Charge Redistribution Effects Research Articles

Heterogeneous NASICON-Type Cathode With Reversible Multielectron Reaction for High-Performance Sodium-Ion Batteries.

Na superionic conductor (NASICON)-structured compounds demonstrate great application potential by their robust framework and compositional diversity. However, they are blamed for the mediocre energy density, and achieving both multielectron reaction and good cycling stability simultaneously is challenging. Herein, a novel heterogeneous Na4Fe3(PO4)2(P2O7)/Na2VTi(PO4)3 (NFPP/NVTP) material with stable multielectron reaction is constructed by spray drying technology. The mutual promotion effect of intergrowth structures effectively improves the purity and the crystallization of NFPP/NVTP during the fabrication process, which is beneficial to the high capacity and cycling stability. As a result, the optimized NFPP/NVTP demonstrates a high reversible capacity of 155.3 mAh g-1 at 20mA g-1 and outstanding cycling stability with 82.9% capacity retention over 2500 cycles at 1 A g-1, which are much superior to those of NFPP and NVTP individually. Even in full cell configuration, the energy density remains high at ≈380Wh kg-1 based on the cathode mass. The high capacity of NFPP/NVTP is also attributed to the successive reduction/oxidation mechanism involving the introduction of Ti3+ and interfacial charge redistribution effect between the heterogeneous phases, which greatly improve the electronic and ionic conductivity. Moreover, high reversible structural evolution during the multisodium storage process further guarantees excellent cycling stability.

Synergistically enhancing ion migration kinetics and inducing orientation deposition for dendrite-free aqueous zinc-ion batteries

Aqueous zinc-ion batteries (ZIBs) have garnered widespread interest owing to their merits of high safety and low cost. Nevertheless, the commercial application of ZIBs is hindered by uncontrollable dendrite growth and adverse side reactions. Herein, a potential spontaneous reducing and assembling strategy has been tailored to generate a uniform and ultra-thin layer of sulfonate modified Mxene (SM-MXene) layer on the Zn surface to regulate electrochemical behavior. Compared with the bare Zn foil, the optimizing SM-MXene layer has an advantageous charge redistribution effect, resulting in a uniform electric field and a lower Zn nucleation energy barrier. The SM-MXene layer can also block the entry of H2O and inhibit the severe side reactions. The zincophilic SM-MXene layer, possessing abundant sulfonic acid groups (−SO3H), can remarkably reduce the surface energy of the Zn (002) crystal plane and induce the preferential growth of (002) horizontally orientation during the electrodeposition process, resulting in highly reversible process between Zn plating and stripping with dendrite-free and corrosion-free behaviors. Accordingly, the symmetric battery, using SM-MXene/ZnSO4 as electrolyte, exhibits ultra-high Coulombic efficiency (99.48 %) and ultra-long cycle life (over 5000 cycles), subsequently enabling the Zn||MnO2 full cell highly rechargeable.

Interface engineering to construct heterostructured SnS2/Sb2S3 on rGO through a targeted-complexation deposition strategy for high-performance lithium-ion capacitors

Accurate synthesis of electrode materials with homogeneous heterostructure is an important approach to eliminate the energy storage dynamics discrepancy between the anode and cathode of lithium-ion capacitors (LICs). However, the complex synergistic effects between two electrodes is yet to materialize due to the lack of effective approach. Herein, a targeted-complexation deposition strategy is proposed to prepare uniform SnS2/Sb2S3 heterostructure attached to reduced graphene oxide (rGO) (SnS2/Sb2S3@rGO) with the aid of L-cysteine. The strong complexation between L-cysteine and metal ions effectively suppresses the hydrolysis reaction of Sb3+ ion and guides the uniform deposition of SnS2/Sb2S3 heterostructures on rGO. Due to the charge redistribution and mutual-support effect, the lithium storage properties of SnS2/Sb2S3@rGO can be integrated and greatly enhanced. Furthermore, a three-dimensional conductive network consisting of polyaniline and rGO heterostructure is synthesized by a self-assembly strategy, which is able to deliver a superior capacity of 178.6 mA h g−1 as well as outstanding rate property as a cathode. The LICs assembled with heterogeneous cathode and anode materials demonstrates an exceptional energy density (reaching 298 W h kg−1), impressive power density (58.5 kW kg−1) and remarkable capacity maintenance (78 %) even over 6000 cycles, providing a valuable guide for producing the high-performance LICs.

