electrosorption capacity. The experimental electrosorption data fits well with Freundlich adsorption isotherm, indicating multilayer adsorption on heterogeneous surface of NCS.

Stable perovskite-fluorite dual-phase composites synthesized by one-pot solid-state reactive sintering for protonic ceramic fuel cells

This work synthesized a series of oxide composites with nominal compositions of BaCe05Zr0.4Y0.1O3-δ (BCZY)-Ce0.5Y0.5O2-δ (YDC) based on the BCZY/YDC molar ratios of 0.5:1, 1:1, 2:1, and 4:1 (BCZY-YDC-0.5–1, BCZY-YDC-1-1, BCZY-YDC-2-1, and BCZY-YDC-4-1) using a one-pot solid state reactive sintering (SSRS) method. The X-ray diffraction (XRD) patterns and refinement proved that the one-pot SSRS at 1450 °C for 12 h could achieve the perovskite-fluorite dual-phase composites (DPCs) with the desired structure compositions. The scanning electron microscopy (SEM) images showed that the two DPCs of BCZY-YDC-1-1 and BCZY-YDC-2-1 formed excellent percolation for perovskite and fluorite phases. The conductivity measurement by electrochemical impedance spectroscopy (EIS) and the transference number measurement by the electromotive force (EMF) test proved that changing the BCZY/YDC molar ratio and operating condition could adjust the DPC's conduction property to make them suitable for electrolytes and electrode scaffolds for protonic ceramic fuel cells (PCFCs). The long-term conductivity testing and the crystal structure analysis after EMF testing under versatile conditions indicated that the DPCs of BCZY-YDC-2-1 and BCZY-YDC-1-1 were durable PCFC component materials. The PCFC button cells with the as-discovered BCZY-YDC-2-1 and BCZY-YDC-1-1 as an electrolyte and an anode scaffold, respectively, and the reported Ba–Ce–Fe–Co–O perovskite-perovskite composite as a cathode showed promising performance under H2/air gradient.

Solid-State Architecture Batteries for Enhanced Rechargeability and Safety (SABERS) for Electric Aircraft

All electric vertical take-off and landing vehicles (eVTOL) for urban air mobility (UAM) concepts face numerous challenging technical barriers before their introduction into the consumer marketplace. The most challenging of these technical barriers to overcome is developing an energy storage system capable of meeting the rigorous aerospace safety and performance criteria. The performance metrics for eVTOL craft are at least 2 times greater than those of electric automobiles. Furthermore, safety is essential for operation of commercial electric aerovehicles. Preliminary systems level analysis has indicated that there are five key properties which must be optimized for successful implementation of battery systems. Those five key criteria are: safety, energy density, power, packaging design and scalability. Current state-of-the-art (SOA) lithium-ion batteries meet or exceed the requirements for electric aviation in the areas of power and scalability, yet are insufficient in the key performance criteria of energy, safety and packaging design. The SABERS concept proposes a battery that meets all five key performance criteria through development of a solid-state architecture battery utilizing high energy density and power density sulfur-selenium cathode with a lithium metal anode. The combination of sulfur and selenium offers a balanced energy-to-power density ratio, which can be tailored to the specific application by altering the stoichiometric ratios of sulfur to selenium. This cathode will be developed by implementing NASA patented holey graphene technology as a highly conductive, ultra-lightweight electrode scaffold. A solid-state electrolyte will be used as a safe, non-flammable replacement to the highly flammable liquid organic electrolytes currently used in SOA lithium-ion batteries. This solid-state lithium-sulfur-selenium cell will be designed into a serial stacking configuration to enable dense packaging of the battery cells. The serial stacking configuration is termed a bipolar stack, which has the advantages of reducing overall cell weight, reducing the amount of interfaced connections for the cell, and minimizing the cooling requirements for the cell. Lastly, optimization of battery components will occur through a robust and rigorous combination of various computational modeling techniques covering multiple length scales. The expected result will be a fully solid-state battery with operational temperatures from 0 °C to 150 °C which provides the required energy density, discharge rates, and inherent safety to meet the strict aerospace performance criteria. This presentation will show initial results that demonstrate the SABERS Team has developed a composite carbon-sulfur cathode which exceeds 1100 Wh/kg at a discharge rate of 0.4C, and 804 Wh/kg at a discharge rate of 1C. Additionally, this presentation will show the SABERS Team multiscale computational modeling approach and has produced a novel particle dynamics method called Solid Electrolyte Sphere Approximation Model (SESAM). SESAM is on the 1-10 µm scale and provides electromechanical and grain interactions for predictive design guidelines for the experimental team to follow. Figure 1

