Atomically dispersed asymmetric cobalt electrocatalyst for efficient hydrogen peroxide production in neutral media.

Electrochemical hydrogen peroxide (H2O2) production (EHPP) via a two-electron oxygen reduction reaction (2e- ORR) provides a promising alternative to replace the energy-intensive anthraquinone process. M-N-C electrocatalysts, which consist of atomically dispersed transition metals and nitrogen-doped carbon, have demonstrated considerable EHPP efficiency. However, their full potential, particularly regarding the correlation between structural configurations and performances in neutral media, remains underexplored. Herein, a series of ultralow metal-loading M-N-C electrocatalysts are synthesized and investigated for the EHPP process in the neutral electrolyte. CoNCB material with the asymmetric Co-C/N/O configuration exhibits the highest EHPP activity and selectivity among various as-prepared M-N-C electrocatalyst, with an outstanding mass activity (6.1 × 105 A gCo-1 at 0.5 V vs. RHE), and a high practical H2O2 production rate (4.72 mol gcatalyst-1 h-1 cm-2). Compared with the popularly recognized square-planar symmetric Co-N4 configuration, the superiority of asymmetric Co-C/N/O configurations is elucidated by X-ray absorption fine structure spectroscopy analysis and computational studies.

Creation of Polymer Datasets with Targeted Backbones for Screening of High-Performance Membranes for Gas Separation.

A simple approach was developed to computationally construct a polymer dataset by combining simplified molecular-input line-entry system (SMILES) strings of a targeted polymer backbone and a variety of molecular fragments. This method was used to create 14 polymer datasets by combining seven polymer backbones and molecules from two large molecular datasets (MOSES and QM9). Polymer backbones that were studied include four polydimethylsiloxane (PDMS) based backbones, poly(ethylene oxide) (PEO), poly(allyl glycidyl ether) (PAGE), and polyphosphazene (PPZ). The generated polymer datasets can be used for various cheminformatics tasks, including high-throughput screening for gas permeability and selectivity. This study utilized machine learning (ML) models to screen the polymers for CO2/CH4 and CO2/N2 gas separation using membranes. Several polymers of interest were identified. The results highlight that employing an ML model fitted to polymer selectivities leads to higher accuracy in predicting polymer selectivity compared to using the ratio of predicted permeabilities.

Costal margin injuries and trans-diaphragmatic intercostal hernia: Presentation, management and outcomes according to the Sheffield classification.

BACKGROUND: Costal margin rupture (CMR) injuries are under-diagnosed and inconsistently managed, while carrying significant symptomatic burden. We hypothesized that the Sheffield Classification system of CMR injuries would relate to injury patterns and management options. METHODS: Data were collected prospectively between 2006 and 2023 at a major trauma center in the United Kingdom. Computed tomography scans were interrogated and injuries were categorized according to the Sheffield Classification. Clinical, radiologic, management and outcome variables were assessed. RESULTS: Fifty-four patients were included in the study. Intercostal hernia (IH) was present in 30 patients and associated with delayed presentation ( p = 0.004), expulsive mechanism of injury (i.e. such as occurs with coughing, sneezing, or retching), higher body mass index ( p < 0.001), and surgical management ( p = 0.02). There was a bimodal distribution of the level of the costal margin rupture, with IH Present and expulsive mechanism injuries occurring predominantly at the ninth costal cartilage, and IH Absent cases and other mechanisms at the seventh costal cartilage ( p < 0.001). There were correlations between the costal cartilage being thin at the site of the CMR and the presence of IH and expulsive etiology ( p < 0.001). Management was conservative in 23 and surgical in 31 cases. Extrathoracic mesh IH repairs were performed in 3, Double Layer Mesh Repairs in 8, Suture IH repairs in 5, CMR plating in 8, CMR sutures in 2, and associated Surgical Stabilization of Rib Fractures in 11 patients. There was one postoperative death. There were seven repeat surgical procedures in five patients. CONCLUSION: The Sheffield Classification is associated statistically with presentation, related chest wall injury patterns, and type of definitive management. Further collaborative data collection is required to determine the optimal management strategies. LEVEL OF EVIDENCE: Therapeutic/Care Management; Level III.

Spectroscopic Identification of Active Sites of Oxygen-Doped Carbon for Selective Oxygen Reduction to Hydrogen Peroxide.

