Highly efficient electrocatalysts are essential for the production of green hydrogen from water electrolysis. Herein, a metal‐organic framework‐assisted pyrolysis‐replacement‐reorganization approach ...is developed to obtain ultrafine Pt‐Co alloy nanoparticles (sub‐10 nm) attached on the inner and outer shells of porous nitrogen‐doped carbon nanotubes (NCNT) with closed ends. During the thermal reorganization, the migration of Pt‐Co nano‐alloys to both surfaces ensures the maximized exposure of active sites while maintaining the robust attachment to the porous carbon matrix. Density functional theory calculations suggest a nearly thermodynamically‐neutral free energy of adsorption for hydrogen intermediates and diversified active sites induced by alloying, thus resulting in a great promotion in intrinsic activity towards the hydrogen evolution reaction (HER). Benefiting from the delicate structural design and compositional modulation, the optimized Pt3Co@NCNT electrocatalyst manifests outstanding HER activity and superior stability in both acidic and alkaline media.
Ultrafine Pt‐Co alloy nanoparticles confined on the inner and outer surfaces of porous nitrogen‐doped carbon nanotubes (Pt‐Co@NCNT) have been synthesized through a metal–organic framework (MOF)‐assisted pyrolysis‐replacement‐reorganization approach. With the structural and compositional merits, the Pt3Co@NCNT electrocatalyst presents superior activity and stability in both acidic and alkaline media for the hydrogen evolution reaction.
Organic electrical gas sensors have been developed for many decades because of their high sensitivity and selectivity. However, their industrialization is severely hindered by their intrinsic ...humidity susceptibility and poor recovery. Conventional organic sensory materials can only operate at room temperature owing to their weak intermolecular interactions. Herein, we demonstrate using a croconate polymer (poly‐4,4′‐biphenylcroconate) that the “ion‐in‐conjugation” concept enables organic gas sensors to operate at 100 °C and 70 % relative humidity with almost complete recovery. The fabricated sensor had a parts‐per‐billion (ppb) detection limit for NO2 and showed the highest sensitivity (2526 ppm−1 at 40 ppb) of all reported NO2 chemiresistive sensors. Furthermore, charge transfer increased with temperature. Theoretical calculations and in situ FTIR spectra confirmed the ion‐in‐conjugation‐inspired hydrogen bond as key for excellent sensitivity. A NO2 alarm system was assembled to demonstrate the feasibility of this sensor.
A robust NO2 sensor device based on an ion‐in‐conjugation structure maintained its performance at high temperature, which counteracted the effects of humidity (see picture; NO2 blue/red, H2O green/yellow). Charge transfer between NO2 and the chemiresistor was more efficient at 100 °C than at room temperature. The fabricated sensor had a parts‐per‐billion (ppb) NO2 detection limit and showed the highest sensitivity of all reported NO2 chemiresistive sensors.
Highly ordered three-dimensional α-Fe2O3@PANI core–shell nanowire arrays with enhanced specific areal capacity and rate performance are fabricated by a simple and cost-effective electrodeposition ...method. The α-Fe2O3@PANI core–shell nanowire arrays provide a large reaction surface area, fast ion and electron transfer, and good structure stability, which all are beneficial for improving the electrochemical performance. Here, high-performance asymmetric supercapacitors (ASCs) are designed using α-Fe2O3@PANI core–shell nanowire arrays as anode and PANI nanorods grown on carbon cloth as cathode, and they display a high volumetric capacitance of 2.02 mF/cm3 based on the volume of device, a high energy density of 0.35 mWh/cm3 at a power density of 120.51 mW/cm3, and very good cycling stability with capacitance retention of 95.77% after 10 000 cycles. These findings will promote the application of α-Fe2O3@PANI core–shell nanowire arrays as advanced negative electrodes for ASCs.
