X-ray Techniques Research Articles

Adsorption-desorption of propyrisulfuron in six typical agricultural soils of China: kinetics, thermodynamics, influence of 38 environmental factors and its mechanisms.

Propyrisulfuron, a novel sulfonylurea herbicide, effectively suppresses intracellular acetolactate synthase activity for weed control, but its adsorption behavior in the soil environment remains unclear. To assess potential agroecosystem risks, the adsorption-desorption behavior and mechanism of propyrisulfuron in six typical agricultural soils of China were investigated using a batch equilibrium method, Density Functional Theory (DFT), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy equipped with Energy Dispersive X-ray (SEM-EDX) techniques. It is indicated that the adsorption-desorption of propyrisulfuron in six soils reached equilibrium at 36 hours under the optimum water-to-soil ratio (WSr) of 5:1. Adsorption kinetics followed the quasi-second-order kinetic model, while the Freundlich model best described the adsorption process at equilibrium. The adsorption and desorption were significantly and positively correlated with soil clay content, and 38 environmental factors had varying degrees of influence on its adsorption properties, especially those influenced by microplastics (MPs). Furthermore, the adsorption of propyrisulfuron in six soils was primarily a spontaneous, non-homogeneous, and non-ideal physical process, and special strong forces, such as hydrogen bonding might be involved. Consequently, due to its continuous application, potential persistent residues and pollution may occur in some soils. The investigations systematically reported the adsorption-desorption behavior of propyrisulfuron in various agricultural soils for the first time, providing scientific guidance for environmental risk assessment of groundwater pollution caused by its continuous application in agro-ecosystems.

Comparative study of electron transport through aromatic molecules on gold nanoparticles: insights from soft X-ray spectroscopy of condensed nanoparticle films versus flat monolayer films.

Understanding electron transport in self-assembled monolayers on metal nanoparticles (NPs) is crucial for developing NP-based nanodevices. This study investigates ultrafast electron transport through aromatic molecules on NP surfaces via resonant Auger electron spectroscopy (RAES) with a core-hole-clock (CHC) approach. Aromatic molecule-coated Au NPs are deposited to form condensed NP films, and flat monolayers are prepared for comparison. Soft X-ray techniques, including X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy, confirm oriented monolayers in both NP and flat films. The nuclear dynamics is studied via ion yield measurements. After subtracting secondary processes, the ion yield spectra of the condensed NP films reveal site-selective desorption of the methyl ester group by resonant core excitation. The ultrafast electron transport time from the carbonyl group through the phenyl rings to the metal surfaces in the condensed NP films is successfully determined via the RAES-CHC approach by subtracting inelastic scattering components. The chain length of the aromatic molecules influence the electron transport time in the NP films, reflecting the trends observed in the flat films. This evidence supports ultrafast electron transport via the through-bond model, independent of interactions between the molecules adsorbed on an NP itself or adjacent NPs. Identifying and subtracting background spectral components of the condensed NP films allows accurate analysis of the ultrafast dynamics. This study suggests that insights gained from electron transport processes in the flat monolayer films can be extrapolated to practical NP-molecule interfaces, providing valuable insights for the molecular design of NP-based devices.

Spectroscopic, Crystallographic and Thermal Comparison of Two Asymmetric Tridentate Schiff Base Molecules

Two similar asymmetric ONO type tridentate Schiff Base ligand molecules and their spectroscopic, crystallographic and thermal properties are comparised. Both of molecules obtained in the study were characterized by 1H-NMR, 13C-NMR, thermal analysis, IR spectroscopy and UV-Vis spectroscopy. However molecules were able to be obtained as single crystals and their structures were determined by single crystal X-ray technique. The space group of the geometric shape of the 2'-(2-hydroxy-anilidene)-4-hydroxy-pentane (L1) ligand is P212121. There are 4 molecules in the unit cell of the crystal system of the L1 ligand. The space group of the geometric shape of the 4'(2-hydroxy-5-chlorine-anilidene)-2-hydroxy-pentane (L2) ligand is P21/c. There are four molecules in the unit cell of the crystal system of the ligand. Although they are ligands with similar structure, L1 ligand has an orthorhombic unit cells and L2 ligand has a monoclinic unit cells. Thermal analysis of the ligands showed a state change point. L1 and L2 ligands degraded in a single step. The 1H-NMR spectra of the L1 and L2 ligands, which have similar structures, are similar in outline. However, it is interesting to observe that the peaks of these carbons are observed in a higher area since the chlorine atom attached to the aromatic ring in the L2 ligand increases the screening effect.. The spectroscopic results also show a general similarity, but the effect of the chlorine atom stands out.

