Large Charge Density Research Articles

Pyrenetetrasulfonic Acid Tetrasodium Salt‐Modified CoFe Layered Double Hydroxide Enables Stable Alkaline Seawater Oxidation

AbstractSeawater electrolysis is deemed a green and promising technology for producing hydrogen in coastal areas. Nevertheless, ample chloride ions (Cl–) in seawater can corrode anode, especially at ampere‐level current densities (j), which represents a significant impediment to the seawater‐to‐H2 system. In this study, we present a CoFe layered double hydroxide nanoneedle array modified with 1,3,6,8‐pyrenetetrasulfonic acid tetrasodium salt (PTS) on Ni foam (CoFe LDH@CoFe‐PTS/NF) as a highly efficient electrocatalyst for seawater oxidation. It reveals that PTS with a large negative charge density can effectively repel Cl– and keep active sites working stably during alkaline seawater oxidation. Thus, CoFe LDH@CoFe‐PTS/NF demonstrates excellent OER performance and can achieve j of 500 and 1000 mA cm−2 at low overpotentials (η) of 333 and 364 mV. Moreover, it maintains a stable and continuous electrolysis for 500 h with minimal amounts of active chlorine generation.

Local charge distortion due to Cr in Ni-based concentrated alloys

Due to the presence of multiple elements consisting of a range of atomic radii, local lattice distortion (LLD) is commonly observed in concentrated (and high entropy) alloys. However, since these elements also have diverse electronegativities, recent works show that atoms can have a range of atomic charges. In this work, using density functional theory (DFT), we investigate electronic charge distribution in face centered cubic (FCC) Ni-based alloys and find significant charge-density distortion in HEAs. Specifically, Cr atoms have large charge density distortion that results in a wide range of bond lengths, atomic charges, and electronic density of states in Cr-containing alloys. The charge distortion impacts the stacking fault energies (SFEs) as a wide range of SFEs are observed in Cr-containing alloys (e.g., NiCr, NiFeCr and NiCoCr), which are otherwise narrow and converged in non-Cr containing alloys such as NiFe, NiCo and NiFeCo. These observations provide insights into the role of local charge distortion towards local lattice distortion in HEAs and illustrate the effect of charge distortion on the mechanical properties of the alloys.

Amorphizing MnIn2S4 Atomic Layers Create an Asymmetrical InO1S5 Polarization Plane for Photocatalytic Ammonia Synthesis and CO2 Reduction.

Building a polarization center is an effective avenue to boost charge separation and molecular activation in photocatalysis. However, a limited number of polarization centers are usually created. Here, a polarization plane based on two-dimensional (2D) atomic layers is designed to maximize the surface polarization centers. The Mn in a 2D crystal lattice is etched from the MnIn2S4 atomic layers to build a consecutive symmetry-breaking structure of isolated InO1S5 sites. More charges aggregate around O, making the isolated InO1S5 sites highly polarized. Due to the formation of the InO1S5 polarization plane, an enormous polarized electric field is formed perpendicular to the 2D atomic layers and the carrier lifetime can be prolonged from 93.2 ps in MnIn2S4 to 1130 ps in amorphous MnxIn2Sy. Meantime, the formed large charge density gradient favors coupling and activation of small molecules. Benefiting from these features, a good NH3 photosynthesis performance (515.8 μmol g-1 h-1) can be realized over amorphous MnxIn2Sy, roughly 2.5 and 48.9 times higher than those of MnIn2S4 atomic layers and bulk MnIn2S4, respectively. The apparent quantum yields reach 5.4 and 3.3% at 380 and 400 nm, respectively. Meanwhile, a greatly improved CO2 reduction activity is also achieved over MnxIn2Sy. This strategy provides an accessible pathway for designing an asymmetrical polarization plane to motivate photocatalysis optimization.

Tuning Gate Potential Profiles and Current-Voltage Characteristics of Polymer Electrolyte-Gated Transistors by Capacitance Engineering.