The electrochemical synthesis of hydrogen peroxide (H2 O2 ) via a two-electron (2 e- ) oxygen reduction reaction (ORR) process provides a promising alternative to replace the energy-intensive anthraquinone process. Herein, we develop a facile template-protected strategy to synthesize a highly active quinone-rich porous carbon catalyst for H2 O2 electrochemical production. The optimized PCC900 material exhibits remarkable activity and selectivity, of which the onset potential reaches 0.83 V vs. reversible hydrogen electrode in 0.1 M KOH and the H2 O2 selectivity is over 95 % in a wide potential range. Comprehensive synchrotron-based near-edge X-ray absorption fine structure (NEXAFS) spectroscopy combined with electrocatalytic characterizations reveals the positive correlation between quinone content and 2 e- ORR performance. The effectiveness of chair-form quinone groups as the most efficient active sites is highlighted by the molecule-mimic strategy and theoretical analysis.

Right upper lobe pulmonary sequestration masquerading clinically and radiologically as malignancy: a case report.

Bronchopulmonary sequestration is a rare disease in which a non-functional region of pulmonary tissue receives an aberrant vascular supply and lacks normal communication with the tracheobronchial tree. We present the case of a 30-year-old female with a primary complaint of unexplained weight loss and no other additional signs or symptoms. In view of this, computed tomography imaging was ordered, showing a 33HU mass in the right upper lobe. A specialist radiologist reviewed the images and concluded that the most likely differentials were mediastinal lymphoma or thymic malignancy. Video-assisted thoracoscopic surgery was performed, when it was seen that no malignancy was present, but rather a bronchopulmonary sequestration. Histology confirmed the diagnosis; the patient fared well post-operatively. Bronchopulmonary sequestration is a rare pathology, with most cases occurring in the lower lung lobes. This case is highly atypical, due to the lack of clinical features and the lesion radiologically mimicking the appearance of malignancy.

Tracking single adatoms in liquid in a transmission electron microscope.

Single atoms or ions on surfaces affect processes from nucleation1 to electrochemical reactions2 and heterogeneous catalysis3. Transmission electron microscopy is a leading approach for visualizing single atoms on a variety of substrates4,5. It conventionally requires high vacuum conditions, but has been developed for in situ imaging in liquid and gaseous environments6,7 with a combined spatial and temporal resolution that is unmatched by any other method-notwithstanding concerns about electron-beam effects on samples. When imaging in liquid using commercial technologies, electron scattering in the windows enclosing the sample and in the liquid generally limits the achievable resolution to a few nanometres6,8,9. Graphene liquid cells, on the other hand, have enabled atomic-resolution imaging of metal nanoparticles in liquids10. Here we show that a double graphene liquid cell, consisting of a central molybdenum disulfide monolayer separated by hexagonal boron nitride spacers from the two enclosing graphene windows, makes it possible to monitor, with atomic resolution, the dynamics of platinum adatoms on the monolayer in an aqueous salt solution. By imaging more than 70,000 single adatom adsorption sites, we compare the site preference and dynamic motion of the adatoms in both a fully hydrated and a vacuum state. We find a modified adsorption site distribution and higher diffusivities for the adatoms in the liquid phase compared with those in vacuum. This approach paves the way for in situ liquid-phase imaging of chemical processes with single-atom precision.

Computational Screening of Physical Solvents for CO2 Pre-combustion Capture.