Synchrotron-Based X-ray Techniques for Probing Electronic and Structural Dynamics in Energy Storage Materials

Synchrotron-Based X-ray Techniques for Probing Electronic and Structural Dynamics in Energy Storage Materials

Non-Aqueous Electrochemical CO2 Reduction to Multivariate C2-Products Over Single Atom Catalyst at Current Density up to 100mAcm-2.

Electrochemical CO2 reduction reaction (CO2-RR) in non-aqueous electrolytes offers significant advantages over aqueous systems, as it boosts CO2 solubility and limits the formation of HCO3 - and CO3 2- anions. Metal-organic frameworks (MOFs) in non-aqueous CO2-RR makes an attractive system for CO2 capture and conversion. However, the predominantly organic composition of MOFs limits their electrical conductivity and stability in electrocatalysis, where they suffer from electrolytic decomposition. In this work, electrically conductive and stable Zirconium (Zr)-based porphyrin MOF, specifically PCN-222, metalated with a single-atom Cu has been explored, which serves as an efficient single-atom catalyst (SAC) for CO2-RR. PCN- 222(Cu) demonstrates a substantial enhancement in redox activity due to the synergistic effect of the Zr matrix and the single-atom Cu site, facilitating complete reduction of C2 species under non-aqueous electrolytic conditions. The current densities achieved (≈100mAcm- 2) are 4-5 times higher than previously reported values for MOFs, with a faradaic efficiency of up to 40% for acetate production, along with other multivariate C2 products, which have never been achieved previously in non-aqueous systems. Characterization using X-ray and various spectroscopic techniques, reveals critical insights into the role of the Zr matrix and Cu sites in CO2 reduction, benchmarking PCN-222(Cu) for MOF-based SAC electrocatalysis.

Diagnostic development and needs for laser driven MeV x-ray radiography.

Laser-driven MeV x-ray radiography of dynamic, dense objects demands a small, high flux source of energetic x-rays to generate an image with sufficient quality. Understanding the multi-MeV x-ray spectrum underscores the ability to extrapolate from the current laser sources to new future lasers that might deploy this radiography modality. Here, we present a small study of the existing x-ray diagnostics and techniques. We also present work from National Ignition Facility-Advanced Radiographic Capability, where we deploy three diagnostics to measure the x-ray spectrum up to 30MeV. Finally, we also discuss the needs and developments of two new diagnostics: a single crystal scintillator spectrometer and a fast decay activation.

Development of Polyurethane Elastomer-Based Bio-Composites Reinforced with Basaltic Pumice

Basaltic pumice has a black or gray appearance due to its iron and magnesium-rich komatiitic tuff composition. Pumice's porous structure allows the production of various polymer-based bio-composite materials for biomedical applications. This study developed bio-composite samples by incorporating basaltic pumice powder at 2.5, 5.0, 7.5, and 10.0 percent concentrations into an elastomeric polyurethane (EPU) matrix. The surface and elemental structure of basaltic pumice particles were investigated using the SEM/energy diffraction X-ray technique. The physical, mechanical, thermal, melt-flow, and morphological properties of bio-composites were studied experimentally. Findings showed a rise in Shore hardness and tensile modulus parameters and declined tensile elongation. According to the thermal study, introducing basaltic pumice resulted in a modest drop in the thermal stability of the EPU and an improvement in stability against mechanical deformations. Pumice loadings raised the melt flow and extrusion torque values of the EPU. The observation of the homogeneously distributed pumice particles in the EPU matrix is used as visual evidence to investigate the highest performance among the composites in the EPU sample with the lowest loading rate of 7.5% pumice. Overall, BP is effective as a reinforcing agent in EPU-based bio-composites at low additive percentages.

