Intrinsic Field Research Articles

Nickel-Based Bifunctional Cocatalyst to Enhance CdS Photocatalytic Hydrogen Production.

The design of nanocomposites as a light-capturing system applied in photocatalytic water splitting is an emerging area of research. In our study, a simple in situ photodeposition method was proposed for the synthesis of CdS nanoflowers modified by nickel-based bifunctional, i.e., Ni/Ni(OH)2, cocatalysts. The introduction of cocatalysts has demonstrated a notable enhancement in the photocatalytic hydrogen evolution efficiency of CdS. The quantity of cocatalysts supported on CdS played an important role in governing the light absorption capability and photocatalytic efficacy. Ni-CdS-10 showed the best photocatalytic activity of 30.51 mmol g-1 h-1, which was 1.8 times and 2.6 times higher activity than Pt-CdS-1 wt % and pure CdS, respectively. Mechanism studies with UV-vis DRS, photoluminescence, and Mott-Schottky plots revealed the intrinsic electric field created at the p-n Ni(OH)2/CdS junctions, which can effectively implement the transport and separation of photoinduced carriers. From linear sweep voltammetry, electrochemical impedance spectroscopy, and DFT calculation, both Ni(OH)2 and Ni can effectively decrease the Gibbs free energies of hydrogen adsorption and reduce the overpotential of hydrogen evolution. As a result, the efficiency of generating H2 through photocatalysis experienced significant improvement, and the participation of bifunctional cocatalysts further reduced the photocorrosion of CdS, enhanced stability, improved low price, and efficient photocatalyst production.

Interface Polarization Effects Enhancing Mn2O3@TiO2@MXene Heterostructures for Aqueous Magnesium Ion Capacitors: Guided Charge Distribution and Transportation via Built‐in Electric Fields

The electrochemical performances of aqueous magnesium ion energy storage devices rely on the transmission capacity of magnesium ions (Mg2+) at the electrode/electrolyte interface. However, the diffusion of Mg2+ is hindered by the strong electrostatic attraction of doubly charged magnesium cations. Herein, novel Mn2O3@TiO2@MXene three‐phase heterostructures with rich phase boundaries and synergistic effects is successfully designed. As expected, the mesoporous Mn2O3/TiO2@MXene can deliver a relatively high specific capacity of 241.5 mAh g−1 at 0.1 A g−1. Moreover, the energy density of the device using mesoporous Mn2O3@TiO2@MXene as cathode can reach 146.62 Wh kg−1. The unique construction of extensive interfaces between different phases creates a polarization effect. This polarization effect leads to intrinsic electric fields that guide charge distribution and promote fast migration of Mg2+ ions. Additionally, the in‐situ growth of TiO2 nanoparticles derived from MXene on Mn2O3 helps mitigate the volume expansion of host material, resulting in enhanced cycle stability. By strategically implementing the interface polarization effect and carefully engineering the heterostructure interfaces, we demonstrate a promising electrode synthesis approach with potential commercial viability and robust performance. This research aims to advance the field of materials science by exploring interface engineering and the multifunctional applications of MXene‐related materials.

GaSe/YAlS3: A type-II van der Waals heterostructure with ultrahigh solar-to-hydrogen efficiency for photocatalytic water splitting

Photocatalytic water splitting, a process aimed at hydrogen production, is considered a pivotal clean energy sources to achieve environmental friendliness and high energy efficiency in the future. The crux of achieving this objective lies in the design of stable and efficient catalysts. Herein, we proposed a novel type-II band alignment GaSe/YAlS3 van der Waals heterostructure with robust stability for photocatalytic water splitting. The intrinsic electric field of YAlS3 monolayer can break the requirement of band gap (>1.23 eV) in traditional photocatalytic water splitting theory and significantly enhancing the utilization of solar energy. Encouragingly, compared to individual monolayers GaSe or YAlS3, the optical absorption coefficients of the GaSe/YAlS3 heterostructure are significantly improved and the corrected solar-to-hydrogen (STH) efficiency is improved by 406% and 132%, respectively, reaching an impressive 29.73% efficiency. Furthermore, the heterostructure demonstrates exceptional overall water splitting performance across a broad pH range and maintains a consistently high STH efficiency (25.41%∼34.71%) under a wide range biaxial strain (−6%–5%). In addition, the designed GaSe/YAlS3 heterostructure showcases enhanced absorption of visible as well as partial absorption of infrared light for photocatalytic water splitting. These compelling findings unequivocally establish GaSe/YAlS3 heterostructure as an excellent and promising candidate for photocatalytic water splitting.

