Hybrid supercapacitors generally show high power and long life spans but inferior energy densities, which are mainly caused by carbon negative electrodes with low specific capacitances. To improve ...the energy densities, the traditional methods include optimizing pore structures and modifying pseudocapacitive groups on the carbon materials. Here, another promising way is suggested, which has no adverse effects to the carbon materials, that is, constructing electron‐rich regions on the electrode surfaces for absorbing cations as much as possible. For this aim, a series of hierarchical porous carbon materials are produced by calcinating carbon dots–hydrogel composites, which have controllable surface states including electron‐rich regions. The optimal sample is employed as the negative electrode to fabricate hybrid supercapacitors, which show remarkable specific energy densities (up to 62.8–90.1 Wh kg−1) in different systems.
Robust carbon negative electrodes for hybrid supercapacitors are fabricated by a new promising method, that is, constructing electron‐rich regions on the electrode surfaces for absorbing cations as much as possible. Correspondingly, hierarchical porous carbon materials are produced by calcinating carbon dots–hydrogel composites, which have controllable surface states including electron‐rich regions.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The hydrogen evolution reaction (HER) based on water electrolysis is a promising strategy for hydrogen energy production, in which the key point is seeking low-cost, high efficiency and stable ...electrocatalysts. Currently, the most efficient electrocatalysts for the HER are Pt-based catalysts (especially commercial Pt/C), but the low abundance and high cost of Pt hinder their widespread application. Herein, we demonstrate that a cobalt molybdenum phosphide nanocrystal coated by a few-layer N-doped carbon shell (CoMoP@C) is an excellent substitute for the HER. CoMoP@C is prepared by a one-step pyrolysis method on a large scale with polyoxometalate (POM) as a molecular platform. The catalytic activity of CoMoP@C is close to that of commercial 20% Pt/C under pH = 0–1 conditions and superior to that of 20% Pt/C under pH = 2–14 conditions at high overpotential ( e.g. η > 240 mV at pH = 2.2). In real seawater, CoMoP@C exhibits stable HER performance with a high Faradaic efficiency (FE) of 92.5%, while the HER activity of 20% Pt/C dramatically decreases after 4 h. The remarkable HER performance of CoMoP@C should be attributed to the low free energy of H on the central CoMoP crystalline core and the multiple functions of the outer N-doped C shell (especially the strong H + absorption behavior). This work may provide new options for the design and preparation of promising HER electrocatalysts superior to Pt/C, which can be used directly in seawater.
Compressive surface strains have been necessary to boost oxygen reduction reaction (ORR) activity in core/shell M/platinum (Pt) catalysts (where M can be nickel, cobalt, or iron). We report on a ...class of platinum-lead/platinum (PtPb/Pt) core/shell nanoplate catalysts that exhibit large biaxial strains. The stable Pt (110) facets of the nanoplates have high ORR specific and mass activities that reach 7.8 milliampere (mA) per centimeter squared and 4.3 ampere per milligram of platinum at 0.9 volts versus the reversible hydrogen electrode (RHE), respectively. Density functional theory calculations reveal that the edge-Pt and top (bottom)-Pt (110) facets undergo large tensile strains that help optimize the Pt-O bond strength. The intermetallic core and uniform four layers of Pt shell of the PtPb/Pt nanoplates appear to underlie the high endurance of these catalysts, which can undergo 50,000 voltage cycles with negligible activity decay and no apparent structure and composition changes.
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Developing highly effective and stable counter electrode (CE) materials to replace rare and expensive noble metals for dye‐sensitized and perovskite solar cells (DSC and PSC) is a research hotspot. ...Carbon materials are identified as the most qualified noble metal‐free CEs for the commercialization of the two photovoltaic devices due to their merits of low cost, excellent activity, and superior stability. Herein, carbonaceous CE materials are reviewed extensively with respect to the two devices. For DSC, a classified discussion according to the morphology is presented because electrode properties are closely related to the specific porosity or nanostructure of carbon materials. The pivotal factors influencing the catalytic behavior of carbon CEs are also discussed. For PSC, an overview of the new carbon CE materials is addressed comprehensively. Moreover, the modification techniques to improve the interfacial contact between the perovskite and carbon layers, aiming to enhance the photovoltaic performance, are also demonstrated. Finally, the development directions, main challenges, and coping approaches with respect to the carbon CE in DSC and PSC are stated.
Carbon counter electrode materials for dye‐sensitized and perovskite solar cells are summarized extensively. The specific morphology and structure design of the carbon counter electrode in dye‐sensitized solar cells and the intrinsic features, energy level alignment, and interface engineering of the perovskite/carbon interface in perovskite solar cells are emphasized.
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1D metal‐oxide nanostructures have attracted much attention because metal oxides are the most fascinating functional materials. The 1D morphologies can easily enhance the unique properties of the ...metal‐oxide nanostructures, which make them suitable for a wide variety of applications, including gas sensors, electrochromic devices, light‐emitting diodes, field emitters, supercapacitors, nanoelectronics, and nanogenerators. Therefore, much effort has been made to synthesize and characterize 1D metal‐oxide nanostructures in the forms of nanorods, nanowires, nanotubes, nanobelts, etc. Various physical and chemical deposition techniques and growth mechanisms are exploited and developed to control the morphology, identical shape, uniform size, perfect crystalline structure, defects, and homogenous stoichiometry of the 1D metal‐oxide nanostructures. Here a comprehensive review of recent developments in novel synthesis, exceptional characteristics, and prominent applications of one‐dimensional nanostructures of tungsten oxides, molybdenum oxides, tantalum oxides, vanadium oxides, niobium oxides, titanium oxides, nickel oxides, zinc oxides, bismuth oxides, and tin oxides is provided.
