Instantaneous Thermal Energy for Swift Synthesis of Single-Atom Catalysts for Unparalleled Performance in Metal-Air Batteries and Fuel Cells

Based on experimental and computational evidence, phthalocyanine (Pc) compounds in the form of quaternary bound metal-nitrogen (N) atoms are the most effective catalysts for oxygen reduction reaction (ORR). However, the heat treatment process used in their synthesis may compromise the ideal structure, causing the agglomeration of transition metals. To overcome this issue, we developed a novel method for synthesizing iron (Fe) single-atom catalysts with ideal structures supported by thermally exfoliated graphene oxide (GO). This was achieved through a short heat-treatment of only 2.5 min involving FePc and N,N-dimethylformamide in the presence of GO. According to the synthesis mechanism revealed by this study, carbon monoxide acts as a strong linker between the single Fe atoms and graphene. It facilitates the formation of a structure containing oxygen species between FeN4 and graphene, which provides high activity and stability for the ORR. These catalysts possess an enormous number of active sites and exhibit enhanced activity towards the alkaline ORR. They have demonstrated excellent performance when applied to real electrochemical devices, such as zinc-air batteries and anion exchange membrane fuel cells. We expect that the instantaneous heat treatment method developed in our study will aid in the development of high-performing single-atom catalysts. This article is protected by copyright. All rights reserved.

High Free Volume Polyelectrolytes for Anion Exchange Membrane Water Electrolyzers with a Current Density of 13.39 A cm-2 and a Durability of 1000 h

The rational design of the current anion exchange polyelectrolytes (AEPs) is challenging to meet the requirements of both high performance and durability in anion exchange membrane water electrolyzers (AEMWEs). Herein, highly-rigid-twisted spirobisindane monomer is incorporated in poly(aryl-co-aryl piperidinium) backbone to construct continuous ionic channels and to maintain dimensional stability as promising materials for AEPs. The morphologies, physical, and electrochemical properties of the AEPs are investigated based on experimental data and molecular dynamics simulations. The present AEPs possess high free volumes, excellent dimensional stability, hydroxide conductivity (208.1 mS cm-1 at 80 °C), and mechanical properties. The AEMWE of the present AEPs achieves a new current density record of 13.39 and 10.7 A cm-2 at 80 °C by applying IrO2 and nonprecious anode catalyst, respectively, along with outstanding in situ durability under 1 A cm-2 for 1000 h with a low voltage decay rate of 53 µV h-1 . Moreover, the AEPs can be applied in fuel cells and reach a power density of 2.02 W cm-2 at 80 °C under fully humidified conditions, and 1.65 W cm-2 at 100 °C, 30% relative humidity. This study provides insights into the design of high-performance AEPs for energy conversion devices.

Triptycene Branched Poly(aryl-co-aryl piperidinium) Electrolytes for Alkaline Anion Exchange Membrane Fuel Cells and Water Electrolyzers

Alkaline polymer electrolytes (APEs) are essential materials for alkaline energy conversion devices such as anion exchange membrane fuel cells (AEMFCs) and water electrolyzers (AEMWEs). Here, we report a series of branched poly(aryl-co-aryl piperidinium) with different branching agents (triptycene: highly-rigid, three-dimensional structure; triphenylbenzene: planar, two-dimensional structure) for high-performance APEs. Among them, triptycene branched APEs showed excellent hydroxide conductivity (193.5 mS cm-1 @80 °C), alkaline stability, mechanical properties, and dimensional stability due to the formation of branched network structures, and increased free volume. AEMFCs based on triptycene-branched APEs reached promising peak power densities of 2.503 and 1.705 W cm-2 at 75/100 % and 30/30 % (anode/cathode) relative humidity, respectively. In addition, the fuel cells can run stably at a current density of 0.6 A cm-2 for 500 h with a low voltage decay rate of 46 μV h-1 . Importantly, the related AEMWE achieved unprecedented current densities of 16 A cm-2 and 14.17 A cm-2 (@2 V, 80 °C, 1 M NaOH) using precious and non-precious metal catalysts, respectively. Moreover, the AEMWE can be stably operated under 1.5 A cm-2 at 60 °C for 2000 h. The excellent results suggest that the triptycene-branched APEs are promising candidates for future AEMFC and AEMWE applications.

