Modulating charge separation and transfer for high-performance photoelectrodes via built-in electric field

Constructing a built-in electric field has emerged as a key strategy for enhancing charge separation and transfer,thereby improving photoelectrochemical performance.Recently,considerable efforts have been devoted to this endeavor.This review systematically summarizes the impact of built-in electric fields on enhancing charge separation and transfer mechanisms,focusing on the modulation of built-in electric fields in terms of depth and orderliness.First,mechanisms and tuning strategies for built-in electric fields are explored.Then,the state-of-the-art works regarding built-in electric fields for modulating charge separation and transfer are summarized and categorized according to surface and interface depth.Finally,current strategies for constructing bulk built-in electric fields in photoelectrodes are explored,and insights into future developments for enhancing charge separation and transfer in high-performance photoelectrochemical applications are provided.

Internal electric field modulation by copper vacancy concentration of cuprous sulfide nanosheets for enhanced selective CO_(2) photoreduction

Although the internal electric field(IEF)of photocatalysts is acknowledged as a potent driving force for photocharge separation,modulating the IEF intensity to achieve enhanced photocatalytic performances remains a challenge.Herein,cuprous sulfide nanosheets with different Cu vacancy concentration were employed to study IEF modulation and corresponding direct charge transfer.Among the samples,Cu_(1.8)S nanosheets possessed intensified IEF intensity compared with those of Cu_(2)S and Cu_(1.95)S nanosheets,suggesting that an enhanced IEF intensity could be achieved by introducing more Cu vacancies.This intensified IEF of Cu_(1.8)S nanosheets induced numerous photogenerated electrons to migrate to its surface,and the dissociative electrons were then captured by Cu vacancies,resulting in efficient charge separation spatially.In addition,the Cu vacancies on Cu_(1.8)S nanosheets accumulated electrons as active sites to lower the energy barrier of rate-determining step of CO_(2)photoreduction,leading to the selective conversion of CO_(2)to CO.Herein,the manipulation of IEF intensity through Cu vacancy concentration regulation of cuprous sulfide photocatalysts for efficient charge separation has been discussed,providing a scientific strategy to rationally improve photocata lytic performances for solar energy conversion.

Hydrogen spillover bridged dual nano-islands triggered by built-in electric field for efficient and robust alkaline hydrogen evolution at ampere-level current density

Employing the alkaline water electrolysis system to generate hydrogen holds great prospects but still poses significant challenges,particularly for the construction of hydrogen evolution reaction(HER)catalysts operating at ampere-level current density.Herein,the unique Ru and RuP_(2)dual nano-islands are deliberately implanted on N-doped carbon substrate(denoted as Ru-RuP_(2)/NC),in which a built-in electric field(BEF)is spontaneously generated between Ru-RuP_(2)dual nano-islands driven by their work function difference.Experimental and theoretical results unveil that such constructed BEF could serve as the driving force for triggering fast hydrogen spillover process on bridged Ru-RuP_(2)dual nano-islands,which could invalidate the inhibitory effect of high hydrogen coverage at ampere-level current density,and synchronously speed up the water dissociation on Ru nano-islands and hydrogen adsorption/desorption on RuP_(2)nano-islands through hydrogen spillover process.As a result,the Ru-RuP_(2)/NC affords an ultra-low overpotential of 218 mV to achieve 1.0 A·cm^(−2)along with the superior stability over 1000 h,holding the great promising prospect in practical applications at ampere-level current density.More importantly,this work is the first to advance the scientific understanding of the relationship between the constructed BEF and hydrogen spillover process,which could be enlightening for the rational design of the cost-effective alkaline HER catalysts at ampere-level current density.