Selective cascade activation of polycyclic aromatic hydrocarbons in human cells: Role of enzyme's intrinsic electric field

Polycyclic aromatic hydrocarbons (PAHs) are major environmental organic pollutants. Some metabolites of PAHs show greater toxicity to humans while the others do not. It is highly important to decipher PAHs' regioselective activation mechanism and identify the major metabolites to accurately evaluate their public health risk. Here, we have performed a thorough computational study of benzo[a]anthracene (BA) metabolized by P450 1A1 by employing molecular docking, molecular dynamics simulations, quantum chemical calculation, and quantum mechanics/molecular mechanics calculations. Our findings show that highly-reactive species such as 3,4-epoxide, 8,9-epoxide, 3,4-diol-1,2-epoxide, and 8,9-diol-10,11-epoxide were major metabolites, which can efficiently react with guanine and damage DNA with extremely low energy barrier, therefore, supports the regioselective metabolism of BA. The origin of this selective activation is mainly contributed to both the oxygen‑carbon distance and previously overlooked enzyme's intrinsic electric field. Consequently, based on the resolved activation selectivity of BA. We built a high-throughput strategy to efficiently predict the metabolites of other PAHs. The accuracy of the strategy is validated by studying 16 PAHs on the priority control list. Hopefully this will aid the accurate evaluation of public health risks associated with PAH emissions.

On the use of error field correction coils in JET

This work describes the usage of Error Field Correction Coil (EFCC) system [Barlow I. et al. 2001 Fusion Eng. Des. 58–59 189], which is a set of 4 coils located external to the vessel of the JET device, with the aim of introducing non-axisymmetric n = 1 magnetic field perturbations in various targeted plasma experiments. Besides being used to characterize and correct the intrinsic error field, the EFCCs system has been exploited to i) probe plasma stability in high-βN regimes through the MHD spectroscopy technique, allowing the identification of resistive-wall mode stable operational scenarios, ii) study radiation asymmetry when testing the shattered pellet injector as the prime candidate for ITER disruption mitigation system, and iii) control edge localized modes, permitting a reduction in heat fluxes and carbon erosion of the divertor target plates.

Examining Energy Storage Potential in Weakly Polar Nematic Liquid Crystals Infused with Anthraquinone Dye: A Comprehensive Approach

The applications of liquid crystals in the field of renewable, clean and sustainable technologies of energy storage are of utmost importance at present. This paper delves into dielectric spectroscopic studies of a weakly polar nematic liquid crystal (NLC) enriched with an anthraquinone dye. The primary objective is to assess the impact of increasing dye concentrations on various properties. Anthraquinone dye has been found to increase the dielectric permittivity of weakly polar NLC, leading to a 4.7-fold increase in dielectric anisotropy. Simultaneously, a reduction of around 11% in threshold and operating voltages of the NLC has also been recorded after using dye as the guest material. The added dipolar contributions provided by dye molecules have been attributed to this surplus permittivity. The NLC has been found to have an approximately 54% faster response to the applied field. The intrinsic polarization field of dye molecules accelerates nearby LC molecule reorientation, leading to a 56.5% faster fall time and a 29.8% faster rise time in a 3.0 wt% dye-doped LC cell. These experimental results have been validated via computational studies as well. The simulation results about dipole moment and polarizability provide robust support for our experimental results. Such composites evince their potential for energy storage and 5G communication technologies with adjustable impedance and permittivity.