Multiscale Architectured Membranes, Electrodes, and Transport Layers for Next-Generation Polymer Electrolyte Membrane Fuel Cells

Over the past few decades, considerable advances have been achieved in polymer electrolyte membrane fuel cells (PEMFCs) based on the development of material technology. Recently, an emerging multiscale architecturing technology covering nanometer, micrometer, and millimeter scales has been regarded as an alternative strategy to overcome the hindrance to achieving high-performance and reliable PEMFCs. This review summarizes the recent progress in the key components of PEMFCs based on a novel architecture strategy. In the first section, diverse architectural methods for patterning the membrane surface with random, single-scale, and multiscale structures as well as their efficacy for improving catalyst utilization, charge transport, and water management are discussed. In the subsequent section, the electrode structures designed with 1D and 3D multiscale structures to enable low Pt usage, improve oxygen transport, and achieve high electrode durability are elucidated. Finally, recent advances in the architectured transport layer for improving mass transportation including pore gradient, perforation, and patterned wettability for gas diffusion layer and 3D structured/engineered flow fields are described.

Pericardial diverticulum arising from the right lateral superior aortic recess: a mimicker of cystic anterior mediastinal mass

AIM

To report the prevalence of pericardial diverticulum of the right lateral superior aortic recess (RSAR) on computed tomography (CT), to analyse the structural CT findings of whether or not the structure is large enough to be seen on chest radiographs, and to describe changes in size and shape of RSAR on follow-up CT.

MATERIALS AND METHODS

A well-circumscribed, fluid-attenuation lesion in the anterior mediastinum with the following CT features was defined as a pericardial diverticulum of the RSAR: no enhancing wall, communication with the RSAR, abutment to the heart with an acute angle, and moulding by adjacent structures. Chest CT images of 31 patients with the diverticulum were evaluated, including four selected from 1,130 consecutive patients (0.4%).

RESULTS

The diverticulum projected ventrally from the RSAR and its largest size on axial CT ranged between 12-56 mm. Although the RSAR and the largest diverticular portion were usually seen on the same axial image (n=19), the latter sometimes lay above (n=1) or below (n=11) the former. On sagittal images, the last 11 diverticula resembled teardrops hanging from the RSAR by small stems. All of the 24 patients, each with 1-31 follow-up CT examinations, showed size fluctuations ranging between 1-46 mm (mean, 16 mm) during a follow-up period of 0.5-172 months (mean, 65 months). The diverticulum was not identifiable in five cases and was identifiable but did not show a connection with the RSAR in three cases when the diverticulum was smallest in size.

CONCLUSIONS

In cases of cystic anterior mediastinal mass, a deliberate search for its connection with the RSAR on all available CT images including previous studies is necessary for the diagnosis of pericardial diverticulum of the RSAR.

Oxygen Plasma-Mediated Microstructured Hydrocarbon Membrane for Improving Interface Adhesion and Mass Transport in Polymer Electrolyte Fuel Cells

Developing a method for fabricating high-efficient and low-cost fuel cells is imperative for commercializing polymer electrolyte membrane (PEM) fuel cells (FCs). This study introduces a mechanical and chemical modification technique using the oxygen plasma irradiation process for hydrocarbon-based (HC) PEM. The oxygen functional groups were introduced on the HC-PEM surface through the plasma process in the controlled area, and microsized structures were formed. The modified membrane was incorporated with plasma-treated electrodes, improving the adhesive force between the HC-PEM and the electrode. The decal transfer was enabled at low temperatures and pressures, and the interfacial resistance in the membrane-electrode assembly (MEA) was reduced. Furthermore, the micropillar structured electrode configuration significantly reduced the oxygen transport resistance in the MEA. Various diagnostic techniques were conducted to find out the effects of the membrane surface modification, interface adhesion, and mass transport, such as physical characterizations, mechanical stress tests, and diverse electrochemical measurements.

Surface Electrochemistry of Carbon Electrodes and Faradaic Reactions in Capacitive Deionization

Recent advances in electrochemical desalination techniques have paved way for utilization of saline water. In particular, capacitive deionization (CDI) enables removal of salts with high energy efficiency and economic feasibility, while its applicability has been challenged by degradation of carbon electrodes in long-term operations. Herein, we report a thorough investigation on the surface electrochemistry of carbon electrodes and Faradaic reactions that are responsible for stability issues of CDI systems. By using bare and membrane CDI (MCDI) as model systems, we identified various electrochemical reactions of carbon electrodes with water or oxygen, with thermodynamics and kinetics governed by the electrode potential and pH. As a result, a complete overview of the Faradaic reactions taking place in CDI was constructed by tracing the physicochemical changes occurring in CDI and MCDI systems.

