Focused Ion Beam Scanning Electron Microscopy Research Articles

Impact of micromechanical properties of organic matter on the micro-mesopore structures of the over-mature shale in the Niutitang Formation

The micromechanical properties of organic matter (OM) and organic pore structures in the over-mature stage are crucial for determining shale reservoir quality and assessing shale gas resource potential. However, there is still debate about the influence of micromechanical properties of OM on the micro-mesopore structures in over-mature shale. In this study, shale cores from the Niutitang Formation have been specifically chosen for OM isolation, adsorption testing, atomic force microscopy examination, and focused ion beam scanning electron microscopy (FIB-SEM) analysis to assess the micromechanical properties of OM and pore structures. The findings indicate that organic micropores and mesopores predominantly exhibit elliptical, circular, or irregular shapes. Organic pores mainly provide pore volume (PV) and specific surface area (SSA) of shale. In the over-mature stage, residual kerogen and pyrobitumen transition towards a graphite structure, increasing Young’s modulus of OM. Additionally, as thermal maturity increases, the absence of a rigid mineral framework and pore fluid pressure results in the compaction of pores, leading to a decrease in PV and SSA. The organic micropores are more vulnerable to collapse and compaction because of the increased brittleness of OM. The organic micropores and mesopores gradually evolve from regular circular and elliptical shapes to irregular shapes during the over-mature stage. The research findings provide valuable insights into the micromechanical mechanism of pore evolution in over-mature marine shale within complex structural regions.

Multi-scale characterization of tight carbonate rocks based on digital cores

The characterization of carbonate microstructure is of great significance for the evaluation of carbonate oil and gas resources. However, due to the complexity and heterogeneity of the pore structure of tight carbonate rocks, high-pressure mercury intrusion, nuclear magnetic resonance (NMR) and other methods have different limitations in the characterization. This study takes tight carbonate core samples in the fourth member of the Ordovician Majiagou Formation in the Ordos Basin as the research object, and the rock physics experiments, computed tomography (CT), high resolution large-scale backscatter scanning electron microscopy (MAPS), quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) and focused ion beam-scanning electron microscopy (FIB-SEM) was utilized to characterize the pore structure from micrometer to nanometer, revealing the main mineral composition, and systematically analyzing the relationship between different mineral and pore structures. The results show that the microscopic reservoir space in the study area is mainly composed of inter-crystalline pores, intra-crystalline pores and microfractures; there are obvious differences in the pore structure of different lithologies. The samples with more dolomite have the largest number of pores and throats, the largest coordination number, and the best connectivity; the samples with more calcite have the smallest pore radius. The presence of quartz is conducive to the preservation of pores. This multi-scale characterization method using digital core technology provides us with comprehensive pore characteristic, provides important clues for further understanding the pore structure of tight carbonate reservoirs.

Antibacterial and photocatalytic activities of biosynthesized zinc oxide nanoparticle using novel plant P. macrosolen L. leaf extract

In this study, ZnO nanoparticles were produced by an easy and cost effective approach using P. macrosolen L. leaf extract and zinc chloride as Zn ion source. The as-biosynthesized ZnO nanoparticles were analyzed by powder-X-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, UV–visible spectroscopy, Focused ion beam-scanning electron microscopy (FIB-SEM) and energy dispersive X-ray (EDX) characterization techniques. The XRD result revealed the formations of ZnO-nanoparticles with hexagonal structure, spherical like shape and average crystalline size of 47 nm. The presence of flavonoids in P. macrosolen L. extracts was confirmed by phytochemical tests, indicating that flavonoids primarily acted as reducing agents during nanoparticle formation. The FTIR spectrum also revealed broad and strong peaks corresponding to –OH groups, confirming the high concentration of phenolic acids present in the extract. The energy band gap of the biosynthesized ZnO Nanoparticles, calculated using the Tauc relation, was found to be 3.0 eV, indicating the presence of a blue shift. FIB-SEM was used to analyze the microstructure and identify any aggregations. The EDX analysis revealed the presence of zinc and oxygen, with weights of 16.33% and 83.67%, respectively. The disk diffusion test was performed on solid agar plates and demonstrated that the substance is effective against E. coli bacteria as an antibacterial agent. The photocatalytic degradation rate constants of the optimized ZnO samples under visible light are approximately 0.06455 min⁻1 for MO and 0.04865 min⁻1 for TB, achieving 94.47% and 92.34% degradation of MO and TB, respectively. These rates are significantly higher compared to unmodified ZnO, which has a degradation rate of 0.0075 min⁻1. The improvement in visible-light photocatalytic performance can be attributed to the formation of ZnO nanoparticles, which arise from the matching of crystal lattices and energy bands in ZnO. ZnO Nanoparticles produce excited electrons under visible light irradiation. These excited electrons in the ZnO nanoparticles are directly transferred to the conduction band (CB), resulting in notable visible light photocatalytic performance.

Site-specific plan-view (S)TEM sample preparation from thin films using a dual-beam FIB-SEM.

To fully evaluate the atomic structure, and associated properties of materials using transmission electron microscopy, examination of samples from three non-collinear orientations is needed. This is particularly challenging for thin films and nanoscale devices built on substrates due to limitations with plan-view sample preparation. In this work, a new method for preparation of high-quality, site-specific, plan-view TEM samples from thin-films grown on substrates, is presented and discussed. It is based on using a dual-beam focused ion beam scanning electron microscope (FIB-SEM) system. To demonstrate the method, the samples were prepared from thin films of perovskite oxide BaSnO3 grown on a SrTiO3 substrate and metal oxide IrO2 on a TiO2 substrate, ranging from 20-80 nm in thicknesses using molecular beam epitaxy. While the method is optimized for the thin films, it can be extended to other site-specific plan-view samples and devices build on wafers. Aberration-corrected STEM was used to evaluate the quality of the samples and their applicability for atomic-resolution imaging and analysis.

