Electrons Research Articles

Reconfiguring FeN4 sites through axial Fe2O3 clusters to enhance d-orbital electronic delocalization for improved oxygen reduction reaction

Effectively controlling the electronic configuration of metal sites within single-atom catalysts (SACs) is essential for improving their oxygen reduction reaction (ORR) performance. Here, we construct hybrid catalysts featuring Fe single atoms and Fe2O3 clusters (Fe SACs/Fe2O3@NHPC) to realize highly efficient ORR. Specifically, the Fe SACs/Fe2O3@NHPC delivers a remarkable half-wave potential (E1/2) of 0.893 V and endures 30,000 cycles with only 12 mV E1/2 loss in alkaline media. Liquid zinc–air batteries (ZABs) utilizing Fe SACs/Fe2O3@NHPC output a power density of 192.7 mW cm−2 and demonstrate rechargeability over 370 h without noticeable voltage degradation. Furthermore, theoretical calculations indicate that the axially coordinated Fe2O3 clusters significantly promote electronic delocalization in the 3d orbitals of the Fe sites. This electronic structure regulation strategy optimizes the hybridization between Fe-3d orbitals and O-2p orbitals, thereby facilitating the *OH dissociation process. This research not only provides intensive insight into the synergistic interactions and complementary effects between single-atom sites and clusters in hybrid catalysts but also lays the groundwork for designing SACs.

Enhancement of Selective Catalytic Oxidation of Lignin β-O-4 Bond via Orbital Modulation and Surface Lattice Reconstruction.

The orbital modulation and surface lattice reconstruction represent an effective strategy to regulate the interaction between catalyst interface sites and intermediates, thereby enhancing catalytic activity and selectivity. In this study, the crystal surface of Au-K/CeO2 catalyst can undergo reversible transformation by tuning the coordination environment of Ce, which enables the activation of the Cβ-H bond and the oxidative cleavage of the Cβ-O and Cα-Cβ bonds, leading to the cleavage of 2-phenoxy-1-phenylethanol. The t2g orbitals of Au 5d hybridize with the 2p orbitals of lattice oxygen in CeO2 via π-coordination, modulating the coordination environment of Ce 4 f and reconstructing the lattice oxygen in the CeO2 framework, as well as increasing the oxygen vacancies. The interface sites formed by the synergy between Au clusters in the reconstructed Ce-OL1-Au structure and doped K play dual roles. On the one hand, it activates the Cβ-H bond, facilitating the enolization of the pre-oxidized 2-phenoxy-1-phenylethanone. On the other hand, through single-electron transfer involving Ce3+ 4f1 and the adsorption by oxygen vacancies, it enhances the oxidative cleavage of the Cβ-O and Cα-Cβ bonds. This study elucidates the complex mechanistic roles of the structure and properties of Au-K/CeO2 catalyst in the selective catalytic oxidation of lignin β-O-4 bond.

A high-resolution photoelectron spectroscopic and computational study of TaX− (X = C, N, O)

We report on the high-resolution photoelectron spectroscopy of diatomic molecules TaX− (X = C, N, O) anions using a cryogenic ion trap combined with the slow electron velocity imaging (cryo-SEVI) method. We determined the electron affinities of TaC, TaN, and TaO to be 2.098(2), 1.576(2), and 1.069(2) eV, respectively. In addition, the electron affinities of TaX molecules were calculated using the CCSD(T) method with the complete basis sets. To interpret the complicated photoelectron spectra, we predicted the excited states of TaX molecules using the MRCI + Q method, accounting for the spin–orbit coupling effects. Several new excited states of these molecules were observed.