We demonstrate that the transfer characteristics of electrolyte-gated transistors (EGTs) with polythiophene semiconductor channels are a strong function of gate/electrolyte interfacial contact area, i.e., gate size. Polythiophene EGTs with gate/electrolyte areas much larger than the channel/electrolyte areas show a clear peak in the drain current vs gate voltage (ID-VG) behavior, as well as peak voltage hysteresis between the forward and reverse VG sweeps. Polythiophene EGTs with small gate/electrolyte areas, on the other hand, exhibit current plateaus in the ID-VG behavior and a gate-size-dependent hysteresis loop between turn on and off. The qualitatively different transport behaviors are attributed to the relative sizes of the gate/electrolyte and channel/electrolyte interface capacitances, which are proportional to interfacial area. These interfacial capacitances are in series with each other such that the total capacitance of the full gate/electrolyte/channel stack is dominated by the interface with the smallest capacitance or area. For EGTs with large gates, most of the applied VG is dropped at the channel/electrolyte interface, leading to very high charge accumulations, up to ∼0.3 holes per ring (hpr) in the case of polythiophene semiconductors. The large charge density results in sub-band-filling and a marked decrease in hole mobility, giving rise to the peak in ID-VG. For EGTs with small gates, hole accumulation saturates near 0.15 hpr, band-filling does not occur, and hole mobility is maintained at a fixed value, which leads to the ID plateau. Potential drops at the interfaces are confirmed by in situ potential measurements inside a gate/electrolyte/polymer semiconductor stack. Hole accumulations are measured with gate current-gate voltage (IG-VG) measurements acquired simultaneously with the ID-VG characteristics. Overall, our measurements demonstrate that remarkably different ID behavior can be obtained for polythiophene EGTs by controlling the magnitude of the gate-electrolyte interfacial capacitance.

Steering CO2 Electroreduction Selectivity U-Turn to Ethylene by Cu-Si Bonded Interface.

Copper (Cu), with the advantage of producing a deep reduction product, is a unique catalyst for the electrochemical reduction of CO2 (CO2RR). Designing a Cu-based catalyst to trigger CO2RR to a multicarbon product and understanding the accurate structure-activity relationship for elucidating reaction mechanisms still remain a challenge. Herein, we demonstrate a rational design of a core-shell structured silica-copper catalyst (p-Cu@m-SiO2) through Cu-Si direct bonding for efficient and selective CO2RR. The Cu-Si interface fulfills the inversion in CO2RR product selectivity. The product ratio of C2H4/CH4 changes from 0.6 to 14.4 after silica modification, and the current density reaches a high of up to 450 mA cm-2. The kinetic isotopic effect, in situ attenuated total reflection Fourier-transform infrared spectra, and density functional theory were applied to elucidate the reaction mechanism. The SiO2 shell stabilizes the *H intermediate by forming Si-O-H and inhibits the hydrogen evolution reaction effectively. Moreover, the direct-bonded Cu-Si interface makes bare Cu sites with larger charge density. Such bare Cu sites and Si-O-H sites stabilized the *CHO and activated the *CO, promoting the coupling of *CHO and *CO intermediates to form C2H4. This work provides a promising strategy for designing Cu-based catalysts with high C2H4 catalytic activity.

Stabilizing Ca-ion batteries with a 7000-cycle lifespan and superior rate capability by a superlattice-like vanadium heterostructure

Calcium-ion batteries (CIBs) by their strong competitiveness in cost and capacities have been considered as a desirable electrochemical energy technology. Nonetheless, the large ion radius and high charge density of Ca2+ lead to sluggish electrochemical reaction kinetics and structural collapse of electrode materials. Herein, we construct a superlattice-like poly 3,4-ethylenedioxythiophene−V2O5 (P–V2O5) heterostructure using an in situ self-assembly strategy and employ it as a CIB cathode. In the heterostructure, the inserted poly 3,4-ethylenedioxythiophene enlarges the interlayer of V2O5, exposing abundant active sites for efficient Ca2+ absorption and transport; meanwhile, it serves as an ‘interlayer linker’ between neighboring layers, which alleviates the volume change of V2O5 during Ca2+ insertion/extraction processes. Under the synergistic effect of these factors, the P–V2O5 electrode exhibits a longer life span and greater rate capability than pristine V2O5. Specifically, the electrode delivers a significant capacity of 157.2 mAh/g at 1 A/g and excellent cycle stability over a long period of 7000 cycles at a high current density of 20 A/g. Furthermore, it has a superior rate capability of 129.0 mAh/g even at 30 A/g. Electrochemical mechanism studies reveal that the insertion/extraction of Ca2+ in P–V2O5 is highly reversible, accompanied by the interlayer contraction/expansion.