Towards green production and efficient utilization of hydrogen, developing renewable clean energy technologies based on hydrogen and oxygen electrocatalysis, especially water electrolysis, zinc-air ...batteries, and fuel cells, is of vital significance. To promote their energy conversion efficiency, low-cost and high-efficiency electrocatalysts are highly desired to accelerate the sluggish kinetics of hydrogen and oxygen electrocatalytic reactions. The emergence of metal-organic frameworks (MOFs) provides new opportunities to obtain high-performance hydrogen and oxygen electrocatalysts with desired composition and structures. However, most of these MOF-based electrocatalysts are powders, resulting in limited active sites, blocked mass/charge transport, and insufficient stability. In this context, we present an up-to-date investigation of self-supporting MOF-based hydrogen and oxygen electrocatalysts with a focus on the synthesis strategy and application. Finally, some personal insights into the current challenges and potential solutions are presented, aiming at providing some guidance for the design and synthesis of advanced self-supporting MOF-based materials in hydrogen/oxygen-related energy technologies.
This article reviews the recent development of self-supporting metal-organic framework-based hydrogen and oxygen electrocatalysts with a focus on the synthesis strategy and application, and concluding with some current challenges and future perspectives.
Single‐atom catalysts (SACs) are being pursued as economical electrocatalysts. However, their low active‐site loading, poor interactions, and unclear catalytic mechanism call for significant ...advances. Herein, atomically dispersed Ni/Co dual sites anchored on nitrogen‐doped carbon (a‐NiCo/NC) hollow prisms are rationally designed and synthesized. Benefiting from the atomically dispersed dual‐metal sites and their synergistic interactions, the obtained a‐NiCo/NC sample exhibits superior electrocatalytic activity and kinetics towards the oxygen evolution reaction. Moreover, density functional theory calculations indicate that the strong synergistic interactions from heteronuclear paired Ni/Co dual sites lead to the optimization of the electronic structure and the reduced reaction energy barrier. This work provides a promising strategy for the synthesis of high‐efficiency atomically dispersed dual‐site SACs in the field of electrochemical energy storage and conversion.
Atomically dispersed Ni/Co dual sites anchored on nitrogen‐doped carbon (a‐NiCo/NC) hollow prisms are synthesized through a templated assisted atom migration‐trapping route. Due to the delicately designed dual‐metal sites and their synergistic interactions, the a‐NiCo/NC electrocatalyst exhibits significantly improved electrocatalytic oxygen evolution performance compared with atomically dispersed single‐metal‐site counterparts.
Herein, we report the synthesis of uniform hollow nanorods of Ni-doped FeP nanocrystals hybridized with carbon as electrocataysts for the electrocatalytic hydrogen evolution reaction (HER). These ...hollow nanorods are prepared based on the etching and coordination reaction between metal-organic frameworks and phytic acid, followed by a pyrolysis process. Benefiting from the abundant active sites, the improved mass and charge transport capability, the optimized Ni-doped FeP/C hollow nanorods exhibit excellent HER activities for achieving a current density of 10 mA cm
at an overpotential of 72, 117, and 95 mV in acidic, neutral, and alkaline media, respectively, as well as superior stability. X-ray photoelectron spectroscopy and basic density functional theory calculations suggest that the improved HER activity originates from the synergistic modulation of the active components, structural and electronic properties. This protocol provides a general and friendly strategy to construct hollow phosphides for energy-related applications.
Recently, organic–inorganic hybrid perovskites (OIHP) are studied in memory devices, but ternary resistive memory with three states based on OIHP is not achieved yet. In this work, ternary resistive ...memory based on hybrid perovskite is achieved with a high device yield (75%), much higher than most organic ternary resistive memories. The pseudohalide‐induced 2D (CH3NH3)2PbI2(SCN)2 perovskite thin film is prepared by using a one‐step solution method and fabricated into Al/perovskite film/indium–tin oxide (glass substrate as well as flexible polyethylene terephthalate substrate) random resistive access memory (RRAM) devices. The three states have a conductivity ratio of 1:103:107, long retention over 10 000 s, and good endurance properties. The electrode area variation, impedance test, and current–voltage plotting show that the two resistance switches are attributable to the charge trap filling due to the effect of unscreened defect in 2D nanosheets and the formation of conductive filaments, respectively. This work paves way for stable perovskite multilevel RRAMs in ambient atmosphere.