Topological insulating phase in nonsymmorphic bulk AX2 (A = Ca, Sr, or Ba; and X = As, Sb, or Bi) compounds

Owing to their unique topologically protected gapless boundary states, topological insulators (TIs) are attracting substantial interest in spintronics and quantum computing. Here, we discuss the structural, electronic, and topological properties of bulk alkaline earth di-pnictides AX2 (where A= Ca, Sr, or Ba and X= As, Sb, or Bi) using first-principles calculations under the hybrid functional approach. Our structural analysis based on phonon dispersion and molecular dynamics calculations establishes the thermodynamic stability of these materials and indicates their potential for synthesis. All investigated compounds are shown to host nontrivial phases upon including spin–orbit coupling. CaAs2, SrSb2, and BaSb2 are found to be strong TIs with sizable bandgaps of up to 213 meV. Nontrivial topology in the case of SrSb2 was further confirmed through surface state computations which showed the presence of gapless surface states. In addition, we demonstrate that using the hybrid functional approach can enhance the accuracy of the calculations to predict experimental findings. Finally, our study suggests that the alkaline earth di-pnictide family would provide a promising materials platform for developing applications of TIs.

Improved long-term prediction of chaos using reservoir computing based on stochastic spin–orbit torque devices

Predicting chaotic systems is crucial for understanding complex behaviors, yet challenging due to their sensitivity to initial conditions and inherent unpredictability. Probabilistic reservoir computing (RC) is well suited for long-term chaotic predictions by handling complex dynamic systems. Spin–orbit torque (SOT) devices in spintronics, with their nonlinear and probabilistic operations, can enhance performance in these tasks. This study proposes an RC system utilizing SOT devices for predicting chaotic dynamics. By simulating the reservoir in an RC network with SOT devices that achieve nonlinear resistance changes with random distribution, we enhance the robustness for the predictive capability of the model. The RC network predicted the behaviors of the Mackey–Glass and Lorenz chaotic systems, demonstrating that stochastic SOT devices significantly improve long-term prediction accuracy.

Leaning Sideways: VHS 1256−1257 b is a Super-Jupiter with a Uranus-like Obliquity

We constrain the angular momentum architecture of VHS J125601.92-125723.9, a 140 ± 20 Myr old hierarchical triple system composed of a low-mass binary and a widely separated planetary-mass companion, VHS 1256 b. VHS 1256 b has been a prime target for multiple characterization efforts, revealing the highest measured substellar photometric variability to date and the presence of silicate clouds and disequilibrium chemistry. Here we add a key piece to the characterization of this super-Jupiter on a Tatooine-like orbit: we measure its spin-axis tilt relative to its orbit, i.e., the obliquity of VHS 1256 b. We accomplish this by combining three measurements. We find a projected rotation rate vsinip=8.7±0.1kms−1 for VHS 1256 b using near-infrared high-resolution spectra from Gemini/IGRINS. Combining this with a published photometric rotation period indicates that the companion is viewed edge on, with a line-of-sight spin axis inclination of i p = 90° ± 18°. We refit available astrometry measurements to confirm an orbital inclination of io=23−13+10 degrees. Taken together, VHS 1256 b has a large planetary obliquity of ψ = 90° ± 25°. In total, we have three measured angular momentum vectors for the system: the binary orbit normal, companion orbit normal, and companion spin axis. All three are misaligned with respect to each other. Although VHS 1256 b is tilted like Uranus, their origins are distinct. We rule out planet-like scenarios including collisions and spin–orbit resonances, and suggest that top-down formation via core/filament fragmentation is promising.

Cobalt/nickel bimetallic ion synergistic effect for enhancing polysulfide adsorption and conversion in Li[sbnd]S batteries

Lithium‑sulfur batteries (LSBs) are regarded as the next generation of batteries due to their exceptionally high theoretical energy density. However, the progress of LSBs is impeded by slow reaction kinetics and the significant issue of lithium polysulfide shuttling. Herein, MOF-74 materials with different Co2+/Ni2+ bimetallic ion ratios were designed to be attached to rGO as sulfur hosts to enhance the adsorption and conversion of polysulfides (CoxNi-MOF-74/rGO (x = 1, 3, 5, 7, 9)). The materials exhibit a spherical and rod-like hybrid structure when the Co2+/Ni2+ is 30 %/70 % (Co3Ni-MOF-74/rGO), which effectively inhibit the shuttle effect of the polysulfide. The cells exhibit an initial capacity of 1391.8 mAh g−1 at 0.5C and the attenuation per cycle is only 0.029 % in 800 cycles. Furthermore, the strong interaction between the electronic clouds of Co2+ and Ni2+ effectively catalyzes the conversion of polysulfides. Experimental results and density functional theory (DFT) calculations indicate that Ni2+ is more effective in facilitating the transition Li2S6→Li2S4, while Co2+ is Li2S4→Li2S. As the result, the cell displays perfect catalytic performance at 7C and ultralong life over 1500 cycles. This study provides insights on the synergistic adsorption and conversion effect of polysulfides by bimetallic ions in advanced lithium‑sulfur battery electrode.

