High-performance lithium-ion batteries are commonly built with heterogeneous composite electrodes that combine multiple active components for serving various electrochemical and structural functions. ...Engineering these heterogeneous composite electrodes toward drastically improved battery performance is hinged on a fundamental understanding of the mechanisms of multiple active components and their synergy or trade-off effects. Herein, we report a rational design, fabrication, and understanding of yolk@shell Bi
S
@N-doped mesoporous carbon (C) composite anode, consisting of a Bi
S
nanowire (NW) core within a hollow space surrounded by a thin shell of N-doped mesoporous C. This composite anode exhibits desirable rate performance and long cycle stability (700 cycles, 501 mAhg
at 1.0 Ag
, 85% capacity retention). By in situ transmission electron microscopy (TEM), X-ray diffraction, and NMR experiments and computational modeling, we elucidate the dominant mechanisms of the phase transformation, structural evolution, and lithiation kinetics of the Bi
S
NWs anode. Our combined in situ TEM experiments and finite element simulations reveal that the hollow space between the Bi
S
NWs core and carbon shell can effectively accommodate the lithiation-induced expansion of Bi
S
NWs without cracking C shells. This work demonstrates an effective strategy of engineering the yolk@shell-architectured anodes and also sheds light onto harnessing the complex multistep reactions in metal sulfides to enable high-performance lithium-ion batteries.
The shape of metal nanoparticles (NPs) is one of the key factors determining their catalytic reactivity. Recent in situ TEM observations show that dynamic reshaping of metal NPs occurs under the ...reaction conditions, which becomes a major hurdle for fully understanding catalytic mechanisms at the molecular level. This Minireview provides a summary of the latest progress in characterizing and modeling the equilibrium shape of metal NPs in various reactive environments through the joint effort of state‐of‐the‐art in situ environmental transmission electron microscopy experiments and a newly developed multiscale structure reconstruction model. The quantitative agreement between the experimental observations and theoretical modeling demonstrate that the fundamental mechanism of the reshaping phenomenon is driven by anisotropically changed surface energies under gas adsorption. The predictable reshaping of metal NPs paves the way for the rational design of truly efficient nanocatalysts in real reactions.
Getting into shape: This Minireview gives a summary of the latest progress in characterizing and modeling the equilibrium shape of metal nanoparticles (NPs) in reactive environments through the combination of state‐of‐the‐art in situ environmental transmission electron microscopy (ETEM) experiments and the multiscale structure reconstruction (MSR) model.
Biodiversity loss and its effects on humanity is of major global concern. While a growing body of literature confirms positive relationships between biodiversity and multiple ecological functions, ...the links between biodiversity, ecological functions and multiple ecosystem services is yet unclear. Studies of biodiversity–functionality relationships are mainly based on computer simulations or controlled field experiments using only few species. Here, we use a trait‐based approach to integrate plant functions into an ecosystem service assessment to address impacts of restoration on species‐rich grasslands over time. We found trade‐offs among functions and services when analysing contributions from individual species. At the community level, these trade‐offs disappeared for almost all services with time since restoration as an effect of increased species diversity and more evenly distributed species. Restoration to enhance biodiversity also in species‐rich communities is therefore essential to secure higher functional redundancy towards disturbances and sustainable provision of multiple ecosystem services over time.
Positive relationships found between biodiversity and multiple ecological functions leading to multiple ecosystem services are mainly based on computer simulations or controlled field experiments using only few species. We use a trait‐based approach to integrate plant functions into an ecosystem service assessment to address impacts of restoration on species‐rich grasslands over time. We show that the existence of trade‐offs among services at the individual species level could be mitigated at community level by high species diversity and more evenly distributed species.
Adding alkali metal salt promoters to calcium-based materials can influence the cycling performance of CaO-based sorbents. So far, most research on alkali metal salts focus on carbonate and chloride ...salts, while little attention is paid to sulfates. In this paper, we present an in-depth study of the role of Na2SO4 in calcium looping via in-situ experiments and DFT simulations. The results show that the effective conversion rate of Na2SO4-CaO after one cycle is 0.779 with the energy storage density of 2476.1 kJ/kg, while the effective conversion rate of CaO is 0.562 with the energy storage density of 1786.4 kJ/kg. After 80 cycles, the effective conversion and energy storage density of Na2SO4-CaO are lower than CaO, which is attributed to Na+ reducing the surface energy and accelerating the sintering. Moreover, an optimization strategy based on coordination effect among Na2SO4, CaO and inert oxides is proposed to slow down the sintering problems. Among them, Na2SO4-(CaO + ZnO) has the best adsorption performance and energy storage performance and ZnO is cheap, which can be considered a cost-effective sorbent. This work provides a new approach for developing efficient, simple and cost-effective calcium-based materials by simultaneously achieving fast reaction rates and good cycling stability of CaL.
