Limited by single metal active sites and low electrical conductivity, designing nickel‐based metal–organic framework (MOF) materials with high capacity and high energy density remains a challenge. ...Herein, a series of bi/multimetallic MOF‐74 family materials in situ grown on carbon cloth (CC) by doping Mx+ ions in Ni‐MOF‐74 is fabricated: NiM‐MOF@CC (M = Mn2+, Co2+, Cu2+, Zn2+, Al3+, Fe3+), and NiCoM‐MOF@CC (M = Mn2+, Zn2+, Al3+, Fe3+). The type and ratio of doping metal ions can be adjusted while the original topology is preserved. Different metal ions are confirmed by X‐ray absorption fine structure (XAFS). Furthermore, these Ni‐based MOF electrodes are directly utilized as cathodes for aqueous nickel–zinc batteries (NZBs). Among all the as‐prepared electrodes, NiCo‐MOF@CC‐3 (NCM@CC‐3), with an optimized Co/Ni ratio of 1:1, exhibits the best electrical conductivity, which is according to the density functional theory (DFT) theoretical calculations. The NCM@CC‐3//Zn@CC battery achieves a high specific capacity of 1.77 mAh cm–2, a high areal energy density of 2.97 mWh cm–2, and high cycling stability of 83% capacity retention rate after 6000 cycles. The synthetic strategy based on the coordination effect of metal ions and the concept of binder‐free electrodes provide a new direction for the synthesis of high‐performance materials in the energy‐storage field.
A series of nickel‐based metal–organic frameworks (MOFs) (bi/multimetallic MOF‐74 family) in situ grown on carbon cloth is fabricated in application of aqueous Ni–Zn batteries. The synthetic strategy based on the coordination effect of metal ions and the concept of binder‐free electrodes provide a new direction for the synthesis of high‐performance materials in the energy‐storage field.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Metal‐containing nanoparticles (M‐NPs) in metal/nitrogen‐doped carbon (M‐N‐C) catalysts have been considered hostile to the acidic oxygen reduction reaction (ORR). The relation between M‐NPs and the ...active sites of metal coordinated with nitrogen (MNx) is hard to establish in acid medium owing to the poor stability of M‐NPs. Herein, we develop a strategy to successfully construct a new FeCo‐N‐C catalyst containing highly active M‐NPs and MN4 composite sites (M/FeCo‐SAs‐N‐C). Enhanced catalytic activity and stability of M/FeCo‐SAs‐N‐C is shown experimentally. Calculations reveal that there is a strong interaction between M‐NPs and FeN4 sites, which can favor ORR by activating the O−O bond, thus facilitating a direct 4 e− process. Those findings firstly shed light on the highly active M‐NPs and FeN4 composite sites for catalyzing acid oxygen reduction reaction, and the relevant reaction mechanism is suggested.
Highly active metal‐containing nanoparticles and FeN4 composite sites have been constructed. Experiment and calculation results reveal the enormous potential for activating the O−O bond and promoting the direct 4 e− dissociation pathway in the acidic oxygen reduction reaction (ORR), which could fundamentally improve ORR activity and inhibit the formation of reactive oxygen species.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Herein we present a new viologen‐based radical‐containing metal–organic framework (RMOF) Gd‐IHEP‐7, which upon heating in air undergoes a single‐crystal‐to‐single‐crystal transformation to generate ...Gd‐IHEP‐8. Both RMOFs exhibit excellent air and water stability as a result of favorable radical‐radical interactions, and their long‐lifetime radicals result in wide spectral absorption in the range 200–2500 nm. Gd‐IHEP‐7 and Gd‐IHEP‐8 show excellent activity toward solar‐driven nitrogen fixation, with ammonia production rates of 128 and 220 μmol h−1 g−1, respectively. Experiments and theoretical calculations indicate that both RMOFs have similar nitrogen fixation pathways. The enhanced catalytic efficiency of Gd‐IHEP‐8 versus Gd‐IHEP‐7 is attributed to intermediates stabilized by enhanced hydrogen bonding.