Si_2O_2 molecule:structure of ground state and the excited properties under different external electric fields

Geometry and vibrational frequencies of the ground state of Si2O2 molecule are studied using density function theory （DFT） at the level of cc-pvtz and 6-311-k＋G^＊＊. It is found that the optimizing value by B31yp/cc-pvtz is closer to the experimental data. The excited properties under different external electric fields are also investigated by the time-dependent-DFT method. Transitions from the ground state of Si2O2 molecule to the first singlet state under different external electric fields can take place more easily. The corresponding absorption spectral line is about 360 nm in wavelength and the excitation energy is about 3.4 eV.

A data complementary method for thunderstorm point charge localization based on atmospheric electric field apparatus array group

Data loss or distortion causes adverse effects on the accuracy and stability of the thunderstorm point charge localization.To solve this problem,we propose a data complementary method based on the atmospheric electric field apparatus array group.The electric field component measurement model of the atmospheric electric field apparatus is established,and the orientation parameters of the thunderstorm point charge are defined.Based on the mirror method,the thunderstorm point charge coordinates are obtained by using the potential distribution formulas.To test the validity of the basic algorithm,the electric field component measurement error and the localization accuracy are studied.Besides the azimuth angle and the elevation angle,the localization parameters also include the distance from the apparatus to the thunderstorm cloud.Based on a primary electric field apparatus,we establish the array group of apparatuses.Based on this,the data measured by each apparatus is complementarily processed to regain the thunderstorm point charge position.The results show that,compared with the radar map data,this method can accurately reflect the location of the thunderstorm point charge,and has a better localization effect.Additionally,several observation results during thunderstorm weather have been presented.

Electronic Structure and Physical Characteristics of Dioxin Under External Electric Field

Dioxin is a highly toxic and caustic substance,which widely existed in the atmosphere,soil and water with tiny particles.Dioxin pollution has become a major problem that concerns the survival of mankind,which must be strictly controlled.The bond length,bond angle,energy,dipole moment,orbital energy level distribution of dioxin under the external field are investigated using DFT(density functional theory)on basis set level of B3LYP/6-31G(d,p).The results indicate that with the increase of the electric field,the length of one Carbon-Oxygen bond increases while another Carbon-Oxygen bond decreases.The energy gradually decreases with the electric field,while the change of the dipole moment has an opposite trend.In the infrared spectra,the vibration frequency decreases with the electric field increasing and shows an obvious red shift.Moreover,the ultraviolet-visible absorption spectra under different electric fields are analyzed with TD-DFT(time-dependent density functional theory)method.The wavelength of the strongest absorption peak increases and occurs red shift with the increase of the electric field.All the above results can provide reference for further research on the properties of dioxin under different external electric field.

Electric field effect in ultrathin zigzag graphene nanoribbons

The electric field effect in ultrathin zigzag graphene nanoribbons containing only three or four zigzag carbon chains is studied by first-principles calculations, and the change of conducting mechanism is observed with increasing in-plane electric field perpendicular to the ribbon. Wider zigzag graphene nanoribbons have been predicted to be spin-splitted for both valence band maximum（VBM） and conduction band minimum（CBM） with an applied electric field and become half-metal due to the vanishing band gap of one spin with increasing applied field. The change of VBM for the ultrathin zigzag graphene nanoribbons is similar to that for the wider ones when an electric field is applied. However, in the ultrathin zigzag graphene nanoribbons, there are two kinds of CBMs, one is spin-degenerate and the other is spin-splitted, and both are tunable by the electric field. Moreover, the two CBMs are spatially separated in momentum space. The conducting mechanism changes from spin-degenerate CBM to spin-splitted CBM with increasing applied electric field. Our results are confirmed by density functional calculations with both LDA and GGA functionals, in which the LDA always underestimates the band gap while the GGA normally produces a bigger band gap than the LDA.