Highly efficient Zr-based coordination polymer for catalytic transfer hydrogenation of 5-hydroxymethylfurfural: Tuning acid strength and enhancing stability

In this study, Zr-based coordination polymers were synthesized via solvothermal method for the Meerwein-Ponndorf-Verley reduction of biomass-derived aldehydes and ketones. The morphology and strength of Lewis acid sites could be tuned by using different solvent during catalyst preparation. A 98.5 % yield of 2,5-bis(hydroxymethyl)furan (BHMF) was achieved at 100 °C using Zr-PDC/DMF-DCB, which was synthesized with pyridine-2,6-dicarboxylic acid (PDC) as ligand in a mixed solvent of N, N-dimethylformamide (DMF) and 1,2-dichlorobenzeneisopropanol (DCB) and exhibited moderate Lewis acid sites. Conversely,while Zr-PDC synthesized in alcohols (Zr-PDC/MeOH and Zr-PDC/EtOH) were used as catalysts, etherification products formed instead of BHMF. Further investigation into the role of solvents during catalyst preparation revealed that coordination between Zr sites and DMF increased the electron cloud density of Zr sites, thus weakening Lewis acidity. In addition, the inclusion of hydrophobic DCB resulted in the formation of spherical morphology, which improved resistance to carbon deposition and enhanced anti-agglomeration properties. This work presents a strategy for controlling acid strength and improving catalytic stability of coordination polymers.

Interband optical absorption coefficient of the diluted magnetic semiconductor ellipsoid quantum dot with Rashba spin orbit interaction

Interband optical absorption coefficient of the diluted magnetic semiconductor ellipsoid quantum dot with Rashba spin orbit interaction

Synergistic enhancement of catalytic hydrodeoxygenation performance by oxygen vacancies and frustrated Lewis pairs

The catalytic hydrodeoxygenation (CHDO) of lignin into saturated cycloalkanes not only enhances the efficient utilization of lignin but also reduces reliance on high-density liquid fuels (HDLFs), given the importance of saturated cycloalkanes as key constituents of HDLFs. The main challenge in lignin CHDO towards HDLFs is efficiently removing oxygen-atom while maintaining high selectivity for the desired saturated cycloalkanes. Herein, we report for the first time the fabrication of a Ni/N0.8-CeO2-500 composite with abundant oxygen vacancies (OVs) and adjacent frustrated Lewis pairs (FLPs), achieved through the capping effect of ionic liquids. The FLPs of N/Ce3+ within Ni/N0.8-CeO2-500, mediated by OVs, not only enhance the dispersion of Ni species but also effectively facilitate the conversion of H2 into active hydrogen (H*) through relay catalysis involving the Ni species. This integration, combining the oxygen atom-specific recognition of OVs with the adjacent FLPs of N/Ce3+ for the tandem generation of H*, significantly promotes the adsorption/cleavage of Car/alk−O−Calk bonds, oxygen-atom removal, and hydrogenation of aromatic rings, ultimately catalyzing the one-step production of saturated cycloalkanes. The synergistic catalytic interplay results in a remarkable yield of saturated cycloalkanes (up to 88.2 wt%) during the CHDO of Kraft lignin, representing the highest reported value under similar conditions to date. A combination of diverse characterizations, experimental analyses, and kinetic studies collectively reinforces the notion that in-situ N-doping of CeO2 increases the electron cloud density around Ce species, forming N-Ceδ+ entities that, at high temperatures, create OVs and adjacent FLPs of N-Ce3+, collectively enhancing lignin CHDO to yield saturated cycloalkanes.