Rapid Synthesis of Nanoporous Zn Powder by Selective Etching of Al from Micrometer-Sized Zn-Al Powder Particles Produced by Gas Atomization and Its Application in Hydrogen Generation.

The scalable synthesis of non-precious nanoporous metals, such as nanoporous zinc (NP-Zn), nanoporous iron (NP-Fe), and nanoporous aluminum (NP-Al), is crucial for large-scale production of hydrogen through the reaction between non-precious metals and water. The fabrication of bulk NP-Zn by selective removal of Al from sub-centimeter-sized arc-melted Zn-Al parent alloys through free corrosion dealloying usually takes a few days. Here, we demonstrate that this free corrosion dealloying process can be reduced from a few days to 4 min simply using micrometer-sized Zn-Al powder particles with nominal composition Zn40Al60 atomic % produced by gas atomization as the parent alloy. Reducing the size of the parent alloy significantly enhances the dealloying rate. Furthermore, Al and Zn are phase-separated in Zn-Al powder particles due to the gas atomization process, making removing the sacrificial Al phase easy. We used various techniques, including X-ray diffraction, Xe+ plasma focused ion beam/scanning electron microscopy (FIB/SEM), energy-dispersive spectroscopy (EDS), and inductively coupled plasma optical emission spectroscopy (ICP-OES) to thoroughly characterize these materials before and after free corrosion dealloying. The fabricated NP-Zn powder exhibits a hierarchical ligament/pore morphology, with tiny structures with a size of ≈10 nm coming from Zn nanoparticle aggregation during dealloying and large structures in the range of ≈50-200 nm coming from the removal of the sacrificial Al phase. We demonstrate that this NP-Zn can spontaneously react with water at near-neutral pH to produce hydrogen and zinc oxide solid byproducts with a hydrogen generation yield of ≈52% within 60 min.

Photonic Band Gap Engineering by Varying the Inverse Opal Wall Thickness.

We demonstrate the band gap programming of inverse opals by fabrication of different wall thickness by atomic layer deposition (ALD). The opal templates were synthesized using polystyrene and carbon nanospheres by the vertical deposition method. The structure and properties of the TiO2 inverse opal samples were investigated using Scanning Electron Microscope (SEM) and Focused Ion Beam Scanning Electron Microscopy (FIB-SEM), Energy Dispersive X-ray analysis (EDX), X-ray Diffraction (XRD) and Finite Difference Time Domain (FDTD) simulations. The photonic properties can be well detected by UV-Vis reflectance spectroscopy, while diffuse reflectance spectroscopy appears to be less sensitive. The samples showed visible light photocatalytic properties using Raman microscopy and UV-Visible spectrophotometry, and a newly developed digital photography-based detection method to track dye degradation. In our work, we stretch the boundaries of a working inverse opal to make it commercially more available while avoiding fully filling and using cheaper, but lower-quality, carbon nanosphere sacrificial templates.

Interface Degradation of LaCl3-Based Solid Electrolytes Coupled with Ultrahigh-Nickel Cathodes.

Despite competitive compatibility with high-nickel cathodes, chloride solid electrolytes (SEs) still experience inevitable side reactions at the cathode/SE interface, causing capacity decay in all-solid-state lithium batteries (ASSLBs) during cycling. Herein, a three-electrode ASSLB testing device is developed to comprehensively reveal the interface failure mechanisms of the ultrahigh-nickel LiNi0.92Co0.05Mn0.03O2 (NCM92) cathode paired with LaCl3-based chloride SE Li0.447La0.475Zr0.059Ta0.179Cl3 (LLZTC). Distribution of relaxation time (DRT) analysis clearly shows the ASSLB degradation accompanied by a significant NCM92/LLZTC interface impedance increase, which becomes more pronounced at the higher cutoff charging voltage of 4.8 V vs Li+/Li. Furthermore, time-of-flight secondary ion mass spectrometry (ToF-SIMS) and focused ion beam scanning electron microscopy (FIB-SEM) analysis also confirm the deterioration arising from active lattice oxygen and loss of physical contact at the NCM92/LLZTC interface. These findings reveal both electrochemical degradation and physical contact failure at the cathode/SE interface as key causes of the ASSLBs' capacity decay.

Influence of Hierarchical Porosity of Electrodes on the Energy and Power Densities of Electrochemical Devices