A computational scheme was used to screen physical solvents for CO2 pre-combustion capture by integrating the commercial NIST database, an in-house computational database, chem-informatics, and molecular modeling. A commercially available screened hydrophobic solvent, diethyl sebacate, was identified from the screening with favorable physical properties and promising absorption performance. The promising performance to use diethyl sebacate in CO2 pre-combustion capture has also been confirmed from experiments. Water loading in diethyl sebacate is very low, and therefore, water is kept with H2 in the gas stream. The favorable CO2 interaction with diethyl sebacate and the intermediate solvent free volume fraction leads to both high CO2 solubility and high CO2/H2 solubility selectivity in diethyl sebacate. An in-house NETL computational database was built to characterize CO2, H2, N2, and H2O interactions with 202 different chemical functional groups. It was found that 13% of the functional groups belong to the strong interaction category with the CO2 interaction energy between -15 and -21 kJ/mol; 62% of the functional groups interact intermediately with CO2 (-8 to -15 kJ/mol). The remaining 25% of functional groups interact weakly with CO2 (below -8 kJ/mol). In addition, calculations show that CO2 interactions with the functional groups are stronger than N2 and H2 interactions but are weaker than H2O interactions. The CO2 and H2O interactions with the same functional groups exhibit a very strong linear positive correlation coefficient of 0.92. The relationship between CO2 and H2 gas solubilities and solvent fractional free volume (FFV) has been systematically studied for seven solvents at 298.2 K. A skewed bell-shaped relation was obtained between CO2 solubility and solvent FFV. When an organic compound has a density approximately 10% lower than its density at 298.2 K and 1 bar, it exhibits the highest CO2 loading at that specific solvent density and FFV. Note that the solvent densities were varied using simulations, which are difficult to be obtained from the experiment. In contrast, H2 solubility results exhibit an almost perfect positive linear correlation with the solvent FFV. The theoretical maximum and minimum physical CO2 solubilities in any organic compound at 298.2 K were estimated to be 11 and 0.4 mol/MPa L, respectively. An examination of 182 experimental CO2 physical solubility data and 29 simulated CO2 physical solubilities shows that all the CO2 physical solubility data are within the maximum and minimum with only a few exceptions. Finally, simulations suggest that in order to develop physical solvents with both high CO2 solubility and high CO2/H2 solubility selectivity, the solvents should contain functional groups which are available to interact strongly with CO2 while minimizing FFV.

Ion exchange in atomically thin clays and micas.

The physical properties of clays and micas can be controlled by exchanging ions in the crystal lattice. Atomically thin materials can have superior properties in a range of membrane applications, yet the ion-exchange process itself remains largely unexplored in few-layer crystals. Here we use atomic-resolution scanning transmission electron microscopy to study the dynamics of ion exchange and reveal individual ion binding sites in atomically thin and artificially restacked clays and micas. We find that the ion diffusion coefficient for the interlayer space of atomically thin samples is up to 104 times larger than in bulk crystals and approaches its value in free water. Samples where no bulk exchange is expected display fast exchange at restacked interfaces, where the exchanged ions arrange in islands with dimensions controlled by the moiré superlattice dimensions. We attribute the fast ion diffusion to enhanced interlayer expandability resulting from weaker interlayer binding forces in both atomically thin and restacked materials. This work provides atomic scale insights into ion diffusion in highly confined spaces and suggests strategies to design exfoliated clay membranes with enhanced performance.

Scalable Polymeric Few-Nanometer Organosilica Membranes with Hydrothermal Stability for Selective Hydrogen Separation.

Nanoporous silica membranes exhibit excellent H2/CO2 separation properties for sustainable H2 production and CO2 capture but are prepared via complicated thermal processes above 400 °C, which prevent their scalable production at a low cost. Here, we demonstrate the rapid fabrication (within 2 min) of ultrathin silica-like membranes (∼3 nm) via an oxygen plasma treatment of polydimethylsiloxane-based thin-film composite membranes at 20 °C. The resulting organosilica membranes unexpectedly exhibit H2 permeance of 280-930 GPU (1 GPU = 3.347 × 10-10 mol m-2 s-1 Pa-1) and H2/CO2 selectivity of 93-32 at 200 °C, far surpassing state-of-the-art membranes and Robeson's upper bound for H2/CO2 separation. When challenged with a 3 d simulated syngas test containing water vapor at 200 °C and a 340 d stability test, the membrane shows durable separation performance and excellent hydrothermal stability. The robust H2/CO2 separation properties coupled with excellent scalability demonstrate the great potential of these organosilica membranes for economic H2 production with minimal carbon emissions.

Nanometre imaging of Fe3GeTe2 ferromagnetic domain walls.

Fe3GeTe2 is a layered crystal which has recently been shown to maintain its itinerant ferromagnetic properties even when atomically thin. Here, differential phase contrast scanning transmission electron microscopy is used to investigate the domain structure in a Fe3GeTe2 cross-sectional lamella at temperatures ranging from 95 to 250 K and at nanometre spatial resolution. Below the experimentally determined Curie temperature (T C) of 191 K, stripe domains magnetised along 〈0001〉, bounded with 180◦ Bloch type domain walls, are observed, transitioning to mixed Bloch-Néel type where the cross-sectional thickness is reduced below 50 nm. When warming towards T C, these domains undergo slight restructuring towards uniform size, before abruptly fading at T C. Localised loss of ferromagnetic order is seen over time, hypothesised to be a frustration of ferromagnetic order from ambient oxidation and basal cracking, which could enable selective modification of the magnetic properties for device applications.