Spontaneous hydrogen production on well-designed two-dimensional MoSi2N2P2 Janus structure: N-face versus P-face tuning

Based on the recently discovered two-dimensional non-Janus MoSi2N4 structure, we here study a well-designed two-dimensional Janus structure (MoSi2N2P2) for potential application in hydrogen evolution reaction (HER) via water splitting. We first confirm the stability of the MoSi2N2P2 structure using first-principles’ calculations in the framework of density functional theory by calculating cohesive energy, phonon dispersion, and ab-initio molecular dynamics evolution. We then investigate electronic and transport properties of the structure. The MoSi2N2P2 Janus structure exhibits an indirect (Γ→M) band gap of only 0.22 eV using PBE and 0.89 eV using the HSE06 hybrid functional. We also find that there is a large intrinsic electric field across the Janus structure, which tends to gather electrons at the P face. We also calculate the mobility of the Janus structure, showing that it has a high electron mobility (409 cm2/Vs) along the zigzag direction. We then show that compared with the P face, the N face gives a lower overpotential against HER, but not sufficient to activate HER process. Therefore, we investigate how the electronic properties and the HER overpotential of the Janus MoSi2N2P2 monolayer are affected by applying biaxial strain and external perpendicular electric field. Thus, the N face exhibits a higher degree of tunability than the P face toward HER overpotential. In particular by applying an electric field of 2.7 V/Å directing from the P face to the N face, the overpotential against the HER reaction on the N face can be adjusted to zero, showing that the well-designed Janus structure can exhibit a potential application for spontaneous HER water splitting.

Scaling priors for intrinsic Gaussian Markov random fields applied to blood pressure data

An Intrinsic Gaussian Markov Random Field (IGMRF) can be used to induce conditional dependence in Bayesian hierarchical models. IGMRFs have both a precision matrix, which defines the neighborhood structure of the model, and a precision, or scaling, parameter. Previous studies have shown the importance of selecting the prior for this scaling parameter appropriately for different types of IGMRF, as it can have a substantial impact on posterior estimates. Here, we focus on cases in one and two dimensions, where tuning of the prior is achieved by mapping it to the marginal SD of an IGMRF of corresponding dimensionality. We compare the effects of scaling various IGMRFs, including an application to real two‐dimensional blood pressure data using MCMC methods.

Dzyaloshinskii–Moriya Interaction of Cr2O2ClI Janus Monolayer: A First‐Principles Calculation

The Dzyaloshinskii–Moriya interactions (DMIs) of Cr2O2ClI Janus monolayer are investigated using the first‐principles calculations. There are three DMI mechanisms (namely, the Half–Fert–Levy mechanism, the Fert–Levy mechanism, and the Rashba mechanism) in Cr2O2ClI Janus monolayer. The Half–Fert–Levy mechanism, by which the I atoms enhance the spin orbit coupling interaction on the type‐I Cr atoms but have no such effect on the type‐II Cr atoms, contributes to the y‐component of the DMI vector between two nearest‐neighbor Cr atoms. Originating from the strong spin orbit coupling interaction of the I atoms, the Fert–Levy mechanism results in a significant DMI vector via the Cr–I–Cr exchange path between two type‐I next‐nearest‐neighbor Cr atoms. Induced by the intrinsic electric field of the Janus structure, the Rashba mechanism results in nonzero in‐plane components of the DMI vectors. This work provides the first‐principles calculations of the DMIs of Cr2O2ClI Janus monolayer and reveals insight into the physics behind the calculated DMIs, which promote the understanding of the complicated DMIs due to multiple mechanisms in 2D magnetic Janus monolayers.

Hexagonal Janus Zn2XY (X=S, Se; Y[dbnd]Se, Te; X≠Y) monolayers: A high-performance photocatalyst for water splitting

Efficient photocatalytic water splitting is of holds paramount importance in addressing contemporary energy and environmental challenges. The emergence of symmetry-deficient Janus two-dimensional materials has opened new avenues for advancing the field of photocatalytic hydrogen production. Using first-principles calculations, we investigated a novel Janus Zn2XY (X = S, Se; YSe, Te; X≠Y) monolayer. The results demonstrate exceptional structural stability and favorable characteristics for water splitting, including direct band gaps and optimal band edge alignment. Spatially separating band edge states and the intrinsic vertical electric field effectively suppress the recombination rate of photogenerated electron-hole pairs. Strain engineering enhances the monolayer's capacity for visible light absorption. Furthermore, All Janus monolayers exhibit an impressive electron mobility of 103 cm2/V/s, with Janus Zn2STe and Zn2SeTe monolayers reaching 16.28% and 16.34% Solar-to-hydrogen (STH) efficiencies, respectively. These findings showcase the superior performance of Janus Zn2XY in water splitting and guide future experimental endeavors.