Influence of specific micropore-, mesopore and total surface areas and pore volumes and other porosity characteristics on the electrochemical parameters and power density of electrochemical devices will be discussed [1-3]. Many ionic liquids (EtMeImBF4, Et4B(CN4)4, etc.) and organic (Et3MeNBF4, Et4NBF4, Et3PrNBF4, etc.) and inorganic salts (LiBF4, NaBF4, LiClO4, NaClO4, LiPF6, NaPF6, Rb2SO4, Li2SO4, Na2SO4, LiI, NaI, NaBr, LiBr, LiCl, NaCl, CsBF4, Cs carborane, etc.) based electrolytes in various solvents (H2O, acetonitrile, ethyl methyl carbonate, propylene carbonate, diethyl carbonate, acetone) and their mixtures with specific chemical additions (fluoroethyl carbonate, propylene sulfite, diethyl sulfite) will be discussed. 1M 3-ethyl-methyl-ammonium tetrafluoroborate (Et3MeNBF4) solution in acetonitrile and on 1-ethyl-3-methylimidazolium tetrafluoroborate (Et3MeImBF4) will be analyzed for all carbon materials as reference data.The pore size distribution calculated from N2, CO2 and Ar adsorption isotherms using mainly Carbon 2D non-local density functional theory for heterogeneous surface (2D-NLDFT-HS) model will be compared with crystallographic characteristics obtained by Raman, X-ray diffraction, focused ion beam scanning electron microscopy (FIB-SEM), high-resolution transmission electron microscopy, (HR-TEM) combined with low electron energy diffraction (EELS) and selected area electron diffraction (SAED) methods. Small angle and wide-angle X-ray scattering (SAXS and WAXS), small-angel neutron diffraction (SANS), quasielastic (QENS) and inelastic neutron scattering (INES) etc. data will be analyzed. Electrochemical temperature dependent XRD will be used for analysis of influence of temperature and electrode potential on the structural parameters at various temperatures and electrode potentials.For surface analysis, electrochemical oxidation and reduction processes at electrode | vacuum and electrode | ionic liquid interfaces have been studied using synchrotron radiation photoelectron spectroscopy (Sr-XPS) and near ambient pressure dual chamber synchrotron beam XPS (Sr-NAP-DC-XPS) methods.Post–mortem analysis of electrodes applied under high temperature and high electrode overpotential conditions was conducted using FIB-TOF-SIMS (secondary ion mass spectroscopy), FIB-SEM –EDX and thermogravimetry methods to determine the effect of electrode polarization and temperature on the intercalation layer formation kinetics (mass-transfer depths) for electrodes with different micro-meso-macro porosity. For selected flatter electrodes, the in situ STM and AFM measurements combined with Raman spectroscopy surface analysis have been used. Surface structures of adsorbed and formed interfacial layers will be simulated by computation analysis using different DFT, molecular dynamic etc. methods.Based on systematic analysis on results collected, it will be demonstrated that the chemical composition and crystallographic structure of precursor material, chemical composition of activators, synthesis and activation conditions have decisive influence on the shape of the pores (spherical, cylindrical or slit-shape pores, mixed cylindrical and slit-shape, etc.) and on the hierarchically porous structure and electrical conductivity of carbon, activated carbon and complex oxide materials. For carbon materials with mixed cylindrical-slit shape hierarchical porosity, very high series and parallel capacitances from 130 to 168 F g-1 in 1M Et3MeNBF4+ acetonitrile and up to 155 F g-1 in EtMeImBF4 ionic liquid have been established. Very high gravimetric power density (up to 150kW kg- 1) has been obtained for optimized EDLCs with sol-gel method fabricated electrodes and moderate gravimetric and volumetric energy densities for d-glucose and Estonian peat derived carbons based electrodes [1-4]. The very short characteristic charging/discharging times (lower than 0.3 s for Et3MeNBF4 +AN and 1.0 s for EtMeImBF4) can be achieved for optimized EDLCs. Complicated adsorption kinetics of halide ions at micro-mesoporous carbon electrodes has been observed and explained by the strong chemical adsorption of halides. Very strong influence of hierarchical porosity and micropores inner surface roughness on the hydrogen adsorption parameters has been established by SANS/SAXS methods [5,6]. Strong influence of preparation conditions of Pt-free electro-catalysts for polymer membrane and alkaline fuel cells and electrolysis cells will be demonstrated.Acknowledgements. This work was supported by the European Regional Development Fund (TK141), Estonian Ministry of Education and Research (TK210), Personal Research Grant PRG676, by the project „Increasing the knowledge intensity of Ida-Viru entrepreneurship” co-funded by the European Union (ÕÜF12, ÕÜF1).

Three-Dimensional Imaging of Large-Volume Lithium Metal Microstructure by Xenon Plasma Focused Ion Beam

Advanced energy storage systems are increasingly in demand due to the rising needs of portable electronics, electric vehicles, and grid-scale energy storage. Lithium (Li) metal stands out as an exceptional battery anode with its high theoretical specific capacity (3860 mA g-1 compared to graphite's 372 mA g-1) and low redox potential (-3.04 V vs. the standard hydrogen electrode). However, practical Li metal anodes often face challenges such as low Coulombic efficiency, short cycle life, and safety concerns, mainly due to the reactive nature of Li metal and the unpredictable deposition with diverse morphologies.Developing advanced Li metal anodes requires a deep understanding of their electrode structure. It is indispensable to find three-dimensional (3D) images. However, obtaining accurate 3D imaging of Li anodes poses significant challenges. On one hand, the non-uniform electrodeposition of Li metal necessitates a large sample to accurately represent the entire electrode. On the other hand, achieving high resolution is essential for distinguishing the complex phases within the Li electrode, including metallic Li, solid electrolyte interphase (SEI), and pores. While popular 3D imaging technologies like X-ray computed tomography and nuclear magnetic resonance imaging offer comprehensive size information, they often struggle with limitations in resolution or imaging contrast. Traditional focused ion beam-scanning electron microscopy (FIB/SEM) can provide high-resolution images at nanoscale, but its use of gallium ion (Ga+) leads to issues such as ion implantation and limited size (≤ 10 μm). An emerging alternative, plasma FIB/SEM (PFIB/SEM), coupled with Xenon (Xe) gas, featured by both high resolution and large volume size, presents a promising solution, making it appealing for characterization of Li electrode.In this presentation, Xe PFIB is employed for 3D imaging of electrodeposited Li with a large volume (200 μm in dimension) and high resolution (50 nm per pixel). This approach facilitates the clear identification of two phases: deposited Li metal and SEI/pores. It enables the quantification of their spatial distribution, packing density, and specific surface area, crucial parameters determining the Coulombic efficiency of the deposited Li anode. Furthermore, the ability to separate individual Li particles provides quantitative information on volume size, particle number, and shape. These quantitative results establish a robust mathematical relationship with the overpotential of Li deposition, significantly enhancing our understanding of the Li electrodeposition process.Leveraging the large volume and high-resolution 3D information obtained through Xe PFIB-SEM, this work demonstrates its significance in assessing and understanding electrodeposited Li, offering valuable insights for designing advanced Li metal anodes. Xe PFIB-SEM methodology is poised to become a pivotal technique for 3D characterization in energy storage materials and related fields.