Preparation of solution processed photodetectors comprised of two-dimensional tin(ii) sulfide nanosheet thin films assembled via the Langmuir-Blodgett method.

We report the manufacture of fully solution processed photodetectors based on two-dimensional tin(ii) sulfide assembled via the Langmuir-Blodgett method. The method we propose can coat a variety of substrates including paper, Si/SiO2 and flexible polymer allowing for a potentially wide range of applications in future optoelectronic devices.

3D printed MOF-based mixed matrix thin-film composite membranes.

MOF-based mixed-matrix membranes (MMMs) have attracted considerable attention due to their tremendous separation performance and facile processability. In large-scale applications such as CO2 separation from flue gas, it is necessary to have high gas permeance, which can be achieved using thin membranes. However, there are only a handful of MOF MMMs that are fabricated in the form of thin-film composite (TFC) membranes. We propose herein the fabrication of robust thin-film composite mixed-matrix membranes (TFC MMMs) using a three dimensional (3D) printing technique with a thickness of 2-3 µm. We systematically studied the effect of casting concentration and number of electrospray cycles on membrane thickness and CO2 separation performance. Using a low concentration of polymer of intrinsic microporosity (PIM-1) or PIM-1/HKUST-1 solution (0.1 wt%) leads to TFC membranes with a thickness of less than 500 nm, but the fabricated membranes showed poor CO2/N2 selectivity, which could be attributed to microscopic defects. To avoid these microscale defects, we increased the concentration of the casting solution to 0.5 wt% resulting in TFC MMMs with a thickness of 2-3 µm which showed three times higher CO2 permeance than the neat PIM-1 membrane. These membranes represent the first examples of 3D printed TFC MMMs using the electrospray printing technique.

Atomic Resolution Imaging of CrBr3 Using Adhesion-Enhanced Grids.

Suspended specimens of 2D crystals and their heterostructures are required for a range of studies including transmission electron microscopy (TEM), optical transmission experiments, and nanomechanical testing. However, investigating the properties of laterally small 2D crystal specimens, including twisted bilayers and air-sensitive materials, has been held back by the difficulty of fabricating the necessary clean suspended samples. Here we present a scalable solution that allows clean free-standing specimens to be realized with 100% yield by dry-stamping atomically thin 2D stacks onto a specially developed adhesion-enhanced support grid. Using this new capability, we demonstrate atomic resolution imaging of defect structures in atomically thin CrBr3, a novel magnetic material that degrades in ambient conditions.

Radiation-resistant metal-organic framework enables efficient separation of krypton fission gas from spent nuclear fuel.

Capture and storage of volatile radionuclides that result from processing of used nuclear fuel is a major challenge. Solid adsorbents, in particular ultra-microporous metal-organic frameworks, could be effective in capturing these volatile radionuclides, including 85Kr. However, metal-organic frameworks are found to have higher affinity for xenon than for krypton, and have comparable affinity for Kr and N2. Also, the adsorbent needs to have high radiation stability. To address these challenges, here we evaluate a series of ultra-microporous metal-organic frameworks, SIFSIX-3-M (M = Zn, Cu, Ni, Co, or Fe) for their capability in 85Kr separation and storage using a two-bed breakthrough method. These materials were found to have higher Kr/N2 selectivity than current benchmark materials, which leads to a notable decrease in the nuclear waste volume. The materials were systematically studied for gamma and beta irradiation stability, and SIFSIX-3-Cu is found to be the most radiation resistant.

Cross-Linked Polyphosphazene Blends as Robust CO2 Separation Membranes.

An effective cross-linking technique allows a viscous and highly gas-permeable hydrophilic polyphosphazene to be cast as solid membrane films. By judicious blending with other polyphosphazenes to improve the mechanical properties, a membrane exhibiting the highest CO2 permeability (610 barrer) among polyphosphazenes combined with a good CO2/N2 selectivity (35) was synthesized and described here. The material demonstrates performance stability after 500 h of exposure to a coal-fired power plant flue gas, making it attractive for use in carbon capture applications. Its CO2/N2 selectivity under conditions up to full humidity is also stable, and although the gas permeability does decline, the performance is fully recovered upon drying. The high molecular weight of these heteropolymers also allows them to be cast as a thin selective layer on an asymmetric porous membrane, yielding a CO2 permeance of 1200 GPU and a CO2/N2 pure gas selectivity of 31, which does not decline over 2000 h. In addition to gas separation membranes, this cross-linked polyphosphazene can potentially be extended to other applications, such as drug delivery or proton exchange membranes, which take advantage of the polyphosphazene's versatile chemistry.

