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.
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.
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.
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.
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.
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.
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.
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.
Combining 2D MoS2 with other transition metal sulfide is a promising strategy to elevate its electrochemical performances. Herein, heterostructures constructed using MnS nanoparticles embedded in ...MoS2 nanosheets (denoted as MnS‐MoS2) are designed and synthesized as anode materials for lithium/sodium‐ion batteries via a facile one‐step hydrothermal method. Phase transition and built‐in electric field brought by the heterostructure enhance the Li/Na ion intercalation kinetics, elevate the charge transport, and accommodate the volume expansion. The sequential phase transitions from 2H to 3R of MoS2 and α to γ of MnS are revealed for the first time. As a result, the MnS‐MoS2 electrode delivers outstanding specific capacity (1246.2 mAh g−1 at 1 A g−1), excellent rate, and stable long‐term cycling stability (397.2 mAh g−1 maintained after 3000 cycles at 20 A g−1) in Li‐ion half‐cells. Superior cycling and rate performance are also presented in sodium half‐cells and Li/Na full cells, demonstrating a promising practical application of the MnS‐MoS2 electrode. This work is anticipated to afford an in‐depth comprehension of the heterostructure contribution in energy storage and illuminate a new perspective to construct binary transition metal sulfide anodes.
A heterostructure composed of MnS and MoS2 (denoted as MnS‐MoS2) possesses a uniform sheet structure. The MnS‐MoS2 heterostructure undergoes phase transition from 2H to 3R of MoS2 and α to γ of MnS during the electrode reaction. A built‐in electric field is introduced to enhance the electrochemical performance. Superior cycling and rate performance are achieved.
Constructing heterojunctions is an efficient approach for enhancing charge separation to optimize photoreactivity. Although the aligned built‐in electric fields across the heterointerface are ...generally considered as the main driving force for charge separation, diffusion‐controlled charge separation also happens, which is poorly investigated in photocatalytic heterojunctions. Here, a perylene‐3,4,9,10‐tetracarboxylic diimide (PDI)–bismuth oxyiodide (BiOI) heterojunction is elaborately fabricated by in situ successive ion layer adsorption and reaction (SILAR) methods. Utilizing Kelvin probe force microscopy (KPFM), the local separation of photogenerated charge carriers across the heterointerface is directly mapped, which obeys a Z‐scheme mechanism. Experimental results and theoretical simulations reveal that the differences of electron densities between PDI and BiOI enable a diffusion‐controlled charge separation process, which overwhelm that of built‐in electric fields across heterointerfaces. Benefiting from the effective charge separation driven by a diffusion‐controlled driving force, this PDI/BiOI heterojunction exhibits superior photocatalytic activities even under infrared (IR)‐light irradiation. These findings highlight the importance of diffusion‐controlled charge separation, and also offer useful roadmaps for the design of high‐performance heterojunction photocatalysts for down‐to‐earth applications.
Swimming upstream driven by the transient diffusion electric field, the photoinduced electrons of perylene‐3,4,9,10‐tetracarboxylic diimide (PDI) swim toward bismuth oxyiodide (BiOI) across the PDI/BiOI heterointerfaces under illumination, overcoming the aligned built‐in electric field.