Microstructural Analysis of Stainless Steel Support/Ni-YSZ Anode Interface in Metal-Supported SOFCs

Solid oxide fuel cells (SOFCs) have attracted attention due to their high energy conversion efficiency and fuel flexibility. However, conventional anode-supported SOFCs composed solely of ceramics are susceptible to thermal stress such as rapid temperature rises and drops, which can cause cell cracks. Therefore, metal-supported SOFCs (MS-SOFCs) have been devised that use a stainless steel with excellent heat resistance as a support. In MS-SOFCs, elemental diffusion from the metal support during the cell manufacturing process causes microstructural changes in electrodes, leading to a reduction in cell performance [1, 2]. Although the microstructure and diffusion state of elements at the support layer/anode interface are different from those of conventional anode-supported cells, the phenomena as well as the chemical and physical states that occur at the interface have not been sufficiently studied. In this study, then, the microstructural characteristics of the stainless steel support/anode interface were quantitatively analyzed to understand the phenomena occurring and to develop methods to suppress the diffusion of metallic elements.Gd-doped CeO2 (GDC) was coated as a diffusion barrier layer (DBL) on a SUS430 stainless steel substrate by magnetron sputtering, followed by the NiO-YSZ (8 mol% Y2O3-ZrO2) slurry coating. The composition of SUS430 is given in Table 1. Samples without DBL were also fabricated. These samples were sintered at 1250 ºC for 10 hours in 50% H2-50% Ar. Three-dimensional reconstruction of the microstructures of these samples was performed using a focused ion beam-scanning electron microscope (FIB-SEM), and microstructural parameters were calculated. In addition, elemental diffusion at the interface was analyzed using an energy dispersive X-ray spectroscopy (EDS) analysis.When the sample was sintered at 1250 °C in a reducing atmosphere, the diffusion of Fe was significantly suppressed by the insertion of DBL. Therefore, it was confirmed that the GDC layer is effective to suppress the Fe diffusion as well as to prevent the formation of solid solution with Ni. However, no significant difference in Cr diffusion was observed. Furthermore, SEM observation revealed that the Ni surface was partially covered with Mn-Cr oxides. The formation of such a characteristic structure had a negative effect to reduce the effective triple phase boundary (TPB) length of the anode. Thus, it was concluded that the insertion of GDC layer suppressed the formation of Ni-Fe solid solution, while the patrial coverage of the Ni surface with Mn-Cr oxides reduced the effective TPB length.AcknowledgementsThis paper is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).[1] M.C. Tucker, J. Power Sources, 195, 15 (2010).[2] T. Franco, et al., ECS Transactions, 7, 771, (2007). Figure 1

Influence of Local Environment Under Polarization on Wettability of Ni/YSZ Interface

In solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs), degradation of hydrogen electrode during long–term operation is one of the issues to be solved. Migration and aggregation of Ni particles are major factors of this degradation, and especially after steam electrolysis operation, intense Ni migration has been observed at the hydrogen electrode/electrolyte interface [1]. This phenomenon is assumed to be related to the change in wettability of the Ni/electrolyte interface under polarization [2]. A quantitative measurement of interface wettability is the concept of contact angle. It is known that the contact angle is determined by the balance between the surface tension of contacting materials and the interfacial tension. Contact angle analysis is usually used for liquid–solid interfaces, but it has also been suggested to be useful for the characterization of solid metal–oxide interfaces [3]. Therefore, the aim of this study was to directly measure the contact angle between Ni and YSZ electrolyte under various conditions in order to quantify the changes in wettability at the interface.Ni thin film electrodes were prepared by sputtering Ni on YSZ electrolyte. Using this model electrode, electrochemical measurements were performed under open circuit holding or a potentiostatic operation (SOFC operation or SOEC operation) at high temperatures. Subsequently, postmorterm analysis of the samples was performed using a Focused Ion Beam–Scanning Electron Microscope (FIB–SEM). Using the cross–sectional SEM images of the model electrode, the contact angle was calculated by distinguishing the three phases of Ni, YSZ, and pores based on the difference in contrast of each phase. The analysis revealed that the wettability of the Ni/YSZ electrolyte interface changed depending on the operation mode. Specifically, the contact angle after SOEC operation increased compared to values after open circuit holding or SOFC operation. This phenomenon is thought to be related to changes in oxygen potential.AcknowledgementsThis paper is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

Understanding Structure Differences of Iridium Oxides Depends on Loading in Proton Exchange Membrane Electrolyzers

