Density Functional Theory Calculations Research Articles

Rapid Surface Reconstruction of Amorphous-Crystalline NiO for Industrial-Scale Electrocatalytic PET Upcycling.

The conversion of plastic waste into valuable chemicals through innovative and selective nano-catalysts offers significant economic benefits and positive environmental impacts. However, our current understanding of catalyst design capable of achieving industrial-grade current densities is limited. Herein, we develop a self-supported amorphous-crystalline NiO electrocatalyst for the electrocatalytic upcycling of polyethylene terephthalate (PET) into formate and hydrogen (H2) fuel. The catalyst achieves an industrial current density of over 1 A cm-2 at 1.5 V vs. RHE, with an 80% Faradaic efficiency and a formate production rate of 7.16 mmol cm-2 h-1. In situ Raman spectroscopy, X-ray absorption spectroscopy, and density functional theory calculations reveal that the rapid transformation of amorphous-crystalline NiO into γ-NiOOH at the amorphous-crystalline interface provides a thermodynamic advantage for formate desorption, leading to the high activity required for industrial applications, which is difficult to achieve for fully crystalline NiO. A techno-economic analysis indicates that recycling waste PET using this catalytic process could generate a profit of $501 per ton. This work presents a cost-effective and highly efficient approach to promoting the sustainable utilization of waste PET.

Impact of Side Chains in 1-n-Alkylimidazolium Ionomers on Cu-Catalyzed Electrochemical CO2 Reduction.

This study presents the impact of the side chains in 1-n-alkylimidazolium ionomers with varying side chain lengths (CnH2n+1 where n = 1, 4, 10, 16) on Cu-catalyzed electrochemical CO2 reduction reaction (CO2RR). Longer side chains suppress the H2 and CH4 formation, with the n-hexadecyl ionomer (n = 16) showing the greatest reduction in kinetics by up to 56.5% and 60.0%, respectively. On the other hand, C2H4 production demonstrates optimal Faradaic efficiency with the n-decyl ionomer (n = 10), a substantial increase of 59.9% compared to its methyl analog (n = 1). Through a combination of density functional theory calculations and material characterization, it is revealed that the engineering of the side chains effectively modulates the thermodynamic stability of key intermediates, thus influencing the selectivity of both CO2RR and hydrogen evolution reaction. Moreover, ionomer engineering enables industrially relevant partial current density of -209.5 mA cm-2 and a Faradaic efficiency of 52.4% for C2H4 production at 3.95 V, even with a moderately active Cu catalyst, outperforming previous benchmarks and allowing for further improvement through catalyst engineering. This study underscores the critical role of ionomers in CO2RR, providing insights into their optimal design for sustainable chemicalsynthesis.

Exploring Electronic and Conformational Attributes of an Organic Donor‐Bridge‐Acceptor Molecular System

AbstractThis research explores the electronic properties and conformational dynamics of the ZnP‐COPV‐ (Zinc Porphyrin ‐ Carbon bridged Oligo Phenylenevinylene ‐ Fullerene) organic semiconductor via specialized Density Functional Theory (DFT) and Molecular Dynamics (MD) computational techniques. First, through DFT calculations, essential HOMO (Highest Occupied Molecular Orbital), LUMO (Lowest Unoccupied Molecular Orbital), and Molecular Electrostatic Potential (MEP) electronic attributes are meticulously dissected providing insights into the intricate charge transfer processes between the constituent donor‐acceptor moieties. Furthermore, MD simulations are employed to unveil the molecular system's multifaceted conformational flexibility and stability. The Root‐mean‐squared deviation (RMSD), end‐to‐end distance, and torsional angles quantitative analysis of conformational attributes support the carbon‐bridged oligo‐phenylenevinylene (COPV) molecular wire's ‐skeleton planar and rigid conformation. This minimal end‐to‐end distance variation (within Å) compared to the initially extended structure and the constrained torsional motion (within for ZnP‐COPV and for COPV‐) after thermalization showcases COPV's ability to maintain structural rigidity over time, aligning with the concept of effective ‐conjugation. Finally, through the lens of time dependent (TD)‐DFT, the dynamic evolution of the HOMO–LUMO energy gap, TD‐DFT excitation energies and oscillator strengths are explored as the molecular structure transforms over time. The observed energy gap variation underscores the molecule's adaptability in the face of structural modifications, hinting at an intriguing connection between structural stability and enhanced electronic properties. The research provides a comprehensive understanding of the intricate interplay between conformational dynamics and electronic attributes in organic semiconductors, providing quantitative insights crucial for designing stable, high‐performance materials for cutting‐edge optoelectronic applications and helping advance the collective understanding of sustainable energy conversion.

