Measurement of electric fields is crucial for the evaluation of the electromagnetic environment in electric power transmission system. Due to limited transmission corridor resources, the hybrid ...transmission lines including high-voltage alternating current and high-voltage direct current (HVAC/HVDC) are more common nowadays. However, commonly used field-mill direct current electric field sensors (DC EFSs) can only be used beneath HVDC lines and the emergence of alternating current (AC) electric fields has adversely affected measurement results recorded by DC EFS. In this work, a DC EFS was designed that is capable of measuring ground-level DC electric fields generated by overhead HVAC/HVDC transmission lines in a hybrid corridor. A field-mill structure was used to modulate the DC and AC hybrid electric field and then a narrow band-pass filter was used to realise suppression of the AC electric field signal. Subsequently, the phase-sensitive detection method was used to realise amplitude demodulation and phase discrimination of the DC electric field. Sensor prototypes based on the foregoing method were experimentally tested in the China national high-voltage base. These DC EFSs could be mass-produced conveniently from current field-mill for hybrid corridors application.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
In recent years, external electric fields (EEFs) have captured some spotlight as novel effectors of chemical change. EEFs directly impact the structure of molecular systems. For example, aligning an ...electric field along a specific bond‐axis leads to either shortening or elongation of the bond (and ultimately bond breaking). Furthermore, EEFs enable unprecedented control over chemical reactivity. Orienting an electric field along the so‐called “reaction‐axis,” the direction in which the electrons reorganize during the conversion from reactant to product, leads to catalysis or inhibition and can induce mechanistic crossover from concerted to stepwise reactions. Off‐reaction‐axis orientation enables control over the stereoselectivity of reactions and disables forbidden–orbital mixing. Two‐directional fields enable control over both reactivity and selectivity. In this advanced review, we offer an overview of this rapidly evolving research field with a focus on the valence bond modeling of EEF effects and the insight it offers. A wide variety of examples will be considered and a link to the experiment will be made throughout. We end by offering some perspectives in which we postulate that, as experimental techniques continue to mature, EEFs could potentially become a generally applicable “zapping” tool to facilitate elaborate chemical syntheses.
This article is categorized under:
Structure and Mechanism > Reaction Mechanisms and Catalysis
External electric fields enable an unprecedented control over chemical structure and reactivity/selectivity: they induce bond dissociation, catalysis/inhibition, and regio‐/stereocontrol. Harnessing electrostatics could be a real game‐changer in chemical synthesis.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, OILJ, SBCE, SBMB, UPUK
A highly crystalline perylene imide polymer (Urea‐PDI) photocatalyst is successfully constructed. The Urea‐PDI presents a wide spectrum response owing to its large conjugated system. The Urea‐PDI ...performs so far highest oxygen evolution rate (3223.9 µmol g−1 h−1) without cocatalysts under visible light. The performance is over 107.5 times higher than that of the conventional PDI supramolecular photocatalysts. The strong oxidizing ability comes from the deep valence band (+1.52 eV) which is contributed by the covalent‐bonded conjugated molecules. Besides, the high crystallinity and the large molecular dipoles of the Urea‐PDI contribute to a robust built‐in electric field promoting the separation and transportation of photogenerated carriers. Moreover, the Urea‐PDI is very stable and has no performance attenuation after 100 h continuous irradiation. The Urea‐PDI polymer photocatalyst provides with a new platform for the use of photocatalytic water oxidation, which is expected to contribute to clean energy production.
A crystalline perylene imide polymer photocatalyst with the highest oxygen evolution performance is achieved. The polymer can be reused over 100 h without any decrease in performance overcoming the poor stability of the organic photocatalysts. The superior photocatalytic performance comes from the suitable energy band and the robust built‐in electric field contributed by the highly crystallinity and large molecular dipole.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
A highly crystalline perylene imide supramolecular photocatalyst (PDI‐NH) is synthesized via imidazole solvent method. The catalyst shows a breakthrough oxygen evolution rate (40.6 mmol g−1 h−1) with ...apparent quantum yield of 10.4% at 400 nm, which is 1353 times higher than the low crystalline PDI‐NH. The highly crystalline structure comes from the ordered self‐assembly process in molten imidazole solvent via π–π stacking and hydrogen bonding. Further, the excellent performance ascribes to the robust built‐in electric field induced by its high crystallinity, which greatly accelerates the charge separation and transfer. What is more, the PDI‐NH is quite stable and can be reused over 50 h without performance attenuation. Briefly, the crystalline PDI‐NH with strong built‐in electric field throws light on photocatalytic oxygen evolution, showing a new perspective for the design of organic photocatalysts.