Proton exchange membrane water electrolyzers (PEMWEs) have drawn attention among various hydrogen production technologies due to their zero-emission, high conversion efficiency, high hydrogen purity (>99.99%), and quick response under dynamic operation.1,2 With these auspicious characteristics in PEMWEs, they are believed to produce 40 % of green hydrogen by 2050 among all electrolyzer technologies. Nonetheless, many bottlenecks within PEMWEs still hinder their broader commercialization. Iridium oxide is the most widely used oxygen evolution reaction (OER) electrocatalyst at the anode. Moreover, this catalyst occupies the biggest portion (26–47%) of the overall cost of PEMWE systems, mostly due to the scarcity of iridium.3 Commercial iridium oxide catalysts are generally two types depending on the material structure: amorphous IrOx and crystalline IrO2. The trade-off relationship exists in catalytic activity vs. stability between amorphous and crystalline IrOx catalysts.4–6 To overcome these problems, fundamental studies of iridium oxide need to be conducted to reduce catalyst loading while maintaining high performance.Herein, we report the new iridium oxide catalysts (amorphous IrOx, crystalline IrO2, Ishifuku Metal) for the first time. These new iridium oxide catalysts are physically and electrochemically characterized. To be specific, we confirm the distinct characteristics of each catalyst using scanning electron microscopy (SEM), focused ion beam SEM (FIB-SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) analysis with nitrogen adsorption isotherm, Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). As a result, the crystalline IrO2 has a unique morphology with grown needles onto catalyst particles thereby the BET specific surface area of crystalline IrO2 (~110 m2 g-1) is over two times higher than amorphous IrOx (~50 m2 g-1). Electrochemical performance is evaluated for varied catalyst loadings of membrane electrode assembly (MEA). The catalyst loadings (0.10, 0.26, 0.35, and 0.85 mgIrOx cm-2) for both anode catalysts were prepared. The CV results of amorphous IrOx exhibit unique redox peaks under specific voltage (~0.8 and ~1.2 V vs. RHE), which indicates the transition of oxidation state. These peaks develop with CV cycling and become fully developed after 100 cycles, indicating that the surface of the catalyst takes some time to activate. On the other hand, crystalline IrO2 shows no specific redox peaks but rather has a double-layer capacitance under lower voltage (<0.5 V vs. RHE). Figure 1 shows 1.92 V (amorphous) and 1.94 V (crystalline) at 5 A cm-2 for 0.85 mg cm-2 loading, respectively. Both catalysts showed relatively low Tafel slopes of 43.8 mV dec-1 (amorphous IrOx) and 53.7 mV dec-1 (crystalline IrO2). This presentation will correlate the electrochemical performance described here to the structural properties of these two types of IrOx catalysts. Figure 1. Polarization curve for prepared iridium oxide catalysts (amorphous IrOx and crystalline IrO2). Both cells have anode loadings of 0.85 mg cm-2, cell temperature at 60 °C, 10 sccm for H2O flow rate at the anode, and dry for the cathode.

Ionomer-Free Electrocatalyst of Sulfonate Chemical Group Introduced on Carbon As a Proton-Conductive Support for PEMFC

The needs of find diversify energy resources and new energy media to replace the fossil fuel to overcome the environment pollution problem. Owing to their cleanliness and high energy densities, polymer electrolyte membrane fuel cell (PEMFC) are vital devices for realizing a sustainable society. Reduce the cost of Pt catalyst from catalyst layer (CL) in PEMFC is the key to realize commercialization. Especially, the Pt utilization efficiency is highly dependent on the structure of Pt interface in cathode, where proton and electrons are delivered though a proton-conductive carbon support, while the O2 diffused though the porous network. Therefore, optimizing Pt interface structure and porous network in CL are important for the efficiency and utilization. To control the structure of the CL, especially for the coverage of the ionomer, significantly related to the proton conduction and O2 diffusion, namely, increasing the ionomer content increases proton conductivity but decreases O2 diffusivity in the porous network. In addition, sulfate anions or sulfonate groups in ionomers strongly adsorb on the Pt surface and acts as barriers for O2 permeation, resulting in increased overpotentials at the cathode. Therefore, even if the ionomer content is optimized, the presence of ionomers on Pt catalysts inevitably causes Pt poisoning.In this study, to avoid these issues, we prepared proton-conductive carbon supports, in which acid groups were grafted on the surface of carbon black (CB) to afford surface proton conduction. Then, these carbon supports with Pt loaded on the surface were tested as ionomer-free electrocatalysts for PEMFCs. As the acid grafted, sulfonated aryl diazonium was chosen since their radical addition process proceeds under mild condition.The acid-grafted carbon named SCB was characterized by X-ray photoelectron spectroscopy (XPS), resulting a new S 2p and S 2s peaks at ~168mV and ~232mV, respectively, from sulfonated aryl diazonium. The loading of Pt nanoparticles was carried out using Pt(acac)2 as the Pt precursor to reducing Pt particles under H2 atmosphere, resulting a homogeneous dispersion of Pt nanoparticels with diameters of 2.6 ± 0.3 nm on SCB. While control Pt nanoparticles on CB (CB/Pt) using H2PtCl6·6H2O and ethylene glycol as the Pt source and reducing agent, respectively (polyol method) had nanoparticles with diameters of 2.1 ± 0.5 nm. Using SCB/Pt and CB/Pt, SCB/Pt ink without ionomer added and CB/Pt ink with ionomer 28wt% were casted on Nafion membrane to evaluate the single cell performance.In-situ CV of SCB/Pt cell and CB/Pt cell were measured by using H2 and N2 at the anode and cathode, respectively. Interestingly, the ECSA of SCB/Pt (38.0 m2 g−1) was comparable to that of CB/Pt (37.1 m2 g−1). Polarization curves of SCB and CB cell are measured at 80 °C with 100% RH to confirm to activation of acid-grafted carbon support catalyst. In most of the current density regions, the potential of SCB/Pt cell was lower than that of CB/Pt cell and the maximum power density of SCB/Pt cell (0.49 W cm−2) was slightly lower than that of CB/Pt cell (0.58 W cm−2), which is likely caused by the higher proton resistance of SCB/Pt cell with 2.9 Ω cm−2, but 0.14 Ω cm−2 for CB/Pt cell. However, at lower voltages, SCB/Pt cell showed a higher current density (>1.8 A cm−2) than CB/Pt cell (∼1.7 A cm−2). As potential drops are often observed in the high current region when the O2 supply in the CL is insufficient, we concluded that superior O2 diffusion is a unique characteristic of this ionomer-free system.Furthermore, to elucidate the superior performance of SCB/Pt cell at high current densities, the microporous structure of the cathode CL was analyzed using cross-section images collected using focused ion beam scanning electron microscopy (FIB-SEM). The three-dimensional (3D) reconstructed structures CLs revealed that the CL of SCB/Pt contained smaller agglomerations than that of CB/Pt. In addition, the calculated porosity for the CL of SCB/Pt (0.614) was larger than that for the CL of CB/Pt (0.561). It is indicated that the higher potentials observed at high currents are associated with the formation of a porous structure with larger pores in SCB/Pt CL as compared to that in CB/Pt CL [1].[1] Yoshihara R, Wu D, Phua YK, Nagashima A, Choi E, Jayawickrama SM, et al. Ionomer-free electrocatalyst using acid-grafted carbon black as a proton-conductive support. Journal of Power Sources. 2022;529:231192. Figure 1