Effect of Buffer Charge Redistribution on RF Losses and Harmonic Distortion in GaN-on-Si Substrates

Effect of Buffer Charge Redistribution on RF Losses and Harmonic Distortion in GaN-on-Si Substrates

Novel UV-LED-driven photocatalysis-chlorine activation for carbamazepine degradation by sulfur-doped NH2-MIL 53 (Fe) composites: Electronic modulation effect and the dual role of chlorine

Chlorine activation-inefficient and the generation of disinfection by-products (DBPs) has indeed limited the application of UV/chlorine process. In this study, the typical metal-organic frameworks (MOFs) NH2-MIL53(Fe) were successfully modified with organic ligands containing sulfur functional groups and applied to construct a novel UV-LED-driven heterogeneous chlorine activation system. The generation of intermediate energy levels and the charge redistribution effect on Fe-S bond facilitated the excitation of electrons and realized the effective separation of photohole (hvb+) and photoelectron (ecb-). The involvement of S-NH2-MIL53(Fe) improved the efficiency of UV-LED/chlorine process by 6 times. The effective activation of HOCl/OCl- by hvb+ and ecb- significantly enhanced the yield of HO· and Cl·. More importantly, HOCl/OCl- played a dual role in UV-LED/chlorine/S-NH2-MIL53(Fe) process as a precursor for the generation of free radicals and a catalyst for the enhancement of HO· yield, which could achieve efficient removal of the target pollutants at lower chlorine doses. In addition, the presence of low-valent sulfur species and ecb- accelerated the cycle of Fe(II)/Fe(III) and in-situ generation of HO· and Cl·. The known generation of DBPs in UV-LED/chlorine/S-NH2-MIL53(Fe) process decreased by 37.9% compared to UV-LED/chlorine process. Developing novel UV-LED/chlorine/S-NH2-MIL53(Fe) processes provided a reliable strategy to efficiently purify actual micro-polluted water bodies.

Surface evolution of AlGaN nanowire decorated by cesium atoms: A first principle study

Surface decoration with cesium on the photocathode is an effective method to reduce surface barriers and promote electron emission. In this study, we investigated the changes in surface properties of AlGaN nanowire coated with Cs atoms using first-principle calculations. The N bridge site is the most stable site for a single atom deposition. As more Cs atoms are deposited on the surface, the average adsorption energy increases along with the weakened ionization of Cs adatoms. The Bader charge of surface Al and Ga atoms undertake significant changes in comparison with tiny alteration of N atoms, especially for Al atom with a decrease of 0.41 |e|/atom. The variation in surface work function reaches a maximum of 2.3 ∼ 2.5 eV at Cs coverage of 0.5 ∼ 0.75 ML, which can be attributed to the synergistic effect of dipole length and charge redistribution. The donor states underneath CBM induced by the orbital overlap of Al-p, Ga-p and Cs-d electrons accompanied by the downward band bending in the band structures. This work provides theoretical insight into the surface evolution of Cs-decorated AlGaN nanowires and offers guidance for the development of state-of-the-art nanostructured vacuum devices.

Engineering a Ni-Al Brucite-Based Interface Layer with Regulated Zn2+ Flux for Highly Reversible Zn Metal Anodes.