Heterogenization of a Sandwich [(PW9O34)2Co4(H2O)2]10− in PCN–222/PCN–222(M): Exploring the Electron Transfer for Electrocatalytic CO2 Reduction

In this study, we designed and prepared polyoxometalate@metal‐organic framework (POM@MOF) composite catalysts through the anchoring of a sandwich POM [(PW9O34)2Co4(H2O)2]10− (shortened as P2W18Co4) to the hexagonal channel of the PCN–222 (metal‐free) or PCN–222(M) (M=Fe, Co) frameworks. The composite materials were applied to the electrocatalytic reduction of CO2 reaction (CO2RR) to analyse the effect of incorporating P2W18Co4 on catalytic activity. The P2W18Co4@PCN–222 composite exhibited enhanced activity across a wide potential range (–0.60~ –0.85 V vs. RHE) and an optimal FECO of 72% at –0.75 V vs. RHE, which was more than double that of PCN–222 (FECO= 33%). The current density surpassed that of the PCN–222 precursors by over sixteen times at the same potential. In contrast, the P2W18Co4@PCN–222(M) composite demonstrated decreased current density, minimal enhancement in CO2RR activity, and a competing HER behaviour. Density functional theory calculations were conducted on simplified models of P2W18Co4@H2–TCPP and P2W18Co4@M–TCPP to elucidate the divergent catalytic performances. The findings revealed that while both configurations exhibited the same rate‐limiting step (formation of the *COOH intermediate), a significantly reduced reaction barrier was only observed in the P2W18Co4@H2–TCPP setup, explaining its substantial activity improvement.

Hierarchical Flower Array NiCoOOH@CoLa‐LDH Nanosheets for High‐Performance Supercapacitor and Alkaline Zn Battery

AbstractNickel oxyhydroxide based energy storage materials have been largely confined by insufficient exposure of active sites which results in low energy efficiency and poor stability. In order to resolve the problems, hierarchical flower array heterostructure NiCoOOH@CoLa‐LDH (denoted as NC@CL) nanosheets are designed with NiCo oxyhydroxide (NiCoOOH, denoted as NC) being tightly covered on CoLa layered double hydroxide (CoLa‐LDH, denoted as CL) nanosheet. This rational design creates more active sites, enlarges the electrode‐electrolyte contact area, improves electron conductivity, and prevents agglomeration during the cycling charge–discharge processes. Density functional theory calculations and differential charges concurrently illustrate that heterostructure formation optimizes the reaction kinetics and promotes electron redistribution. Benefiting from the heterogeneous structure and rich electro‐active sites caused by NC, NC@CL displays outstanding reversible specific capacitance (3228 F g−1 at 1 A g−1). The aqueous rechargeable alkaline Zn battery NC@CL//Zn exhibits a high capacity of 381.1 mA h g−1 at 0.5 A g−1 and cycling durability (98% capacity retention after cycling at 5 A g−1 for 2000 cycles). The excellent electrochemical performances indicate that NC@CL has great application potential as electrode material for aqueous energy storage device.

Phosphine-Catalyzed [3 + 4] Annulations of Salicylaldehyde Schiff Bases with α-Substituted Allenes: Construction of Functionalized Benzoxepine Fused Succinimide Derivatives.