Metastable hexagonal close-packed palladium hydride in liquid cell TEM

Metastable phases-kinetically favoured structures-are ubiquitous in nature^1,2. Rather than forming thermodynamically stable ground-state structures, crystals grown from high-energy precursors often initially adopt metastable structures depending on the initial conditions, such as temperature, pressure or crystal size^1,3,4. As the crystals grow further, they typically undergo a series of transformations from metastable phases to lower-energy and ultimately energetically stable phases^1,3,4. Metastable phases sometimes exhibit superior physicochemical properties and, hence, the discovery and synthesis of new metastable phases are promising avenues for innovations in materials science^1,5. However, the search for metastable materials has mainly been heuristic, performed on the basis of experiences, intuition or even speculative predictions, namely 'rules of thumb'. This limitation necessitates the advent of a new paradigm to discover new metastable phases based on rational design. Such a design rule is embodied in the discovery of a metastable hexagonal close-packed (hcp) palladium hydride (PdH_x) synthesized in a liquid cell transmission electron microscope. The metastable hcp structure is stabilized through a unique interplay between the precursor concentrations in the solution: a sufficient supply of hydrogen (H) favours the hcp structure on the subnanometre scale, and an insufficient supply of Pd inhibits further growth and subsequent transition towards the thermodynamically stable face-centred cubic structure. These findings provide thermodynamic insights into metastability engineering strategies that can be deployed to discover new metastable phases.

Combined Effect of Catholyte Gap and Cell Voltage on Syngas Ratio in Continuous CO2/H2O Co-electrolysis

Electrochemical devices are constructed for continuous syngas (CO + H2) production with controlled selectivity between CO2 and proton reduction reactions. The ratio of CO to H2, or the faradaic efficiency toward CO generation, was mechanically manipulated by adjusting the space volume between the cathode and the polymer gas separator in the device. In particular, the area added between the cathode and the ion-conducting polymer using 0.5 M KHCO3 catholyte regulated the solution acidity and proton reduction kinetics in the flow cell. The faradaic efficiency of CO production was controlled as a function of the distance between the polymer separator and cathode in addition to that manipulated by the electrode potential. Further, the electrochemical CO2 reduction device using Au NPs presented a stable operation for more than 23 h at different H2:CO production levels, demonstrating the functional stability of the flow cell utilizing the mechanical variable as an important operational factor.

Emerging carbon shell-encapsulated metal nanocatalysts for fuel cells and water electrolysis

The development of low-cost, high-efficiency electrocatalysts is of primary importance for hydrogen energy technology. Noble metal-based catalysts have been extensively studied for decades; however, activity and durability issues still remain a challenge. In recent years, carbon shell-encapsulated metal (M@C) catalysts have drawn great attention as novel materials for water electrolysis and fuel cell applications. These electrochemical reactions are governed mainly by interfacial charge transfer between the core metal and the outer carbon shell, which alters the electronic structure of the catalyst surface. Furthermore, the rationally designed and fine-tuned carbon shell plays a very interesting role as a protective layer or molecular sieve layer to improve the performance and durability of energy conversion systems. Herein, we review recent advances in the use of M@C type nanocatalysts for extensive applications in fuel cells and water electrolysis with a focus on the structural design and electronic structure modulation of carbon shell-encapsulated metal/alloys. Finally, we highlight the current challenges and future perspectives of these catalytic materials and related technologies in this field.

Feasibility of a Spherical Hollow Carbon Framework as a Stable Host Material for Reversible Metallic Li Storage

A spherical hollow carbon framework decorated with functional heteroatoms is designed and synthesized using ultrasonic spray pyrolysis as a potential anode material for lithium metal batteries (LMBs). The pore structure of the hollow carbon framework can be tailored by melamine, which is a functional additive for integrating abundant nanopores and the uniform decoration of heteroatoms in the structure. The large surface area and pore volume of the hollow carbon framework offer enhanced reversibility and capability for metallic Li storage. In addition, the dendritic growth of Li and volume changes induced by repeated Li plating and stripping can be effectively suppressed during cycling. More importantly, atomic-scale decorations of heteroatoms can effectively lower the overpotential for the nucleation and growth of metallic Li inside the hollow carbon framework. It is mainly responsible for improving the cycle performance and rate capability, even at a high current density. Finally, the hollow carbon framework anode shows stable behavior toward Li plating and stripping without significant capacity fading in the LMBs than conventional Li metal anodes.