A single‐crystal‐to‐single‐crystal (SCSC) transformation of stable radical‐containing MOF Gd‐IHEP‐7 generates Gd‐IHEP‐8. It is accompanied by a marked increase in efficiency of sacrificial agent‐free photocatalytic nitrogen fixation to yield NH3 from H2O and N2 under simulated solar light irradiation at ambient temperature. The NH3 production rate of 220 μmol h−1 g−1 for Gd‐IHEP‐8 is a new record for MOF photocatalysts.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The conductive hydrogels always suffered from high internal friction, large hysteresis, and low capability of accurately predicting physical deformation, which seriously restricted their application ...in smart wearable devices. To address these problems, solvent molecules are directionally inserted into the polymer molecule chains via bridge effect to effectively reduce the molecular internal friction. Moreover, swelling is also combined to eliminate the temporary entanglements in the hydrogel system. The cooperation between the bridge and swollen effect endows the prepared polyacrylamide (PAM)/laponite/H3BO3/ethylene glycol (Eg) organohydrogel (PLBOH) ultralow hysteresis (1.38%, ε = 100%), ultrafast response (≈10 ms), and high linearity in the whole‐strain‐range (R2 = 0.996) with a great sensitivity (GF = 2.68 at the strain range of 0–750%). Meanwhile, the prepared PL10B30OH exhibits long‐term stability, excellent stretchability, and low dissipated energy. Furthermore, the assembled triboelectric nanogenerator (TENG) displays an outstanding energy harvesting performance with an output voltage of 200 V with the size of 20 mm × 20 mm. The assembled strain sensors can monitor the small strain of facial expressions and large strain of human movements, indicating the tremendous applications in self‐powered intelligent and flexible wearable electronics under harsh environmental conditions.
An innovative method is developed to prepare the hydrogel via bridge effect to directionally insert solvent molecules into the hydrogel, which effectively acts as lubricate to reduce the molecular internal friction. The developed hydrogel exhibits ultralow‐hysteresis, ultrafast‐response, and whole‐strain‐range linearity contributed by the special molecular structure, which also holds great potential in flexible wearable devices.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Three types of membrane-less photoelectrochemical (PEC) devices for solar-driven hydrogen peroxide (H2O2) production have been proposed, including (a) a H2O2 electrolyzer; (b) a photoelectrode-based ...PEC device; and (c) particulate photocatalysts in a suspension reactor. These devices can produce H2O2 from sunlight, water, and oxygen in air as the only inputs. Their respective efficiency limits were calculated by using the measured performance of H2O2 evolving electrocatalysts and by assuming idealized 100% selectivity for H2O2 accumulation, and by using the energy-conversion performance of light absorbers at their Shockley–Queisser limit. Multi-physics models for the three device configurations were employed for evaluating their electrochemical polarization behaviour as a function of the operating current density and for quantifying the respective contribution from the catalyst overpotential loss, the resistive loss between the cathode and anode, and the Nernstian potential loss due to pH gradients across the electrolyte. For particulate photocatalysts in a suspension, the concept of a non-zero light intensity threshold was for the first time applied to account for net positive H2O2 accumulation, which implies that the most efficient photocatalyst suspension should not fully absorb sunlight. The maximum solar-to-H2O2 conversion efficiency for a photoelectrode-based device was found to be 20.0%, fundamentally limited by the photocurrent density that is matched by dual absorbers in tandem series under 1-sun illumination. The maximum solar-to-H2O2 conversion efficiency for a particulate photocatalyst suspension can achieve 24.5–27.5% with a single-absorber band gap of 1.5–1.7 eV, depending on particle sizes. The modelling outcomes emphasize the importance of water-oxidation selectivity for achieving H2O2 accumulation towards molar concentration levels, and should guide the PEC H2O2 device implementation as the activity and selectivity of H2O2-evolving electro-catalysts continue to improve.
The endocannabinoid system consists of endogenous cannabinoids (endocannabinoids), the enzymes that synthesize and degrade endocannabinoids, and the receptors that transduce the effects of ...endocannabinoids. Much of what we know about the function of endocannabinoids comes from studies that combine localization of endocannabinoid system components with physiological or behavioral approaches. This review will focus on the localization of the best-known components of the endocannabinoid system for which the strongest anatomical evidence exists.