The rGO@AuNPs modified label-free electrochemical immunosensor to sensitive detection of CP-BNYVV protein of Rhizomania disease agent in sugar beet

For the first time, a novel simple label-free electrochemical immunosensor was fabricated for sensitive detection of the coat protein of beet necrotic yellow vein virus (CP-BNYVV) as the causal agent of Rhizomania disease in sugar beet. To boost the amplification of the electrochemical signal, gold nanoparticles-reduced graphene oxide (AuNPs-rGO) nanocomposite was employed to modify the glassy carbon electrode. Anti-BNYVV polyclonal was immobilized onto a modified electrode by applying a thiol linker via a self-assembly monolayer (SAM) and activating the functionalized surface using (3-aminopropyl triethoxysilane) and glutaraldehyde. The determination step relied on the forming of an immunocomplex between the antigen and oriented antibody, resulting in a decrease in current in the [Fe (CN)6]3−/4− redox reaction. The response value exhibited direct proportionality to the concentrations of CP-BNYVV. Scanning electron microscopy, energy dispersive x-ray, cyclic voltammetry, and electrochemical impedance spectroscopy techniques collectively provided a comprehensive understanding of the structural, morphological, and electrochemical features during the modification steps. Under optimized experimental conditions, the fast Fourier transform square wave voltammetry responds to the logarithm of CP-BNYVV concentrations in a wide linear range from 0.5 to 50000 pg/mL and the limit of detection is calculated to be 150 fg/mL, implying the admirable sensitivity. Selectivity assay exhibited no cross-reactivity with other proteins from interfering virus samples. Satisfactory reproducibility and stability were achieved with a relative standard deviation of 3.1% and a stable value of 90% after 25 days, respectively. More importantly, the high performance of the immunosensor resulted in the direct detection of CP-BNYVV in spiked and infected plant samples, which affords a sensing platform with huge potential application for the early detection of BNYVV virus in field conditions.Graphical

Graphene oxide functionalized halloysite nanotubes for voltammetric determination of psychoactive drug from alcoholic and non-alcoholic drinks

In context to the widespread misuse of benzodiazepines, a novel platform based on the graphene oxide functionalized halloysite nanotubes (HNT/GO) has been introduced for the electrochemical detection of commonly abused date rape drug-nitrazepam (NZP). In this work, HNT/GO composite has been synthesized via simple stirring method and the fabricated materials were characterized by using combination of spectroscopic, microscopic, X-ray and voltammetric techniques i.e., FTIR, FE-SEM-EDX, TEM, XRD, XPS and Cyclic voltammetry. Surface modification of HNTs with GO increased the synergistic properties of both the materials for electrochemical sensing of nitrazepam. Specifically, HNTs provided high surface area, nanotubular morphology with unique surface functionalities and GO added electron rich functional sites. Combination of HNTs with GO significantly increased electrochemical active surface area from 0.06 to 0.236 cm2 which increased electron transfer on the surface of electrode towards electrochemical reduction of nitrazepam. The developed sensor showed excellent electrochemical response for nitrazepam detection with a linear dynamic range of 0.16–150 μM and limit of detection 0.79 μM. The proposed sensor has successfully been employed for electrochemical determination of nitrazepam in non-alcoholic and alcoholic drinks without any sample pre-treatment.

Fabrication of Co(II)-based coordination polymer for photocatalytic degradation: Selective removal of cationic methyl violet dye

In this study, a new coordination polymer (CP) was designed and synthesized to evaluate the photocatalytic properties for water remediation. The Co(II)-based CP {[Co(HL)(bid)(H2O)]·2H2O}n (1) was hydrothermally synthesized using the ligand 5-(4′-carboxyphenoxy)isophthalic acid (H3L) and 1,4-bis(1-imidazolyl)-2,5-dimethylbenzene (bid). The coordination polymer (1) has been characterized by various spectral techniques, thermogravimetric (TGA), and single crystal X-ray technique. X-ray data revealed that (1) exhibits 2D framework having an octahedral coordination geometry around the Co(II) ions, having μ1:η1-η1 mode with chromophore CoO4N. FT-IR analysis confirmed the asymmetric monodentate binding modes of the carboxylate ligand. The CP 1 has demonstrated optical semiconducting properties, rendering them promising candidates for photocatalytic applications. The catalyst (1) has been effectively utilized in the breakdown of several organic dyes, such as methylene blue (MB), methyl orange (MO), methyl violet (MV), and rhodamine B (RhB). The results showed that at pH 4, with a dosage of 30 mg of catalyst (1), 92.08 % of MV was degraded at a concentration of 20 ppm. Additionally, the mechanistic pathway for light-driven MV decomposition was investigated through experimental approaches, specifically radical trapping experiments.