Atomic reconstruction in twisted bilayers of transition metal dichalcogenides.

Van der Waals heterostructures form a unique class of layered artificial solids in which physical properties can be manipulated through controlled composition, order and relative rotation of adjacent atomic planes. Here we use atomic-resolution transmission electron microscopy to reveal the lattice reconstruction in twisted bilayers of the transition metal dichalcogenides, MoS2 and WS2. For twisted 3R bilayers, a tessellated pattern of mirror-reflected triangular 3R domains emerges, separated by a network of partial dislocations for twist angles θ < 2°. The electronic properties of these 3R domains, featuring layer-polarized conduction-band states caused by lack of both inversion and mirror symmetry, appear to be qualitatively different from those of 2H transition metal dichalcogenides. For twisted 2H bilayers, stable 2H domains dominate, with nuclei of a second metastable phase. This appears as a kagome-like pattern at θ ≈ 2°, transitioning at θ → 0 to a hexagonal array of screw dislocations separating large-area 2H domains. Tunnelling measurements show that such reconstruction creates strong piezoelectric textures, opening a new avenue for engineering of 2D material properties.

Enhanced Superconductivity in Few-Layer TaS2 due to Healing by Oxygenation.

When approaching the atomically thin limit, defects and disorder play an increasingly important role in the properties of two-dimensional (2D) materials. While defects are generally thought to negatively affect superconductivity in 2D materials, here we demonstrate the contrary in the case of oxygenation of ultrathin tantalum disulfide (TaS2). Our first-principles calculations show that incorporation of oxygen into the TaS2 crystal lattice is energetically favorable and effectively heals sulfur vacancies typically present in these crystals, thus restoring the electronic band structure and the carrier density to the intrinsic characteristics of TaS2. Strikingly, this leads to a strong enhancement of the electron-phonon coupling, by up to 80% in the highly oxygenated limit. Using transport measurements on fresh and aged (oxygenated) few-layer TaS2, we found a marked increase of the superconducting critical temperature (Tc) upon aging, in agreement with our theory, while concurrent electron microscopy and electron-energy loss spectroscopy confirmed the presence of sulfur vacancies in freshly prepared TaS2 and incorporation of oxygen into the crystal lattice with time. Our work thus reveals the mechanism by which certain atomic-scale defects can be beneficial to superconductivity and opens a new route to engineer Tc in ultrathin materials.

Polymers of Intrinsic Microporosity Chemical Sorbents Utilizing Primary Amine Appendance Through Acid-Base and Hydrogen-Bonding Interactions.

Here, we present novel chemical sorbents based on polymers with intrinsic microporosity (PIMs). For the first time, alkylamines were incorporated in PIMs through an acid-base interaction to create a chemisorbent. The amine-appended PIMs not only showed a nearly four-fold enhancement in CO2 loading capacity (36.4 cc/g at 0.15 bar and 298 K) and very high CO2/N2 selectivity compared to neat PIM-1 but also proved to have stable performance when cycled between adsorption and desorption isotherms under both dry and humid conditions that are typical for postcombustion CO2 capture.

Formation and Healing of Defects in Atomically Thin GaSe and InSe.

Two dimensional III-VI metal monochalcogenide materials, such as GaSe and InSe, are attracting considerable attention due to their promising electronic and optoelectronic properties. Here, an investigation of point and extended atomic defects formed in mono-, bi-, and few-layer GaSe and InSe crystals is presented. Using state-of-the-art scanning transmission electron microscopy, it is observed that these materials can form both metal and selenium vacancies under the action of the electron beam. Selenium vacancies are observed to be healable: recovering the perfect lattice structure in the presence of selenium or enabling incorporation of dopant atoms in the presence of impurities. Under prolonged imaging, multiple point defects are observed to coalesce to form extended defect structures, with GaSe generally developing trigonal defects and InSe primarily forming line defects. These insights into atomic behavior could be harnessed to synthesize and tune the properties of 2D post-transition-metal monochalcogenide materials for optoelectronic applications.