Flexible heteroatom‐doped porous carbon nanofiber cages for electrode scaffolds

AbstractPorous carbon nanofibers (PCNFs) with rich functionalities and high surface areas are important electrode scaffolds to load active materials, but increasing their pore volumes and strength simultaneously is a challenge. Here, we report a scalable method to fabricate B‐F‐N triply doped PCNF cages with high porosity of greater than 92.8% and small bending stiffness of 10 mN by electrospinning the mixed sol of poly(tetrafluoroethylene), poly(vinyl alcohol), boric acid, and carbon nanotubes (CNTs) followed by pyrolysis. The macro‐micro dual‐phase separation creates well‐controlled macropores (>60 nm) and meso‐micropores with large pore volumes (0.55 cm3/g) on carbon nanofibers, while the interior CNTs can cushion the applied stress and render the PCNF films with superior flexibility. Fabricated symmetrical supercapacitors with the PCNF cages exhibit high gravimetric capacitance of 164 F/g at 20 mV/s and 92.5% capacity retention after 20 000 cycles at 2 A/g. The reported approach allows the green synthesis of a new PCNF scaffold material with properties appealing for applications.

Semi-transparent, flexible, and electrically conductive silicon mesh by capillarity-driven welding of vapor-liquid-solid-grown nanowires over large areas

Bottom-up synthesis of semiconductor nanowires (NWs) by the vapor-liquid-solid (VLS) mechanism has enabled diverse technological applications for these nanomaterials. Unlike metallic NWs, however, it has been challenging to form large-area interconnected NW networks. Here, we generate centimeter-scale meshes of mechanically and electrically interconnected Si NWs by sequentially growing, collapsing, and joining the NWs using a capillarity-driven welding mechanism. We fabricate meshes from VLS-grown NWs ranging in diameter from 20 to 100 nm and find that the meshes are three-dimensional with a thickness ranging from ~ 1 to ~ 10 microns depending on the NW diameter. Optical extinction measurements reveal that the networks are semi-transparent with a color that depends on the absorption and scattering characteristics of individual NWs. Moreover, active voltage contrast imaging of both centimeter- and micron-scale meshes reveals widespread electrical connectivity. Using a sacrificial layer, we demonstrate that the mesh can be liberated from the growth substrate, yielding a highly flexible and transparent film. Electrical transport measurements both on the growth substrate and on liberated, flexible films reveal electrical conduction across a centimeter scale with a sheet resistance of ~ 160–180 kΩ/square that does not change significantly upon bending. Given the ability to encode complex functionality in semiconductor NWs through the VLS process, we believe these meshes of networked NWs could find application as neuromorphic memory, electrode scaffolds, and bioelectronic interfaces.

Noncovalent Integration of a Bioinspired Ni Catalyst to Graphene Acid for Reversible Electrocatalytic Hydrogen Oxidation.

Efficient heterogeneous catalysis of hydrogen oxidation reaction (HOR) by platinum group metal (PGM)-free catalysts in proton-exchange membrane (PEM) fuel cells represents a significant challenge toward the development of a sustainable hydrogen economy. Here, we show that graphene acid (GA) can be used as an electrode scaffold for the noncovalent immobilization of a bioinspired nickel bis-diphosphine HOR catalyst. The highly functionalized structure of this material and optimization of the electrode-catalyst assembly sets new benchmark electrocatalytic performances for heterogeneous molecular HOR, with current densities above 30 mA cm–2 at 0.4 V versus reversible hydrogen electrode in acidic aqueous conditions and at room temperature. This study also shows the great potential of GA for catalyst loading improvement and porosity management within nanostructured electrodes toward achieving high current densities with a noble-metal free molecular catalyst.