High-entropy Li-rich layered oxide cathode for Li-ion batteries

High-entropy oxides (HEOs) are emerging as promising cathode materials for Li-ion batteries (LIBs) due to their stable solid-state phase and compositional flexibility. Herein, we investigate the structural and electrochemical properties of a novel non-equimolar high-entropy cathode material, termed high-entropy Li-rich layered oxide (HE-LLO, Li1.15Na0.05Ni0.19Mn0.56Fe0.02Mg0.02Al0.02O1.97F0.03), in comparison to a pristine Li-rich layered oxide (PR-LLO, Li1.2Ni0.2Mn0.6O2). The incorporation of multiple cations (Na+, Al3+, Mg2+, Fe3+) and anion (F−) into HE-LLO introduces compositional diversity, enhancing structural stability through the entropy stabilization effect. Theoretical calculations confirm a significantly higher configurational entropy in HE-LLO compared to PR-LLO, supporting its high-entropy nature. Electrochemical evaluations demonstrate that HE-LLO exhibits considerable capacity retention, preserving 76.8 % of its discharge capacity at 0.5C after 200 cycles, compared to only 36.2 % for PR-LLO. Even under high-temperature conditions, HE-LLO outperformed PR-LLO, maintaining 76.1 % of its discharge capacity after 100 cycles at 5C, while PR-LLO retained only 12.4 %. These enhancements are attributed to the improved phase reversibility and higher Li+ ion diffusion coefficients of HE-LLO, validated by ex-situ characterizations using a synchrotron X-ray technique, along with density functional theory (DFT) calculations. These findings highlight the promise of non-equimolar HEOs as a novel design strategy for high-performance cathode materials.

Tailoring Surface Oxygen Environments in LiNi0.5Mn0.3Co0.2O2 Via Post-Calcination Anneal

Oxygen release in layered transition metal oxide cathodes leads to changing intercalation kinetics in lithium-ion batteries. Oxygen loss behavior during extended electrochemical cycling is well understood, but tailoring the oxygen environment of pristine cathode materials to reduce oxygen release remains a challenge. In this work we perform simple 30-minute post-calcination gas treatments to systematically modify the surface of single-crystalline LiNi0.5Mn0.3Co0.2O2 (NMC532). We use two gas environments (Ar and 21% O2 in Ar) and a range of temperatures (600-800 °C) to investigate the effect of low oxygen partial pressure on pristine NMC532. Using electrochemical and X-ray techniques, we observe changes in electrochemical cycling behavior and surface and bulk structure that are monotonic with temperature for the argon annealed material, while changes in the oxygen annealed material are mostly invariant with respect to temperature. From in situ heating X-ray photoelectron spectroscopy and in situ heating X-ray absorption spectroscopy, we demonstrate the removal of surface carbon species and oxidation of transition metals in an oxygen containing environment; in an argon environment we observe transition metal reduction, consistent with oxygen release. These findings suggest 1) a simple oxygen environment anneal can remove resistive surface contaminants commonly formed during material storage, and 2) oxygen-deficient anneals can be used to systematically alter the surface oxygen environments of stoichiometric cathode materials. This can be a powerful method to understand the relationship between the surface oxygen sublattice and the kinetics of lithium intercalation.

(Invited) Using X-Ray Microscopy Techniques to Advance Fuel Cell Catalyst Layers

Despite the tremendous progress that has been made in developing polymer electrolyte membrane (PEM) fuel cells, there are still key challenges in optimizing the catalyst coated membrane. The catalyst layer has long been the focus of driving down cost and striving for long lifetimes and better performance, and these challenges are only heightened when we consider the evolving application focus – from a past focus on automotives to now the inclusion of heavy-duty vehicles and aviation. In this talk, I will discuss our approach to informing next generation catalyst coated membrane development. I will discuss how our work from the flow field and gas diffusion layer have informed our approach to the catalyst coated membrane. I will then focus on X-ray techniques that provide high spatial and temporal resolution for examining experimental performance and materials characterization, and I will discuss numerical modelling approaches, such as our work to uncover the impact of compression. I will discuss the advancement we are making in characterizing the spatio-chemical speciation of custom catalyst layers. Specifically, we probe the carbon, fluorine, and oxygen spectral K-edges on commercial catalyst layers using near-edge X-ray absorption fine structure spectroscopy (NEXAFS) in conjunction with scanning transmission X-ray microscopy (STXM) to provide a comprehensive two-dimensional map of the PEM fuel cell catalyst layer. I will discuss the structural characteristics of the CL, which will be highly valuable for informing the design of next generation PEM fuel cell catalyst layers.