Herein we reported a novel strategy for constructing benzoxepine fused succinimide derivatives via a phosphine-catalyzed [3 + 4] cyclization of α-substituted allenes and salicylaldehyde Schiff bases. This methodology serves as a conduit for the construction of benzoxepine derivatives in good yields under mild conditions by an unprecedented mode involving the β'-carbon of allenes. Density functional theory calculations were conducted to study the possible mechanism. Moreover, this class of compounds exhibited the potential ability of cytotoxicity toward cancer cells.

Wane-and-wax mechanism of nitrogenous disinfection byproducts with constant Cl/N peak under UV/chlorine treatment: Implication for new drinking water disinfection strategy

Nitrogenous disinfection byproducts (N-DBPs) are notorious for their serious health risks, yet nitrate (NO3-) mediates N-DBPs generation during UV/chlorine treatment remains unexplored. This study investigated the interaction of chlorine and NO3- on N-DBPs formation and developed a specific fragment-based screening method using UPLC-QTOF-MS to explore the underlying mechanism. Results showed that the chlorine-to-nitrogen (Cl/NO3--N) molar ratio significantly affects dichloroacetonitrile (DCAN) and dichloroacetamide (DCAM) generation, with peak concentrations at a Cl/NO3--N molar ratio of around 15. NO3- promotes the production of HO•, which positively correlates with DCAN and DCAM concentrations, also peaking at this ratio. Utilizing our developed method, three key hydroxyl-substituted intermediates that circumvent the previously reported “limiting-steps” in DCAN formation were identified. This reaction proceeds via a stepwise mechanism involving hydroxylation and chlorine substitution to produce hydroxyl-phenylacetonitrile and hydroxyl-chlorine-phenylacetonitrile. The conversion rate of hydroxyl-chlorine-phenylacetonitrile to DCAN was 8.6 times higher at Cl/NO3--N molar ratio of 15 compared to conditions without NO3-, attributed to the weakened bond strength of the side chain, as supported by density functional theory calculations. This study provides novel insights into the mechanistic pathways of DCAN and DCAM formation, critical for developing more effective drinking water disinfection technologies to control N-DBPs.

Magnetic‐induced isomerization of paramagnetic bridged azobenzene derivatives with conjugated alkyl chains

AbstractInducing a reversible structural transformation in organic photochromophores under the effect of a magnetic field is challenging owing to their poor magnetic properties. Compared with common azobenzene materials, bridged azobenzene materials exhibit a considerable potential for rapid trans‐cis isomerization induced by an external magnetic field because of the restricted torsion of N=N bonds during the transformation. Herein, we designed and synthesized pentenyl‐grafted bridged azobenzene (BA‐X5), hexenyl‐grafted bridged azobenzene (BA‐X6), and pentynyl‐grafted bridged azobenzene (BA‐Q5). Density functional theory calculations indicate that the activation energy for the trans‐cis transition of BA‐X5 and BA‐X6 is ~18.0 kcal/mol, which is 8.2% lower than that of BA‐Q5 (19.6 kcal/mol). The results obtained using EPR and a superconducting quantum interference device demonstrate that during the isomerization process, a net spin reduction of bridged azobenzene occurred because of the aggregation of the electron cloud toward the C−N bond, leading to a reduction in the paramagnetism of the materials. BA‐X5 and BA‐X6 exhibit a clear and rapid magnetically induced trans‐cis isomerization with short half‐lives, which are 10.4% and 16.9%, respectively, lower than those obtained under dark conditions. In contrast, the isomerization of BA‐Q5 under the effect of the same magnetic field does not change. Magnetically induced isomerization might be attributed to the combined effect of the magnetothermal effect, changes in the net spin density of the electron cloud, and regularity of molecular arrangement under the effect of the magnetic field. These results provide a basis for exploring the design and research of magnetically controlled azobenzene derivatives.