Hanle effect in transport through single atoms in spin-polarized STM

Following recent achievements in quantum-coherent manipulation and detection of individual atomic spins with the use of spin-polarized scanning tunneling microscope, we propose how to observe and utilize the Hanle effect in electronic transport in such setups. We show that the Hanle experiment can be used to observe the single spin precession driven by the intrinsic exchange field. This field is a result of virtual particle exchange processes, and its magnitude and sign can be controlled electrically. We also show that from detailed analysis of the Hanle resonance curve one can determine the spin relaxation time from dc current measurements.

Unveiling the synergistic interplay of appropriate oxygen vacancies and S-scheme heterojunction structures in OVs-TiO2/g-C3N4 catalyst for efficient RhB photodegradation and H2 production

This study presents a facile synthesis for an efficient S-scheme OVs-TiO2/g-C3N4 heterojunction (OVs-TCN) enriched with oxygen vacancies, demonstrating exceptional performance in photocatalytic RhB degradation and H2 production. Controlled introduction of g-C3N4 into OVs-TiO2 modulates appropriate oxygen vacancies within the OVs-TCN10 heterojunction. Under visible irradiation, OVs-TCN10 achieves a remarkable 97.2 % degradation of RhB over 120 min with 5 cycles, with an apparent rate constant of 0.021 min−1. Impressively, OVs-TCN10 exhibits significant H2 production from RhB degradation, reaching a rate of 150 µmol h−1 under visible irradiation for 30 h, with a 15 % AQY at 420 nm. Experimental and DFT analyses of charge density difference, along with Mulliken analysis at the OVs-TiO2/g-C3N4 interface, confirm the existence of an intrinsic electric field flowing from g-C3N4 to OVs-TiO2. This internal electric field enhances photogenerated electron-hole separation and transfer, facilitating the redox process via the S-scheme mechanism in the heterojunction for photocatalytic RhB degradation and H2 production. This work offers new insights into the controlled defects and interfacial mechanisms in heterojunctions, propelling advanced photocatalytic applications.

Two-dimensional ferroelectric heterostructures for overall water-splitting from DFT aspects

Currently, the construction of direct Z-type heterojunctions is an effective way to improve the overall water splitting catalytic efficiency of existing two-dimensional(2D) materials, which can simultaneously combine spatial separation of active sites and enhanced redox ability. In particular, when the internal structure of heterojunction was polarized, the polarization can effectively tune electronic properties and remove band gap (1.23 eV) limitation on water splitting. So far, the effect of polarization on water-splitting reactivity in heterojunctions based on the 2D layered polarized In2Y3 (Y = S, Se) and the nonpolarized 2D β-Sb monolayer is unclear. Therefore, we constructed a series of such heterojunctions and made theoretical predictions of overall water splitting performance by first-principles calculations. The predictions shown that As/In2Se3(up), Sb/In2Se3(down) and Sb/In2S3(down) are potential photocatalysts with direct Z-scheme band positions, and hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) will occur on different surfaces of system. It is found that the intrinsic polarization electric field of In2Y3 (Y = S, Se) monolayer effectively enhances photogenerated carrier driving force of reaction. Notably, the promising photocatalysts have a high solar-hydrogen (STH) efficiency of 17.71 %, which has potential commercial applications. Also, Bi/In2S3up (S) and As/In2Te3up (As) exhibit desirable electrocatalytic HER performance. These insights provide an important strategy for application of ferroelectric heterojunctions in water splitting.