Unexpected XPS Binding Energy Observations Further Highlighted by DFT Calculations of Ruthenocene-Containing [IrIII(ppy)2(RCOCHCORc)] Complexes: Cytotoxicity and Crystal Structure of [Ir(ppy)2(FcCOCHCORc)

The series of iridium(III) complexes, [Ir(ppy)2(RCOCHCOR')], with R = CH3 and R' = CH3 (1), Rc (2), and Fc (3), as well as R = Rc and R' = Rc (4) or Fc (5), and R = R' = Fc (6), ppy = 2-phenylpyridinyl, Fc = FeII(η5-C5H4)(η5-C5H5), and Rc = RuII(η5-C5H4)(η5-C5H5), has been investigated by single-crystal X-ray crystallography and X-ray photoelectron spectroscopy (XPS) supplemented by DFT calculations. Here, in the range of 3.74 ≤ ΣχR ≤ 4.68, for Ir 4f, Ru 3d and 3p and N 1s orbitals, binding energies unexpectedly decreased with increasing ΣχR (ΣχR = the sum of Gordy group electronegativities of the R groups on β-diketonato ligands = a measure of electron density on atoms), while in Fe 2p orbitals, XPS binding energy, as expected, increased with increasing ΣχR. Which trend direction prevails is a function of main quantum level, n = 1, 2, 3…, sub-quantum level (s, p, d, and f), initial state energies, and final state relaxation energies, and it may differ from compound series to compound series. Relations between DFT-calculated orbital energies and ΣχR followed opposite trend directions than binding energy/ΣχR trends. X-ray-induced decomposition of compounds was observed. The results confirmed good communication between molecular fragments. Lower binding energies of both the Ir 4f7/2 and N 1s photoelectron lines are associated with shorter Ir-N bond lengths. Cytotoxic tests showed that 1 (IC50 = 25.1 μM) and 3 (IC50 = 37.8 μM) are less cytotoxic against HeLa cells than cisplatin (IC50 = 1.1 μM), but more cytotoxic than the free β-diketone FcCOCH2COCH3 (IC50 = 66.6 μM).

Chirality-induced phonon spin selectivity by elastic spin–orbit interaction

Spin and orbital degrees of freedom are crucial in not only fundamental particles but also classical waves such as optical systems, wherein the spin-orbit interaction (SOI) of light provides new perspectives for manipulating electromagnetic waves. Elastic waves possess similar spin angular momentum (SAM) and orbital angular momentum (OAM). However, the elastic counterpart of SOI remains unexplored, even for ubiquitous elastic waveguides (WG). Here, we demonstrate the existence of elastic SOI in helical WG. We prove that the torsion and curvature of helical WG induces synthetic gauge potentials in describing the elastic vibrations. Through analytical theory and simulations, we unveil the interplay among elastic SAM, intrinsic OAM, and extrinsic OAM, impacted by the elastic SOI. Importantly, results show that elastic SOI can introduce the Chirality-Induced Phonon Spin Selectivity. These findings advance our understanding of angular momentum physics in elastic waves and enable practical strategies for wave manipulation.

Optimizing Cu 3d Bands with Nanotubular SnO2 to Boost Their Catalytic Transfer Hydrogenation Activity.

Catalytic transfer hydrogenation (CTH) using Cu nanocatalysts offers significant advantages over direct high-pressure hydrogenation. However, the active hydrogen (H*) in this process exhibits poor adsorption and tends to release H2 readily due to the fully occupied 3d states of Cu. To address this issue, a tubular SnO2 support with electron-accepting ability was selected to host Cu nanoparticles, aiming to optimize the Cu 3d bands. The Cu/SnO2 nanohybrids were prepared through an electrospinning technique, followed by hydrothermal synthesis. As evidenced by X-ray photoelectron spectroscopy (XPS) binding energy shifts and density functional theory (DFT) simulations, some electrons from Cu transferred to SnO2 in the Cu/SnO2 nanohybrids due to their different work functions. Such electron transfer enables the Cu 3d orbitals to lose electrons and alters its valence configuration from 3d10 to 3d10-x, which enhances the adsorption of active H* atoms and thereby inhibits undesirable H2 release. The 15 wt % Cu/SnO2 exhibits improved catalytic hydrogenation of 4-nitrophenol with NaBH4, with an optimal normalized rate constant of 56.98 mg-1 min-1 and a turnover frequency of 4.82 min-1, surpassing most reported catalysts. The enhanced activity is attributed to the optimized electronic states, improved hydrogen adsorption, and the tubular structure of the support. This work might shed light on developing more non-noble metal nanocatalysts for CTH by tuning their d bands with appropriate oxide supports.