Electron beam modeling and analyses of the electric field distribution and space charge effect

In electron beam technology, one of the critical focuses of research and development efforts is on improving the measurement of electron beam parameters. The parameters are closely related to the generation, emission, operation environment, and role of the electron beam and the corresponding medium. In this study, a field calculation method is proposed, and the electric field intensity distribution on the electron beam’s cross-section is analyzed. The characteristics of beam diffusion caused by the space charge effect are investigated in simulation, and the obtained data are compared with the experiment. The simulation demonstrated that the cross-sectional electric field distribution is primarily affected by the electron beam current, current density distribution, and electron beam propagation speed.

The Possible Relationship between the Atmospheric Electric Field and High Energy Charged Particles and the COVID-19 Cases in the Central Arabian Peninsula

Background: Since the beginning of the global COVID-19 pandemic, several studies have been carried out to investigate its spread, with a wide range of factors to understand the influence of the factors that contribute to its spread and to reduce the ongoing threat of COVID-19 pandemic. Methods: In this study, the relationships between the Earth’s electric field and cosmic ray charged particles of different energy ranges and the daily confirmed COVID-19 infections in Riyadh, Saudi Arabia have been investigated using non-parametric statistical tests. The data covered the period between 3 April 2020 and 1st August 2021 and were obtained from the King Abdulaziz City for Science and Technology (KACST) CARPET detector, Riyadh, Saudi Arabia. The electric fields data were obtained from electric field monitor (EFM) deployed on the rooftop of the KACST laboratory. The data of the daily COVID-19 cases were obtained from the official webpage of the Saudi Arabian Ministry of Health (MOH). Results: The results revealed that that the number of COVID-19 cases is correlated with cosmic ray charged particles and anti-correlated with the Earth’s electric field. Conclusion: While the exact mechanism explaining the influence of Earth’s electric field and cosmic rays variations on the reported number of COVID-19 cases is not yet established, the results presented in this study can add additional knowledge to our understanding of the effects of additional factors on influenza activities.

Hybrid inversion method for equivalent electric charge of thunder cloud based on multi-station atmospheric electric field

This article proposes the hybrid method to inverse the equivalent electric charge of thunder cloud based on the data of multi-station atmospheric electric field. Firstly,the method combines the genetic algorithm( GA) and New ton method through the mosaic hybrid structure. In addition,the thunder cloud equivalent charge is inversed based on the forw ard modeling results by giving the parameters of the thunder cloud charge structure. Then an ideal model is built to examine the performance compared to the nonlinear least squares method. Finally,a typical thunderstorms process in Nanjing is analyzed by Genetic-New ton algorithm with the help of weather radar. The results show the proposed method has the strong global searching capability so that the problem of initial value selection can be solved effectively,as well as gets the better inversion results. Furthermore,the mosaic hybrid structure can absorb the advantages of tw o algorithms better,and the inversion position is consistent with the strongest radar echo.The inversion results find the upper negative charge is small and can be ignored,w hich means the triple-polarity charge structure is relatively scientific,w hich could give some references to the research like lightning forecasting,location tracking.

Influence of Electric Field on Mechanical Properties of Al-Li Alloy Containing Cerium and Electronic Mechanism

The effect of electric field on the mechanical properties and microstructure of AI-Li alloy containing Ce was investigated, and mechanism was discussed. The experimental results show that the ductility of the alloy is enhanced by the electric field. The fracture features are changed and the precipitates are dispersed under the effect of the electric field. The mechanism discussion reveals that the effects of the electric field on the alloy are due to the change of the electron density in the alloy.

Induced Charge of Spherical Dust Particle on Plasma-facing Wall in Non-uniform Electric Field

Induced charge of a spherical dust particle on a plasma-facing wall was investigated analytically, where non-uniform electric field was applied externally. The one-dimensional nonuniform electrostatic potential was approximated by the polynomial of the normal coordinate toward the wall. The bipolar coordinate was introduced to solve the Laplace equation of the induced electrostatic potential. The boundary condition at the dust surface determines the unknown coefficients of the general solution of the Laplace equation for the induced potential. From the obtained potential the surface induced charge can be calculated. This result allows estimating the effect of the surrounding plasma, which shields the induced charge.

