We developed a tandem electrocatalyst for CO2‐to‐CO conversion comprising the single Cu site co‐coordinated with N and S anchored carbon matrix (Cu‐S1N3) and atomically dispersed Cu clusters (Cux), ...denoted as Cu‐S1N3/Cux. The as‐prepared Cu‐S1N3/Cux composite presents a 100 % Faradaic efficiency towards CO generation (FECO) at −0.65 V vs. RHE and high FECO over 90 % from −0.55 to −0.75 V, outperforming the analogues with Cu‐N4 (FECO only 54 % at −0.7 V) and Cu‐S1N3 (FECO 70 % at −0.7 V) configurations. The unsymmetrical Cu‐S1N3 atomic interface in the carbon basal plane possesses an optimized binding energy for the key intermediate *COOH compared with Cu‐N4 site. At the same time, the adjacent Cux effectively promotes the protonation of *CO2− by accelerating water dissociation and offering *H to the Cu‐S1N3 active sites. This work provides a tandem strategy for facilitating proton‐coupled electron transfer over the atomic‐level catalytic sites.
A tandem catalyst composed of single Cu sites co‐coordinated with N and S and atomically dispersed Cu clusters (Cu‐S1N3/Cux) was developed for CO2‐to‐CO conversion. The Cu‐S1N3/Cux exhibited a 100 % Faradaic efficiency for CO formation (FECO), outperforming the single‐atomic Cu‐N4 analogue (FECO=54 %).
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
GeTe is a promising thermoelectric material at medium temperature, but its carrier concentration tends to go beyond the optimal range for thermoelectrics. This work realized a significant ZT ...enhancement from 1.0 to 2.0 by suppressing the formation of Ge vacancies and band convergence. By simply optimizing the amount of excessive Ge, the hole carrier concentration is greatly reduced. It is demonstrated that the suppression of Ge vacancies can not only optimize the carrier concentration but also recover the mobility to a high value of 90 cm 2 V −1 s −1 , which well exceeds the previously reported data and guarantees superior electrical transport properties, leading to a ZT of 1.6. Further Bi doping facilitates band convergence as featured by the increased band effective mass and high mobility, which in turn yields large power factors and low electronic thermal conductivity. Bi doping induced mass and strain fluctuation also favors the reduction of the lattice thermal conductivity. Consequently, a maximum ZT of ∼ 2.0 at 650 K with an average ZT of over 1.2 is achieved in the nominal composition Bi 0.05 Ge 0.99 Te, which is one of the best thermoelectric materials for medium temperature applications.
Abstract
A new physics package containing revised convection and planetary boundary layer (PBL) schemes in the National Centers for Environmental Prediction’s Global Forecast System is described. The ...shallow convection (SC) scheme in the revision employs a mass flux parameterization replacing the old turbulent diffusion-based approach. For deep convection, the scheme is revised to make cumulus convection stronger and deeper to deplete more instability in the atmospheric column and result in the suppression of the excessive grid-scale precipitation. The PBL model was revised to enhance turbulence diffusion in stratocumulus regions. A remarkable difference between the new and old SC schemes is seen in the heating or cooling behavior in lower-atmospheric layers above the PBL. While the old SC scheme using the diffusion approach produces a pair of layers in the lower atmosphere with cooling above and heating below, the new SC scheme using the mass-flux approach produces heating throughout the convection layers. In particular, the new SC scheme does not destroy stratocumulus clouds off the west coasts of South America and Africa as the old scheme does. On the other hand, the revised deep convection scheme, having a larger cloud-base mass flux and higher cloud tops, appears to effectively eliminate the remaining instability in the atmospheric column that is responsible for the excessive grid-scale precipitation in the old scheme. The revised PBL scheme, having an enhanced turbulence mixing in stratocumulus regions, helps prevent too much low cloud from forming. An overall improvement was found in the forecasts of the global 500-hPa height, vector wind, and continental U.S. precipitation with the revised model. Consistent with the improvement in vector wind forecast errors, hurricane track forecasts are also improved with the revised model for both Atlantic and eastern Pacific hurricanes in 2008.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Atomically thin boron nitride (BN) is an important 2D nanomaterial, with many properties distinct from graphene. In this feature article, these unique properties and associated applications, often ...not feasible with graphene, are outlined. The article starts with characterization and identification of atomically thin BN. It is followed by demonstrating their strong oxidation resistance at high temperatures and applications in protecting metals from oxidation and corrosion. As flat insulators, BN nanosheets are ideal dielectric substrates for surface enhanced Raman spectroscopy (SERS) and electronic devices based on 2D heterostructures. The light emission of BN nanosheets in the deep ultraviolet (DUV) and ultraviolet (UV) regions is also included for its scientific and technological importance. The last part is dedicated to synthesis, characterization, and optical properties of BN nanoribbons, a special form of nanosheets.
Boron nitride (BN) nanosheets have many properties distinct from graphene, and therefore enable applications not available to the carbon counterpart. In this Feature Article, the unique properties and novel applications of BN nanosheets are summarized.
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The widespread application of thermoelectric (TE) technology demands high‐performance materials, which has stimulated unceasing efforts devoted to the performance enhancement of Bi2Te3‐based ...commercialized thermoelectric materials. This study highlights the importance of the synthesis process for high‐performance achievement and demonstrates that the enhancement of the thermoelectric performance of (Bi,Sb)2Te3 can be achieved by applying cyclic spark plasma sintering to BixSb2–xTe3‐Te above its eutectic temperature. This facile process results in a unique microstructure characterized by the growth of grains and plentiful nanostructures. The enlarged grains lead to high charge carrier mobility that boosts the power factor. The abundant dislocations originating from the plastic deformation during cyclic liquid phase sintering and the pinning effect by the Sb‐rich nano‐precipitates result in low lattice thermal conductivity. Therefore, a high ZT value of over 1.46 is achieved, which is 50% higher than conventionally spark‐plasma‐sintered (Bi,Sb)2Te3. The proposed cyclic spark plasma liquid phase sintering process for TE performance enhancement is validated by the representative (Bi,Sb)2Te3 thermoelectric alloy and is applicable for other telluride‐based materials.