(Invited) Coherent X-ray Studies of Electrode Nanoparticles and Surfaces

Coherent X-rays provide a unique structural and dynamical viewpoint of electrode surfaces and nanoparticles. Using the coherent X-ray techniques, we have been studying several electrochemical phenomena such as electrochemical dissolution reactions of silver surfaces and nanoparticles, oxygen reduction/evolution reactions of platinum and platinum alloy nanoparticles, and the surface reconstruction dynamics of gold surfaces and nanoparticles. The coherent X-ray techniques are typically developed for real-space images and real-time dynamics. For imaging techniques, X-ray imaging such as Bragg Coherent Diffraction Imaging (BCDI) is used to image nanoparticles, and X-ray Ptychography is used to image electrode surfaces, and X-ray photon correlation spectroscopy (XPCS) is used to monitor the electrode surface dynamics.In this talk, we will present a broad overview of the examples based on our previous studies and provide each example with an emphasis on the uniqueness of the coherent X-ray techniques and the structural and dynamical aspects of the electrodes, unavailable in traditional X-ray techniques. We will also provide a perspective of the coherent X-ray techniques using the more powerful and brilliant coherent X-rays becoming available in the newest generation X-ray photon sources such as upgraded Advanced Photon Source (APS-U).

Deconvolved First Cycle Capacity Loss Mechanisms in All-Solid-State Batteries

Deconvolved First Cycle Capacity Loss Mechanisms in All-Solid-State Batteries All-solid-state batteries (SSBs) fail to compete with their traditional lithium-ion battery (LIB) counterparts due to severe capacity loss in their first cycle. While the key contributors to capacity loss have been identified, it remains unknown the relative contribution of each loss mechanism due to solid electrolyte (SE) redox and worsening kinetics which obscure the measure of capacity. For the chemically abundant sulfur-based composite electrodes in particular, these parallel processes present a formidable challenge to addressing first cycle Coulombic inefficiency.1 Using near-equilibrium electrochemical and X-ray techniques, we demonstrate a full accounting of the sources of capacity loss within our argyrodite SE (Li5PS6Cl) | uncoated Li(Ni0.5Mn0.3Co0.2)O2 (NMC) | carbon composite cathode. By modifying the components of the composite electrode, we differentiate between electrolyte redox at the electronic conductor (current collector + carbon)|SE and NMC|SE interfaces. Using these cell formats we investigate the persistence of electronic conductor interfacial redox across many cycles, as well as the impact of self-discharge on long-term cycling behavior. By modifying the cycling window, we also investigate sluggish discharge kinetics of cathode and oxidation reversibility. Using operando XRD, we compare LIBs and SSBs to track cathode redox throughout cycling, enabling us to differentiate and quantify sources of capacity loss. These findings highlight the need to address overlooked sources of resistance and active material loss in SSBs which are not mitigated by cathode coating solutions.[1] Janek, J., Zeier, W.G. Challenges in speeding up solid-state battery development. Nat Energy 8, 230–240 (2023).

(Invited) Development of a 5D Analytical Tool for Probing Electrochemical Reactions in Composite Solid-State Battery Electrodes: Toward Designing Better Electrodes