Practical aqueous Zn-ion batteries are appealing for grid-scale energy storage with intrinsic safety and cost-effectiveness, yet their cycling stability and reversibility are limited by unwanted dendrite growth and water-induced erosions on Zn. Herein, a hydrophilic and Zn2+-conductive Ni-Al layered double hydroxide (NiAl-LDH) interphase layer is constructed on the surface of Zn, in which NiAl-LDH enables a more uniformly distributed Zn2+ concentration and interfacial electric field owing to its large internal Zn2+ channels and favorable charge redistribution effect. Consequently, the NiAl-LDH-integrated Zn anode achieves low voltage hysteresis and high reversibility of Zn plating/stripping with uniform underneath deposition behaviors. Remarkably, the resultant NiAl-2 LDH@Zn delivers superior cycling durability over 2800 h (∼4 months, 0.5 mA cm-2), realizes high reversibility with 99.4% average Coulombic efficiency over 1400 cycles, and confers stable operation of full Zn cells with high V2O5 mass loadings. This work offers a facile and instructive interface design approach for achieving highly stable Zn metal anodes.

Lattice Strain and Charge Redistribution of Pt Cluster/Ir Metallene Heterostructure for Ethylene Glycol to Glycolic Acid Conversion Coupled with Hydrogen Production.

Upgrading overall water splitting (OWS) system and developing high-performance electrocatalysts is an attractive way to the improve efficiency and reduce the consumption of hydrogen (H2 ) production from electrolyzed water. Here, a Pt cluster/Ir metallene heterojunction structure (Pt/Ir hetero-metallene) with a unique Pt/Ir interface is reported for the conversion of ethylene glycol (EG) to glycolic acid (GA) coupled with H2 production. With the assistance of ethylene glycol oxidation (EGOR), the Pt/Ir||Pt/Ir hetero-metallene two-electrode water electrolysis system exhibits a lower cell voltage of 0.36V at 10mA cm-2 . Furthermore, the Faradaic efficiency of EG to GA is as high as 87%. The excellent performance of this new heterostructure arise from the charge redistribution and strain effects induced by Pt-Ir interactions between the heterogeneous interfaces, as well as the larger specific surface area and more active sites due to the metallene structure.

Effects of Stone-Wales defects on structure and electrical properties of double-walled silicon nanotubes by SCC-DFTB method

In this work, the geometric structure, system stability, electrical properties and charge distribution of zigzag double-walled silicon nanotubes (DWSiNTs) (nin,0)@(nout,0) (nin = 5–7, nout = 8–13) perfect tubes and defective tubes with three types of Stone-Wales (SW) defects were studied using the self-consistent charge density functional tight-binding (SCC-DFTB) method. The change of the chirality index between the inner and outer walls was simulated. The results show that the symmetry of the structure disappears, and the warping of the tube wall changes from order to disorder after introducing SW defects. The warps of outer tube are obviously higher than that of inner tube. The perfect tubes with inner wall chirality index (6,0) are more stable than other tubes. SW defects of outer wall tubes have a higher effect on system stability than those of inner wall tubes. The difference of inner and outer wall chirality indices plays an obvious role in regulating the energy gap of the system, half of which are near-metal properties and the other half semiconductor properties, and the regulation range is 0.1075–0.8519 eV. All types of SW defects at all locations have a certain regulatory effect on the energy gap of DWSiNTs, and the effect of type III defect is the most obvious. The effect of atomic charge redistribution in the tube is related to the structure, and the charge transfer in a perfect tube is symmetrical. The number of electrons obtained at the defect is increased, and the electronegativity is stronger, due to the curvature of local atoms produced at the defect. This study provides a reference for the preparation and future application of DWSiNTs.

Cu-Doped WS2/Ni3S2 Coral-Like Heterojunction Grown on Ni Foam as an Electrocatalyst for Alkaline Oxygen Evolution Reaction

Finding an efficient and stable non-noble-metal catalyst for oxygen evolution reaction (OER) in alkaline environments is of great significance for reducing the cost of the catalyst. In this work, we doped Cu to the surface of WS2/Ni3S2 coral-like heterojunction grown on Ni foam substrate by physical deposition, which can promote the transfer of interface charge. An excellent OER catalytic performance with an overpotential as low as 281 mV at a current density of 100 mA·cm−2 is reached. At the same time, the attenuation of the sample is not significant after the durability test for 20 h in a current density of 100 mA·cm−2. Theoretical calculations and experimental results show that the synergistic effect of interfacial charge redistribution through the Cu-doped WS2/Ni3S2 heterojunction accelerates the process of alkaline OER reaction. This study provides a novel idea for the synthesis of non-noble metal alkaline OER catalysts.