A highly crystalline perylene imide supramolecular photocatalyst (PDI‐NH) is successfully constructed via π–π interaction and hydrogen bonding. The PDI‐NH performs a breakthrough oxygen evolution rate (40.6 mmol g−1 h−1), exceeding most of photocatalysts. The high crystallinity of PDI‐NH ensures the built‐in electric field, acting as a kinetic force to promote the charge separation.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The practical application of Li‐rich Mn‐based oxide cathode is predominately retarded by the capacity decline and voltage fading, associated with the structure distortion and anionic redox reactions. ...Here, a linkage‐functionalized modification approach to tackle these challenges via a synchronous lithium oxidation strategy is reported. The doping of Ce in the bulk phase activates the pseudo‐bonding effect, effectively stabilizing the lattice oxygen evolution and suppressing the structure distortion. Interestingly, it also induces the formation of spinel phase Li4Mn5O12 in the subsurface, which in turn constructs the phase boundaries, thereby arousing the interior self‐built‐in electric field to prevent the outward migration of bulk oxygen anions and boost the charge transfer. Moreover, the formed coating layer Li2CeO3 with oxygen vacancies accelerates Li+ diffusion and mitigates electrolyte cauterization. The corresponding cathode exhibits superior long‐cycle stability after 300 cycles with only a 0.013% capacity drop and 1.76 mV voltage decay per cycle. This work sheds new light on the development of Li‐rich Mn‐based oxide cathodes toward high energy density applications.
The practical application of Li‐rich Mn‐based oxide cathodes is limited by the capacity decline and voltage fading, associated with the structure distortion and anionic redox reactions. Here, a linkage‐functionalized modification approach to tackle these challenges via a synchronous lithium oxidation strategy is reported. This work sheds new light on the development of Li‐rich Mn‐based oxide cathodes toward high energy density applications.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Integrating sulfur cathodes with effective catalysts to accelerate polysulfide conversion is a suitable way for overcoming the serious shuttling and sluggish conversion of polysulfides in ...lithium–sulfur batteries. However, because of the sharp differences in the redox reaction kinetics and complicated phase transformation of sulfur, a single‐component catalyst cannot consistently accelerate the entire redox process. Herein, hierarchical and defect‐rich Co3O4/TiO2 p–n junctions (p‐Co3O4/n‐TiO2‐HPs) are fabricated to implement the sequential catalysis of S8(solid) → Li2S4(liquid) → Li2S(solid). Co3O4 sheets physiochemically immobilize the pristine sulfur and ensure the rapid reduction of S8 to Li2S4, while TiO2 dots realize the effective precipitation of Li2S, bridged by the directional migration of polysulfides from p‐type Co3O4 to n‐type TiO2 attributed to the interfacial built‐in electric field. As a result, the sulfur cathode coupled with p‐Co3O4/n‐TiO2‐HPs delivers long‐term cycling stability with a low capacity decay of 0.07% per cycle after 500 cycles at 10 C. This study demonstrates the synergistic effect of the built‐in electric field and heterostructures in spatially enhancing the stepwise conversion of polysulfides, which provides novel insights into the interfacial architecture for rationally regulating the polysulfide redox reactions.
Novel hierarchical and defect‐rich Co3O4/TiO2 p–n junctions with built‐in electric field are designed as the host materials of sulfur electrodes for Li–S batteries. The elaborate p–n junctions not only induce the directional migration of lithium polysulfides to suppress the dissolution of sulfur intermediates into the electrolyte but also implement the spatially sequential catalysis to ensure the superior utilization of sulfur.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The DEVCOM Army Research Laboratory (ARL) electric field “cage” generates a uniform E-field over a large working volume, along the lines of the IEEE-Std 1308–1994. The end plates are spaced farther ...apart than the IEEE standard field source, and the fringing fields are controlled by the addition of “guard tubes.” This chamber was originally constructed to calibrate and characterize electric field sensors, and it has been redesigned to support quasi-static electric field imaging applications. A planar array of sensors forms a grounded end plate of the cage and is used to measure distortions in the uniform field generated by the cage due to objects placed inside. However, the array itself distorts this field and introduces significant errors. Several modifications were made to mitigate the errors, including adding nonfunctional “dummy” elements, a border around the array, and a back plane behind it. The parameter space for these additions is very large, since the number of nonfunctional elements, the width of the border, and the size and placement of the back plane can all be tuned independently. Extensive computer modeling was used to explore this parameter space and test thousands of possible designs. The design chosen yields modeled absolute field errors over a 1.2-m × 0.8-m sensing plane that are less than 0.5 % for a uniform ambient field (empty cage), and less than 1 % for a sphere with a 0.5-m radius in an ambient field.