The emergence of solid lithium superionic conductors exhibiting conductivity surpassing that of liquid electrolytes has positioned solid-state batteries (SSBs) as one of the most promising and realistic next-generation energy storage devices. SSBs are expected to demonstrate superior safety, as well as higher capacity and power density compared to conventional lithium-ion batteries. In practice, however, SSBs often fail to achieve the high performance expected from the superior properties of their individual constituent materials. This is partly because the performance of SSBs is not solely dependent on the constituent materials but also heavily influenced by the design of each battery component. For example, for the electrode of SSBs, composite electrodes consisting of active materials and solid electrolytes (and conductive additives, if necessary) are often employed. Within these composite electrodes, particles of active materials and solid electrolytes, along with voids, are randomly interspersed, forming a complex microstructure. This intricate microstructure creates highly tortuous electron and ion conduction pathways and complex heterogeneous material interfaces within the electrode. Consequently, particularly under high current charging/discharging, local stagnation of ion/electron transport within the electrode can arise, leading to spatially inhomogeneous electrochemical reactions throughout the entire electrode or within individual active material particles. Such inhomogeneous electrochemical reactions hinder the materials from fully exhibiting their inherent performance, potentially leading to severe degradation of battery capacity, power output, as well as the impairment of cycle life due to localized overcharging/overdischarging. To suppress the occurrence of such inhomogeneous reactions and maximize battery performance and lifespan, it is necessary to directly observe the electrochemical reaction within composite electrodes during (dis)charging and establish appropriate design guidelines based on these observations. However, conventional characterization techniques have been unable to directly observe the time-varying electrochemical reactions that take place three-dimensionally and inhomogeneously within electrodes at both the particle scale (~few micron) and electrode scale (~hundreds of microns) during (dis)charging. Therefore, previous studies have been limited to obtaining averaged information on the overall electrochemical reactions within electrodes using conventional electrochemical measurements, estimating the electrochemical reactions in electrodes through numerical simulations, or conducting lower-dimensional (1D or 2D) observations of the 3D electrochemical reaction using X-ray or electron probe imaging techniques. Against this background, we have developed operando 3D imaging techniques for probing electrochemical reactions in SSB electrodes based on computed tomography combined with X-ray absorption near-edge structure spectroscopy (CT-XANES)1–4. These techniques can track the spatiotemporal evolution of the electrochemical reaction within composite electrodes during (dis)charge cycles, thereby allowing for the analysis of electrochemical reactions in five dimensions (5D), encompassing 3D spatial coordinates, time, and chemical state information. As shown in Fig. 1a1, our technique based on micro CT-XANES enables the operando 3D imaging of the evolution of the electrochemical reactions at the electrode scale with a spatial resolution of a few micrometers and a temporal resolution of approximately 30 minutes. This allows for the evaluation of the state of charge (SOC) distribution at any arbitrary cross-section in the thickness and in-plane directions within the same bulk region in electrodes at any given time. Consequently, it enables the quantitative analysis of when, where, how, and why low SOC regions appear within the electrode1,2,4, and allows for uncovering the correlation between local capacity degradation during cycling and electrode microstructures or the reaction history in previous (dis)charge cycles3. Furthermore, our advanced technique based on nano CT-XANES enables the operando, 3D, and simultaneous observation of the intra- and inter-particle reaction distributions among thousands of active material particles within SSB electrodes with a spatial resolution of sub-micrometers and a temporal resolution of approximately 30 minutes, as illustrated in Fig. 1b. The obtained information allows for the quantitative and statistical analysis of the correlations between the reaction characteristics of each active particle and its morphological features, facilitating the data-driven determination of optimal active material particle parameters, such as particle size, shape, arrangement, and size distribution. In the presentation, we will demonstrate how our 5D electrochemical reaction analysis techniques can provide useful insights for battery research. References Y. Kimura et al., J. Phys. Chem. Lett., 11, 3629–3636 (2020).Y. Kimura et al., ACS Appl. Energy Mater., 3, 7782–7793 (2020).Y. Kimura et al., Small Methods, 7, 2300310 (2023).S. Huang et al., J. Phys. Chem. C (2024) https://doi.org/10.1021/acs.jpcc.4c00318. Acknowledgements This work was supported by JST PRESTO Grant Number JPMJPR23J3, JST Mirai Program Grant Number JPMJMI21G3, and JST GteX Grant Number JPMJGX23S2, Japan. Figure 1

Revealing Structure-Property Correlations in New Solid Electrolyte Materials for All-Solid-State-Batteries Using Synchrotron X-Ray Analysis

There have been enormously increasing demands for developing next-generation Li-ion batteries with enhanced energy & power density and safety features compared with the current state-of-the-art LIB technology. Such advances necessitate the successful development and implementation of the new cathode, anode, and (solid)electrolyte materials. In this regard, understanding the structure-property correlation of advanced battery materials has now become a central aspect of battery research. Synchrotron-based x-ray techniques such as x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS) have been identified as ideal and powerful tools for in situ studies of lithium-ion battery materials. This presentation will discuss how such advanced characterization tools can be employed in the diagnostic study of battery materials to reveal the working and failure mechanism. I will present the application of various synchrotron x-ray tools, including pair distribution function (PDF) analysis and tender x-ray absorption spectroscopy, to investigate sulfide and halide-based solid-electrolyte materials. The correlation between local atomic structure changes and ionic conductivity will be discussed.