Synergistic proton and Mg2+/Ca2+ insertion boosting aqueous divalent ion batteries

Divalent ion batteries (Mg2+, Ca2+) are promising candidates for next-generation energy storage devices. However, divalent ions’ large radius and high charge density commonly lead to sluggish diffusion kinetics, resulting in an inferior capacity and rate capability. Herein, using an organic anode, 3,4,9,10-perylenetetracarboxylic diimide, as the model system, we report incorporating proton insertion with the metal ion to boost the reaction kinetics in aqueous electrolyte, as revealed by the combined spectroscopic analysis and theoretical simulations. The co-storage strategy enables an attractive specific capacity of 110 mAh g−1 at 0.2 A g−1 and capacity retention of 80% at 2 A g−1, compared to 60 mAh g−1 and 56% for single Mg2+ insertion in the Mg-ion battery. A similar phenomenon is observed in the Ca-ion system, thus allowing the stable cycling of 1.1 V-class aqueous Mg-/Ca-ion full cells for over 2000 cycles. This work suggests the great potential of building high-power and long-lifespan aqueous divalent ion batteries enabled by the proton-assisted storage behavior.

Achieving High‐Efficiency Wind Energy Harvesting Triboelectric Nanogenerator by Coupling Soft Contact, Charge Space Accumulation, and Charge Dissipation Design

AbstractTo enhance the durability of a triboelectric nanogenerator (TENG), soft contact is an effective approach due to its flexible and elastic contact mode. However, soft contact is hard to obtain with a large charge density by triboelectrification, resulting in low power output. Herein, a novel blade soft contact TENG (BSC‐TENG), coupling flexible functional blades with shielded electrodes on the rotor, charge accumulation, and charge dissipation design on the stator, is proposed. Extra polishing blades and debris storage grooves are adopted in the BSC‐TENG to further ensure high durability. A remarkable charge density of 328 µC m−2 is achieved, setting a new record for soft contact TENGs. Besides, the output charge remains at 100% even after 200 000 cycles. The wind‐driven BSC‐TENG not only can power 3840 green LEDs and 80 parallel hygrothermometers but also can drive electronic devices for smart farms, establishing self‐powered sensing systems. This work provides a novel strategy for enhancing soft contact TENG output and durability.

Calculation of critical shear stress for binary magnesium alloys: A first-principles study

The selection of alloying elements with the effect of “Solid solution strengthening and ductilizing” (SSDD) is an important way to develop high-performance magnesium (Mg) alloys recently, and the critical shear stress (CRSS) is an intrinsic parameter that characterizes the effect of SSDD. In this study, the CRSS of four slip systems in Mg-X (X = Al, Zn, Ca, Li, Mn, Sn, Bi, Ag Ga, In, Zr), all of which have a solid solubility (>0.5 at%) in Mg, are calculated using a combination of first-principles and the Peierls-Nabarro (P–N) model, and the SSDD effect of the alloying elements is studied systematically and experimentally verified. Calculations indicate that solid solutions of Mn, Ag, and Li can increase the CRSS of basal system and reduce the difference between the three non-basal and basal systems. Solid solutions of Zn, Ca and Zr can narrow the CRSS gap between at least one non-basal slip system and the basal slip system, but other elements have no positive effect. A smaller equilibrium volume and larger charge density around Mn or Ag element than that of Li, which makes CRSS larger. At the same time, the simulation results are validated by experiment. Mg–Ag alloy exhibits improved strength and plasticity, as well as a large number of <c+a> dislocations under TEM, which is consistent with the calculation finding that Ag promotes < c+a> dislocation slip. This study can provide guidance for the selection of solid solution elements for Mg alloys.