Bimetallic sulfides regulate the balance of adsorption and dissociation for polysulfides

Regulating the adsorption and dissociation equilibrium of electrocatalytic materials towards lithium polysulfides (LiPS) is a crucial yet challenging step in achieving efficient conversion and utilization of LiPS. To address this, we employed theoretical calculations and designed a carbon hollow cage (CHC) structure embedded with nano-heterostructure particles of Co9S8/Ni3S4, leveraging the dual interaction of strong adsorption from Co9S8 and high catalysis from Ni3S4. Theoretical simulations demonstrated that Co9S8, acting as an electron acceptor, forms a built-in electric field with Ni3S4, enhancing intrinsic conductivity and optimizing electron cloud structure. The Co9S8/Ni3S4 heterostructure regulated the adsorption and dissociation capabilities of LiPS, lowering Gibbs free energy. Simultaneously, three-dimensional computed tomography (3D-CT) found that the skeleton of the electrode sheet was stable before and after cycling and effectively alleviated the sulfur volume change. Multiple in-situ characterization techniques validated the in-situ phase transformation of sulfur-active materials, confirming the outstanding reversibility of the Co9S8/Ni3S4@CHC/S cathode. Especially under the high current of 5C, the capacity decay rate is only 0.021 % after 400 cycles. These findings indicate that the nano-heterostructure regulates the balance of adsorption and dissociation of LiPS, offering new insights into the control and mechanism of nano-heterostructure electronic structures.

Magnetothermal effect and first-principles calculations of Zn-doped Mn5Ge3-based alloys

This study investigates the compound system Mn5−xZnxGe3 (x = 0.1, 0.2, and 0.3) through experimental investigations and theoretical calculations. Zn doping lowers the Curie temperature and magnetic entropy change of Mn5−xZnxGe3 alloys. Analysis of phenomenological curves, including Landau theories, normalized curves, and Arrott curves during the study of isothermal magnetization curves, reveals a second-order phase transition in this system. Through an extensive investigation of critical behavior using critical isotherm curves and the Kouvel–Fisher (KF) method, the consistency and reliability of these critical indices are validated by the prediction of the scaling theory in the critical region. By scaling the dependence of |ΔSM| on M and applying crucial exponen21t values, an efficient new approach is utilized to calculate the spontaneous magnetization that agrees well with the values deduced from the KF method. Additionally, first-principles calculations reveal that the Mn atoms' 3d orbitals are more significantly close to the Fermi energy level, with Zn doping generally reducing both the electronic density of states and the total magnetic moment of the Mn 3d orbitals. Consequently, the introduction of Zn leads to a decrease in the Mn–Mn atom exchange coupling, resulting in a deterioration of the total exchange interaction. This phenomenon also explains the decrease in the Curie temperature TC due to Zn doping, aligning with experimental observations.

Regulating the Spin‐State of Cobalt in Three‐Dimensional Covalent Organic Frameworks for High‐Performance Sodium‐Iodine Rechargeable Batteries

AbstractAlthough the catalytic activity is heavily reliant on the electronic structure of the catalyst, understanding the impact of electron spin regulation on electrocatalytic performance is still rarely investigated. This work presents a novel approach involving the single‐atom coordination of cobalt (Co) within metalloporphyrin‐based three‐dimensional covalent organic frameworks (3D‐COFs) to facilitate the catalytic conversion for sodium‐iodine batteries. The spin state of Co is modulated by altering the oxidation state of the porphyrin‐centered Co, achieving optimal catalysis for iodine reduction. Experimental results demonstrate that CoII and CoIII are incorporated into the 3D‐COFs, exhibiting spin ground states of S=1/2 and S=0, respectively. The low spin state of CoIII is favorable to hybridize with the sp 3d orbitals of I3−, thus facilitating the conversion of I3− to I−. Density‐functional theory (DFT) calculations further reveal that the presence of CoIII enhances iodide adsorption and accelerates the formation of NaI in 3D‐COFs‐CoIII, thereby promoting its rapid kinetic behaviors. Notably, the I2@3D‐COFs‐CoIII cathode achieves a high reversible capacity of 227.7 mAh g−1 after 200 cycles at 0.5 C and demonstrates exceptional cyclic stability, exceeding 2000 cycles at 10 C with a minor capacity fading rate of less than one 0.01 % per cycle.