Combining Microscopy and Synchrotron X-Ray Diagnostics to Study Catalyst Degradation in PEFCs

Polymer electrolyte fuel cells (PEFCs) suffer from performance degradation during operation due to transformations in the catalyst (Pt or Pt/Co particles) and their carbon support. However, nano-structural diagnostic methods are not readily applicable in the humid, high-temperature, and gas environments of PEFC operation. This hinders elucidation of the mechanisms behind catalyst property evolution (size, shape, lattice parameters), which directly affects the electrocatalytic surface area (ECSA), a critical factor in catalyst performance.1 Here, we employ a combined methodology to study the changes in catalyst particle properties using identical location scanning transmission electron microscopy (IL-STEM)2 and Operando synchrotron X-ray measurements, particularly small angle X-ray scattering technique (SAXS)3. While IL-STEM offers high-resolution imaging for estimating local particle size, shape, and lattice parameters, SAXS provides statistically reliable data on the overall particle size distribution.4 These complementary techniques, with their inherent strengths, allow for a comprehensive understanding of the mechanisms involved during particle transformation.Electrochemical cycling of the catalysts was performed using a square wave potential pattern cycling between 0.6 and 1.0 VRHE at 6 seconds/cycle. A gold STEM grid was mounted on a specially designed working electrode for electrochemical cycling, which is performed ex-situ. STEM images, of the same areas, before and after electrochemical cycling were recorded using JEOL NEOARM operated at an accelerating voltage of 200 kV. SAXS experiments were conducted at BL40B2 beamline of SPring-8. An electrochemical cell (PECC-2, Zahner, Germany) was modified to increase X-ray transmittance. The thickness of its electrolyte layer was minimized to 1.5 mm, the upstream window was a 7.5 µm thick Kapton film. Its downstream window, a 50 µm thick graphite window onto which a catalyst film was deposited, acted as the working electrode. A PILATUS 2M detector was used to record scattering data with exposure time of 100 seconds.Scanning transmission electron microscopy revealed a comparable mean particle radius before electrochemical cycling (1.60 ± 0.44 nm) to that obtained by small-angle X-ray scattering (1.62 ± 0.32 nm), Table 1. Furthermore, STEM analysis of the same locations before (607 particles) and after (494 particles) cycling showed a similar trend in particle size growth as observed in operando SAXS measurements. However, the estimated sizes after cycling differed slightly, with SAXS data indicating a larger mean radius (2.08 ± 0.53 nm) compared to STEM (1.88 ± 0.49 nm). This discrepancy is attributed to the smaller probed volume by STEM, which was also limited to the same locations, potentially excluding other growing particles from analysis compared to the bulk characterization offered by SAXS.These results highlight the potential of combining microscopy with synchrotron X-ray SAXS for studying catalyst growth mechanisms with greater accuracy. In addition, by incorporating complementary synchrotron X-ray techniques like wide-angle X-ray scattering (WAXS) and X-ray fluorescence (XRF) during analysis, a more comprehensive understanding of catalyst degradation can be achieved. This combined approach can pave the way for the development of more informed catalyst engineering strategies.Table 1 summarising the mean particle sizes obtained from both methods. BEFORE (nm)AFTER (nm)Peak radiusMean radiusFWHMPeak radiusMean radiusFWHMSTEM1.38 ± 0.011.60 ± 0.440.86 ± 0.031.66± 0.021.88 ± 0.490.95 ± 0.04SAXS1.47 ± 0.011.62 ± 0.320.60 ± 0.021.84 ± 0.022.08 ± 0.531.04 ± 0.04 References Lyth, S. M. & Mufundirwa, A. Electrocatalysts in polymer electrolyte membrane fuel cells. Heterog. Catal. Adv. Des. Charact. Appl. 2, 571–592 (2021).Yu, H. et al. Tracking Degradation in Individual Catalyst Nanoparticles Under Fuel Cell-Relevant Cycling Conditions by Identical-Location STEM. Microsc. Microanal. 28, 2614–2617 (2022).C. Smith, M., A. Gilbert, J., R. Mawdsley, J., Seifert, S. & J. Myers, D. In Situ Small-Angle X-ray Scattering Observation of Pt Catalyst Particle Growth During Potential Cycling. J. Am. Chem. Soc. 130, 8112–8113 (2008).Mufundirwa, A. et al. Contrast variation method applied to structural evaluation of catalysts by X - ray small - angle scattering. Sci. Rep. 1–9 (2024) doi:10.1038/s41598-024-52671-7.