Contribution of modified P-enriched biochar on pH buffering capacity of acidic soil

Biochar can directly hold cations in soil because of the negative charge that exists on its surfaces. Besides, improving soil cation exchange capacity, the negative charges on biochar surfaces can buffer acid soil by protonation and deprotonation mechanisms. Moreover, biochar ameliorates soil acidity due to the presence of oxides, carbonates, and hydroxides of its basic cations (Ca, Na, K, and Mg). Both biochar surface functional group and basic cation concentrations can be altered by modification with chemical agents which can affect its soil pH buffering capacity. However, the impact of modified biochar application on soil pH buffering capacity is still scanty. This study investigated the pH buffering capacity of acidic soil amended with three P-enriched modified Douglas fir biochars and compared this buffering capacity to amendment with untreated Douglas fir biochar. These three P-enriched biochars, were prepared by treating Douglas fir biochar (DFB), respectively, with: 1) anhydrous calcium chloride (CaCl2) and potassium phosphate monobasic (KH2PO4), 2) calcium carbonate (CaCO3) and diammonium phosphate {(NH4)2HPO4} and 3) an aqueous solution of magnesium sulfate (MgSO4), potassium hydroxide (KOH) and potassium phosphate monobasic (KH2PO4). The three P-enriched biochars were designated as CCPP, CAPP and MSPP, respectively. The soil pH buffering abilities were largely dependent on the added biochar's alkalinity and ash contents. The residual soil CEC was highly correlated (r ≥ 0.9), with the soil buffering capacity. Both alkalinity and pH buffering capacity improved following the order CCAP > CCPP > MSPP > DFB, while residual soil CEC followed the order CAPP > MSPP > CCPP > DFB. The pH buffering capacity of the soil after amendments with 10% CAPP, CCPP MSPP and BFB rose by 84.8, 58.3, 3.0 and 2.5%, respectively. Whereas MSPP had higher concentrations of K+ and Mg2+, greater concentrations of Ca2+ were present in CCAP and CCPP than MSPP. So, Ca2+ concentrations in biochar exerts a greater influence on alkalinity and buffering capacity than Mg2+ and K+ because of 1) its smaller effective hydration radius and larger charge density. 2) calcium hydroxide has a greater water solubility than magnesium hydroxide providing more available base. Since pH buffering capacity depends on cation exchange sites, soil additives containing Ca2+ are prone to create greater impacts than Mg2+ and K+ additives.

Structure-Performance Relationships of Complexing Agents on the Chemical Mechanical Polishing of 6063 Aluminum Alloy

Aluminum alloy has wide applications in many industries due to its unique properties. Chemical mechanical polishing (CMP) is commonly used to treat aluminum alloy to generate mirror-finish surface. In this study, the effects of pH and H2O2 concentration on the CMP of 6063 aluminum alloy were studied. Better CMP performance was obtained in basic media with 1.0 wt% H2O2. Moreover, complexing agents with different structures and functional groups were evaluated for the CMP of Al-alloy, and their structure-performance relationship was systematically studied. It was found that complexing power, steric hindrance and electrostatic repulsion of complexing agents were important factors determining material removal rate and surface roughness. The complexing agent with high complexing power can favor the dissolution and Al substrate. The complexing agent with large steric hindrance and high charge density can form a stable boundary layer on the surface of substrate and improve its dispersion ability, thereby improving MRR and surface quality. In addition, the amino functional groups of complexing agents exist in the form of neutral molecules at pH 10, which is inferior to carboxyl complexing agents due to their poor static repulsion. XPS analysis confirmed the anchoring of carboxylate anions on the sample surface.

