Synchrotron Radiation Facility Research Articles

Noncontact Respiratory Motion Detection in Anesthetized Rodents.

Small animal physiology studies are often complicated, but the level of complexity is greatly increased when performing live-animal X-ray imaging studies at synchrotron radiation facilities. This is because these facilities are typically not designed specifically for biomedical research, and the animals and image detectors are located away from the researchers in a radiation enclosure. In respiratory X-ray imaging studies one challenge is the detection of respiration in free-breathing anaesthetised rodents, to enable images to be acquired at specific phases of the breath and for detecting changes in respiratory rate. We have previously used a Philtec RC60 sensor interfaced to a PowerLab data acquisition system and custom-designed timing hub to perform this task. Here we evaluated the Panasonic HL-G108 for respiratory sensing. The performance of the two sensors for accurate and reliable breath detection was directly compared using a single anesthetized rat. We also assessed how an infrared heat lamp used to maintain body temperature affected sensor performance. Based on positive results from these comparisons, the HL-G108 sensor was then used for respiratory motion detection in tracheal X-ray imaging studies of 21 rats at the SPring-8 Synchrotron, including its use for gated image acquisition. The results of that test were compared to a similar imaging study that used the RC60 for respiratory detection in 19 rats. Finally, the HL-G108 sensor was tested on 5 mice to determine its effectiveness on smaller species. The results showed that the HL-G108 is much more robust and easier to configure than the RC60 sensor and produces an analog signal that is amenable to stable peak detection. Furthermore, gated image acquisition produced sequences with substantially reduced motion artefacts, enabling the additional benefit of reduced radiation dose through the application of shuttering. Finally, the mouse experiments showed that the HL-G108 is equally capable of detecting respiration in this smaller species.

A dedicated application of evolutionary algorithms: synchrotron X-ray radiation optimization based on an in-vacuum undulator

Following the rapid growth in accelerator-based light sources research since the mid of 20th century, miscellaneous third generation synchrotron radiation (SR) facilities such as SSRL, APS, ESRF, PETRA-III, and SPring-8 have come into existence. These SR source facilities provide 1020–1025 photons/s/mrad2/mm2/0.1%BW peak brightness within the photon energy range of 10–105 eV. Since different measurement techniques are utilized at X-ray beamlines of SR facilities, many kinds of insertion devices (i.e., undulators and wigglers) and optical components (e.g., high-resolution monochromators, double-crystal monochromators, lenses, mirrors, etc.) are employed for each experimental setup as a matter of course. Under the circumstances, optimization of a synchrotron beamline is a big concern for many scientists to ensure required radiation characteristics (i.e., photon flux, spot size, photon energy, etc.) for dedicated user experiments. In this respect, an in-vacuum hybrid undulator driven by a 6 GeV synchrotron electron beam is optimized using evolutionary algorithms (EA). Finally, it is shown that EA results are well consistent with both the literature and the analytical calculations, resulting in a promising design estimation for beamline scientists.

In-house design hard X-ray transmission microscope at SSRF

A hard X-ray full field transmission X-ray microscopy (TXM) based on zone plate optics has been constructed at BL18B beamline at Shanghai Synchrotron Radiation Facility (SSRF). This beamline aims to the frontier science issues demands in many fields including nanomaterials, energy and life sciences, providing advanced nanostructure characterization for submicron-sized samples. It uses a bending-magnet source and works in the range of energies from 5 keV to 14 keV. The achieved spatial resolution of TXM imaging is 20 nm. This paper describes the details of the design, characterization, stability testing, TXM, CT and 2D TXM-XANES performance of this beamline.

Monocrystalline diamond detector for online monitoring during synchrotron microbeam radiotherapy.