Regulating the Spin-State of Cobalt in Three-Dimensional Covalent Organic Frameworks for High-Performance Sodium-Iodine Rechargeable Batteries.

Although the catalytic activity is heavily reliant on the electronic structure of the catalyst, understanding the impact of electron spin regulation on electrocatalytic performance is still rarely investigated. This work presents a novel approach involving the single-atom coordination of cobalt (Co) within metalloporphyrin-based three-dimensional covalent organic frameworks (3D-COFs) to facilitate the catalytic conversion for sodium-iodine batteries. The spin state of Co is modulated by altering the oxidation state of the porphyrin-centered Co, achieving optimal catalysis for iodine reduction. Experimental results demonstrate that CoII and CoIII are incorporated into the 3D-COFs, exhibiting spin ground states of S=1/2 and S=0, respectively. The low spin state of CoIII is favorable to hybridize with the sp 3d orbitals of I3 -, thus facilitating the conversion of I3 - to I-. Density-functional theory (DFT) calculations further reveal that the presence of CoIII enhances iodide adsorption and accelerates the formation of NaI in 3D-COFs-CoIII, thereby promoting its rapid kinetic behaviors. Notably, the I2@3D-COFs-CoIII cathode achieves a high reversible capacity of 227.7 mAh g-1 after 200 cycles at 0.5 C and demonstrates exceptional cyclic stability, exceeding 2000 cycles at 10 C with a minor capacity fading rate of less than one 0.01 % per cycle.

Capping Effects on Spin and Charge Excitations in Parent and Superconducting Nd_{1-x}Sr_{x}NiO_{2}.

Superconductivity in infinite layer nickelates Nd_{1-x}Sr_{x}NiO_{2} has so far been achieved only in thin films, raising questions on the role of substrates and interfaces. Given the challenges associated with their synthesis it is imperative to identify their intrinsic properties. We use resonant inelastic x-ray scattering to investigate the influence of the SrTiO_{3} capping layer on the excitations of Nd_{1-x}Sr_{x}NiO_{2} (x=0 and 0.2). Spin excitations are observed in parent and 20% doped Nd_{1-x}Sr_{x}NiO_{2} regardless of capping, proving that magnetism is intrinsic to infinite-layer nickelates and appears in a significant fraction of their phase diagram. In parent and superconducting Nd_{1-x}Sr_{x}NiO_{2}, the spin excitations are slightly hardened in capped samples compared to the noncapped ones. Additionally, a weaker Ni-Nd charge transfer peak at ∼0.6 eV suggests that the hybridization between Ni 3d and Nd 5d orbitals is reduced in capped samples. From our data, capping induces only minimal differences in Nd_{1-x}Sr_{x}NiO_{2} and we phenomenologically discuss these differences based on the reconstruction of the SrTiO_{3}-NdNiO_{2} interface and other mechanisms such as crystalline disorder.

Enlarged Thickness Window and Maintained High Spin–Orbit Torque Efficiency for Metastable Tungsten by Increasing Amorphous Crystalline: A Path toward Low-Power MRAM

Enlarged Thickness Window and Maintained High Spin–Orbit Torque Efficiency for Metastable Tungsten by Increasing Amorphous Crystalline: A Path toward Low-Power MRAM

Creation of Two-Dimensional Electron Gas at the Heterointerface of CaZrO3/KTaO3 with Tunable Rashba Spin–Orbit Coupling

Creation of Two-Dimensional Electron Gas at the Heterointerface of CaZrO₃/KTaO₃ with Tunable Rashba Spin–Orbit Coupling