Nanoscale in-Situ Effects of Humidity on Proton Exchange Membrane Fuel Cell Catalyst Layers Using Scanning Transmission X-Ray Microscopy

Polymer electrolyte membrane (PEM) fuel cells produce clean energy using hydrogen and oxygen with water and heat as the only byproducts. However, their widespread adoption is still hindered by high cost and low efficiency. PEM fuel cells have a proton exchange membrane (ionomer) supported by platinum (Pt) catalyst layers to facilitate the hydrogen oxidation (anode) and the oxygen reduction (cathode) reactions. While sufficient membrane hydration is necessary to maintain proton conductivity, excess water in the catalyst layer can severely inhibit electrochemical reactions, limiting efficient fuel cell operation.To design high performance catalyst layer nanostructures, the formation of liquid water and the ionomer swelling with humidity in PEM fuel cell catalyst layers need to be investigated. In-situ hard X-ray techniques have been used to study the incipience of water; however, the high energy hard X-rays prevent spectroscopy of the low-Z membrane elements like carbon, fluorine, oxygen, and sulfur. Soft X-ray scanning transmission X-ray microscopy (STXM) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy can uniquely perform high resolution (30 nm) imaging of the chemical constituents of catalyst layers with minimal radiation damage. In this work, we report a novel in-situ characterization of ionomer swelling with humidity in fuel cell catalyst layers using STXM and NEXAFS spectroscopy to reveal the nanoscale reactant and proton transport pathways in PEM fuel cell catalyst layers. Pristine catalyst coated membrane samples were cut using an ultramicrotome to obtain 300 nm thick sections and mounted in a custom cell to observe the in-situ effects of humidity. The thickness of liquid water in the membrane and catalyst layer as a function of relative humidity was obtained by performing in-situ imaging at the oxygen K-edge. We observed that at 55% relative humidity (RH), a through-plane water accumulation of 10-20 nm on the silica nanoparticles maintained the membrane proton conductivity and at 90% relative humidity, the hydration of the sulfonic acid sidechains of Nafion promoted nanoscale proton transport in the catalyst layers. Moreover, in-situ characterization of ionomer swelling with humidity was performed for the first time using NEXAFS at the fluorine K-edge. The ionomer volume fraction increased from 28% to 36% from dry (~6% RH) to humidified conditions (~90% RH) and resulted in higher nanoscale oxygen and water diffusion resistance. From these analyses, the effects of hydration on nanoscale mass transport and proton conductivity were quantified to inform the design of next-generation proton exchange membrane fuel cells. Figure 1

A self-healing plastic ceramic electrolyte by an aprotic dynamic polymer network for lithium metal batteries.

Oxide ceramic electrolytes (OCEs) have great potential for solid-state lithium metal (Li0) battery applications because, in theory, their high elastic modulus provides better resistance to Li0 dendrite growth. However, in practice, OCEs can hardly survive critical current densities higher than 1 mA/cm2. Key issues that contribute to the breakdown of OCEs include Li0 penetration promoted by grain boundaries (GBs), uncontrolled side reactions at electrode-OCE interfaces, and, equally importantly, defects evolution (e.g., void growth and crack propagation) that leads to local current concentration and mechanical failure inside and on OCEs. Here, taking advantage of a dynamically crosslinked aprotic polymer with non-covalent -CH3⋯CF3 bonds, we developed a plastic ceramic electrolyte (PCE) by hybridizing the polymer framework with ionically conductive ceramics. Using in-situ synchrotron X-ray technique and Cryogenic transmission electron microscopy (Cryo-TEM), we uncover that the PCE exhibits self-healing/repairing capability through a two-step dynamic defects removal mechanism. This significantly suppresses the generation of hotspots for Li0 penetration and chemomechanical degradations, resulting in durability beyond 2000 hours in Li0-Li0 cells at 1 mA/cm2. Furthermore, by introducing a polyacrylate buffer layer between PCE and Li0-anode, long cycle life >3600 cycles was achieved when paired with a 4.2 V zero-strain cathode, all under near-zero stack pressure.