Giant piezoelectricity in antiferromagnetic CrS2 and CrSe2 monolayers

Abstract Two-dimensional (2D) materials, particularly transition metal dichalcogenides (TMDs), have garnered significant attention in the nanoscale piezoelectric field due to their high crystallinity and ability to withstand large strains. Through density-functional theory calculations, we have discovered that monolayer H-phase CrS2 and CrSe2 exhibit antiferromagnetic semiconducting properties, in contrast to the previously held belief that they were nonmagnetic (NM) semiconductors. While the piezoelectric coefficients of NM CrS2 and CrSe2 are comparable to those of MoS2, their antiferromagnetic ground states demonstrate significantly enhanced piezoelectric coefficients ( d 11 ) of 27.66 pm V−1 and 52.36 pm V−1, respectively. These values exceed that of MoS2 by an order of magnitude, marking the highest recorded for TMD materials and the highest in 2D magnetic materials to date. The greatly enhanced piezoelectric responses in the antiferromagnetic states of CrS2 and CrSe2 compared to their NM states arise from three primary factors. Firstly, the displacement of the Wannier center under strain is more pronounced in the antiferromagnetic state, leading to a greater change in dipole moment (enhanced clamped-ion contribution). Secondly, there is a heightened polarization change due to internal atomic distortions (internal-strain term) in response to macroscopic strain in the antiferromagnetic state. Thirdly, the material undergoes a softening of the elastic coefficient in its antiferromagnetic state. These findings open new avenues for designing high-performance piezoelectric and magnetic multifunctional materials.

Regulating surface terminals and interlayer structure of Ti3C2Tx for superior NH3 sensing

MXene materials have exhibited potential in electrochemistry, particularly in gas sensing, due to their excellent conductivity, large specific surface area of layered materials, and unique functional groups. However, the gas sensing performance of intrinsic 2D MXene materials is often limited by their fluorine-containing terminals and interfacial structure. In this study, based on intrinsic Ti3C2Tx, we employed alkali treatment and annealing to prepare oxygen-rich Ti3C2(OH)x/Ti3C2Ox with expanded interlayer spacing, achieving enhanced gas sensing performance for NH3. The surface chemistry and structure of the sensing materials have been optimized through the synergistic regulation of MXene's unique surface terminations and the intercalation effect of layered materials. Compared to intrinsic Ti3C2Tx, the interlayer spacing of oxygen-rich Ti3C2(OH)x/Ti3C2Ox increased from 9.1 Å to 12.1 Å. The surface terminations of oxygen-rich Ti3C2(OH)x/Ti3C2Ox have been defluorinated and oxygenated. The maximum response value of oxygen-rich Ti3C2(OH)x/Ti3C2Ox to NH3 was 35.66, approximately twice that of the original Ti3C2Tx at an NH3 concentration of 200 ppm. DFT (Density functional theory) calculations and DRIFT (In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy) tests explained the interaction between the surface terminals and NH3, indicating good selectivity and sensitivity of oxygen-rich Ti3C2(OH)x/Ti3C2Ox to NH3. The results demonstrated that the synergistic effects of surface chemistry and structural engineering are crucial for MXene to optimize the electrochemical performance, particularly the gas sensing performance. This provides a feasible approach for the performance optimization of intrinsic MXene materials.

Templates effects on the morphological, optical, and photocatalytic properties of ZnO nanostructures synthesized via precipitation method

A simple and effective method was used to synthesize zinc oxide (ZnO) nanoparticles in the presence of chitosan (Cs) and Pluronic 123 (P) as templates. A comparative study was then conducted to evaluate the optical, morphological, and photocatalytic properties of the resulting materials. The synthesized nanoparticles were characterized using various techniques, including XRD, FTIR, DRS, EDX, SEM, and N2 adsorption–desorption. Additionally, density functional theory (DFT) calculations were employed to explore the electronic properties of the nanoparticles. The results demonstrated that the templates significantly influenced in the morphology of materials. Additionally, ZnO-Cs showed a lower band gap and the highest specific surface area (20.57 m2/g). The samples showed good stability and significant photocatalytic activity under UV-B radiation at the natural solution pH (without adjustment). The degradation of methylene blue (MB) was confirmed by liquid chromatography-mass spectrometry (LC-MS) analysis. Furthermore, the mechanism of photocatalytic degradation of the organic dye was investigated using conceptual DFT analysis and validated through comparison with previously reported experimental data.