Raman spectroscopy is a crucial technology in geoscience and often employed in in situ quantification experiments to investigate fluid compositions at elevated temperatures. Raman spectroscopic ...quantification is fundamental to understanding the hydrothermal behaviors of aqueous species, such as SO42− and H3PO40. Considering that SO42− and PO43− are closely associated with metal transportation and deposition, investigating the hydrothermal behaviors of these species, via Raman spectroscopic quantification, can give an assistance for the comprehension of relative ore-forming processes. During Raman spectroscopic quantification, the accuracy of the calibration coefficient (k), which bridges the concentration of a species (Cspecies) and its Raman peak area (Anormalized) in the form of Cspecies = k · Anormalized, is the key to accurate measurement of fluid composition. For high-temperature experiments, quantification of fluid composition is complicated because the coefficient k varies with varying temperatures. In this study, the temperature dependence of the calibration coefficients is retrieved, based on experiments on solutions containing SO42− and H3PO40 using the fused silica capillary capsules. The results show a well-established linear relationship between the k and 1/T (absolute temperature in Kelvin) for both SO42− and H3PO40. The reported linear k − 1/T relationship simplifies Raman-based fluid composition investigation at elevated temperatures: the k values throughout the whole temperature range of interest can be retrieved by measuring the room-temperature Raman intensity of a standard sample (i.e., with known composition) and one single data point at high temperature. We speculate that this linear k − 1/T relationship method may be established for other species (e.g., carbonate ions) and can be applied for experiments using other technics (e.g., hydrothermal diamond anvil cell) or retrieving the compositions of natural or synthetic fluid inclusions. For example, the empirical linear relationship can facilitate the measurements of gas concentrations (e.g., CO2) in natural fluid inclusions.
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•An empirical method in Raman spectroscopic quantification.•The coefficient (k) shows linear relationship with 1/T (absolute temperature).•The linear relationship can be used in in situ fluid composition investigation.
Transmission electron microscopy is an indispensable tool in modern materials science. It enables the structure of materials to be studied with high spatial resolution, and thus makes a decisive ...contribution to the fact that it is now possible to understand the microstructure-related physical and chemical characteristics and to correlate these with the macroscopic materials properties. It was tantamount to a paradigm shift when electron microscopy reached atomic resolution in the late 1990s due to the invention of aberration-corrected electron optics. It is now generally accepted practice to perform picometer-scale measurements and chemical analyses with reference to single atomic units. This review has three objectives. Microscopy in atomic dimensions is applied quantum physics. The consequences of this for practical work and for the understanding and application of the results shall be worked out. Typical applications in materials science will be used to show what can be done with this kind of microscopy and where its limitations lie. In the absence of relevant monographs, the aim is to provide an introduction to this new type of electron microscopy and to enable the reader to access the literature in which special issues are addressed. The paper begins with a brief presentation of the principles of optical aberration correction. It then discusses the fundamentals of atomic imaging and covers typical examples of practical applications to problems in modern materials science. It is emphasized that in atomic-resolution electron microscopy the quantitative interpretation of the images must always be based on the solution of the quantum physical and optical problem on a computer.
The cooling of PV has been shown to increase electricity production. Among passive techniques, evaporative cooling has one of the greatest potentials. In this work, the efficiency and sustainability ...of this technique have been investigated for various climatic conditions. In-situ experiments were conducted to develop parametric models for PV cell temperatures and back surface convective heat transfer coefficient. Experiments have revealed an up to 20.1 °C lower peak PV temperature and up to 9.6% increased electric power. Year-round analysis was made for eight cities to determine the required roof size to capture precipitation and the volume of rainwater storage for sustainable evaporative cooling. The study shows that sustainable PV evaporative cooling is possible in cities with temperate and continental climates, where 1–3 m2 of roof area and 50–150 l of rainwater storage are needed for 1 m2 of PV. The annual electricity production can increase by 5.9–9.4 kWh/m2a, which is a 3.6–4.6% increase. In the semi-arid climate of Lampedusa, a roof above 4 m2 and a storage of up to 500 l per m2 of PV are required. In the desert climate of Almeria and Athens, sustainable evaporative cooling is not feasible.
•The efficiency and sustainability of evaporative cooling of PV cells was evaluated.•Parametric models for PV temperature and heat transfer coefficient were developed.•Heat and mass transfer analogy was validated and used to determine the water demand.•With sustainable evaporative cooling 5.9 to 11.3 kWh/m2PV more energy can be produced.•Up to 3 m2 of roof and 150 l of rainwater storage are required in continental climate.
Generator‐collector experiments offer insights into the mechanisms of electrochemical reactions by correlating the product and generator currents. Most commonly, these experiments are performed using ...commercially‐available rotating ring‐disk electrodes (RRDE). We developed a modular double electrode flow cell (DEFC) with exchangeable generator and detector electrodes where the electrode width equals the channel width. As a test case, we considered the ferri‐/ferrocyanide redox couple in experiments, analytical calculations and multiphysics simulations. Wall effects reduce the current density by less than 10 % in our geometry for the investigated conditions and the analytical solution for the limiting current at the generator electrode applies to widths up to 5 mm. The collection efficiency for all investigated electrode widths is close to the expected 35.4 % above a flow rate of 1.0 (mL/min)1/3 but only independent of the flow rate for electrodes with width 5 mm and larger. Kinetic constants of 1.3–1.9 ⋅ 10−3 cm/s are obtained from Koutecký‐Levich analysis and 21.0–5.0 ⋅ 10−3 cm/s from Nicholson analysis for the DEFC, which falls within the range reported previously. We conclude that our DEFC with exchangeable electrodes is an attractive alternative to commercial RRDEs which offers the flexibility to optimize both the generator and collector materials for the desired reaction.
Generator‐collector experiments offer insights into the mechanisms of electrochemical reactions. A geometry was reported where wall effects can be neglected.
•Review of dislocation dynamics simulations & micro-scale experiments of metal fatigue.•Fatigue dislocation structure evolution, size effects and crack.•Current limitations and future outlook ...regarding the modeling and experiments are discussed.
This review paper providing a comprehensive review of insights gained from cyclic loading discrete dislocation dynamics simulations and micro-scale fatigue experiments on dislocation structure evolution, size effects on fatigue life and fatigue strength, and crack initiation/propagation in metals.
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