Unraveling a Novel Degradation Mechanism in Industrial Scale PEM Electrolytic Cells by Multimodal Analysis Based on X-Ray Computed Tomography

Proton exchange membrane electrolytic cell (PEMEC) is a key technology in the production of sustainable “green” hydrogen. In such systems, as an electrolyte and physical barrier, a proton exchange membrane (PEM) is applied [1]. Overall, the performance of a PEMEC depends on many factors, such as the catalyst material and its loading, the thickness of electrodes and membrane and the interface roughness for example. While studies have reported changes in PEM microstructures, even in operando [2], there is still limited data regarding process heterogeneity in large industrial-scale cells operating over long periods. However, enhancing the performance and durability of PEMEC is crucial to propel this technology forward, enabling its up-scaling and market introduction on an industrial level.In this study, we investigated the morphology and degradation mechanisms of membrane electrode assemblies (MEAs) in PEMEC using a multimodal analytical approach. The investigated MEAs, which were operated for 5000 hours, consisted of an Ir coated anode and a Pt cathode and were as large as several hundred cm².Firstly, the morphology of post-test MEAs was analyzed by the means of X-ray computed tomography (XCT). Here, a measurement protocol provided imaging data at multiple scales. Furthermore, the field-of-view was greatly increased by rolling the MEA and later unwrapping the reconstructed image. A simple, yet robust segmentation algorithm, allowed to automatically delineate features like agglomerates and cracks inside the electrodes post-test. This thorough XCT study led to the discovery of a novel degradation mechanism in PEMEC, which, to the best of our knowledge, has not yet been discussed in literature. The found morphological anomaly was linked to electrochemical behavior of the cell by analyzing electrochemical impedance spectra (EIS) and measuring the gas permeation through the MEA. Current sensing atomic force microscopy (AFM) was used to analyze the electrical properties in the vicinity of the detected anomalies.Additionally, metallographic techniques such as focused ion beam scanning electron microscopy (FIB/SEM) and transmission electron microscopy (TEM), combined with energy-dispersive X-ray spectroscopy (EDS) and Raman spectroscopy, provided high-resolution local morphology and the chemical composition within the affected regions. Finally, after collecting all this data, we were able to propose physical 1-D and 3-D models for the observed phenomena and their effects on PEMEC.In conclusion, this study on a previously unknown degradation mechanism inside MEAs demonstrates the significance of a multimodal analytical approach when it comes to detecting, understanding and mitigating the degradation in PEMEC. Such an approach will further pave the way for enhanced performance and durability in PEMEC on an industrial scale.[1] B. Han et al., Electrochimica Acta, 2016, 188, 317-326.[2] E. Leonard et al., Sustainable Energy Fuels, 2020, 4, 921-931. Figure 1

Effect of Contamination in the Carbon Catalyst Support on Chemical Degradation of Polymer Electrolyte Membranes in Fuel Cells