Flash Bottom-Up Arc Synthesis of Nanocarbons as a Universal Route for Fabricating Single-Atom Electrocatalysts

Despite considerable development in the field of single-atom catalysts (SACs) on carbon-based materials, the reported strategies for synthesizing SACs generally rely on top-down approaches, which hinder achieving both simple and universal synthesis routes that are simultaneously applicable to various metals and nanocarbons. Here, a universal strategy for fabricating nanocarbon based-SACs using a flash bottom-up arc discharge method to mitigate these issues is reported. The ionization of elements and their recombination process during arc discharge allows the simultaneous incorporation of single metal atoms (Mn, Fe, Co, Ni, and Pt) into the crystalline carbon lattice during the formation of carbon nanohorns (CNHs) and N-doped arc graphene. The coordination environment around the Co atoms of Co₁ /CNH can be modulated by a mild post-treatment with NH₃ . As a result, Co₁ /CNH exhibits good oxygen reduction reaction activity, showing a 1.92 times higher kinetic current density value than the commercial Pt/C catalyst in alkaline media. In a single cell experiment, Co₁ /CNH exhibits the highest maximum power density of 472 mW cm^-2 compared to previously reported nonprecious metal-based SACs.

Hydrogen-Mediated Thin Pt Layer Formation on Ni3N Nanoparticles for the Oxygen Reduction Reaction

A simple wet-chemical route for the preparation of core-shell-structured catalysts was developed to achieve high oxygen reduction reaction (ORR) activity with a low Pt loading amount. Nickel nitride (Ni₃N) nanoparticles were used as earth-abundant metal-based cores to support thin Pt layers. To realize the site-selective formation of Pt layers on the Ni₃N core, hydrogen molecules (H₂) were used as a mild reducing agent. As H₂ oxidation is catalyzed by the surface of Ni₃N, the redox reaction between H₂ and Pt(IV) in solution was facilitated on the Ni₃N surface, which resulted in the selective deposition of Pt on Ni₃N. The controlled Pt formation led to a subnanometer (0.5-1 nm)-thick Pt shell on the Ni₃N core. By adopting the core-shell structure, higher ORR activity than the commercial Pt/C was achieved. Electrochemical measurements showed that the thin Pt layer on Ni₃N nanoparticle exhibits 5 times higher mass activity and specific activity than that of commercial Pt/C. Furthermore, it is expected that the proposed simple wet-chemical method can be utilized to prepare various transition-metal-based core-shell nanocatalysts for a wide range of energy conversion reactions.

Poly(fluorenyl aryl piperidinium) membranes and ionomers for anion exchange membrane fuel cells

Low-cost anion exchange membrane fuel cells have been investigated as a promising alternative to proton exchange membrane fuel cells for the last decade. The major barriers to the viability of anion exchange membrane fuel cells are their unsatisfactory key components-anion exchange ionomers and membranes. Here, we present a series of durable poly(fluorenyl aryl piperidinium) ionomers and membranes where the membranes possess high OH- conductivity of 208 mS cm-1 at 80 °C, low H2 permeability, excellent mechanical properties (84.5 MPa TS), and 2000 h ex-situ durability in 1 M NaOH at 80 °C, while the ionomers have high water vapor permeability and low phenyl adsorption. Based on our rational design of poly(fluorenyl aryl piperidinium) membranes and ionomers, we demonstrate alkaline fuel cell performances of 2.34 W cm-2 in H2-O2 and 1.25 W cm-2 in H2-air (CO2-free) at 80 °C. The present cells can be operated stably under a 0.2 A cm-2 current density for ~200 h.

Polystyrene-Based Hydroxide-Ion-Conducting Ionomer: Binder Characteristics and Performance in Anion-Exchange Membrane Fuel Cells

Polystyrene-based polymers with variable molecular weights are prepared by radical polymerization of styrene. Polystyrene is grafted with bromo-alkyl chains of different lengths through Friedel-Crafts acylation and quaternized to afford a series of hydroxide-ion-conducting ionomers for the catalyst binder for the membrane electrode assembly in anion-exchange membrane fuel cells (AEMFCs). Structural analyses reveal that the molecular weight of the polystyrene backbone ranges from 10,000 to 63,000 g mol^-1, while the ion exchange capacity of quaternary-ammonium-group-bearing ionomers ranges from 1.44 to 1.74 mmol g^-1. The performance of AEMFCs constructed using the prepared electrode ionomers is affected by several ionomer properties, and a maximal power density of 407 mW cm^-2 and a durability exceeding that of a reference cell with a commercially available ionomer are achieved under optimal conditions. Thus, the developed approach is concluded to be well suited for the fabrication of next-generation electrode ionomers for high-performance AEMFCs.