Analysis of interaction between dislocation and interface of aluminum matrix/second phase from electronic behavior

• Difficulty in dislocation movement at interface is studied by electron transport • Change in valence electrons density at α-Al/second phase interface is calculated • Differential charge density at α-Al/second phase interfaces is analyzed • Inhibitory effect of α-Al/second phase interface on dislocation were studied The inhibitory effect of the second phase on dislocation movement has long been deemed as a great contribution to the strengthening of alloys. We investigate the electronic behavior at the α-Al matrix/second phase interface to explore its inhibitory effect on dislocation movement. This work focuses on the difficulty in dislocation movement on the interface of α-Al/Al 3 Sc, α-Al/θ'(Al 2 Cu), and α-Al/T 1 (Al 2 CuLi) of aluminum-lithium-scandium alloy based on detailed transmission electron microscopy investigation and electron transport calculation. The more drastic the electron transport between two atoms at the interface, the more intense the interaction between them, corresponding to the larger difficulty in breaking and forming bonds between them during the movement process of the extra half plane of dislocation on the interface. The calculated difference in density of valence electrons and differential charge density at α-Al/second phase interface reveals that Al 3 Sc is characterized by the largest resistance to dislocation movement compared to θ'(Al 2 Cu) and T 1 (Al 2 CuLi). The large differential charge density between the interface of (1 0 0) Al3Sc /(1 0 0) Al demonstrates the strong bonds between α-Al and Al 3 Sc and the large difficulty for the extra half plane of dislocation to form or break bonds during the movement process at α-Al/Al 3 Sc interface. The dislocation pile-up indicates a discernible hindering effect of the α-Al/Al 3 Sc interface on dislocation movement. The hindering effect presented by α-Al/Al 3 Sc interface is favorable for the tensile strength.

Biaxial Stretching Array Based on High-Energy-Efficient MXene-Based Al-Ion Micro-supercapacitor Island and Editable Stretchable Bridge.

Employment of multivalent charge carriers with higher charge density to replace frequently used univalent ones can effectively increase the areal capacitance of micro-supercapacitors utilizing few-layered MXene self-assembled electrodes. However, their larger charge density and ionic size usually lead to a sluggish extraction/insertion dynamic between MXene interlayers with limited free space, greatly offsetting the benefits. Herein, we show how to facilitate de-/intercalation of high-valence charge carriers (Al3+) by using polypyrrole-coated bacterial cellulose (BC@PPy) nanospacers to expand MXene interlayer space. Together with the longitudinal electron transport path between interlayers synchronously constructed by the conductive PPy shell, a significant 496% areal capacitance enhancement (232.79 mF cm-2) is realized in the fabricated symmetric Al3+-ion micro-supercapacitors (AMSCs) with the obtained MXene/BC@PPy hybrid film electrodes employing polyacrylamide/1 M AlCl3·6H2O hydrogel electrolyte relative to the cell with pure MXene film electrodes (39.02 mF cm-2). Further benefiting from a high output voltage of 1.2 V, the AMSCs acquire an areal energy density up to 45.3 μW h cm-2. As a device demonstration, we further fabricate a biaxially stretchable AMSC array, simulate its spatial strain distribution during biaxial stretching, and characterize its electrochemical and mechanical properties up to an extreme areal strain of 300%. The proposed rational fabrication paradigm achieves a new level of combined energy density, stretch performance, and architectural simplicity, which presents a route toward a commercially viable stretchable micro energy-storage system with high energy efficiencies.

Photoelectrochemical study of Ti3+ self-doped Titania nanotubes arrays: A comparative study between chemical and electrochemical reduction

Water splitting through the photoelectrochemical process is a solid strategy to produce clean hydrogen for which TiO2 isconsideredthe most potential photoanode due to its unique properties. However, its wideband gap and high charge carrier recombination rate limit its solar-to-hydrogen conversion efficiency. Here in we report the fabrication of the Ti3+ self-doped TiO2 nanotube samples prepared through electrochemical and Chemical (NaBH4 treatment) reduction. Structural and morphological analysis carried through XRD and FESEM respectively confirmed the formation of TiO2 nanotube arrays. XPS spectra were used to affirm the presence of Ti3+ states in the reduced sample. The absorption edge observed in the 430–500 nm range validated the reduction of the band gap to the visible range in Ti3+ self-doped samples. Photoelectrochemical results of both the reduced samples evince their potential applicability as a photoanode for hydrogen generation through PEC water splitting. EIS and absorbance spectra reveal that larger charge density, faster electron-hole separation, and better visible light absorption may be thefactors that contribute to reducing TiO2′s superior photoelectrochemical performance. However, a comparative study shows better results for electrochemically reduced samples, suggesting it is an effective technique than chemical reduction.