Microbeam radiation therapy (MRT) is a radiotherapy technique combining spatial fractionation of the dose distribution on a micrometric scale, X-rays in the 50-500 keV range and dose rates up to 16 × 103 Gy s-1. Nowadays, in vivo dosimetry remains a challenge due to the ultra-high radiation fluxes involved and the need for high-spatial-resolution detectors. The aim here was to develop a striped diamond portal detector enabling online microbeam monitoring during synchrotron MRT treatments. The detector, a 550 µm bulk monocrystalline diamond, is an eight-strip device, of height 3 mm, width 178 µm and with 60 µm spaced strips, surrounded by a guard ring. An eight-channel ASIC circuit for charge integration and digitization has been designed and tested. Characterization tests were performed at the ID17 biomedical beamline of the European Synchrotron Radiation Facility (ESRF). The detector measured direct and attenuated microbeams as well as interbeam fluxes with a precision level of 1%. Tests on phantoms (RW3 and anthropomorphic head phantoms) were performed and compared with simulations. Synchrotron radiation measurements were performed on an RW3 phantom for strips facing a microbeam and for strips facing an interbeam area. A 2% difference between experiments and simulations was found. In more complex geometries, a preliminary study showed that the absolute differences between simulated and recorded transmitted beams were within 2%. Obtained results showed the feasibility of performing MRT portal monitoring using a microstriped diamond detector. Online dosimetric measurements are currently ongoing during clinical veterinary trials at ESRF, and the next 153-strip detector prototype, covering the entire irradiation field, is being finalized at our institution.

Experimental Demonstration to Control the Pulse Length of Coherent Undulator Radiation by Chirped Microbunching.

In seeded free electron lasers (FELs), the temporal profile of FEL pulses usually reflects that of the seed pulse, and, thus, shorter FEL pulses are available with shorter seed pulses. In an extreme condition, however, this correlation is violated; the FEL pulse is stretched by the so-called slippage effect in undulators, when the seed pulse is ultimately short, e.g., few-cycles long. In a previous Letter, we have proposed a scheme to suppress the slippage effect and reduce the pulse length of FELs ultimately down to a single-cycle duration, which is based on "chirped microbunching," or an electron density modulation with a varying modulation period. Toward realization of FELs based on the proposed scheme, experiments have been carried out to demonstrate its fundamental mechanism in the NewSUBARU synchrotron radiation facility, using an ultrashort seed pulse with the pulse length shorter than five cycles. Experimental results of spectral and cross-correlation measurements have been found to be in reasonable agreement with the theoretical predictions, which strongly suggests the successful demonstration of the proposed scheme.

A novel integrated time-resolved array avalanche photodiode detection system for nuclear resonant scattering measurements.

The nuclear resonant scattering (NRS) experiment requires photon-counting detectors with high time resolution, short dead time, large dynamic range, low noise, and large detection area. An 8-channel avalanche photodiode (APD) array detector system with high integrity, flexibility, and reliability has been developed to adapt to the demands of NRS experiments. The detector system mainly consists of four key parts: (i) an array-APD sensor, (ii) 8-channel integrated fast preamplifiers, (iii) the time-to-digital converter readout electronics, and (iv) a data acquisition system and EPICS support software. Remarkably, the system exhibits a time resolution of better than 500ps and has a sufficiently low noise level, allowing for the lowest detection energy threshold of 4keV. The performance of the new array-APD system as well as its real application in nuclear forward scattering (NFS) and nuclear resonant inelastic x-ray scattering (NRIXS) experiments was tested in two synchrotron facilities. With the new system, the NFS signal very close to the prompt electronic scattering signal can be extracted. Thanks to the customized EPICS-areaDetector-based control software, NRIXS spectra can be readily measured with time and energy information of the NRIXS signal stored in the raw data, which is promising for developing NRIXS data analysis in the time domain. The array-APD detector can be deployed for nuclear resonant scattering experiments at various synchrotron radiation facilities.

Simulation of Beamline Motion Control System of Shanghai Synchrotron Radiation Facility BL13U

The Shanghai Synchrotron Radiation Facility’s hard X-ray nanoprobe wire station is currently under construction, so it is unable to conduct research on online testing, however, beamline adjustment is crucial prior to conducting experiments at the wire station, this challenge can be more effectively addressed by using simulation testing instead of online testing. In order to carry out intelligent beamline adjusting research before the online station is completed, this paper designs a beamline adjusting test simulation platform based on the EPICS software. Through the software simulation of the motor control system of the above-mentioned beamline, the beamline adjusting application of intelligent control methods is realized. The test results show that the system runs well and the intelligent beamline adjusting algorithm can efficiently and automatically optimize the motors in the system. The beamline adjusting test platform based on EPICS software can be further applied to the simulation and testing of other beamlines at the Shanghai Synchrotron Radiation Facility.

