Rational designing of the composition and structure of electrode material is of great significance for achieving highly efficient energy storage and conversion in electrochemical energy devices. ...Herein, MoS2/NiS yolk–shell microspheres are successfully synthesized via a facile ionic liquid‐assisted one‐step hydrothermal method. With the favorable interface effect and hollow structure, the electrodes assembled with MoS2/NiS hybrid microspheres present remarkably enhanced electrochemical performance for both overall water splitting and asymmetric supercapacitors. In particular, to deliver a current density of 10 mA cm−2, the MoS2/NiS‐based electrolysis cell for overall water splitting only needs an output voltage of 1.64 V in the alkaline medium, lower than that of Pt/C–IrO2‐based electrolysis cells (1.70 V). As an electrode for supercapacitors, the MoS2/NiS hybrid microspheres exhibit a specific capacitance of 1493 F g−1 at current density of 0.2 A g−1, and remain 1165 F g−1 even at a large current density of 2 A g−1, implying outstanding charge storage capacity and excellent rate performance. The MoS2/NiS‐ and active carbon‐based asymmetric supercapacitor manifests a maximum energy density of 31 Wh kg−1 at a power density of 155.7 W kg−1, and remarkable cycling stability with a capacitance retention of approximately 100% after 10 000 cycles.
MoS2/NiS yolk–shell microspheres exhibit prominent electrochemical performance for both overall water splitting and asymmetric supercapacitors, which can be attributed to the advanced structural features of the interface effect and hollow structure.
This study describes possible transmission of novel coronavirus disease 2019 (COVID-19) from an asymptomatic Wuhan resident to 5 family members in Anyang, a Chinese city in the neighboring province ...of Hubei.
Aiming at the construction of novel platform for efficient light harvesting, the precise synthesis of a new family of AIEgen‐branched rotaxane dendrimers was successful realized from an ...AIEgen‐functionalized 2rotaxane through a controllable divergent approach. In the resultant AIE macromolecules, up to twenty‐one AIEgens located at the tails of each branches, thus making them the first successful example of AIEgen‐branched dendrimers. Attributed to the solvent‐induced switching feature of the rotaxane branches, the integrated rotaxane dendrimers displayed interesting dynamic feature upon the aggregation‐induced emission (AIE) process. Moreover, novel artificial light‐harvesting systems were further constructed based on these AIEgen‐branched rotaxane dendrimers, which revealed impressive generation‐dependent photocatalytic performances for both photooxidation reaction and aerobic cross‐dehydrogenative coupling (CDC) reaction.
A novel artificial light‐harvesting system based on AIEgen‐branched rotaxane dendrimers has been successfully constructed which displayed impressive generation‐dependent photocatalytic performances for both photooxidation reaction and aerobic cross‐dehydrogenative coupling reaction.
This cross-sectional study investigated the relationships between teacher mindfulness, work engagement, and classroom emotions composed of positive and negative emotions. A sample of 498 Chinese ...primary, secondary, and high school teachers completed an anonymous online questionnaire. Descriptive analysis, bivariate correlation, and a series of regression equations were conducted to analyze the data. The results indicate that teacher mindfulness, work engagement, and classroom emotions are all at the intermediate level, and significantly correlated. The effect of teacher mindfulness on classroom emotions is partially mediated by work engagement. In addition, negative emotions partially mediate the effect of teacher mindfulness on work engagement, while positive emotions fully mediate it. These results highlight the importance of fostering teacher mindfulness through mindfulness-based intervention, developing teacher emotion regulation competence in teacher education, and cultivating supportive classroom and school culture for teachers to experience more positive emotions from students and administrators.
Layered antiferromagnetism is the spatial arrangement of ferromagnetic layers with antiferromagnetic interlayer coupling. The van der Waals magnet chromium triiodide (CrI3) has been shown to be a ...layered antiferromagnetic insulator in its few-layer form, opening up opportunities for various functionalities in electronic and optical devices. Here we report an emergent nonreciprocal second-order nonlinear optical effect in bilayer CrI3. The observed second-harmonic generation (SHG; a nonlinear optical process that converts two photons of the same frequency into one photon of twice the fundamental frequency) is several orders of magnitude larger than known magnetization-induced SHG and comparable to the SHG of the best (in terms of nonlinear susceptibility) two-dimensional nonlinear optical materials studied so far (for example, molybdenum disulfide). We show that although the parent lattice of bilayer CrI3 is centrosymmetric, and thus does not contribute to the SHG signal, the observed giant nonreciprocal SHG originates only from the layered antiferromagnetic order, which breaks both the spatial-inversion symmetry and the time-reversal symmetry. Furthermore, polarization-resolved measurements reveal underlying C2h crystallographic symmetry-and thus monoclinic stacking order-in bilayer CrI3, providing key structural information for the microscopic origin of layered antiferromagnetism. Our results indicate that SHG is a highly sensitive probe of subtle magnetic orders and open up possibilities for the use of two-dimensional magnets in nonlinear and nonreciprocal optical devices.