All‐Printed Wearable Triboelectric Nanogenerator with Ultra‐Charged Electron Accumulation Polymers Based on MXene Nanoflakes

AbstractThe multilayer triboelectric nanogenerators (TENGs) are widely developed to enhance the output performance of device. However, these TENGs consisting of electron transfer, transport, trap layers toward a large volumetric charge density should be wearable and mass‐produced for commercialization. Thus, appropriate material selection in respective layers and fabrication method are crucial for the commercialization of multilayer TENG. This study presents all‐printed, sustainable wearable TENGs based on electron accumulation polymers (EAPs) with superior charge retention capability. The EAPs consisting of polytetrafluoroethylene (PTFE), carboxyl functionalized single‐walled carbon nanotubes (SWCNTs:COOH), and Ti3C2Tx (MXene) in a fluorinated polymer matrix, are used. Compared to the reference, the EAPs not only lead to approximately six times higher output performance (300 V and 40 µA) but also four times more sustainable charge retention capability (92%) for an hour. These are attributed to the three‐step electron‐trapping mechanism with electron transfer/transport from PTFE/SWCNT and electron trapping in MXene. In addition, TENGs with EAPs exhibit excellent mechanical stability and reliability with fascinating single‐electrode demonstrations. Finally, the TENG with EAPs can efficiently operate various portable electronics and pH monitoring systems with a pH sensor and a seven‐segment display in realistic scenarios.

Essence of the Enhanced Osmotic Energy Conversion in a Covalent Organic Framework Monolayer.

Low membrane conductivity originated from a high membrane thickness has long been the "Achilles heel" of the conventional polymeric membrane, greatly hampering the improvement of the output power density in osmotic power generation. Herein, we demonstrate a molecularly-thin two-dimensional (2D) covalent organic framework (COF) monolayer membrane, featured with ultimate thickness, high pore density, and tight pore size distribution, which performs as a highly efficient osmotic power generator. Despite the large pore size up to 3.8 nm and relatively low surface charge density of 2.2 mC m-2, the monolayer COF membrane exhibits a high osmotic current density of 16.7 kA m-2 and an output power density of 102 W m-2 under 50 times the NaCl salinity gradient (0.5 M/0.01 M). This superior power density could be further improved to 170 W m-2 in the real seawater/river water gradient system. When the large pore size and low surface charge density are considered, this superior performance is not expected. Computational studies further reveal that the ultimate membrane permeability originated from the high membrane porosity, rather than ion selectivity, plays a dominant role in the production of high current density, especially under high salinity. This work provides an alternative strategy to realize improved output power density in ultrapermeable membranes.

Intrinsic Carbon Defects for the Electrosynthesis of H2O2.

Carbon materials have manifested promising potential in electrochemical reduction of O2 to H2O2. The oxygen functional groups have been identified as the catalytic sites. However, the intrinsic carbon defects abundant in carbon materials have often been neglected. Herein, a three-dimensional carbon framework with abundant intrinsic defects and oxygen functional groups (the oxygen content and chemical states of oxygen are comparable to those of commercial carbon black) was introduced and exhibited outstanding catalytic activity and selectivity toward H2O2 electrosynthesis. Through a combination of in situ Raman spectroscopy and density functional theory calculations, the intrinsic carbon defects, such as zigzag edge and zigzag pentagon sites with optimal binding energy for OOH, were also determined to be active sites. It was further revealed that intrinsic carbon defects with large negative charge density and asymmetric spin density may have high activity toward H2O2 production.