Controllable Synthesis of Oxa‐/Thia‐Spirohydroquinolines by [3+(2+1)] Annulation of Aromatic Amines with Bimolecular O/S‐Heterocyclic Ketones

Abstract[3+(2+1)] Annulation represents the most straightforward and atom‐economical strategies in organic synthesis for the efficient construction of diverse cyclic structural units and complex molecules. Herein, we present a Lewis acid Sc(OTf)3‐catalyzed controlled synthesis of two different regioselective oxa/thia‐spirohydroquinolines (C=C at the α/β‐site of O/S‐atom) from aromatic amines and bimolecular O/S‐heterocyclic ketones via intermolecular [3+(2+1)] annulation. This method features mild reaction conditions, high step economy and atom utilization, and the O/S‐heterocyclic ketone can act as both two‐ and one‐carbon synthons. Furthermore, density functional theory (DFT) calculations indicate that the intrinsic cause of this unique regioselectivity is caused by the proton abstraction step.

Unique role of doped Mo into Fe-based catalyst to intensify peroxydisulfate activation for micropollutants degradation: Promote the conversion of SO4•- to FeIV = O

Herein, Fe/Mo-based composite catalyst (FeMo@CN) was synthesized to catalyze peroxydisulfate (PDS) for efficient bisphenol A (BPA) degradation. Within 1 h, the FeMo@CN/PDS system could degrade BPA fully (kobs = 0.12 min−1, which was 129 times higher than system without Mo introduction). Probe experiments and 57Fe Mossbauer indicated that BPA degradation was dominated by SO4•- and FeIV = O converted from SO4•- (Fe(II)-PDS → Fe(III)-SO4•-→FeIV = O-HSO4-). This finding broke down the boundary between radical and non-radical, proposing a new path from SO4•- to FeIV = O. As Density functional theory (DFT) calculations revealed, Mo in FeMo@CN promoted PDS adsorption and reduced generation energy barrier of SO4•- and FeIV = O, achieving a dual improvement. Besides, the stable and efficient BPA degradation in dynamic degradation experiment demonstrated the application potential of FeMo@CN. This work provides a novel method to solve blocked Fe(II)/Fe(III) cycle and re-reveals FeIV = O generation mechanism in SR-AOPs.

Plasma-induced aging of microplastics and its effect on mercury transport and transformation

Microplastics are known to adsorb heavy metals, with aged microplastics exhibiting greater adsorption capacity. This study investigates the impact of microplastic aging on the transport and transformation of mercury (Hg), a highly toxic heavy metal. Polystyrene (PS) and polyvinyl chloride (PVC) were aged using plasma treatment to simulate environmental conditions. Characterization of virgin and plasma-treated microplastics revealed aging mechanisms induced by plasma treatment. Notably, aged PS, unlike PVC, did not show a decrease in particle size but exhibited a decrease in specific surface area, likely due to chain cleavage and re-polymerization of polystyrene fragments, and thermal effects during plasma treatment. Both aged PS and PVC demonstrated increased hydrophilicity, enhanced negative charge, and a higher presence of nitrogen- and oxygen-containing functional groups. These changes were correlated with a significant increase in Hg adsorption capacity. Density functional theory (DFT) calculations further indicated that the adsorption of Hg2+ by microplastics is promoted by the presence of oxygen- and nitrogen-containing functional groups. The particularly strong influence of nitrogen-containing functional groups on Hg2+ adsorption was confirmed through both experimental and theoretical approaches. Adsorption kinetics and isothermal experiments, along with X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) analyses, were conducted to elucidate the Hg adsorption mechanism of on microplastics before and after aging. The mechanisms involved include pore filling, van der Waals’ forces, electrostatic interactions, hydrophobic interactions, and functional group complexation. The intraparticle diffusion model indicated that adsorption is controlled by multiple steps. Importantly, the surface functional groups of aged microplastics can reduce Hg2+ to Hg+ and adsorb it, suggesting a more complex adsorption process for Hg on aged microplastics. This study provides a scientific basis for understanding microplastic aging and the Hg adsorption mechanism on microplastics, highlighting the complex dynamics of combined microplastic and heavy metal contamination.