Prenatal diagnosis of vascular ring: evaluation of fetal diagnosis and postnatal outcomes

Funding Acknowledgements

Type of funding sources: None.

Background

The performance of fetal echocardiogram in diagnosing vascular ring (VR) and its impact on postnatal outcomes has not been well examined.

Methods

We reviewed all patients with VR diagnosis from 2000-2020.

Results

50 patients with antenatal diagnosis of VR; 42(84%) with right aortic arch aberrant left subclavian artery and left-sided ductus arteriosus ((RAA-ALS) and 8(16%) with double aortic arch (DAA) were compared to 120 patients with postnatal diagnosis; 90(75%) with DAA, 22(18%) with RAA-ALS (Table 1). Prenatal diagnosis of VR increased over study period; 4 vs 31, 10 vs 29, 14 vs 25, 22 vs 35 between 2000-2005, 2005-2010, 2010-2015, and 2015-2020 respectively, p< 0.01. Prenatal diagnosis of VR was associated with less symptoms [26(52%) vs 72(60%), p < 0.003] and less cross-sectional imaging [22(44%) vs 82(69%), p = 0.0001]. Postnatal diagnosis of VR was associated with more surgical interventions (102(85%) vs 28(56%), p = 0.002), later surgical repair (22.9 ± 35 vs 12.6 ± 10.2 months, p < 0.01), more postoperative complications [8/102 (7.8%) vs 1/28 (3.5%), p = 0.04] and more residual symptoms (2/28(7%) vs 30/102(29%), p = 0.001 respectively].

Conclusion

Prenatal diagnosis of VR has evolved over time. RAA-ALS versus DAA were dominant in the prenatally and postnatally diagnosed cohorts respectively. Prenatal diagnosis of VR was associated less symptoms, less cross-sectional imaging, earlier age of surgical intervention and less residual symptoms.

Table 1 Prenatal Diagnosis (N = 50) Postnatal Diagnosis (N = 120) p-value Gestational Age (weeks) 39 ± 3 38 ± 2 0.9 Male (%) 31 (62%) 69(58%) 0.8 Subtype of vascular ring: Double aortic arch RAA-ALSA Others 8 (16%) 42 (80 %) 0 (0 %) 90 (72%) 22 (17%) 8 (11%) 0.002 0.01 Associated intracardiac CHD: VSD TOF DORV AVSD Coarctation of aorta Others 11 (22%) 1 1 3 0 3 3 24 (20%) 5 7 2 2 3 5 0.8 Associated genetic diagnosis: 22q11 deletion Trisomy 21 Others 9 (18%) 6 3 0 32 (26%) 29 3 0 0.1 Symptomatic presentation: Respiratory Gastrointestinal 26 (52 %) 15 11 72 (60 %) 57 15 <0.03 Age at first symptoms (month) 3.2 ± 2.8 21.6 ± 37 0.01 Diagnostic modalities: Fetal echocardiogram Postnatal echocardiogram Barium swallow Bronchoscopy CT scan MRI 50 (100%) 50 (100%) 2 (4%) 3 (6%) 18 (36 %) 4 (8%) 0 (0%) 120 (100%) 23 (25 %) 18 (15 %) 65 (54%) 7 (14%) Surgical repair 28 (56%) 102 (85%) 0.02 Age at surgical repair (month) 12.6 ± 10.2 22.9 ± 35 <0.01 Postoperative complications 1 (3%) 8 (7%) 0.03 Residual symptoms 2 (1%) 30 (25%) 0.001 Age at most recent follow up (mo) 26 ± 7 60 ± 7 0.02 Table 1: Comparison of patients with prenatal versus postnatal diagnosis of vascular ring

Effects of Inflammatory Disease on Clinical Progression and Treatment of Ischiogluteal Bursitis: A Retrospective Observational Study

Introduction:

The symptoms of Ischiogluteal Bursitis (IGB) are often nonspecific and atypical, and its diagnosis is more challenging. Moreover, it is difficult to predict cases of chronic progression or poor treatment response. Therefore, the aim of this study was to investigate the clinical course of IGB patients and identify factors that are predictive of failure of conservative treatment.