A comparative photophysical study on the structurally related coumarin 102 and coumarin 153 dyes

Photophysical properties of two 7-aminocoumarin dyes, namely, coumarin 102 (C102) and coumarin 153 (C153), have been investigated in different aprotic solvents to understand their polarity dependent behaviors. Both the dyes have the same closed-ring amine (julolidyl) substituent at 7-th position of their 1,2-benzopyrone moiety, but differ in regard to their 4-CH3 and 4-CF3 substituents, respectively. For both the dyes, absorption and fluorescence spectra undergo red shift, peak energies of these transitions decrease and the Stokes’ shifts follow linear correlations with the increasing solvent polarity parameter Δf, as defined by Lippert-Mataga. While fluorescence quantum yield (Φf) and lifetime values (τf) of C102 dye undergo linear changes with Δf, both these parameters for C153 display quite unusual deviations from linearity in the lower polarity solvents. For C102, the estimated fluorescence decay rates (kf) are significantly higher than C153 dye. The nonradiative decay rates (knr) are also substantially higher for C102 dye than C153 in most of the solvents. Interestingly, while kf values for both the dyes change linearly with Δf, the knr values show complete linearity with Δf for C102 dye only, but these values for C153 dye show quite substantial enhancements and an unusual positive deviation from linearity in lower polarity solvent. Quantum chemical studies indicate that for C153 dye in lower polarity solvents, especially, there is a possible involvement of intersystem crossing process, which might induce an additional nonradiative channel (kadd-nr) for the dye. Further, though we could not obtain any direct evidence in the present study, yet it is felt that some kind of fluorous effect, as might be arising due to large negative charge density on bulky perfluomethyl group of C153 dye, can also introduce additional kadd-nr, specifically in the nonpolar solvents, for which further investigations are continuing in our group.

Microsolvation versus Encapsulation in Mono, Di, and Trivalent Cations.

The effects of the formal charge in the stability and bonding of water cavities when solvating a cation are studied here using [X(H2 O)20 ]q+ clusters starting with the well known 512 isomer of (water)20 , placing a single mono, di, or trivalent Xq+ cation at the interior, and then optimizing and characterizing the resulting clusters. Highly correlated interaction and deformation energies are calculated using the CCSD(T)-DLPNO formalism. Bonding interactions are characterized using the tools provided by the quantum theory of atoms in molecules, natural bond orbitals, and non-covalent surfaces. Our results indicate that water to water hydrogen bonds are sensibly strengthened resulting in strong cooperative effects, which amount to kcal/mol per hydrogen bond in the bare cavity and to larger values for the systems including the cations. Approximate encapsulation, that is, surrounding the cation by a network of hydrogen bonds akin to the well known methane clathrate seems to be preferred by cations with smaller charge densities while microsolvation, that is, cluster structures having explicit X⋯O contacts seem to be preferred by cations with larger charge densities which severely deform the cavity.

An Ultrafast Self‐Polarization Effect in Barium Titanate Filled Poly(Vinylidene Fluoride) Composite Film Enabled by Self‐Charge Excitation Triboelectric Nanogenerator

AbstractAlthough charge excitation is an effective approach to achieve high charge density for triboelectric nanogenerators (TENGs), high output charge is limited by air‐breakdown. Due to capacitor structure, there are two ways to reduce the influence of air‐breakdown in TENG: decrease in thickness and increase in permittivity of dielectric film. Obviously, the increase in permittivity is more reliable in applications. Herein, a double‐layer TENG shared with one floating metal electrode is proposed, on which charge is injected by a self‐excitation circuit. An ultrafast self‐polarization effect is found in two barium titanate filled poly(vinylidene fluoride) composite films in the TENG by high electrical field produced from the floating electrode. According to comparison and analysis, the speed of polarization to saturation of dielectric composite films in self‐charge excitation approach is ≈3 times faster than that of external‐charge excitation. Optimization of various parameters is investigated to enhance the output performance of the TENG. A large output charge density of 1.67 mC m–2 is achieved in the atmosphere with 40% relative humidity due to self‐polarization effect of the dielectric composite film. This study provides insights into understanding the polarized behavior of molecules in dielectrics and further optimizing the output performance of TENGs in self‐charge excitation systems.