Rational design of SiC/SnSSe heterostructure for efficient photovoltaic and photocatalytic applications

The search for highly efficient and eco-friendly photocatalysts and photovoltaic solar cells is now in progress, however, it still remains challenging. By first-principles calculations, we demonstrate that Janus SiC/SnSSe van der Waals heterostructures (vdWHs) with a typical type-II band alignment possess great potential in photocatalytic and photovoltaic applications. An intrinsic electric field induced by the Janus feature of SnSSe alongside an interfacial built-in electric field caused by charge transfer from SiC to SnSSe monolayer significantly fosters spatial separation of photogenerated electron-hole pairs in two layers. Since the reduced bandgap of the vdWHs promotes an enhancement of optical absorption in the visible and even infrared regions in comparison with that of their constituting monolayers, the solar-to-hydrogen conversion efficiency reaches as high as 41.5 %, making it a highly efficient photocatalyst. The high photoresponsivity in the visible region endows the proposed system with a powerful potential for photovoltaic applications. Besides, we also find that the optical absorption and photocurrent can be effectively tuned by applying biaxial strains. For instance, the latter increases to 31 % at 4 % tensile strain. These findings provide new prospects for designing direct Z-scheme photocatalysts and photovoltaic devices based on vdWHs.

Differences in Conformational Sampling and Intrinsic Electric Fields Drive Ion Binding in Telomeric and TERRA G-Quadruplexes.

The formation of G-quadruplexes (GQs) occurs in guanine-rich sequences of DNA and RNA, producing highly stable and structurally diverse noncanonical nucleic acid structures. GQs play crucial roles in regulating transcription, translation, and replication and maintaining the genome, among others; thus, changes to their structures can lead to diseases such as cancer. Previous studies using polarizable molecular dynamics simulations have shown differences in ion binding properties between telomeric and telomeric repeat-containing RNA GQs despite architectural similarities. Here, we used volume-based metadynamics and repulsive potential simulations in conjunction with polarizable force fields to quantify the impact of ion binding on the GQ dynamics and ion binding free energies. Furthermore, we describe how GQs exert electric fields on their surroundings to link dynamics with variations in the electronic structure. Our findings provide new insights into the energetic, physical, and conformational properties of GQs and expose subtle but important differences between DNA and RNA GQs with the same fold.

Phase transition guided V2O5/β-Bi2O3 Z-scheme heterojunctions for efficient photocatalytic Hg0 oxidation

The incorporation of vanadium during the synthesis process induced a spontaneous and complete thermal phase transition from α-Bi2O3 to β-Bi2O3. This phase transition facilitated the development of intrinsic electric field at the interface between V2O5 and β-Bi2O3, consequently establishing a novel carrier transfer pathway. As a result, the fabricated V2O5/β-Bi2O3 heterojunction exhibited an outstanding removal efficiency of over 98 % for gaseous mercury (Hg0) under UV light, and this efficiency of 95.0 % even after 35 h of testing. Introducing vanadium enhanced the light absorption capacity in the ultraviolet region and effectively separated photoinduced charge carriers. As revealed by density functional theory calculations, the photoinduced electron–hole transfer in the V2O5/β-Bi2O3 heterojunction followed the Z-scheme mechanism. This mechanism significantly contributed to the long-term stability of photocatalytic Hg0 removal, even when H2O and NO were present. This study presents a novel material composited by a thermal phase transition technique, aimed at the highly effective and green removal of Hg0 in the environment.

Spontaneous Iodide Activation at the Air-Water Interface of Aqueous Droplets.

We present experimental evidence that atomic and molecular iodine, I and I2, are produced spontaneously in the dark at the air-water interface of iodide-containing droplets without any added catalysts, oxidants, or irradiation. Specifically, we observe I3- formation within droplets, and I2 emission into the gas phase from NaI-containing droplets over a range of droplet sizes. The formation of both products is enhanced in the presence of electron scavengers, either in the gas phase or in solution, and it clearly follows a Langmuir-Hinshelwood mechanism, suggesting an interfacial process. These observations are consistent with iodide oxidation at the interface, possibly initiated by the strong intrinsic electric field present there, followed by well-known solution-phase reactions of the iodine atom. This interfacial chemistry could be important in many contexts, including atmospheric aerosols.