Materials and Methods:

Our study consisted of IGB patients diagnosed between 2010 March and 2016 December who had been followed-up for at least one year. Structured questionnaires and medical records were reviewed to analyse demographic characteristics, lifestyle patterns, blood tests, and imaging studies. We categorized the cases into two groups based on the response to conservative treatment and the need for surgical intervention.

Results:

The most common initial chief symptoms were buttock pains in 24 patients (37.5%). Physical examinations showed the tenderness of ischial tuberosity area in 59 (92.2%) patients, but no specific findings were confirmed in 5 patients (7.8%). 51 patients (79.7%) responded well to the conservative management, 11 patients (17.2%) needed injection, and 2 patients (3.1%) had surgical treatment performed due to continuous recurrence. There was no difference in demographic and blood lab data between the two groups. However, the incidence of inflammatory diseases (response group: 10.3% vs non-response group: 66.7%, p=0.004) was significantly different between the two groups.

Conclusion:

The diagnosis of IGB can be missed due to variations in clinical symptoms, and cautions should be exercised in patients with inflammatory diseases as conservative treatment is less effective in them, leading to chronic progression of IGB.

Monolayer Quantum-Dot Based Light-Sensor by a Photo-Electrochemical Mechanism

Monolayer nanocrystal-based light sensors with cadmium-selenium thin film electrodes have been investigated using electrochemical cyclic voltammetry tests. An indium tin oxide electrode system, with a monolayer of homogeneously deposited cadmium-selenium quantum dots was proven to work as a photo-sensor via an electrochemical cell mechanism; it was possible to tune current densities under light illumination. Electrochemical tests on a quantum dot capacitor, using different sized (red, yellow and green) cadmium-selenium quantum dots on indium tin oxide substrates, showed typical capacitive behavior of cyclic voltammetry curves in 2M H2SO4 aqueous solutions. This arrangement provides a beneficial effect in, both, charge separation and light sensory characteristics. Importantly, the photocurrent density depended on quantum yield rendering tunable photo-sensing properties.

Direct Synthesis of Intermetallic Platinum-Alloy Nanoparticles Highly Loaded on Carbon Supports for Efficient Electrocatalysis

Compared to nanostructured platinum (Pt) catalysts, ordered Pt-based intermetallic nanoparticles supported on a carbon substrate exhibit much enhanced catalytic performance, especially in fuel cell electrocatalysis. However, direct synthesis of homogeneous intermetallic alloy nanocatalysts on carbonaceous supports with high loading is still challenging. Herein, we report a novel synthetic strategy to directly produce highly dispersed MPt alloy nanoparticles (M = Fe, Co, or Ni) on various carbon supports with high catalyst loading. Importantly, a unique bimetallic compound, composed of [M(bpy)₃]²⁺ cation (bpy = 2,2'-bipyridine) and [PtCl₆]^2- anion, evenly decomposes on carbon surface and forms uniformly sized intermetallic nanoparticles with a nitrogen-doped carbon protection layer. The excellent oxygen reduction reaction (ORR) activity and stability of the representative reduced graphene oxide (rGO)-supported L1₀-FePt catalyst (37 wt %-FePt/rGO), exhibiting 18.8 times higher specific activity than commercial Pt/C catalyst without degradation over 20 000 cycles, well demonstrate the effectiveness of our synthetic approach toward uniformly alloyed nanoparticles with high homogeneity.

Formation Mechanism and Gram-Scale Production of PtNi Hollow Nanoparticles for Oxygen Electrocatalysis through In Situ Galvanic Displacement Reaction

Galvanic displacement reaction has been considered a simple method for fabricating hollow nanoparticles. However, the formation of hollow interiors in nanoparticles is not easily achieved owing to the easy oxidization of transition metals, which results in mixed morphologies, and the presence of surfactants on the nanoparticle surface, which severely deteriorates the catalytic activity. In this study, we developed a facile gram-scale methodology for the one-pot preparation of carbon-supported PtNi hollow nanoparticles as an efficient and durable oxygen reduction electrocatalyst without using stabilizing agents or additional processes. The hollow structures were evolved from sacrificial Ni nanoparticles via an in situ galvanic displacement reaction with a Pt precursor, directly following a preannealing process. By sampling the PtNi/C hollow nanoparticles at various reaction times, the structural formation mechanism was investigated using transmission electron microscopy with energy-dispersive X-ray spectroscopy mapping/line-scan profiling. We found out that the structure and morphology of the PtNi hollow nanoparticles were controlled by the acidity of the metal precursor solution and the nanoparticle core size. The synthesized PtNi hollow nanoparticles acted as an oxygen reduction electrocatalyst, with a catalytic activity superior to that of a commercial Pt catalyst. Even after 10 000 cycles of harsh accelerated durability testing, the PtNi/C hollow electrocatalyst showed high performance and durability. We concluded that the Pt-rich layers on the PtNi hollow nanoparticles improved the catalytic activity and durability considerably.