Desolvation Effect Triggered by TiS2‐TiO2 Heterostructure for Ultrahigh‐Rate Aqueous Zinc‐Ion Batteries

AbstractAqueous Zn ion batteries (AZIBs) represent a promising candidate for the next‐generation energy storage and conversion systems due to their high safety and cost‐effectiveness. However, sluggish kinetics arising from interface desolvation processes pose challenges in achieving high‐power density and long cycle life for AZIBs. Here, it is discovered for the first time that heterostructures utilize built‐in electric field forces to promote the desolvation process at the electrode‐electrolyte interface. Density functional theory (DFT) calculations and structural characterization demonstrate that heterogeneous structures simultaneously accelerate the desolvation process and enhance ion diffusion, resulting in the outstanding rate performance (160.9 mA h g−1 at 5 A g−1) of TiS2‐TiO2 heterostructures, far exceeding that of a conventional TiS2 electrode with 14.2% capacity retention. Meanwhile, the insertion/extraction of the desolvated charge carriers reduced the volume change of TiS2‐TiO2 material during the charging/discharging processes, enabling the long‐lasting cycling stability (108.6 mA h g−1 after 2000 cycles at 0.5 A g−1). This study provides instructive electrode design strategies for the construction of fast‐charging electrochemical energy storage systems.

Enhancing Hydrogen Evolution Reaction through the Improved Mass Transfer and Charge Transfer by Bimetal Nodes.

The high cost of hydrogen production by water electrolysis severely challenges its commercial application. It is highly desirable to develop efficient electrocatalysts and innovative electrolytic cells. Introducing additional metal nodes to form bimetallic metal-organic framework (MOF) is a simple, feasible strategy to overcome the poor electrocatalytic performance of single-metal MOF. In this study, the hydrothermal method is used to synthesize bimetallic NixCoy-BTC. It is found that for hydrogen evolution reaction (HER), Ni0.8Co0.2-BTC merely requires a potential of -0.203 V (vs reverse hydrogen electrode, RHE) to achieve 10 mA cm-2, which is significantly lower than that of Ni-BTC (-0.341 V vs RHE). Notably, electrochemical impedance spectroscopy (EIS) and distribution of relaxation time (DRT) analysis indicate that NixCoy-BTC has improved charge transfer and mass transfer process, compared with Ni-BTC. Electron paramagnetic resonance (EPR) confirms that Ni0.8Co0.2-BTC has more unpaired electrons than Ni-BTC. Density functional theory (DFT) calculations show that compared with Ni-BTC, NixCoy-BTC is more thermodynamically favorable for the adsorption of H+, OH-, and H2O. It demonstrates that the change of mass transfer caused by bimetallic nodes and the delicate variation of MOF surface play an important role in the electrochemical process. Moreover, a novel electrolytic cell was developed using a methanol oxidation reaction (MOR) to replace oxygen evolution reaction (OER). In this MOR-based electrolytic cell, a current density of 50 mA cm-2 can be achieved at only a cell voltage of 1.85 V, which is lower than the 2.22 V of OER-based electrolytic cell, suggesting that 16.7% electric energy can be saved. At the same time, the Faraday efficiency (FE, 98.2%) of the MOR-based cell is higher than that (94.5%) of the OER-based cell. This research offers a promising strategy for low-cost hydrogen production.

Scalar and vectorized implementations of the density functional theory via Geant4 and GeantV project

In this paper, we present the implementation of the Density Functional Theory (DFT) method using the Geant4-DNA framework in the Single Instruction Single Data (SISD) mode. Furthermore, this implementation is improved in terms of execution time within the GeantV project with vectorization techniques such as Single Instruction Multiple Data (SIMD). Within this framework, a set of SIMD strategies in molecular calculation algorithms such as one-electron operators, two-electron operator, quadrature grids, and functionals, was implemented using the VecCore library. The applications developed in this work implement two DFT functionals, the Local Density Approximation (LDA) and the General Gradient Approximation (GGA), to approximate the molecular ground-state energies of small molecules and amino acids. To assess the performance of the implementations, a standard test simulation was performed in multiple CPU platforms. The SIMD vectorization strategy significantly accelerates DFT calculations, leading to time ratios ranging from 1.6 to 5.4 in either individual steps or entire implementations when compared with the scalar process within Geant4.