High‐Performance Flexible Asymmetric Supercapacitors Facilitated by N‐doped Porous Vertical Graphene Nanomesh Arrays

AbstractThe design of self‐supporting electrode scaffold with large surface area, good flexibility, and high electrical conductivity is of great significance to the development of high performance flexible supercapacitors. Herein, we report the fabrication of N‐doped porous vertical graphene nanomesh arrays (NVGMs) on flexible carbon cloth (CC) substrate (CC@NVGMs) via a facile self‐sacrificing template method. The NVGMs provide large surface area, more growth sites of active materials, good electrical conductivity and short diffusion paths, leading to greatly enhanced performance. After decorating MnO2 nanosheets and polypyrrole films on the NVGMs, the hierarchical nanohybrid electrodes show notable improvement of areal capacitances, greatly decrease of equivalent series resistance, significantly enhancement of rate performance, compare to those of the active materials on bare CC. Furthermore, the flexible asymmetric supercapacitor is assembled by these two nanohybrid electrodes has an energy density of up to 1.92 mWh cm−3.

Boosting the Oxygen Electrode Performance of Reversible Protonic Ceramic Electrochemical Cells By Interfacial Engineering

Reversible protonic ceramic electrochemical cell (RePCEC) is one of the most promising energy conversion and storage devices. Because of the low to intermediate operating temperatures (300-650oC), RePCECs demonstrated great potential for simultaneously achieving high performance, long-term durability and low cost of materials 1,2. However, the state-of-the-art RePCECs still cannot satisfy with practical demand, which is significantly ascribed to the high polarization resistance from oxygen (O2) electrode 3. Modification of the phase interfaces in the composite O2 electrodes played vital roles in enhancing the performance by extending active sites, which were extensively investigated in the field of oxygen-ion conducting solid oxide electrochemical cells (O-SOECs) 4,5. However, the engineering of the interfaces in the composite O2 electrode, especially in nanoscale, has not been extensively studied for RePCECs 6. In this work, O2 electrode scaffolds based on the barium cerate-zirconate co-doped with ytterbium and yttrium (BaCe0.7Zr0.1Y0.1Yb0.1O3-δ) are decorated by dual phase triple (e-/O2-/H+) conducting oxide (TCO) nanoparticles of BaCeFeCoO, BaCeFeO and BaCeYCoFeO, respectively. The low O2 electrode polarization resistance, excellent power output and water electrolysis performance were achieved below 600℃. References Duan, C., Kee, R., Zhu, H., Sullivan, N., Zhu, L., Bian, L., Jennings, D. and O’Hayre, R., 2019. Highly efficient reversible protonic ceramic electrochemical cells for power generation and fuel production. Nature Energy, 4(3), p.230.Duan, C., Tong, J., Shang, M., Nikodemski, S., Sanders, M., Ricote, S., Almansoori, A. and O’Hayre, R., 2015. Readily processed protonic ceramic fuel cells with high performance at low temperatures. Science, 349(6254), pp.1321-1326.Fabbri, E., Pergolesi, D. and Traversa, E., 2010. Materials challenges toward proton-conducting oxide fuel cells: a critical review. Chemical Society Reviews, 39(11), pp.4355-4369.Dai, H., He, S., Chen, H., Yu, S. and Guo, L., 2015. Performance enhancement for solid oxide fuel cells using electrolyte surface modification. Journal of Power Sources, 280, pp.406-409.Chao, C.C., Hsu, C.M., Cui, Y. and Prinz, F.B., 2011. Improved solid oxide fuel cell performance with nanostructured electrolytes. ACS nano, 5(7), pp.5692-5696.Bi, L., Shafi, S.P., Da'as, E.H. and Traversa, E., 2018. Tailoring the Cathode-Electrolyte Interface with Nanoparticles for Boosting the Solid Oxide Fuel Cell Performance of Chemically Stable Proton‐Conducting Electrolytes. Small, 14(32), p.1801231.

Facile One Step Rapid Laser Reactive Processing of Protonic Ceramic Electrochemical Cells