PMMA based compound kinoform lenses for sub-150 nm hard x-rays focusing

It is the first time to fabricate the polymethyl methacrylate (PMMA) based compound kinoform lenses (CKLs) for nano-focusing of hard x-rays. The PMMA CKLs with a physical aperture of 160 µm and a focal length of 20 mm are designed and fabricated by x-ray LIGA technology at the Beijing Synchrotron Radiation Facility. To improve the stiffness of the PMMA lines, PMMA sheets with high molecular weight are fabricated, and the results revealed that the PMMA lines with higher molecular weight were much stronger. After optimization, CKLs with the narrowest lines of 4 µm width can achieve 110 µm height and 2.99 nm surface roughness without deformation. The CKLs were tested at the Diamond Light Source, which provided a focal width of 122 nm for 12 keV x rays. Though the PMMA has a poor radiation tolerance, it has a better process tolerance, and it can lay a good foundation for the fabrication of SU8 based CKLs by LIGA technology, which has a better radiation tolerance. Compared to the Si CKLs fabricated by dry etching, the PMMA CKLs are higher in depth, smoother at the sidewall, and have better nanofocusing.

Concepts for the data flow control on the XIDer readout ASIC

XIDer is a 2D pixelated hybrid X-ray detector that is supposed to act as a multi-purpose platform for diffraction experiments at fourth-generation high-energy synchrotron light sources like the Extremely Brilliant Source of the European Synchrotron Radiation Facility (ESRF-EBS). As such it needs to tackle a wide variety of requirements. These include x-ray energies of 30keV to 100keV imposing the utilisation of high-Z sensors, a wide dynamic range from single photons to fluxes of 1 × 109photonspixel−1s−1 and expected raw data rates up to the order of TBs−1 in the final detector design.As a result, XIDer’s readout ASIC has to provide smart and flexible ways for on-chip data pre-processing to reduce the output data rate to manageable sizes. This article focusses on introducing the ASIC’s novel and unique data-handling concepts like the custom-designed telegram protocol followed by the presentation of exemplary configurations and use cases.

Research on an active control method of double crystal monochromator with disturbance observer

The double crystal monochromator (DCM) is the core equipment of high flux and high monochromatic light on the synchrotron beamline, which directly affects the performance of the synchrotron hard X-ray beamline in terms of stability. To meet the requirements for the stability of the nano-radian magnitude of the DCM for the 4th-generation synchrotron light source, this paper presents a method to suppress the primary resonance of the system using an integral lead compensation notch filter and eliminate the higher-order positive and negative resonance peaks with a dual second-order notch filter. The bandwidth of the DCM system is enhanced to meet the system speed requirements. Meanwhile, the mechanical coupling is considered equivalent to the system's internal disturbance. The disturbance observer is designed to ensure the stability and dynamic performance of the DCM system. The simulation results show that after correction by the integral lead compensation notch filter and the dual second-order notch filter, the system bandwidth can reach 308Hz while maintaining a phase margin of approximately 25°. Furthermore, the stability of DCM can reach an RMS of 0.139 nrad, 16.610 nrad, and 1.431 nm in the Pitch, Roll, and Gap direction, respectively, with the help of a disturbance observer. The paper proposes a method to develop stable DCMs in 4th-generation synchrotron radiation facilities while improving the X-ray beamline performance.

Exploring the time-resolving capabilities of XIDer assemblies

The XIDer R&D project, between the European Synchrotron Radiation Facility (ESRF) and Heidelberg University, is developing state-of-the-art detectors for the high-energy, high-flux beamlines of the ESRF Extremely Brilliant Source (EBS). In particular, the XIDer detector aims to tackle the significant challenges posed by time-resolved experiments analysing the pattern of diffracted or scattered X-rays.To fulfil the needs of these experiments, a novel on-chip incremental digital integration readout scheme with per-pixel digital data output has been implemented. The EBS beam operates with different time structures: from a near-100% duty cycle X-ray beam to an up to 5.7MHz pulsed X-ray beam. For the latter EBS mode, the XIDer ASIC has been designed to have a fast front-end and memory storage cells, such that the pulsed EBS beam can be exploited by time-resolved experiments. Recent measurements of the time-resolving capabilities of XIDer ASICs hybridised cadmium telluride and cadmium zinc telluride sensors are presented.