Abstract
The novel coronavirus disease 2019 (COVID-19) produced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is sweeping the world in a very short time. Although much has been ...learned about the clinical course, prognostic inflammatory markers, and disease complications of COVID-19, the potential interaction between SARS-CoV-2 and the thyroid is poorly understood. In contrast to SARS-CoV-1, limited available evidence indicates there is no pathological evidence of thyroid injury caused by SARS-CoV-2. However, subacute thyroiditis caused by SARS-CoV-2 has been reported for the first time. Thyroid dysfunction is common in patients with COVID-19 infection. By contrast, certain thyroid diseases may have a negative impact on the prevention and control of COVID-19. In addition, some anti–COVID-19 agents may cause thyroid injury or affect its metabolism. COVID-19 and thyroid disease may mutually aggravate the disease burden. Patients with SARS-CoV-2 infection should not ignore the effect on thyroid function, especially when there are obvious related symptoms. In addition, patients with thyroid diseases should follow specific management principles during the epidemic period.
The realization that nanostructured graphene featuring nanoscale width can confine electrons to open its bandgap has aroused scientists’ attention to the regulation of graphene structures, where the ...concept of graphene patterns emerged. Exploring various effective methods for creating graphene patterns has led to the birth of a new field termed graphene patterning, which has evolved into the most vigorous and intriguing branch of graphene research during the past decade. The efforts in this field have resulted in the development of numerous strategies to structure graphene, affording a variety of graphene patterns with tailored shapes and sizes. The established patterning approaches combined with graphene chemistry yields a novel chemical patterning route via molecular engineering, which opens up a new era in graphene research. In this review, the currently developed graphene patterning strategies is systematically outlined, with emphasis on the chemical patterning. In addition to introducing the basic concepts and the important progress of traditional methods, which are generally categorized into top‐down, bottom‐up technologies, an exhaustive review of established protocols for emerging chemical patterning is presented. At the end, an outlook for future development and challenges is proposed.
Graphene patterning has attracted widespread attention owing to its ability to tailor the structures and properties of graphene, targeting high‐tech applications. The established strategies have been evolved from the initial dimension regulation to the emerging molecular engineering of graphene sheets. In general, these methods can be divided into top‐down/bottom‐up and chemical patterning routes as comprehensively discussed in this review.
Graphene with massless Dirac fermions can have exceptionally strong third-order optical nonlinearities. Yet reported values of nonlinear optical susceptibilities for third-harmonic generation (THG), ...four-wave mixing (FWM) and self-phase modulation vary over six orders of magnitude. Such variation likely arises from frequency-dependent resonance effects of different processes in graphene under different doping. Here, we report an experimental study of THG and FWM in graphene using gate tuning to adjust the doping level and vary the resonant condition. We find that THG and sum-frequency FWM are strongly enhanced in heavily doped graphene, while the difference-frequency FWM appears just the opposite. Difference-frequency FWM exhibited a novel divergence towards the degenerate case in undoped graphene, leading to a giant enhancement of the nonlinearity. The results are well supported by theory. Our full understanding of the diverse nonlinearity of graphene paves the way towards future design of graphene-based nonlinear optoelectronic devices.
Abstract
Developing robust nonprecious electrocatalysts towards hydrogen/oxygen evolution reactions is crucial for widespread use of electrochemical water splitting in hydrogen production. Here, we ...report that intermetallic Co
3
Mo spontaneously separated from hierarchical nanoporous copper skeleton shows genuine potential as highly efficient electrocatalysts for alkaline hydrogen/oxygen evolution reactions in virtue of in-situ hydroxylation and electro-oxidation, respectively. The hydroxylated intermetallic Co
3
Mo has an optimal hydrogen-binding energy to facilitate adsorption/desorption of hydrogen intermediates for hydrogen molecules. Associated with high electron/ion transport of bicontinuous nanoporous skeleton, nanoporous copper supported Co
3
Mo electrodes exhibit impressive hydrogen evolution reaction catalysis, with negligible onset overpotential and low Tafel slope (~40 mV dec
−1
) in 1 M KOH, realizing current density of −400 mA cm
−2
at overpotential of as low as 96 mV. When coupled to its electro-oxidized derivative that mediates efficiently oxygen evolution reaction, their alkaline electrolyzer operates with a superior overall water-splitting output, outperforming the one assembled with noble-metal-based catalysts.
•Cold plate cooling of prismatic Li-ion battery under 5C discharging is modeled.•Temperature patterns on Li-ion battery with cold plate cooling are discussed.•Thermal responses of Li-ion battery ...under external shorting are simulated.•3D thermal modeling of 50 V Li-ion battery pack with 14 20 Ah cells is performed.•Multi-scale multi-domain modeling is demonstrated for large Li-ion battery pack.
In this work, three-dimensional (3D) thermal modeling of a single Li-ion battery cell and a 50 V Li-ion battery pack composed of 14 prismatic batteries is performed. Equivalent circuit model is used for subscale electrochemical modeling. The heat generated by electrical resistance and electrochemistry reactions is then solved in the cell domain which resolves the heat transfer in battery and battery pack. The modeling provides highly resolved temporal 3D insight into thermal and battery dynamics under fast discharging and abusive condition. It is found that with low coolant velocity, the cell temperature easily exceeds 40 °C, and temperature non-uniformity exceeds the limit value of 5 °C under 5C discharging condition; and under external shorting condition, temperature rises fast and reaches the 80 °C point quickly which can further trigger thermal runaway. On the other hand, with adequate coolant flow rate, the cell temperature and temperature gradients are effectively limited to tolerable level under both 5C discharging and external shorting conditions. Thus, coolant rate needs to be carefully designed to prevent high temperature and localized high temperature spot in Li-ion battery. The modeling method used in this study can be applied to general Li-ion battery and Li-ion battery pack designing.
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