Greenhouse gas emissions are becoming more and more serious issue with fossil fuels combustion. Renewable energy sources are the key to solve this problem. Protonic ceramic electrochemical cell (PCEC) is a high-efficiency and cost-effective device for the conversion of renewable electricity into storable fuels (e.g., hydrogen). Because the poor sintering properties of protonic ceramics, conventional furnace sintering methods for PCECs are usually ineffective, which needs long-term and high-temperature firing. A new one-step rapid laser reactive sintering method was developed for achieving fully densified protonic ceramic electrolyte films [1]. Motived by the discovery of rapid laser processing method , we fabricated PCEC single cells through one-step rapid laser scanning. In this cell, the BaCe0.7Zr0.1Y0.1Yb0.1O3-δ (BCZYYb) was selected as electrolyte materials duo to the high ionic conductivity at relatively low temperatures [2]. (BCZYYb) with NiO cermet materials (40:60 wt%) were selected as fuel electrode. BaCe0.6Zr0.3Y0.1O3-δ (BCZY63) was selected oxygen electrode scaffold for further nanoscale phase catalyst infiltration. The porous fuel electrode layer of cell was prepared by 3D printing from the paste comprised of the mixed powders of NiO and BCZYYb stoichiometric amounts precursor solids (BaCO3, CeO2, ZrO2, Y2O3, and Yb2O3). The electrolyte was spray coated on the fuel electrode surface. The coating slurry was composed of BCZYYb stoichiometric amounts precursor solids, 1 wt% NiO was added in it as sintering aid. Then, the scaffold pastes of BCZY63 stoichiometric amounts precursor solids was spray coated on the top surface of BCZYYb green layer. Laser irradiation on the surface of this green single cells in few seconds. Those precursor solids converted into pure BCZYYb phase (both in fuel electrode and electrolyte layer) and BCZY63 phase (scaffold) by solid-state reactive during the laser scanning processing. The fuel electrode layer and oxygen electrode scaffold layer exhibited expected nanoporous microstructure. The BCZYYb electrolyte layer was fully densified with a thickness of ~20 μm, and bond together with the porous electrodes tightly without crack and curvature. The active oxygen electrode material BaCo0.4Fe0.4Zr0.1Y0.1O3−δ nanoparticles were infiltrated into the porous BCZY63 scaffold and calcinated at moderate temperatures. A protonic ceramic electrochemical cell was manufactured successfully with Ideal sandwich structure. This cell exhibited a moderate electrochemical performance. Keywords: Rapid Laser sintering, Protonic ceramic fuel cell, Solid-state reactive sintering, 3D printing.

Rapid Reactive Laser Processing of Protonic Ceramics

Protonic ceramics possess low transport activation energies, which allow for high ionic conductivity at low operating temperatures (250–600°C). The protonic ceramic energy devices such as protonic ceramic fuel cells, protonic ceramic electrolyzers, solid state ammonia synthesis cells, hydrogen or water sensors, steam permeable membrane reactors, and hydrogen permeable membrane reactors, etc., have attracted significant attention recently. It has been recognized that the processing of protonic ceramics with high phase purity and controlled microstructure is equally significant compared with the development of new materials. Though the recently discovered solid state reactive sintering method has been proven as an effective method for processing of protonic ceramics from cost-effective raw materials such as oxides and carbonates, the traditional long-term (more than 10 hours) furnace sintering at high temperatures (>1400°C) is still inevitable. In this work, by combining the selective laser sintering/melting technique and the solid state reactive sintering technique, we developed a new rapid laser reactive processing method for selectively and instantaneously processing protonic ceramics with well-engineered microstructures and high phase purity. More than 10 perovskite oxides and cermets have been successfully fabricated for using as the protonic electrolyte and highly porous protonic electrode scaffolds.

Facile, Solvent‐Free Preparation of High Density, High Mass Loading Sulfur Cathodes Enabled by Dry‐Pressable Holey Graphene Scaffolds

AbstractFor lithium‐sulfur (Li−S) batteries to be practically applicable in large scale, high mass loading and high S content are required for the sulfur (S) cathodes. Most reported S cathode preparation procedures, such as melt infiltration of S into carbon scaffolds followed by conventional solvent‐based slurry casting, are time‐consuming, costly, and lack control with respect to the electrode composition and quality. Here we report the use of a facile room‐temperature procedure that is especially useful in the preparation of high density, high mass loading S cathodes with convenient control of S content and electrode architecture. The solvent‐free and binder‐free procedure is enabled by the use of holey graphene (hG) as a unique dry‐pressable electrode scaffold host to effectively encapsulate S in the conductive matrix. The entire process can be completed within just a few minutes at room temperature, in comparison to much longer time required for most other methods. With effective S utilization, the high mass loadings and high densities of the dry‐pressed hG‐hosted S cathodes result in excellent areal (up to 20 mAh/cm2) and volumetric performance (1787 mAh/cm3 is the highest reported to date), respectively. The hG‐enabled dry‐press method therefore offers an attractive processing option for S composite cathode fabrication toward practical applications.