Introduction One of the key components of polymer electrolyte fuel cells (PEFCs) is the polymer electrolyte membrane (PEM). The PEM facilitates the transport of protons from the anode to the cathode, acts as an electronic insulator to prevent short circuits, and plays a role in preventing the direct reaction of hydrogen gas and oxygen in air. One of the major technical issues with PEMs is their chemical degradation, causing decomposition of their molecular structure. This leads to reduced protonic conductivity, increased hydrogen and oxygen crossover, and reduced mechanical strength, all of which significantly affect the power generation performance and durability of PEFCs (1). In addition, in our laboratory, the use of SnO2 and mesoporous carbon (MC) as cathode catalyst supports has been suggested to suppress membrane degradation (2). However, the relationship between the cathode catalyst materials and the chemical degradation of PEM has not yet been fully understood. Here in this study, we conduct durability tests such as accelerated chemical degradation of PEM in cells using cathode electrocatalysts with different carbon support materials, aiming to clarify the effects of carbon support materials properties (structure, contaminants, and graphitization) on the chemical degradation of electrolyte membranes. Experimental A commercial Pt/KB catalyst (TEC10E50E, Tanaka Kikinzoku Kogyo, Japan) was used as the anode catalyst. Several types of cathode catalysts were applied and compared: the commercial Pt/KB; Pt/MC where Pt was directly deposited on the MC; and various electrocatalysts where Pt was directly deposited on carbon supports such as graphitized AB (acetylene black). The durability test at open circuit voltage (OCV) was performed for 100 h. Before and after the durability test, cell performance, hydrogen crossover current density, and electrochemical surface area (ECSA) were characterized. The degree of membrane degradation was evaluated by measuring fluoride-ion emission rate (FER) by ion chromatography, and membrane thickness by cross-sectional observation with a focused-ion-beam scanning electron microscope (FIB-SEM), as illustrated in Fig.1. Moreover, contaminants and graphitization of the carbon support materials were also analyzed, and their relationship to membrane degradation was considered. Results and discussion The results of OCV holding tests up to 100 h for four different MEAs are shown in Fig. 2. The voltage drop in using Pt/MC as cathode catalysts was smaller than that in using Pt/KB. The FER of Pt/MC as cathode catalysts was lower than that of Pt/KB as shown in Fig. 3, suggesting that the use of MC as carbon supports may suppress PEM degradation. In this presentation, we will show the effects of carbon support materials properties (structure, contaminants, and graphitization) in cathode catalysts on PEM degradation, and discuss possible mechanisms based on the characteristics of various carbon supports. Acknowledgements This paper is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). An educational part for young scientists was supported by the Japan Science and Technology Agency (JST) through the program “Adopting Sustainable Partnerships for Innovative Research Ecosystem” (ASPIRE), Grant Number JPMJAP2307. The presenting author (S. Nakamura) is supported by the Miyamoto Jun-ichi Hydrogen Research Award, and the Kyushu University Q-PIT Support Program for Young Researchers and Doctoral Students. References M. Zatoń, J. Rozière, and D. J. Jones, Sustain. Energy Fuels, 1, 409 (2017).S. Nakamura, T. Ogawa, Z. Gautama, Z. Noda, M. Yasutake, S. M. Lyth, J. Matsuda, A. Hayashi, M. Nishihara, and K. Sasaki, ECS Trans., 112 (4), 315 (2023). Figure 1

Quantitative Non-Destructive Morphological Characterization of All-Solid-State Batteries

In recent years, all-solid-state batteries (ASSBs) have attracted considerable attention within the scientific community owing to their potential for achieving high energy density, enhanced safety characteristics, and a broader operational temperature window. Specifically, sulfide-based solid-state electrolytes (SSEs) demonstrated the most promising ASSB chemistry with their room-temperature Li+ ionic conductivity comparable or exceeding to that of conventional liquid electrolytes (~10 mS cm-1). Our previous works showcased the superior cyclability of ASSB implementing sulfide-SSEs and carbon-free silicon anode with phenomenal stable cycling for 500 cycles1. Recently, we further demonstrated the scalability of carbon-free Si anode at the pouch cell level with cell capacity reaching 100 mAh under significantly low stacking pressure of 5 MPa2-3, showing promise to accelerate the development and commercialization of ASSBs.Characterizing ASSBs during and after operation is critical for their further development. Crucially, scaling up ASSBs to pouch-cell level introduces new challenges as characterizing the internal microstructure and morphological evolution at a larger scale becomes difficult and time-consuming. Previous works using destructive focus-ion beam-scanning electron microscope (FIB-SEM) can only visualize several tens of micrometers with long imaging times for 3D reconstruction up to hours. Thus, techniques with larger field of view (FOV) and shorter imaging time are inevitably needed to have a better statistical analysis. This study leverages the non-destructive nature of synchrotron X-ray micro-computed tomography (CT) to visualize the morphology and microstructure of each component within an ASSB pouch cell. Leveraging the large FOV of X-ray micro-CT, up to several millimeters and shorter imaging time, we are able to perform a quantitative analysis of the extracted microstructural information, including porosity, loss of contact, and tortuosity. These findings will provide a broader understanding of the structural evolution in ASSB pouch cells, bridging the gap between lab-level research and application-level production.Reference: Tan, D. H. S.; Chen, Y. T.; Yang, H.; Bao, W.; Sreenarayanan, B.; Doux, J. M.; Li, W.; Lu, B.; Ham, S. Y.; Sayahpour, B.; Scharf, J.; Wu, E. A.; Deysher, G.; Han, H. E.; Hah, H. J.; Jeong, H.; Lee, J. B.; Chen, Z.; Meng, Y. S., Carbon-free high-loading silicon anodes enabled by sulfide solid electrolytes. Science 2021, 373(6562), 1494-1499. Tan, D. H. S.; Meng, Y. S.; Jang, J., Scaling up high-energy-density sulfidic solid-state batteries: A lab-to-pilot perspective. Joule 2022, 6 (8), 1755-1769. Chen, Y.-T.; Jang, J.; Oh, J. A. S.; Ham, S.-Y.; Yang, H.; Lee, D.-J.; Vicencio, M.; Lee, J. B.; Tan, D. H. S.; Chouchane, M.; Cronk, A.; Song, M.-S.; Yin, Y.; Qian, J.; Chen, Z.; Meng, Y. S., Enabling Uniform and Accurate Control of Cycling Pressure for All-Solid-State Batteries. 2023.

Correlating the 3D Morphology of Polymer-Based Battery Electrodes with Effective Transport Properties.

