Trace polytetrafluoroethylene constructing Na3V2(PO4)3/Na3V2(PO4)2F3 heterostructure with multi-electron reaction and self-enhanced built-in electric field

Porous V2C@VSe2 heterostructure with built-in electric field as catalytic host materials for high-performance aqueous Cu-Se batteries.

Trigger a multi-electron reaction by tailoring electronic structure of VO2 toward more efficient aqueous zinc metal batteries

The built-in electric field formed between the involved species at the heterogeneous interface can affect the overall performance of dye-sensitized solar cells (DSSCs). The direct experimental observation on the built-in electric field is challenging due to the intricate heterogeneous interface itself. Herein, we propose a novel strategy for exploring the nature of the built-in electric field in the functionality of DSSCs by using externally applied electric field as perturbation to couple to the built-in electric field. As a matter of fact, the built-in electric field refers to the interfacial electric field (Fdipole) induced by the charge separation occurring at heterogeneous dye/semiconductor interface. On the basis of theoretical calculations, we found that Fdipole couples to external electric field through the electric dipole moment change (ΔμET) at dye/semiconductor heterointerface to affect the photoelectronic properties in DSSCs. In essence, the influence of gap states and conduction bands is determined by the overlap between the applied electric field and intrinsic dipole moment change of charge-separated dye/semiconductor. Furthermore, the electron-transfer rate (kET) is also intrinsically related to the coupling of Fdipole with external electric field in the form of electric dipole moment at dye/semiconductor interface. In addition, applying external electric field is demonstrated to be an approach to modulate the interfacial electric dipole moment field to achieve better performance of DSSCs. Our theoretical finding can provide insight into designed strategies for understanding the functionality of DSSCs and offer a universal route to study the heterogeneous interfaces in DSSCs experimentally and theoretically.

Interfacial electric fields are important in several areas of chemistry, materials sciences, and device physics. However, they are poorly understood, partly because they are difficult to measure directly and model accurately. We present both a spectroscopic experimental investigation and a theoretical model for the interfacial field at the junction of a conductor and a dielectric. First, we present vibrational sum frequency generation (VSFG) results of the nitrile (CN) stretch of 4-mercaptobenzonitrile (4-MBN) covalently attached to a gold surface and in contact with a variety of liquid dielectrics. It is found that the CN stretch frequency red-shifts with increasing dielectric constant. Second, we build a model in direct analogy to the well-known Onsager reaction field theory, which has been successful in predicting vibrational frequency shifts in bulk dielectric media. Clearly, due to the asymmetric environment, with metal on one side and a dielectric on the other, the bulk Onsager model is not applicable at the interface. To address this, we apply the Onsager model to the interface accounting for the asymmetry. The model successfully explains the red-shift of the CN stretch as a function of the dielectric constant and is used to estimate the reaction field near the interface. We show the similarities and differences between the conventional bulk Onsager model and the interfacial reaction field model. In particular, the model emphasizes the importance of the metal as part of the solvation environment of the tethered molecules. We anticipate that our work will be of fundamental value to understand the crucial and often elusive electric fields at interfaces.

A classical analysis of the radiation reaction associated with a rotating charge distribution is carried out. This analysis is analogous to Lorentz's classic description of radiation reaction for a charge in translational motion. As in the Lorentz analysis, reaction fields are found that are independent of the structural details of the charge distribution. In addition, if it is also assumed that the distribution's magnetic moment M does not go to zero as the charge volume goes to zero, then some of the reaction fields also remain constant in that limit. For example, it is found that the charge distribution experiences a spatially uniform magnetic field of the form (2/3${c}^{3}$)${d}^{3}$M/${\mathrm{dt}}^{3}$, which is formally similar to the Lorentz's radiation reaction electric field which is expressed in terms of the system's electric dipole moment d as (2/3${c}^{3}$)${d}^{3}$d/${\mathrm{dt}}^{3}$. However, the two fields have fundamentally different effects since a magnetic field can do no work on the charge distribution.Expressions are found for the electric fields that react back on the charge distribution to produce the self-torques necessary to conserve energy during magnetic dipole and electric quadrupole radiation. The analysis is then specialized to study the motion of a rigid, spinning, spherically symmetric charge distribution. A nonlinear equation of motion is found that describes the motion of the system, in an externally applied, constant magnetic field for all orders of the expansion parameter a/c, where a is the radius of the distribution. An approximate solution of this equation is found that describes the ``spinning'' charge precessing in the external magnetic field and spontaneously emitting magnetic dipole radiation. The magnitude of the magnetic moment and angular velocity of the ``spin'' rotation remain constant while the ``spin'' axis rotates to a position parallel to the magnetic field. The time dependence of this rotation is expressed in terms of a hyperbolic tangent. The power radiated varies as the square of a hyperbolic secant. In addition, the reaction field causes a small time-dependent shift in the frequency of radiation away from the Larmor frequency. Finally, a radiation reaction field is incorporated into the phenomenological Bloch equations of magnetic resonance to include the effects of magnetic dipole radiation.

The reaction-field concept is examined quantitatively using nuclear magnetic spectroscopy by determining the magnetic shielding constants of three protons within the same molecule as a function of dielectric constant: the results are based on the fact that the magnetic shielding constant of a bonded proton depends linearly on the effective electric field along the bond axis. It is shown that (1) the reaction field must take on different values at different points in the molecule, and (2) the calculated reaction field's dependence on ε for a dipole in a spherical or spheroidal cavity does not adequately describe the experimental reaction field's dependence on ε.