MOF-Derived Nitrogen-Rich Hollow Nanocages as a Sulfur Carrier for High-Voltage Aluminum Sulfur Batteries.

Aluminum-sulfur batteries (ASBs) are emerging as promising energy storage systems due to their safety, low cost, and high theoretical capacity. However, it remains a challenge to overcome voltage hysteresis and short cycle life in the sulfur/Al2S3 conversion reaction, which hinders the development of ASBs. Here, we studied a high-voltage ASB system based on sulfur oxidation in an AlCl3/urea electrolyte. Nitrogen-doped hollow nanocages (HNCs) synthesized from MOF precursors were rationally designed as sulfur/carbon composite electrodes (S@HNC), and the impact of the nitrogen species on the electrochemical performance of sulfur electrodes was systematically investigated. The S@HNC-900 achieved efficient conversion at 1.9 V, delivering a stable capacity of 197.3 mA h g-1 and a Coulombic efficiency of 93.28% after 100 cycles. Furthermore, the S@HNC-900 electrode exhibited exceptional rate capacity and 800th long-term cycling stability, retaining a capacity of 87.1 mA h g-1 at 500 mA g-1. Ex situ XPS and XRD characterizations elucidated the redox mechanism, revealing a four-electron transfer process (S/AlSCl7) at the S@HNC-900 electrode. Density functional theory calculations demonstrated that pyridinic nitrogen-enriched HNC-900 significantly enhanced the sulfur conversion reaction and facilitated the adsorption of sulfur intermediates (SCl3+) on the carbon interface. This work provides critical insights into the high-voltage sulfur redox mechanism and establishes a foundation for the rational design of carbon-based electrocatalysts for the enhancement of ASB performance.

Catalytic performances of Ag/SiC catalysts for styrene epoxidation in O2 atmosphere

SiC supported Ag catalysts were prepared by an impregnation-reduction method for styrene epoxidation in O2 atmosphere. Under the condition of 100 °C, 0.5 MPa O2 and 4 h, 5 wt% Ag/SiC catalyst achieved styrene conversion of 98.5 % and styrene oxide selectivity of 69.7 %. Further studies show that O2 was activated on the Ag surface and then formed reactive oxygen species, 1O2 and •O2-. Based on the O2 adsorption results, the atomic ratio of O/Ag larger than 0.5 indicated that more oxygen species had spilled over to the SiC surface. In-situ diffuse reflectance Fourier transform infrared spectroscopy and Density Functional Theory calculation results showed that styrene was adsorbed on the SiC surface. The active oxygen species generated on the Ag surface could spill over to the SiC surface, reacting with the adsorbed styrene to produce styrene oxide or benzaldehyde. In addition, the catalyst exhibits good stability.

Polarization Pinning at Antiphase Boundaries in Multiferroic YbFeO3

Abstract The switching characteristics of ferroelectrics and multiferroics are influenced by the interaction of topological defects with domain-walls. We report on the pinning of polarization due to antiphase boundaries in thin films of the multiferroic hexagonal YbFeO3. We have directly resolved the atomic structure of a sharp antiphase boundary (APB) in YbFeO3 thin films using a combination of aberrationcorrected scanning transmission electron microscopy (STEM) and total energy calculations based on density-functional theory (DFT). We find the presence of a layer of FeO6 octahedra at the APB that bridge the adjacent domains. STEM imaging shows a reversal in the direction of polarization on moving across the APB, which DFT calculations confirm is structural in nature as the polarization reversal reduces the distortion of the FeO6 octahedral layer at the APB. Such APBs in hexagonal perovskites are expected to serve as domain-wall pinning sites and hinder ferroelectric switching of the domains.