Recent processing of interaction mechanisms of single metallic atom/clusters in energy electrocatalysis

Understanding the interactions between single metallic atom/clusters (SMACs) has been taken to an unprecedented level, due to the delicate conditions required to produce exotic phenomena in electrode materials, such as thermocatalysis, electrocatalysis, and energy storage devices. Recently, state-of-the-art synthesis methods, such as one-step pyrolysis and multistep pyrolysis, have been developed for SMACs. Herein the interactions between SMACs such as synergetic, charge redistribution effects, and mutual assistance effects, are studied. SMACs have the advantage of maximum utilization of atoms and scattered active sites compared to single metal atoms, and they also have flexible and tunable atom clusters. SMACs have been widely developed and have shown excellent catalytic performance in electrocatalysis. Herein, the self-interaction between SMACs and their catalytic mechanisms are systematically described. The challenges in current synthesis strategies, catalytic mechanisms, and industrial applications of SMACs are analyzed, and a possible synthesis method for SMACs is proposed.

Band Alignment in Black Phosphorus/Transition Metal Dichalcogenide Heterolayers: Impact of Charge Redistribution, Electric Field, Strain, and Layer Engineering

The objective of this work is to study the effects of charge redistribution, applied layer-normal electric fields, applied strain, and layer engineering on the band alignment of Black Phosphorus (BP)/Molybdenum disulphide (MoS2) heterostructure through Density Functional Theory (DFT) simulations. Black phosphorus works as a p-type material with high mobility, mechanical flexibility, and sensitivity to number of layers. Combining it with the more electronegative material, MoS2 results in strong carrier confinement and a Type II heterostructure. Charge redistribution among the layers shifts the band alignment expected from the Electron Affinity Rule. Applied external fields, strain and multiple BP layers provide band-alignment tunability within the Type II range and/or, transition to Type I and Type III heterostructures. The tunability in BP/MoS2 heterostructure may be useful as tunnel field effect transistors, rectifier diodes with tunable barrier height, reconfigurable FETs, and electro-optical modulators. Furthermore, considering heterostructures of monolayer BP with other monolayer Transitional Metal Dichalcogenides (TMD) suggests the ability to achieve different band alignment types. In our simulations, a Type I alignment is found with Tungsten diselenide (WSe2), Molybdenum diselenide (MoSe2), and Tungsten disulphide (WS2), and a Type III for Hafnium disulphide (HfS2) and Hafnium diselenide (HfSe2).

Catalytic Synergies in Bimetallic RuPt Single–Atom Catalysts via Speciation Control

AbstractBimetallic single–atom catalysts (b–SACs) have recently gained prominence by virtue of the unique catalytic cooperative interactions they can exhibit, intertwining electronic and geometric effects. To date, research efforts have exclusively focused on direct mechanisms such as electron density transfer or sequential reactivity. Herein, the first study on indirect, coordination–induced catalytic synergies in carbon‐supported RuPt SACs is conducted. To this end, a holistic approach is developed, combining i) precision synthesis, ii) advanced characterization, iii) exploration of single–site adsorption properties via the hydrogen evolution reaction, and iv) modeling through density functional theory. Despite the lack of both intermetallic coordination in the first or second shell and charge redistribution effects, the RuPt SACs exhibit a H2 formation rate enhanced up to 15–fold compared with their monometallic counterparts. To unfold the origin of the intermetallic cooperativity, modifications of the structural and catalytic properties induced by the integration of a second metal species are investigated. Thus, Pt atoms are found to selectively occupy the most energeticallyfavorable cavities in the support, prompting Ru atoms to assume a distinct, more active, configuration. This contribution unveils a novel principle of bimetallic cooperativity, demonstrating the key role of integrative experimental and computational analyses in studying b–SACs.