Construction and enhancement of built-in electric field for efficient oxygen evolution reaction

Vanadium‐based materials are considered promising cathodes for high‐energy‐density zinc‐ion batteries (ZIBs) owing to their open skeleton structure and multielectron redox reactions. However, most vanadium‐based materials have low intrinsic conductivities and sluggish reaction kinetics, resulting in poor cycling properties. Herein, a layer‐stacked MnxV2O6+V2CTx (MVO+V2C) heterostructure cathode with high capacity and superior cyclic stability based on an electrostatic self‐assembly strategy is proposed. The abundant heterointerfaces between MVO and V2C dramatically enhanced the intrinsic conductivity of the composites. Moreover, the generation of built‐in electric fields at the layer‐stacked MVO/V2C heterointerface reduced the migration energy barrier of Zn2+, accelerated charge carrier transport, and enhanced the reaction kinetics of the cathode. In addition, the abundance of nano‐channels in the heterostructures facilitates rapid electrolyte transport in composites. Therefore, the MVO+V2C cathode showed a capacity of 389.4 mAh g−1 after 590 cycles at 0.5 A g−1 and 290.2 mAh g−1 after 6000 cycles at 5 A g−1, demonstrating its superior cycling stability. In particular, the assembled MVO+V2C batteries exhibited remarkable electrochemical performance at −20–40 °C, revealing its excellent wide‐temperature adaptability. This work offers important insights into the design of cathode materials for long‐lifespan and wide‐temperature ZIBs.

Integrated reactor architecture of conductive network and catalytic nodes to accelerate polysulfide conversion for durable and high-loading Li-S batteries

Electrochemically constructing V-doped BiFeO3 nanoflake network anodes for flexible asymmetric micro-supercapacitors

Electrocatalytic ammonia oxidation reaction (AOR), as a promising energy conversion technology, also offers ideas for the synthesis of high-value nitrogenous compounds such as nitrites and nitrates. However, the sluggish kinetics of AOR at the anode leads to high overpotential and elevated energy consumption, necessitating advanced catalysts. Here, we engineer a NiO/CuO heterojunction on a copper mesh (NiO/CuO@Cu), which generates a robust internal electric field at the NiO-CuO interface. The built-in electric field facilitates interface electron redistribution and surface electronic state modulation, significantly enhancing the charge transfer and AOR kinetics. The NiO/CuO@Cu catalyst exhibits a low onset potential of 1.38 V vs RHE, along with 95.8% ammonia conversion efficiency and 90.6% nitrite selectivity during 8-h operation at 1.6 V vs RHE. Notably, the catalyst shows excellent operation stability for over 56 h. This work presents interface engineering through heterojunction design as an effective strategy for AOR enhancement, providing valuable insights for developing high-performance electrocatalysts in energy conversion technologies.

New measurements of the solvent effect on the nitrogen hyperfine coupling constant of di-tert-butyl nitroxide are reported. These, together with literature data, are used to test various models for the solvent effect. At the Hückel level of approximation, aN is a linear function of the applied electric field. Thus various reaction field theories may be considered. The widely used Onsager reaction field does not account for the effects of the more polar solvents or for the differences between polar and nonpolar solvents. The Wertheim and Block–Walker reaction fields are better, especially for very polar solvents. However none of these continuum reaction fields is entirely satisfactory theoretically or experimentally. We propose a dipole–dipole model for polar solvents which is superior to the continuum models. From the dipole–dipole model, we suggest that the quantity μρ/M is a convenient linear parameter for polar solvent effects, the factors being solvent dipole moment, density, and molecular weight. The dipole–dipole model should apply to a wide range of polar solutes. Some special situations are not explained by the model, including hydrogen-bonding solvents, halogenated aromatics, and solvents with more than one conformation. The temperature dependence of the solvent effect is also considered.

New measurements of the solvent effect on the nitrogen hyperfine coupling constant of di‐tert‐butyl nitroxide are reported. These, together with literature data, are used to test various models for the solvent effect. At the Huckel level of approximation, aN is a linear function of the applied electric field. Thus various reaction field theories may be considered. The widely used Onsager reaction field does not account for the effects of the more polar solvents or for the differences between polar and nonpolar solvents. The Wertheim and Block–Walker reaction fields are better, especially for very polar solvents. However none of these continuum reaction fields is entirely satisfactory theoretically or experimentally. We propose a dipole–dipole model for polar solvents which is superior to the continuum models. From the dipole–dipole model, we suggest that the quantity μρ/M is a convenient linear parameter for polar solvent effects, the factors being solvent dipole moment, density, and molecular weight. The...

A microscopic derivation using the average Maxwell electric field is given for fluctuation formulas for the dielectric constant of a simulation sample for both periodic and reaction field boundary conditions. The reaction field case is for a spherical cavity reaction field. The derivations put both boundary conditions on an equal footing of microscopic theory and the only nonrigorous part of the derivation is the assumption that the region used to average the electric field is large enough. The fluctuation formula for reaction field boundary conditions is rather different from that used heretofore. The method is applied to a subregion of an isolated spherical system.

Can the geometry of an acid-base complex in solution be reproduced in calculations using an implicit accounting for the solvent effect in the form of a macroscopic reaction field? The answer is, "Yes, it can." Is this field equal to the real electric field experienced by the complex in solution? The answer is, "No, it is not." How can the geometry be correct under wrong conditions? This question is answered using density functional theory modeling of geometric and NMR parameters of pyridine⋯HF⋯(HCF3)n adducts in the absence and presence of an external electric field. This adduct under field approach shows that the N⋯H distance is a function of the H-F distance whatever method is used to change the geometry of the latter. An explicit account for solute-solvent interactions is required to get a realistic value of the solvent reaction field. Besides that, this approach reveals how certain NMR parameters depend on the solvent reaction field, the solute-solvent interactions, and the geometry of the N⋯H-F hydrogen bond. For some of them, the obtained dependences are far from self-evident.