Collapse of Four-Arm Stars Polyelectrolyte Brushes Under An Electric Field in the Presence of Trivalent Salt Coions

Langevin dynamics simulations were conducted to study the collapse of grafted partially charged 4-arm star chains onto the oppositely charged grafting electrode in the presence of trivalent salt coions.Simulation results reveal that the average charge fraction of the grafted star chains and the salt concentration play critical roles in the competitive adsorption of charged monomers and trivalent salt coions onto the oppositely charged electrode.For grafted star chains with relatively high charge fraction,charged monomers are the dominant species collapsing on the oppositely charged electrode with the emergence of charge reversal on the grafting electrode.At a low charge fraction such that the total amount of charges on a grafted star molecule is comparable to that of a trivalent salt coion,trivalent salt coions absorb more strongly onto the electrode than grafted stars even at very low salt concentration.It is found that at relatively low charge fraction of star chains,the addition of trivalent salt coions does not lead to charge overcompensation of the surface charges on the grafting electrode.The stretching of star brushes under an electric field in the presence of trivalent salt coions was also briefly investigated.

Studies on the Second-Order Nonlinear Optical Properties of Parabolic andSemi-parabolic Quantum Wells with Applied Electric Fields

Within the framework of compact density matrix approach and iterative procedure, a detailed procedure for the calculation of the second-harmonic generation (SHG)susceptibility tensor is given in the electric-field-biased parabolic and semi-parabolic quantum wells (QWs). The simple analytical formula for the SHG susceptibility in the systems is also deduced. Numerical results on typical AlGaAs/GaAs materials show that, for the same effective width,the SHG susceptibility in semi-parabolic QW is larger than that in parabolic QW due to the self-asymmetry of the semiparabolic QW, and the applied electric field can make the SHG susceptibilities in both systems enhance remarkably.Moreover, the SHG susceptibility is also related to the parabolic confinement frequency and the relaxation rate of the systems.

Silicon Solar Cell Space Charge Region and Capacitance Behavior under Electric Field

This paper investigates theoretically the behavior of the space charge region of a silicon solar cell and its associated capacitance under the effect of an external electric field. The purpose of this work is to show that under illumination the solar cell’s space charge region width varies with both operating point and the external induced electric field and how the solar cell capacitance varies with the space charge region width. Based on a 1D modelling of the quasi-neutral p-base, the space charge region width is determined and the associated capacitance is calculated taking into account the external electric field and the junction dynamic velocity. Based on the above calculations and simulations conducted with Mathcad, we confirmed the linear dependence of the inverse capacitance with space charge region width for thin space charge region and we exhibit an exponential dependence for large space charge region.

Heterogeneous FASnI3 Absorber with Enhanced Electric Field for High-Performance Lead-Free Perovskite Solar Cells

Lead-free tin perovskite solar cells(PSCs)have undergone rapid development in recent years and are regarded as a promising ecofriendly photovoltaic technology.However,a strategy to suppress charge recombination via a built-in electric field inside a tin perovskite crystal is still lacking.In the present study,a formamidinium tin iodide(FASnI;)perovskite absorber with a vertical Sn;gradient was fabricated using a Lewis base-assisted recrystallization method to enhance the built-in electric field and minimize the bulk recombination loss inside the tin perovskites.Depth-dependent X-ray photoelectron spectroscopy revealed that the Fermi level upshifts with an increase in Sn;content from the bottom to the top in this heterogeneous FASnI;film,which generates an additional electric field to prevent the trapping of photo-induced electrons and holes.Consequently,the Sn;-gradient FASnI;absorber exhibits a promising efficiency of 13.82%for inverted tin PSCs with an open-circuit voltage increase of 130 mV,and the optimized cell maintains over 13%efficiency after continuous operation under 1-sun illumination for 1,000 h.