P1488 Anomalous origin of left coronary artery from right pulmonary artery in association with scimitar syndrome

Clinical Presentation

A full-term neonate was referred to our institution because of respiratory distress. CXR was significant for right lung hypoplasia and mild cardiomegaly. ECG showed normal sinus rhythm, right atrial enlargement, and right ventricular hypertrophy with no signs of ischemia.

Imaging Findings

The initial echocardiogram demonstrated PAPVD with the right upper pulmonary vein draining into IVC/RA junction with flow acceleration (mean gradient= 7 mmHg), moderate ASD, small muscular VSD with left-right shunting, moderate PDA with bidirectional shunting. Forward flow was seen in the proximal part of left main coronary artery (LMCA). RV systolic pressure was supra-systemic with a qualitatively moderately reduced RV systolic function.

The patient was taken to the catheterization lab where MPA angiography revealed an antegrade flow from the RPA into LMCA supplying both the anterior descending and the circumflex arteries. A selective injection within the scimitar vein showed drainage of the right lung into a vertical vein connecting with stenosis to IVC.

A follow up echocardiogram to re-examine the coronary origin revealed an anomalous origin of LMCA from proximal RPA; 3 mm distal to branch pulmonary artery bifurcation with mainly antegrade low velocity flow into LMCA and LAD. (Image 1)

Role of Imaging in Patient Care

- Imaging of the coronary origin in patients with ALCAPA can be challenging especially if the LMCA originates from RPA. Also, the presence of pulmonary hypertension might contribute to maintain coronary perfusion and lead to misinterpretation of the antegrade flow in LMCA and its branches.

- In certain situations, cardiac catheterization is essential to make the diagnosis of ALCAPA which prevented a potentially catastrophic outcome. Catheter intervention with a series of balloon dilations of the stenotic scimitar vein was successful in relieving the stenosis.

Summary/Discussion Points:

- Extensive review of the available literature revealed only three cases of Scimitar syndrome associated with ALCAPA. In all of these cases, the LMCA originated from the posterior sinus of MPA. Our case is the first to report ALCAPA from RPA in association with Scimitar syndrome. This presentation might have led to the initial misinterpretation of the echocardiography images.

- The presence of pulmonary hypertension in our patient maintained an adequate antegrade flow across the LMCA preventing significant coronary steal and signs of myocardial ischemia.

- The report highlights the challenges in making the diagnosis of ALCAPA with echocardiograms. Moreover, we discuss the role of cross-sectional and invasive imaging to rule out potential coronary arteries anomalies in patients with Scimitar syndrome, as this a rare although a very significant association that may have important implications in their outcomes.

Abstract P1488 Figure. ALCAPA origin from RPA

Membrane/Electrode Interface Design for Effective Water Management in Alkaline Membrane Fuel Cells

The recent development of ultrathin anion exchange membranes and optimization of their operating conditions have significantly enhanced the performance of alkaline-membrane fuel cells (AMFCs); however, the effects of the membrane/electrode interface structure on the AMFC performance have not been seriously investigated thus far. Herein, we report on a high-performance AMFC system with a membrane/electrode interface of novel design. Commercially available membranes are modified in the form of well-aligned line arrays of both the anode and cathode sides by means of a solvent-assisted molding technique and sandwich-like assembly of the membrane and polydimethylsiloxane molds. Upon incorporating the patterned membranes into a single-cell system, we observe a significantly enhanced performance of up to ∼35% compared with that of the reference membrane. The enlarged interface area and reduced membrane thickness from the line-patterned membrane/electrode interface result in improved water management, reduced ohmic resistance, and effective utilization of the catalyst. We believe that our findings can significantly contribute further advancements in AMFCs.