The thermoelectric power factor and figure of merit of the BiSbTe alloy are significantly improved by cyclic liquid‐phase aided spark plasma sintering process. The present proposed fabrication process modulates the microstructure in a wide range of scale from nano‐sized dislocations to micrometer grain size, leading to a synergistic control of charge carriers and phonon transport.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Stimuli‐responsive DNA‐functionalized nano‐ and microcontainers composed of mesoporous SiO2 nanoparticles (MP SiO2 NPs), microcapsules, or micelles/vesicles act as carriers for the transport and ...release of drugs. The information encoded in the DNA sequences provides instructive information for the gating of drug‐loaded pores of MP SiO2 NPs, for the assembly and degradation of microcapsules or lipid–DNA micelles/vesicles, and for the targeting of nano‐/microcontainers to cancer cells. Different triggers are applied to release the drugs loaded in the nano‐/microcontainers by unlocking the pores of the MP SiO2 NPs or by degradation of the containers. These include the use of switchable DNA nanostructures (nucleic acid hairpins, i‐motif, G‐quadruplexes) and the implementation of chemical, thermal, or photonic stimuli. Also, catalytic processes stimulated by DNAzymes or enzymes are used to release drugs from the nano‐/microcontainers.
DNA gates: Stimuli‐responsive DNA‐functionalized nano‐ and microcontainers composed of mesoporous SiO2 nanoparticles, microcapsules, or micelles/vesicles act as drug carriers for targeted controlled release. Different stimuli such as chemical, photonic, thermal, and biocatalytic triggers are used to release the loaded drugs.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Electrochemically converting NO3− into NH3 offers a promising route for water treatment. Nevertheless, electroreduction of dilute NO3− is still suffering from low activity and/or selectivity. Herein, ...B as a modifier was introduced to tune electronic states of Cu and further regulate the performance of electrochemical NO3− reduction reaction (NO3RR) with dilute NO3− concentration (≤100 ppm NO3−−N). Notably, a linear relationship was established by plotting NH3 yield vs. the oxidation state of Cu, indicating that the increase of Cu+ content leads to an enhanced NO3−‐to‐NH3 conversion activity. Under a low NO3−−N concentration of 100 ppm, the optimal Cu(B) catalyst displays a 100 % NO3−‐to‐NH3 conversion at −0.55 to −0.6 V vs. RHE, and a record‐high NH3 yield of 309 mmol h−1 gcat−1, which is more than 25 times compared with the pristine Cu nanoparticles (12 mmol h−1 gcat−1). This research provides an effective method for conversion of dilute NO3− to NH3, which has certain guiding significance for the efficient and green conversion of wastewater in the future.
B as a modifier was introduced to tune the oxidation state of Cu and further regulate the performance of electrochemical NO3− reduction reaction with dilute NO3− concentration (≤100 ppm NO3−−N). The optimal Cu(B) exhibits a 100 % ammonia Faraday efficiency (FENH3) and a record‐high yield of 309 mmol h−1 gcat−1, superior over the pristine Cu (FENH3=23 %, 12 mmol h−1 gcat−1).
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Microstructure engineering is an effective strategy to reduce lattice thermal conductivity (κl) and enhance the thermoelectric figure of merit (zT). Through a new process based on melt‐centrifugation ...to squeeze out excess eutectic liquid, microstructure modulation is realized to manipulate the formation of dislocations and clean grain boundaries, resulting in a porous network with a platelet structure. In this way, phonon transport is strongly disrupted by a combination of porosity, pore surfaces/junctions, grain boundaries, and lattice dislocations. These collectively result in a ≈60% reduction of κl compared to zone melted ingot, while the charge carriers remain relatively mobile across the liquid‐fused grains. This porous material displays a zT value of 1.2, which is higher than fully dense conventional zone melted ingots and hot pressed (Bi,Sb)2Te3 alloys. A segmented leg of melt‐centrifuged Bi0.5Sb1.5Te3 and Bi0.3Sb1.7Te3 could produce a high device ZT exceeding 1.0 over the whole temperature range of 323–523 K and an efficiency up to 9%. The present work demonstrates a method for synthesizing high‐efficiency porous thermoelectric materials through an unconventional melt‐centrifugation technique.
The melt‐centrifugation technique is demonstrated to be able to decrease the thermal conductivity while preserving the good electrical properties. By introducing a unique porous structure with microscale dislocation, ≈60% reduction in lattice thermal conductivity compared to conventional zone melted ingots is achieved. Such a method paves a new way for top‐down introduction of large porosity and dense dislocations in bulk materials.
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This review focuses on classifying different types of long wavelength absorbing BODIPY dyes based on the wide range of structural modification methods that have been adopted, and on tabulating their ...spectral and photophysical properties. The structure-property relationships are analyzed in depth with reference to molecular modeling calculations, so that the effectiveness of the different structural modification strategies for shifting the main BODIPY spectral bands to longer wavelengths can be readily compared, along with their effects on the fluorescence quantum yield (ΦF) values. This should facilitate the future rational design of red/NIR region BODIPY dyes for a wide range of different applications.
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