Large-view x-ray imaging for medical applications using the world’s only vertically polarized synchrotron radiation beam and a single asymmetric Si crystal

Objective. X-ray microangiography provides detailed information on the internal structure and function of a biological subject. Its ability to evaluate the microvasculature of small animals is useful for acquiring basic and clinical medical knowledge. The following three conditions are necessary to attain detailed knowledge of biological functions: (1) high temporal resolution with sufficient x-ray intensity, (2) high spatial resolution, and (3) a wide field of view. Because synchrotron radiation microangiography systems provide high sapatial resolution and high temporal resolution as a result of their high x-ray intensity, such systems have been developed at various synchrotron radiation facilities, starting with the photon factory, leading to numerous medical discoveries. However, the three aforementioned functions are incompatible with the use of synchrotron radiation because the x-ray intensity decreases when a wide field of view is obtained. To overcome these problems, we developed a new x-ray optical system for microangiography in rats using synchrotron radiation x-rays. Approach. Instead of using monochromatic synchrotron radiation x-rays with a conventional double-crystal monochromator, we used white synchrotron radiation x-rays and an asymmetric Si crystal to simultaneously monochromatize the beam and widen the field of view. Main results. The intensity profile and spatial resolution of the x-ray images were then evaluated. The proposed x-ray optics increased the x-ray intensity and beam width by factors of 1.3 and 2.7, respectively, compared with those of conventional monochromatic x-rays. In addition, in vivo studies on microangiography in rats were performed to confirm that the images had sufficient intensity, spatial resolution, and field of view. One of a series of images taken at 50 ms frame−1 was shown as an example. Significance. This x-ray optics provides sufficient x-ray intensity, high spatial resolution, and a wide field of view. This technique is expected providing new insights into the evaluation of the vascular system.

A high-throughput big-data orchestration and processing system for the High Energy Photon Source.

High-data-throughput and multimodal-acquisition experiments will prevail in next-generation synchrotron beamlines. Orchestrating dataflow pipelines connecting the data acquisition, processing, visualization and storage ends are becoming increasingly complex and essential for enhancing beamline performance. Mamba Data Worker (MDW) has been developed to address the data challenges for the forthcoming High Energy Photon Source (HEPS). It is an important component of the Mamba experimental control and data acquisition software ecosystem, which enables fast data acquisition and transmission, dynamic configuration of data processing pipelines, data multiplex in streaming, and customized data and metadata assembly. This paper presents the architecture and development plan of MDW, outlines the essential technologies involved, and illustrates its current application at the Beijing Synchrotron Radiation Facility (BSRF).

Evaluation of high intensity synchrotron radiation x-ray imaging using Si crystals with lapped surface at 33.3 keV.

In x-ray imaging methods, such as synchrotron radiation microangiography, the x-ray intensity has become more important in recent years for real-time dynamic observations to evaluate temporal changes in samples. Many synchrotron radiation facilities use x-rays monochromated by diffraction from perfect Si crystals to improve the spatial resolution of x-ray images and obtain detailed information about a sample. In this paper, monochromatic synchrotron x-ray images were acquired using Si crystals lapped with abrasives to enhance the x-ray intensity using white synchrotron radiation x-rays for observing dynamic changes in samples. The x-ray intensity, spatial resolution, and contrast noise ratio (CNR) in the acquired x-ray images were quantitatively evaluated using a state-of-the-art high-spatial-resolution detector. The x-ray intensity was substantially increased by a factor of ∼8 when a lapped Si crystal was used. When the lapped Si crystal was used, the spatial resolution of x-ray images in the diffraction-plane direction was ∼70% lower than when an etched Si crystal was used at a spatial resolution of 10 lp/mm. By contrast, the CNR in x-ray images, which is important for observing the interior of a sample, increased threefold when a contrast agent containing iodine at a concentration of 38 wt. % was used. It was confirmed that the combination of white synchrotron radiation x-rays and a lapped crystal produces an intense monochromatic x-ray, providing an important evaluation for the use of optics for each research purpose.

A machine-learning based closed orbit feedback for a synchrotron light source

In order to improve the stability of synchrotron radiation, we developed a new method of machine learning-based closed orbit feedback, and piloted it in the storage ring of the Shanghai Synchrotron Radiation Facility (SSRF). In our experiments, the machine learning-based closed orbit feedback can carry out horizontal, vertical and RF main frequency feedback simultaneously. What's more, the residual values of variations in the correctors' currents before vs. after correction can be almost ignored. This machine learning-based new method is expected to establish a new closed orbit feedback system and improve the orbit stability of the storage ring in daily operation.