Bio-Derived Co2 P Nanoparticles Supported on Nitrogen-Doped Carbon as Promising Oxygen Reduction Reaction Electrocatalyst for Anion Exchange Membrane Fuel Cells

Recently, nonnoble-metal catalysts such as a metal coordinated to nitrogen doped in a carbon matrix have been reported to exhibit superior oxygen reduction reaction (ORR) activity in alkaline media. In this work, Co₂ P nanoparticles supported on heteroatom-doped carbon catalysts (NBSCP) are developed with an eco-friendly synthesis method using bean sprouts. NBSCP can be easily synthesized through metal precursor absorption and carbonization at a high temperature. It shows a very large specific surface area with various dopants such as nitrogen, phosphorus, and sulfur derived from small organic molecules. The catalyst can exhibit activity in various electrochemical reactions. In particular, excellent performance is noted for the ORR. Compared to the commercial Pt/C, NBSCP exhibits a lower onset potential, higher current density, and superior durability. This excellent ORR activity and durability is attributable to the synergistic effect between Co₂ P nanoparticles and nitrogen-doped carbon. In addition, superior performance is noted on applying NBSCP to a practical anion exchange membrane fuel cell system. Through this work, the possibility of applying an easily obtained bio-derived material to energy conversion and storage systems is demonstrated.

Boosting Fuel Cell Durability under Shut-Down/Start-Up Conditions Using a Hydrogen Oxidation-Selective Metal-Carbon Hybrid Core-Shell Catalyst

Performance degradation generated by reverse current flow during fuel cell shut-down/start-up is a big challenge for commercialization of polymer electrolyte membrane fuel cells in automobile applications. Under transient operating conditions, the formation of H₂/O₂ boundaries on Pt surfaces and the occurrence of undesired oxygen reduction reaction (ORR) in an anode cause severe degradation of carbon supports and Pt catalysts in a cathode because of an increase of the cathode potential up to ∼1.5 V. Herein, to directly prevent the formation of H₂/O₂ boundaries in the anode, we propose a unique metal-carbon hybrid core-shell anode catalyst having Pt nanoparticles encapsulated in nanoporous carbon shells for selective H₂ permeation. This hybrid catalyst exhibits high hydrogen oxidation reaction (HOR) selectivity along with fully subdued ORR activity during long-term operation because of the excellent stability of the carbon molecular sieves. Furthermore, the HOR-selective catalyst effectively suppresses the reverse current flow in a single cell under shut-down/start-up conditions.

A new etching process for zinc oxide with etching rate and crystal plane control: experiment, calculation, and membrane application

The etching process can be a useful method for the morphology control of nanostructures. Using precise experiments and theoretical calculations, we report a new ZnO etching process triggered by the reaction of ZnO with transition metal cations and demonstrate that the etching rate and direction could be controlled by varying the kind of transition metal cation. In addition, the developed etching process was introduced to form a thin and uniform ZnO layer, which was utilized for the fabrication of an improved propylene-selective ZIF-8 membrane via conversion seeding and secondary growth.

Genetic evolution of classical swine fever virus under immune environments conditioned by genotype 1-based modified live virus vaccine

Modified live vaccines (MLVs) based on genotype 1 strains, particularly C-strain, have been used to prevent and control classical swine fever virus (CSFV) worldwide. Nevertheless, a shift in the predominant CSFV strains circulating in the field from genotype 1 or 3 to genotype 2 is seen. Genotype 2 is genetically distant from the vaccine strains and was recently reported during outbreaks after vaccine failure; this has raised concerns that vaccination has influenced viral evolution. In Korea in 2016, there was an unexpected CSF outbreak in a MLV-vaccinated commercial pig herd. The causative CSFV strain was genetically distinct from previously isolated Korean strains but similar to recent Chinese strains exhibiting enhanced capacity to escape neutralization; this suggests the need for global cooperative research on the evolution of CSFV. We analysed global E2 sequences, using bioinformatics tools, revealing the evolutionary pathways of CSFV. Classical swine fever virus genotypes 1 and 2 experienced different degrees and patterns of evolutionary growth. Whereas genotype 1 stayed relatively conserved over time, the genetic diversity of genotype 2 has progressively expanded, with few fluctuations. It was determined that genotype 2 evolved under lower immune pressures and at a higher evolutionary rate than genotype 1. Further, several selected codons, under diversifying selection in genotype 1 but under purifying selection in genotype 2, correspond to antigenic determinants, which could lead to evasion of vaccine-induced immunity. Our findings provide evidence that evolutionary changes in CSFV are the result of the disproportionate usage of the CSF MLVs in endemic areas; this underscores the need to develop mitigation strategies to minimize the substantial risk associated with the emergence of vaccine-escaping mutants.