•An electric field calibration chamber was fitted with an array of sensors at one end for quasi-static electric field imaging.•The design of the sensor array was optimized using extensive computer modeling.•E-field >99.5 % uniform over entire array when chamber is empty, >99 % uniform when chamber contains a 1-m conducting sphere.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Starch is a versatile and a widely used ingredient, with applications in many industries including adhesive and binding, paper making, corrugating, construction, paints and coatings, chemical, ...pharmaceutical, textiles, oilfield, food and feed. However, native starches present limited applications, which impairs their industrial use. Consequently, starch is commonly modified to achieve desired properties. Chemical treatments are the most exploited to bring new functionalities to starch. However, those treatments can be harmful to the environment and can also bring risks to the human health, limiting their applications. In this scenario, there is a search for techniques that are both environmentally friendly and efficient, bringing new desired functionalities to starches. Therefore, this review presents an up-to-date overview of the available literature data regarding the use of environmentally friendly treatments for starch modification. Among them, we highlighted an innovative chemical treatment (ozone) and different physical treatments, as the modern pulsed electric field (PEF), the emerging ultrasound (US) technology, and two other treatments based on heating (dry heating treatment - DHT, and heat moisture treatment - HMT). It was observed that these environmentally friendly technologies have potential to be used for starch modification, since they create materials with desirable functionalities with the advantage of being categorized as clean label ingredients.
Full text
Available for:
BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Potassium‐ion batteries hold practical potential for large‐scale energy storage owing to their appealing cell voltage and cost‐effective features. The development of anode materials with high rate ...capability and satisfactory cycle lifespan, however, is one of the key elements for exploiting this electrochemical energy storage system at practical levels. Here, a template‐assisted strategy is reported for acquiring a bimetallic telluride heterostructure which is supported on N‐doped carbon shell (ZnTe/CoTe2@NC) that promotes diffusion of K+ ions for rapid charge transfer. It is shown that in telluride heterojunctions, electron‐rich Te sites and built‐in electric fields contributed by electron transfer from ZnTe to CoTe2 concomitantly provide abundant cation adsorption sites and facilitate interfacial electron transport during potassiation/depotassiation. The relatively fine ZnTe/CoTe2 nanoparticles imparted by the heterojunction result in high structural stability, together with a highly reversible capacity up to 5000 cycles at 5 A g−1. Moreover, using judiciously combined experiment and theoretical computation, it is demonstrated that the energy barrier for K+ diffusion in telluride heterojunctions is significantly lower than that in individual counterparts. This quantitative design for fast and durable charge transfer in telluride heterostructures can be of immediate benefit for the rational design of batteries for low‐cost energy storage and conversion.
The development of anode materials with high rate capability and satisfactory cycle lifespan is one of the key elements for exploiting the potassium‐ion batteries at practical levels. Here, a template‐assisted strategy is reported for acquiring a bimetallic telluride heterostructure which is supported by N‐doped carbon shell that promotes the diffusion of K+ ions for rapid charge transfer.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Li‐rich Mn‐based cathode materials (LRMs) are potential cathode materials for high energy density lithium‐ion batteries. However, low initial Coulombic efficiency (ICE) severely hinders the ...commercialization of LRM. Herein, a facile oleic acid‐assisted interface engineering is put forward to precisely control the ICE, enhance reversible capacity and rate performance of LRM effectively. As a result, the ICE of LRM can be precisely adjusted from 84.1% to 100.7%, and a very high specific capacity of 330 mAh g−1 at 0.1 C, as well as outstanding rate capability with a fascinating specific capacity of 250 mAh g−1 at 5 C, are harvested. Theoretical calculations reveal that the introduced cation/anion double defects can reduce the diffusion barrier of Li+ ions, and in situ surface reconstruction layer can induce a self‐built‐in electric field to stabilize the surface lattice oxygen. Moreover, this facile interface engineering is universal and can enhance the ICEs of other kinds of LRM effectively. This work provides a valuable new idea for improving the comprehensive electrochemical performance of LRM through multistrategy collaborative interface engineering technology.
Introduced cation/anion double defects can reduce the interface charge transfer resistance and enhance the Li+ ion diffusion coefficient. The induced in situ surface reconstruction layer can increase the electronic conductivity and stabilize the surface lattice oxygen. As a result, the initial Coulombic efficiency of Li‐rich Mn‐based cathode material is controlled precisely.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