Pseudohalide‐induced 2D (CH3NH3)2PbI2(SCN)3 perovskite film is prepared. The as‐fabricated memory devices perform ternary write‐once‐read‐many‐times memory behavior with high ternary device yield (74%). Even after 500 times bending, the ternary memory behavior is still maintained, indicating potential applications of 2D perovskite materials in high‐density data storage via random resistive access memory technology.
The expansion of anatomically modern humans (AMHs) from Africa around 65,000 to 45,000 y ago (ca. 65 to 45 ka) led to the establishment of present-day non-African populations. Some ...paleoanthropologists have argued that fossil discoveries from Huanglong, Zhiren, Luna, and Fuyan caves in southern China indicate one or more prior dispersals, perhaps as early as ca. 120 ka. We investigated the age of the human remains from three of these localities and two additional early AMH sites (Yangjiapo and Sanyou caves, Hubei) by combining ancient DNA (aDNA) analysis with a multimethod geological dating strategy. Although U-Th dating of capping flowstones suggested they lie within the range ca. 168 to 70 ka, analyses of aDNA and direct AMS
C dating on human teeth from Fuyan and Yangjiapo caves showed they derive from the Holocene. OSL dating of sediments and AMS
C analysis of mammal teeth and charcoal also demonstrated major discrepancies from the flowstone ages; the difference between them being an order of magnitude or more at most of these localities. Our work highlights the surprisingly complex depositional history recorded at these subtropical caves which involved one or more episodes of erosion and redeposition or intrusion as recently as the late Holocene. In light of our findings, the first appearance datum for AMHs in southern China should probably lie within the timeframe set by molecular data of ca. 50 to 45 ka.
In the early February, 2020, we called up an experts’ committee with more than 30 Chinese experts from 11 national medical academic organizations to formulate the first edition of consensus statement ...on diagnosis, treatment and prevention of coronavirus disease 2019 (COVID-19) in children, which has been published in this journal. With accumulated experiences in the diagnosis and treatment of COVID-19 in children, we have updated the consensus statement and released the second edition recently. The current version in English is a condensed version of the second edition of consensus statement on diagnosis, treatment and prevention of COVID-19 in children. In the current version, diagnosis and treatement criteria have been optimized, and early identification of severe and critical cases is highlighted. The early warning indicators for severe pediatric cases have been summarized which is utmost important for clinical practice. This version of experts consensus will be valuable for better prevention, diagnosis and treatment of COVID-19 in children worldwide.
2,3,5,6-Tetramethylpyrazine (TMP) as an active ingredient extracted from a traditional Chinese herbal medicine
. has been proved to penetrate blood-brain barrier (BBB) and show neuroprotective ...effects on cerebral ischemia. However, whether TMP could regulate astrocytic reactivity to facilitate neurovascular restoration in the subacute ischemic stroke needs to be urgently verified. In this research, permanent occlusion of the middle cerebral artery (MCAO) model was conducted and TMP (10, 20, 40 mg/kg) was intraperitoneally administrated to rats once daily for 2 weeks. Neurological function was evaluated by motor deficit score (MDS). Magnetic resonance imaging (MRI) was implemented to analyze tissue injury and cerebral blood flow (CBF). Magnetic resonance angiography (MRA) was applied to exhibit vascular signals. Transmission electron microscopy (TEM) was performed to detect the neurovascular unit (NVU) ultrastructure. Haematoxylin and eosin (HE) staining was utilized to evaluate cerebral histopathological lesions. The neurogenesis, angiogenesis, A1/A2 reactivity, aquaporin 4 (AQP4) and connexin 43 (Cx43) of astrocytes were observed with immunofluorescent staining. Then FGF2/PI3K/AKT signals were measured by western blot. Findings revealed TMP ameliorated neurological functional recovery, preserved NVU integrity, and enhanced endogenous neurogenesis and angiogenesis of rats with subacute ischemia. Shifting A1 to A2 reactivity, suppressing excessive AQP4 and Cx43 expression of astrocytes, and activating FGF2/PI3K/AKT pathway might be potential mechanisms of promoting neurovascular restoration with TMP after ischemic stroke.
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