Interface engineering of hollow CsPbBr3/Co3O4 p-n heterojunction with rich oxygen vacancy for highly enhanced photocatalytic CO2 reduction

Surface defect or p-n heterojunction is considered as an efficient strategy to fabricate intrinsic built-in electric field and facilitate the charge separation and transfer. Herein, a novel p-n heterojunction photocatalyst CsPbBr3/Co3O4 was constructed by a facile microwave-assisted method, in which CsPbBr3 QDs anchored on ZIF-67 derived Co3O4 nanocage can simultaneously introduce oxygen vacancies and strengthen the interfacial interaction. As a result, the as-prepared CsPbBr3/Co3O4 displays the satisfactory photocatalytic CO2 reduction performance without photosensitizer and sacrificial agent, and the optimal catalyst exhibits that the average electron consumption rate (Relectron) is 158.80 μmol‧g−1‧h−1, which is 12.41 times higher than that of pure CsPbBr3. Photoassisted Kelvin probe force microscopy (KPFM) and experimental characterizations exhibit the formation of strong built-in electric fields probably due to the rich oxygen vacancies in this p-n heterojunction. Besides, DFT calculations confirm that the charge transfer pathway, where the electrons are quickly migrated to the catalytic active sites through the formed Cs-O bonds, thus accelerating the charge separation. This work could establish an effective strategy for the rational design of p-n heterojunctionto achieve high-performance CO2 conversion.

Studies on EU-DEMO 3D coils requirements and conceptual design for error field correction and plasma control

This work presents the initial studies on the requirements for the design of 3D coils on EU-DEMO. The use of 3D coils in present machines includes two main purposes: the first one is the Error Field Correction (EFC). The EFC aims at minimizing the intrinsic non-axisymmetric fields in the machine. Fulfilling the requirements is evaluated with the minimization of residual error fields, both in vacuum and with plasma response. The second purpose relates to the application of 3D fields to control the plasma. The first of these control functions includes the manipulation of the locked neoclassical tearing modes (NTMs) phase, and their positioning in front of the electron cyclotron antennae, for optimum stabilization. A second function is the application of 3D perturbation of the plasma edge to suppress ELMs. As the fastest required time constant of the applied 3D fields is comparable or longer with respect to that of the vacuum vessel, ex-vessel coils can be considered. Another constraint considered is that the 3D fields applied do not generate 3D power exhaust effects, such as divertor lobes, that jeopardize the protection of the machine divertor/wall. This constriant is met in the finding of this work, in the case considered of the ELMs suppression. The aim of this study is to assess if one set of coils could be designed that fulfills all these purposes/functions. The results show that, by using ITER tolerances for the TF, CS and PF coils, all these functions on EFC (using the overlap criterion assumption, which includes the plasma response), NTM phase control and ELMs suppression can be met with the proposed design of one row of ex vessel coils. An additional activity has started to study if the non-resonant perturbations generated by this set of coils could lead to detrimental effects via neoclassical toroidal viscosity (NTV) torque. Preliminary considerations on the coil technology, are also presented, with no showstopper found in this preliminary phase.

Intrinsic Stress‐strain in Barium Titanate Piezocatalysts Enabling Lithium−Oxygen Batteries with Low Overpotential and Long Life

AbstractRechargeable lithium−oxygen (Li−O2) batteries with high theoretical energy density are considered as promising candidates for portable electronic devices and electric vehicles, whereas their commercial application is hindered due to poor cyclic stability caused by the sluggish kinetics and cathode passivation. Herein, the intrinsic stress originated from the growth and decomposition of the discharge product (lithium peroxide, Li2O2) is employed as a microscopic pressure resource to induce the built‐in electric field, further improving the reaction kinetics and interfacial Lithium ion (Li+) transport during cycling. Piezopotential caused by the intrinsic stress‐strain of solid Li2O2 is capable of providing the driving force for the separation and transport of carriers, enhancing the Li+ transfer, and thus improving the redox reaction kinetics of Li−O2 batteries. Combined with a variety of in situ characterizations, the catalytic mechanism of barium titanate (BTO), a typical piezoelectric material, was systematically investigated, and the effect of stress‐strain transformation on the electrochemical reaction kinetics and Li+ interface transport for the Li−O2 batteries is clearly established. The findings provide deep insight into the surface coupling strategy between intrinsic stress and electric fields to regulate the electrochemical reaction kinetics behavior and enhance the interfacial Li+ transport for battery system.