Three processes are involved in the vapor‐solid (VS) growth mechanism for the synthesis of 1D metal‐oxide nanostructures: i) thermal sublimation from the hot metal filament, ii) chemical vapor reaction of the sublimated heavy metal vapor with ambient oxygen gas, and iii) condensation of the heavy metal‐oxide vapor into 1D nanostructures.
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The purpose of the present study was to investigate whether catalpol exhibited neuroprotective effects in chronic unpredictable mild stress (CUMS) mice through oxidative stress-mediated ...nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin-domain-containing 3 (NLRP3) inflammasome and neuroinflammation. Deficits in behavioral tests, including open field test (OFT), forced swim test (FST), and elevated plus-maze test (EPM), were ameliorated following catalpol administration. To study the potential mechanism, western blots, quantitative real-time PCR (qRT-PCR) analysis and immunofluorescence imaging were performed on the hippocampus samples. We found that the defects of behavioral tests induced by CUMS could be reversed by the absence of NLRP3 and NLRP3 inflammasome might be involved in the antidepressant effects of catalpol on CUMS mice. Similar to the NLRP3 inflammasome, the expression of interleukin-1 beta (IL-1β), tumor necrosis factor alpha (TNF-α), and inducible nitride oxide synthase (iNOS) were increased after CUMS. The current study demonstrated that catalpol possessed anti-inflammatory effect on CUMS mice and inhibited microglial polarization to the M1 phenotype. In addition, the activity of mitochondrial oxidative stress might be involved in the NLRP3 activation, which was proved by the downregulation of NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC), and cleaved IL-1β, after the administration of mitochondrion-targeted antioxidant peptide SS31. Taken together, we provided evidence that catalpol exhibited antidepressive effects on CUMS mice possibly via the oxidative stress-mediated regulation of NLRP3 and neuroinflammation.
A
bstract
Defect extremal surface is defined by extremizing the Ryu-Takayanagi formula corrected by the quantum defect theory. This is interesting when the AdS bulk contains a defect brane (or ...string). We introduce a defect extremal surface formula for reflected entropy, which is a mixed state generalization of entanglement entropy measure. Based on a decomposition procedure of an AdS bulk with a brane, we demonstrate the equivalence between defect extremal surface formula and island formula for reflected entropy in AdS
3
/BCFT
2
. We also compute the evolution of reflected entropy in evaporating black hole model and find that defect extremal surface formula agrees with island formula.
Exploring high-performance electrocatalysts for sustainable hydrogen production is an essential prerequisite of a further hydrogen economy. Integrating multiple interfaces in two-component ...electrocatalysts is expected to be a feasible strategy to optimize the intrinsic electronic structure of hybrid catalysts and improve their catalytic property. Herein, we report a new type of multi-interfacial nickel/tungsten carbide (Ni/WC) hybrid nanoparticles anchored on N-doped carbon sheets (Ni/WC@NC), which can efficiently and robustly catalyze the hydrogen evolution reaction (HER) with striking kinetic metrics in a wide pH range. In 0.5 M H 2 SO 4 , Ni/WC@NC displays a low overpotential (53 mV at current density of 10 mA cm −2 ), a small Tafel slope (43.5 mV dec −1 ), a high exchange current density (0.83 mA cm −2 ), as well as excellent stability, outperforming most of the current noble-metal-free electrocatalysts. A series of controlled experiments, DFT calculations and in situ XAS measurements reveal that the remarkable HER activity is mainly attributed to abundant interfaces between Ni and WC domains, which induce a synergistic optimization of the electronic configuration of Ni and WC through electron transfer process from WC to Ni along with potential mass transport, thus promoting the HER kinetics and accelerating the reaction. Our work suggests a potentially powerful interface-engineering strategy for designing high-performance electrocatalysts for the HER.
A new cationic triazole‐based metal–organic framework encapsulating Keggin‐type polyoxometalates, with the molecular formula Co(BBPTZ)3HPMo12O40⋅24 H2O compound 1; ...BBPTZ=4,4′‐bis(1,2,4‐triazol‐1‐ylmethyl)biphenyl is hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, powder X‐ray diffraction, and single‐crystal X‐ray diffraction. The structure of compound 1 contains a non‐interpenetrated 3D CdSO4 (cds)‐type framework with two types of channels that are interconnected with each other; straight channels that are occupied by the Keggin‐type POM anions, and wavelike channels that contain lattice water molecules. The catalytic activity of compound 1 in the oxidative desulfurization reaction indicates that it is not only an effective and size‐selective heterogeneous catalyst, but it also exhibits distinct structural stability in the catalytic reaction system.
Sulfur no more: A cationic triazole‐based metal–organic framework encapsulating Keggin‐type polyoxometalates, with the molecular formula Co(BBPTZ)3HPMo12O40⋅24 H2O BBPTZ=4,4′‐bis(1,2,4‐triazol‐1‐ylmethyl)biphenyl, is synthesized, characterized and shown to be active in oxidative desulfurization catalysis. POM=polyoxometalate; MOF=metal–organic framework; cds=CdSO4.
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Deep learning has become a widespread tool in both science and industry. However, continued progress is hampered by the rapid growth in energy costs of ever-larger deep neural networks. Optical ...neural networks provide a potential means to solve the energy-cost problem faced by deep learning. Here, we experimentally demonstrate an optical neural network based on optical dot products that achieves 99% accuracy on handwritten-digit classification using ~3.1 detected photons per weight multiplication and ~90% accuracy using ~0.66 photons (~2.5 × 10
J of optical energy) per weight multiplication. The fundamental principle enabling our sub-photon-per-multiplication demonstration-noise reduction from the accumulation of scalar multiplications in dot-product sums-is applicable to many different optical-neural-network architectures. Our work shows that optical neural networks can achieve accurate results using extremely low optical energies.
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