Polymer-based batteries represent a promising candidate for next-generation batteries due to their high power densities, decent cyclability, and environmentally friendly synthesis. However, their performance essentially depends on the complex multiscale morphology of their electrodes, which can significantly affect the transport of ions and electrons within the electrode structure. In this paper, we present a comprehensive investigation of the complex relationship between the three-dimensional (3D) morphology of polymer-based battery electrodes and their effective transport properties. In particular, focused ion beam scanning electron microscopy (FIB-SEM) is used to characterize the 3D morphology of three polymer-based electrodes which differ in material composition. The subsequent segmentation of FIB-SEM image data into active material, carbon-binder domain and pore space enables a comprehensive statistical analysis of the electrode structure and a quantitative morphological comparison of the electrode samples. Moreover, spatially resolved numerical simulations allow for computing effective properties of ionic and electronic transport. The obtained results are used for establishing analytical regression formulas which describe quantitative relationships between the 3D morphology of the electrodes and their effective transport properties. To the best of our knowledge, this is the first time that the 3D structure of polymer-based battery electrodes is quantitatively investigated at the nanometer scale.

Comprehensive characterization of micro-pore structures in different lithologies of the lacustrine fine-grained mixed sedimentary reservoir of the Shahejie Formation in the Jiyang Depression

Several methods, such as field-emission environmental scanning electron microscope (FE-SEM), low-temperature nitrogen adsorption-desorption, high-pressure mercury injection tests, focused ion beam scanning electron microscope (FIB-SEM), and high-magnification and large-scale quantitative analytical methods involving argon ion polishing-FE-SEM, have been carried out on lacustrine fine-grained mixed sedimentary reservoirs of the upper fourth-lower third members of the Shahejie Formation in the Jiyang Depression, with the aim of clarifying their microstructural characteristics. Five types of reservoir spaces of fine-grained mixed sedimentary reservoirs were recognized in this study, including intergranular, dissolution, intercrystalline and intracrystalline pores, and fractures. The favorable reservoir spaces are pores with diameters ranging from 40 nm to 300 nm, which are dominated by intergranular pores, grain edge seams, and dissolution pores. The high-pressure mercury injection curves can be divided into three types. Types I and II, with good pore structures, occur mainly in mudstone and dolomite facies, whereas type III, with poor pore structures, is present in limestone facies. The low-temperature nitrogen adsorption-desorption showed that the adsorption volume of dolomite facies is the highest, and the pore morphologies are plate-like. The adsorption amount of mudstone facies is higher than limestone facies, and the pore morphologies are dominated by ink bottle-shaped and parallel plate-like. FIB-SEM analyses reveal that the samples display moderate connectivity. These findings suggest that the different types of lithologic reservoirs of fine-grained mixed sedimentary rocks in the Jiyang Depression have different microstructures, with the argillaceous dolomite, calcareous mudstone, calciferous mudstone, and argillaceous limestone changing gradually from good to poor.

Application of Advanced Microscopy Techniques to the Characterization of Mixed Matrix Membranes.

Mixed matrix membranes (MMMs) have emerged as promising materials for various separation processes due to their tunable properties, enhanced separation performance and reproducibility. In this review paper, we provide a comprehensive overview of the methodologies, challenges, and applications associated with the characterization of MMMs using two advanced imaging techniques: Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) and Transmission Electron Microscopy (TEM). We begin by outlining the principles and capabilities of FIB-SEM and TEM, emphasizing their suitability for studying the microstructure, morphology, and composition of MMMs at nanoscale resolution. Subsequently, we discuss the specific challenges and limitations encountered in the characterization of MMMs using these techniques, including sample preparation, image acquisition, and data interpretation. Furthermore, we review the diverse applications of FIB-SEM and TEM in elucidating the structure-property relationships of MMMs. Through illustrative examples, we highlight the valuable insights gained from these imaging techniques in optimizing MMMs for various separation applications. Finally, we propose future directions and emerging trends in MMM characterization, including the integration of lasers into FIB-SEM and in situ characterization techniques, to address current challenges and push the boundaries of MMM design and performance. Overall, this review provides a comprehensive overview of the state-of-the-art methodologies for characterizing MMMs using FIB-SEM and TEM, identifies key challenges, and offers insights into future research directions aimed at harnessing the full potential of MMMs for sustainable separation technologies.

Correlating Heterogeneities in Support Fragmentation to Polymer Morphology in Metallocene‐Based Propylene Polymerization Catalysis

AbstractIn the field of olefin polymerization catalysis, metallocenes are heterogenized with methylaluminoxane onto silica supports to yield active catalysts. During olefin polymerization, these silica supports act as a framework to control the fragmentation stage, thereby influencing the final polymer product and preventing reactor fouling and fines formation. This study investigates the influence of different silica supports induced on the final polymer product. To study a broad range of silica supports from an industrial silica database, we utilize a hierarchical clustering method to cluster the supports based on their physical properties. From the clustering method, five supports representing the clusters and an industrial benchmark were analyzed at different polymerization stages using focused ion beam–scanning electron microscopy (FIB–SEM) and microcomputed tomography (microCT). This combined FIB‐SEM/microCT methodology revealed differences in both fragmentation behavior and polymer morphologies based on structural features, including macropores, mesopores, spray‐dried shells, spray‐dried spheres, and denser shells. The heterogeneity and ideal fragmentation behavior was further assessed by calculating the replication factor of each support, indicating that silica materials containing macropores and spray‐dried shells have an almost ideal replication phenomenon. This multiscale analysis revealed new understanding of catalyst fragmentation for different supports. This understanding could in the future be further developed by the addition of more supports or additional analysis of the supports to the industrial database.