Effect of the interfacial electric field on the HER on Pt(111)modified with iron adatoms in alkaline media

The study of the hydrogen evolution reaction(HER)aimed to reach a deeper understanding of the parameters that control the rate of this reaction is of great importance given the technical relevance of hydrogen production as an energy vector in the so-called hydrogen economy.In previous works,laser-induced temperature jump(LITJ)experiments on Pt(111)modified with Ni(OH)_(2)in alkaline media have revealed the importance of the interfacial electric field in the rate of the HER.It was hypothesised that small amounts of Ni(OH)_(2)cause a decrease of the electric field because of a negative shift of the pzfc toward the onset of the hydrogen evolution.In this work,to test the validity of this hypothesis,the study has been extended to Pt(111)surfaces modified with Fe(OH)_(2).The modified surfaces have been studied voltammetrically,and the voltammetric charges have been analysed.The voltammograms show a peak in the hydrogen evolution region that suggest the transformation in the adlayer from Fe(II)to Fe(0).In agreement with the coulometric analysis,the voltammetric features in the OH adsorption region would be related with the oxidation to the+3 valence state.The results obtained with LITJ method reflect the existence of a strong interaction of the Fe oxophilic species with the water molecules,shifting the potential of maximum entropy away from the onset of the HER.Hence,the most catalytic surface is the one with the lowest Fe coverage.

Impact of the Evolution of a Curved Charge Distribution on Electric Field

Theoretically, it is plausible to assume for a chosen charge distribution the electric field can be calculated. However, in practice depending on the geometry of the distribution one faces mathematical challenges. In this research- oriented project, we select a set of related familiar 2D geometric curves addressing the mathematical issues. Specifically, we consider a family of curves that evolved via step-by-step “evolution”. The evolution begins from a segment of a circular arc to a complete circle. The electric fields are formulated, evaluated, and graphed. Accomplishing these objectives relied heavily on utilizing a Computer Algebra System (CAS), specifically Mathematica [1]. The CPU’s expensive runtimes are circumvented by introducing mathematical procedures.

Impact of a Mobile Void within a Charge Distribution on the Electric Field

The electric field of a 3D spherical uniform charge distribution embodying a spherical mobile void at an exterior point is calculated. The size of the void and its path is arbitrary. Specifically, three different trajectories are analyzed. The movement of the void impacts the electric field so that the field becomes time-dependent. In terms of the chosen path and the size of the bubble, we evaluate the time-dependent electric field. The time profile of the field is calculated. Because of the computational challenges, the most of calculation is carried out utilizing a Computer Algebra System (CAS), specifically Mathematica [1]. This project makes the CAS an essential tool not only for calculating the field but for animating the features of the mobile void. An atlas of the study cases is included.

Study on the Physical and Dissociation Properties of Disulfur Dichloride under Electric Fields

Disulfur dichloride is a hazardous substance, which is irritating to the eyes. It is significant to study the physical and dissociation properties under external electric fields. The bond length, energy, dipole moment, orbital energy level distribution, infrared spectra and dissociation properties of disulfur dichloride molecule under different external fields are obtained by using the density functional theory at the B3LYP/6-311++G(d, p) basis set level. In addition, ultraviolet-visible absorption spectra of the molecule in different electric fields are studied with configuration interaction-single excitation(CIS)/6-311++G(d, p) method. According to the results, it has been found that as the electric field exerted along the positive direction of the z-axis increases, the two sulfur-chlorine(S-Cl) bond lengths become longer and tend to break, while the sulfur-sulfur(S-S) bond length becomes shorter and the energy gap decreases. The infrared spectrum and ultraviolet-visible absorption spectra both exhibit red shift under electric field. Moreover, by scanning the potential energy surface of disulfur dichloride about S-Cl bond, the dissociation barrier decreases with the increase of positive electric field. When the external electric field arrives at 0.040 atomic units, the barrier disappears, meaning the dissociation of disulfur dichloride. The present results offer an important reference to further study of disulfur dichloride.