We disclose the intrinsic semiconducting properties of one of the largest mixed‐valent uranium clusters, H3O+UV(UVIO2)8(μ3‐O)6(PhCOO)2(Py(CH2O)2)4(DMF)4 (Ph=phenyl, Py=pyridyl, ...DMF=N,N‐dimethylformamide) (1). Single‐crystal X‐ray crystallography demonstrates that UV center is stabilized within a tetraoxo core surrounded by eight uranyl(VI) pentagonal bipyramidal centers. The oxidation states of uranium are substantiated by spectroscopic data and magnetic susceptibility measurement. Electronic spectroscopy and theory corroborate that UV species serve as electron donors and thus facilitate 1 being a n‐type semiconductor. With the largest effective atomic number among all reported radiation‐detection semiconductor materials, charge transport properties and photoconductivity were investigated under X‐ray excitation for 1: a large on‐off ratio of 500 and considerable charge mobility lifetime product of 2.3×10−4 cm2 V−1, as well as a high detection sensitivity of 23.4 μC Gyair−1 cm−2.
The intrinsic semiconducting properties of one of the largest mixed‐valent uranium(V/VI) clusters are presented. It shows a large on‐off ratio of 500 and considerable charge mobility lifetime product of 2.3×10−4 cm2 V−1, as well as a high detection sensitivity of 23.4 μC Gyair−1 cm−2 under X‐ray excitation.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The effects of pearlite on the initiation and propagation of localized corrosion in Q370qD and Q370qE weathering steels under a simulated marine environment were examined by scanning Kelvin probe ...force microscopy, scanning electron microscope, scanning vibrating electrode technique and X-ray diffraction. Pearlite was uniformly distributed in Q370qD steel, whereas it displayed a banded distribution with a relatively higher proportion in Q370qE steel. Proeutectoid ferrite around pearlite and lamellar ferrite inside pearlite preferentially dissolved as the anode of micro-galvanic couples, and lamellar cementite acted as the cathode. The coarser interlamellar spacing and higher pearlite content enhanced the micro-galvanic effects in the microstructure and promoted localized corrosion propagation rate. The corrosion rate of Q370qE steel was higher than that of Q370qD steel. With the extension of corrosion time, corrosion products preferentially accumulated on the pearlite phase. The banded pearlite microstructure caused surface defects in rust layers. Uniformly distributed pearlite microstructure was more conducive to the formation of a dense rust layer.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Since the first commercialization of the "rocking chair" battery in the 1990s, the energy density of lithium-ion batteries has increased continuously. To reach higher energy density, the anode-free ...configuration has been suggested and intensively studied in recent years. In an anode-free battery, the Li deposits on the bare current collector (CC) in the first discharge without any host materials. Therefore, the anode-free configuration could be considered as a special kind of Li-metal battery. Although the anode-free design enhances the battery's energy density by decreasing network weight, the low coulombic efficiency (CE) and Li dendrite restrict the practical application. The interfacial issues, such as nonuniform deposition of lithium and parasitic reactions at the CC|Li-metal|electrolyte interfaces, are responsible for the low CE value and dendrite growth. To address these problems, tuning the CC|Li-metal|electrolyte interfacial chemistry has been considered as a promising approach. Diverse strategies have been used to modify the CC|Li-metal|electrolyte interfaces in the last few years. This review provides readers an overview of interfacial chemistry in anode-free batteries, including the interfacial problems and interfacial engineering strategies. Moreover, the interfacial modification strategies for the solid-state anode-free battery are also discussed. New approaches are expected to be developed to further improve the cycling stability of the anode-free batteries.
Interfacial engineering strategies in the anode-free battery.
Electroencephalography (EEG) signals can reflect activities of the human brain and represent different emotional states. However, recognizing emotions based on full-channel EEG signals will lead to ...redundant data and hardware complexity, thus it is not suitable for designing wearable devices for daily-life emotion recognition. This paper proposes a channel selection method to select an optimal subset of EEG channels by using normalized mutual information (NMI). Compared with other methods, the proposed method solves the problem of obtaining a higher recognition rate while reducing EEG channels sharply. First, EEG signals are sliced into fixed-length pieces with a sliding window, and short-time Fourier transform is adopted to capture EEG spectrogram. Then inter-channel connection matrix is calculated based on NMI, and channel reduction is conducted by using thresholding and connection matrix analysis. The experiments are based on the widely-used emotion recognition database DEAP. It can be derived from the experimental results that the proposed method can select optimal EEG channel subsets to a certain number while maintaining high accuracy of 74.41% for valence and 73.64% for arousal with support vector machines. Further analysis also reveals that the distribution of the selected channels is consistent with cortical areas for general emotion tasks.
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