SPHIRD–Single Photon Counting Pixel Readout ASIC With Pulse Pile-Up Compensation Methods

This paper presents the design and measurement results of a prototype SPHIRD-1 ASIC in the CMOS 40 nm process. The chip is dedicated to high count rate single photon counting operation at the European Synchrotron Radiation Facility with Extremely Brilliant Source. The core of the prototype IC is the matrix of 64 32 pixels of 50 μm pitch. Each pixel contains a Charge Sensitive Amplifier (CSA) with a fast discharge block and a detector leakage current compensation circuit. The CSA is connected to a set of three discriminators. The readout channel is equipped with additional circuits, which provide different pulse pile-up compensation methods. The priority of the analog front-end electronics is to process the input signal in a short time (the CSA output pulse time width is only 18 ns) and to keep low noise (the equivalent noise charge at the level of 188 el. rms) with a power consumption equals to 26 μW/pixel. The chip is optimized for operation with a monochromatic X-ray beam with an energy of up to 30 keV. The measurements prove the possibility of counting up to 11.5 Gcps/mm2 based on a 10% dead time loss input rate parameter.

Advanced Nanoscale Characterizations of Solid Oxide Cell Electrodes

The growing interest in the transition towards a fossil-free energy system has accelerated research and development on hydrogen-based energy conversion technologies. In this context, solid oxide cells (SOCs) have attracted attention as they can be operated in both electrolysis (SOEC) and fuel cell (SOFC) modes providing a clean and sustainable way of producing both green hydrogen and electricity at high efficiency. Despite their great potential, the current SOC technology faces some challenges due to the significant cell degradation upon operation. The performance loss has been attributed to several factors, such as microstructural evolution in the electrodes [1], and inter-diffusion of elements between the cell layers associated to material decomposition and reactivity [2–4]. Despite several efforts, all these degradation phenomena are still not precisely understood as they involve complex and intricate processes arising at different length scales. To address this issue, durability tests have been performed in representative operating conditions at high current density and humidity at the air side for both SOFC and SOEC modes. In addition, the tested cells were analyzed with advanced characterization techniques to study the material degradation down to the nanometer and the atomic scales.In this work, standard fuel electrode supported cells have been studied. They are composed of a La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) current collecting layer (CCL) and a LSCF/Ce0.8Gd0.2O2-δ (LSCF/GDC) composite functional layer (FL) for the air electrode, GDC for the barrier layer, (Y2O3)0.08(ZrO2)0.92 (YSZ) for the electrolyte and Ni-YSZ for the fuel electrode. The samples were aged for 2000 h in various operating conditions: temperature (750, 800, 850 °C), humidity in the air flow (0%, 3% and 8%) and operating mode (SOEC and SOFC at ±1 A cm-2). The electrochemical behaviour of the cells has been characterized using electrochemical impedance spectroscopy (EIS) and polarization curves. The advanced post-mortem characterizations include techniques such as synchrotron X-ray nano-diffraction and nano-fluorescence (nano-XRD and nano-XRF) spectroscopy performed at the European Synchrotron Radiation Facility (ESRF, ID16B), scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray spectroscopy (EDX), and atom probe tomography (APT). A larger range of information was acquired by using complementary techniques, including focused ion beam scanning electron microscopy (FIB-SEM), X-ray photoelectron spectroscopy (XPS), and high-resolution secondary ion mass spectroscopy (SIMS) imaging.The electrochemical characterizations (Fig. 1a) have shown that the degradation was aggravated by increasing the operating temperature, the presence of humidity at the air side and the operation in electrolysis mode. The impedance spectra have been interpreted using a physically-based multiscale model [5]. The analysis has revealed that the performance loss was mainly due to the fuel electrode degradation, while the air electrode degradation remained limited, except when operated under humid conditions in the SOEC mode. The post-mortem characterizations have shown that such degradation in the SOEC mode was mainly related to a strong Ni depletion, which became more pronounced with increasing operating temperature. For the cell operated under humid air in the SOEC mode, a significant amount of SrCO3 phase was observed on top of the air electrode. On the contrary, the cell operated under humid air in the SOFC mode did not show such phase formation. Advanced characterization techniques (nano-XRD, nano-XRF, STEM-EDX, and APT) put in evidence an intermixing of elements in the air electrode (LSCF/GDC) at the atomic scale (Fig. 1b). Moreover, the presence of an inter-diffusion layer (IDL) between GDC and YSZ phases was observed (Fig. 1c) for all samples, including the freshly prepared sample. Nevertheless, neither the mixing of elements in the air electrode nor the presence of the IDL seem to have a major influence on the cell degradation. It can be speculated that these phenomena make the air electrode more stable against phase decomposition by inhibiting the formation of commonly observed insulating phases such as SrZrO3 and SrO.