Control of protein activity by photoinduced spin polarized charge reorganization

Considerable electric fields are present within living cells, and the role of bioelectricity has been well established at the organismal level. Yet much remains to be learnedabout electric-field effects on protein function. Here, we use phototriggered charge injection from a site-specifically attached ruthenium photosensitizer to directly demonstrate the effect of dynamic charge redistribution within a protein. We find that binding of an antibody to phosphoglycerate kinase (PGK) is increased twofold under illumination. Remarkably, illumination is found to suppress the enzymatic activity of PGK by a factor as large as three. These responses are sensitive to the photosensitizer position on the protein. Surprisingly, left (but not right) circularly polarized light elicits these responses, indicating that the electrons involved in the observed dynamics are spin polarized, due to spin filtration by protein chiral structures. Our results directly establish the contribution of electrical polarization as an allosteric signal within proteins. Future experiments with phototriggered charge injection will allow delineation of charge rearrangement pathways within proteins and will further depict their effects on protein function.

Constructing methyl methacrylate/MXene artificial solid-electrolyte interphase layer for lithium metal batteries with high electrochemical performance

Lithium metal is a promising anode material due to its high theoretical capacity and low redox potential. However, lithium metal anode suffers from lithium dendrite, which reduces the cycle stability and reversibility of lithium metal batteries (LMBs). In order to solve this issue, we designed an in-situ polymerization method of organic–inorganic composite materials (methyl methacrylate (MMA)/MXene) to prepare artificial solid-electrolyte interphase (SEI). The as-prepared LMBs exhibit good interfacial contact and high electrochemical performance owing to the charge redistribution effect of MXene layer for decreasing the nucleation energy barrier and on the lithium metal anode. The specific capacity can sustain 106.6 mAh/g even after 1000 h cycles at 1C, and the capacity retention is 80.1 % with LiFePO4 (LFP) as a cathode material. Therefore, we believe this simple and inexpensive method can effectively restrain the growth of lithium dendrites and improve the cyclic stability and reversibility of the LMBs.

Data‐Driven Approach to Designing 2D Van der Waals Heterostructures: Misjudgment of Band Alignment Type and Its Mechanism

Data‐driven approach, including database building and high‐throughput design, is rapidly applied to various fields, ranging from physics to materials. Predicting the band alignment type at interfaces, which is based on Anderson's rule (AR), is crucial for implementing the data‐driven approach in the field of 2D van der Waals heterostructures (vdWHs). The validity of the AR‐based data‐driven approach, however, is ambiguous, particularly when it involves band alignment. Based on a large‐scale calculation (1231 heterostructures), it is explicitly demonstrated that the current AR‐based data‐driven approach have prediction errors for certain band alignment type, including the inability to predict type‐other band alignment and the partial misclassification of type II band alignment as type III. Such prediction errors are quantitatively explained by geometric deformation, interlayer orbital coupling, and charge redistribution effects. As a result, the current data‐driven design approach is insufficiently reliable for type II, type III, and type‐other heterostructures, which may result in inaccurate or incomplete design results. Herein, a flaw in the current AR‐based data‐driven approach is elucidated as well as important information for reasonably designing 2D vdWHs is provided in general.

Electronic structure of aqueous two-dimensional photocatalyst

The electronic structure, in particular the band edge position, of photocatalyst in presence of water is critical for photocatalytic water splitting. We propose a direct and systematic density functional theory (DFT) scheme to quantitatively predict band edge shifts and their microscopic origins for aqueous 2D photocatalyst, where thousands of atoms or more are able to be involved. This scheme is indispensable to correctly calculate the electronic structure of 2D photocatalyst in the presence of water, which is demonstrated in aqueous MoS2, GaS, InSe, GaSe and InS. It is found that the band edge of 2D photocatalysts are not rigidly shifted due to water as reported in previous studies of aqueous systems. Specifically, the CBM shift is quantitatively explained by geometric deformation, water dipole and charge redistribution effect while the fourth effect, i.e., interfacial chemical contact, is revealed in the VBM shift. Moreover, the revealed upshift of CBM in aqueous MoS2 should thermodynamically help carriers to participate in hydrogen evolution reaction (HER), which underpin the reported experimental findings that MoS2 is an efficient HER photocatalyst. Our work paves the way to design 2D materials in general as low-cost and high-efficiency photocatalysts.