Analysis of Structural Degradation Effects in a Solid Oxide Fuel Cell after Long-Term Operation

The sustainable production of hydrogen as well as its re-conversion into electricity will be a key aspect in a future green energy environment that is depending on regenerative resources. In order to ensure the eminent position of solid oxide cells (SOC) in this future hydrogen economy their reliability and long-term performance still needs to be improved. Having this in mind, we performed detailed investigations on samples from cells that were operated for 100,000h to get a profound understanding of structural degradation effects after long-term operation.The investigated samples originate from a two layer stack of fuel electrode supported solid oxide cells that were operated at 700°C and 0.5 A/cm2 in fuel cell mode. The cells consist of a Ni/Y-stabilized ZrO2 (YSZ) fuel electrode, a dense YSZ electrolyte layer, a Gd doped CeO2 (GDC) barrier layer and a La0.58Sr0.4Co0.2Fe0.8O3-d (LSCF) air electrode. Furthermore, an additional contact layer of La0.97Mn0.4Co0.3Cu0.3O3-d was applied on the air electrode surface and, in order to inhibit Cr-poisoning the interconnector material was coated with a manganese oxide layer by wet powder spraying. The stack represents the usual material status from 2009 when the stack operation has been starting.In the post-test analysis the microstructure and chemical composition was investigated by scanning electron microscopy (SEM) in combination with energy dispersive X-ray spectroscopy (EDS). The EDS analysis revealed localized, correlated enrichments of Sr and Cr in the bulk of the LSCF air electrode as well as at the LSCF / GDC interface. Moreover, non-correlated, localized Co enrichments could also be detected at the LSCF / GDC interface. In order to get an insight into localized structural changes and to identify impurity phases after long-term operation Raman spectroscopy measurements were performed. Hereby, it was for example possible to visualize, in accordance with the EDS analysis, the formation of a SrCrO4 impurity phase on the LSCF air electrode surface as well as inside the bulk of the LSCF by running Raman measurements on the air electrode surface as well as on embedded and polished cross-section samples. To study the structural degradation in detail with high spatial resolution, additional µ-beam Laue diffraction measurements were performed at the CRG-IF BM32 beamline at European Synchrotron Radiation Facility (ESRF).

Monitoring the Particle Size Distribution, Phase Quantification and Chemical Composition of Acid-Leached PtCo Electrocatalyst Under Start-up/Shut-Down Conditions Probed By in-Situ SAXS and WAXS Techniques