Atomic-Scale Superlubricity in Ti2CO2@MoS2 Layered Heterojunctions Interface: A First Principles Calculation Study.

The two dimensional (2D)-layered transition-metal carbides and nitrides (MXene) have been proved to be an excellent solid lubricant owing to their high mechanical strength, low shearing strength, and self-lubricating properties. However, the interfacial friction behavior between Tin+1Cn (n = 1, 2) MXene and its heterogeneous system is not thoroughly exploited yet. Here, four types of van der Waals structures (Ti2CO2@Ti2CO2, Ti3C2O2@Ti3C2O2 MoS2@MoS2, and Ti2CO2@MoS2) have been investigated by density functional theory (DFT) calculations. The results exhibit that Ti2CO2@MoS2 possesses the lowest sliding energy barrier around 0.015 eV/oxygen(O) atom compared with the other three constructed models. Therefore, this work mainly focuses on the inner relation of Ti2CO2@MoS2 interlayer friction behaviors and its attributing factors, including normal force and charge density. The DFT analysis shows that the roughness of the potential energy corrugated plane is positively correlated with normal force and predicted the ultralow friction coefficient (μ) at 0.09 when sliding along the minimum energy potential route. Moreover, friction coefficient fluctuates at the normal force less than 10 nN determined by the combined effect of interfacial charge interlock and redistribution. This work reveals the intrinsic connection between the friction and charge interaction at heterogeneous interfaces.

Vacancy defects in the vertical heterostructures of graphene and MoS2

Van der Waals (vdW) heterostructures of two-dimensional materials have attracted significant attention owing to their potential applications in electronics, optics, and catalysis. In this study, we investigated the energetics and electronic properties of vacancy defects in the vdW heterostructures of graphene and MoS2, based on first-principles density functional theory calculations. The effects of the interlayer interactions modify the atomic and electronic configurations of the defects substantially. As a result, the formation enthalpy of the C vacancies decreases by 0.06–0.54 eV, while that of the S vacancies increases by 0.36–0.53 eV. Interestingly, in the heterostructure, the graphene layer with the C vacancy has a non-planar antiferromagnetic ground structure, which can be attributed to the effects of charge redistribution. In contrast, a competing ferromagnetic state has a planar graphene structure.

Identification of self-discharge mechanisms of ionic liquid electrolyte based supercapacitor under high-temperature operation

Ionic liquids (ILs) are promising electrolytes for supercapacitors (SCs) aimed for high-temperature applications, where increased ionic conductivity results in superior capacitive performance compared to room temperature (RT) performance. However, an increased temperature also accelerates the self-discharge rate that adversely affects energy retention and restricts the usage of SCs in standalone applications. In this study, a detailed electrochemical investigation on the self-discharge behaviour of carbon-based SCs containing an IL, 1-Ethyl-3-methylimidazolium acetate (EMIM Ac), has been carried out in the temperature range RT - 60 °C, and the underlying self-discharge mechanisms are identified. The results reveal that at a high voltage of 1.5 V, the self-discharge is characterized by a combination of charge redistribution and diffusion at both RT and 60 °C. At 60 °C, the diffusion-controlled mechanism dominates at lower voltages over the charge redistribution effect, while at RT both mechanisms contribute to a similar extent. The observed difference in the self-discharge mechanism between RT and 60 °C is explained in terms of a decreased RC time constant (τRC) at elevated temperature, and the same conclusions are potentially applicable to other IL-containing SCs as well.