Large progress has been made towards commercialization of polymer electrolyte membrane fuel cells (PEMFCs) through the development of highly active and robust Pt-Co alloy catalysts for oxygen reduction reaction (ORR).[1,2] However, most ORR catalyst materials suffer from the extremely corrosive conditions occurring during start-up/shut-down (SUSD).[3] Consequently, understanding the degradation mechanisms during SUSD is highly crucial for designing new catalyst materials with enhanced ORR activity and long-term durability.In this work, we show a comprehensive and complementary combination of different advanced techniques such as in-situ small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) as well as ex-situ scanning transmission electron microscopy in combination with electron energy loss spectroscopy (STEM-EELS) to provide deeper insights into the degradation processes of acid-leached Pt-Co catalyst under SUSD conditions.Firstly, Pt-Co nanoparticles supported on high surface area carbon (HSAC) were synthesized using wet impregnation – freeze-drying – thermal annealing method.[4] Compared to our previous works [4-6], an acid-leaching (1 M H2SO4, 15 °C, 2 h) was applied to dissolve the less noble metal from the surface of alloy nanoparticles forming a Pt-enriched skin. STEM-EELS data has also confirmed the formation of the Pt-enriched skin. In addition, ex-situ WAXS data signifies that the acid-leached PtCo catalyst consists of two face-centered cubic (fcc) disordered crystal phases: Pt90Co10 phase with a crystallite size of 3.6 ± 0.4 nm and Pt70Co30 phase with 4.2 ± 0.4 nm size.In terms of ORR performance, the acid-leached PtCo catalyst exhibits a 2.5- & 2-times higher mass activity (0.61 ± 0.12 A mgPt -1) and a 3.5- and 1.3-times higher specific activity (665 ± 84 µA cmPt -2) at 0.9 VRHE compared to commercial ~2 nm Pt/C (0.24 ± 0.05 A mgPt -1, 187 ± 29 µA cmPt -2) and heat-treated 4-5 nm Pt/HSAC (0.30 ± 0.04 A mgPt -1, 297 ± 42 µA cmPt -2), respectively. After SUSD experiments (800 cycles, 0.5 - 1.5 VRHE, 50 mV s-1, 0.1 M HClO4), the mass activity decreases to 0.21 ± 0.06 A mgPt -1 (-65 %) and 0.15 ± 0.03 A mgPt -1 (-38 %) for the acid-leached PtCo catalyst and commercial Pt/C, respectively.To monitor the potential-dependent changes in particle/crystallite size, phase quantification and chemical composition of the acid-leached PtCo catalyst under the SUSD conditions, in-situ SAXS and WAXS experiments were simultaneously performed at the beamline ID31 at European Synchrotron Radiation Facility (ESRF).In-situ WAXS analysis reveals that the lattice parameter of both Pt90Co10 and Pt70Co30 phases increases as a function of the SUSD cycle number, signifying the successive depletion of cobalt mainly from the Pt70Co30 phase. More precisely, the lattice parameter changed from 3.819 ± 0.004 Å (Pt70Co30) to 3.829 ± 0.004 Å (Pt76Co24) during the first 150 SUSD cycles. Only a slight change in lattice parameter for Pt90Co10 phase is observed during the SUSD protocol. Based on the Rietveld quantification, the amount of the Pt70Co30 phase decreases from 61 ± 2 wt.% to 47 ± 2 wt.% during the first 150 SUSD cycles. Afterwards, the Co depletion from this phase is less pronounced with additional cycle number. Furthermore, STEM-EELS investigations on acid-leached PtCo catalyst after first 150 SUSD cycles has confirmed the drastic Co depletion within the nanoparticles. After the SUSD protocol, the chemical composition of the acid-leached PtCo catalyst alters from Pt67±3Co33±3 to Pt81±3Co19±3 (-42 at.%) obtained from the bulk techniques like EDX and µ-XRF.In addition, the Rietveld refinement reveals an increase in crystallite sizes for both Pt-Co crystal phases over the course of the SUSD protocol which is in excellent agreement to the in-situ SAXS and ex-situ TEM results (from 4.1 ± 1.0 nm to 5.2 ± 0.8 nm, +27 %). In detail, the initial larger Pt70Co30 phase shows only a small increase in crystallite size (from 4.3 ± 0.4 nm to 4.8 ± 0.4 nm, +12 %), whereas for the initial smaller Pt90Co10 phase a gradual increase from 3.2 ± 0.3 nm to 4.5 ± 0.4 nm (+41 %) is observed during the SUSD experiment.Based on the in-situ SAXS/WAXS and the ex-situ STEM-EELS data, the Co depletion is the dominant degradation mechanism for the disordered fcc Pt70Co30 phase during the first 150 SUSD cycles. With increasing SUSD cycle number, the particle growth via Ostwald ripening and particle coalescence predominates. Our degradation model can be used to further improve the ORR performance and durability of acid-leached Pt-Co catalysts under the SUSD conditions.Literature:[1] L.R.Borup et al.,Curr.Opin.Electrochem.,2020,21,192-200.[2] C.Wang et al.,Energies,2016,9,603-642.[3] Y.Yu, et al.,J.Power Sources,2012,205,10-23.[4] M.Oezaslan et al.,J.Electrochem.Soc.,2012,159,B394-B405.[5] D.J.Weber et al.,J.Mater.Chem.A,2021,9,15415-15431.[6] P.Weber et al.,ACS Catal.,2022,12,6394-6408.

Tin/Tin Oxide Nanostructures: Formation, Application, and Atomic and Electronic Structure Peculiarities.

For a very long period, tin was considered one of the most important metals for humans due to its easy access in nature and abundance of sources. In the past, tin was mainly used to make various utensils and weapons. Today, nanostructured tin and especially its oxide materials have been found to possess many characteristic physical and chemical properties that allow their use as functional materials in various fields such as energy storage, photocatalytic process, gas sensors, and solar cells. This review discusses current methods for the synthesis of Sn/SnO2 composite materials in form of powder or thin film, as well as the application of the most advanced characterization tools based on large-scale synchrotron radiation facilities to study their chemical composition and electronic features. In addition, the applications of Sn/SnO2 composites in various fields are presented in detail.