Precisely constructing orbital coupling-modulated iron dinuclear site for enhanced catalytic ozonation performance.

The advancement of atomically precise dinuclear heterogeneous catalysts holds great potential in achieving efficient catalytic ozonation performance and contributes to the understanding of synergy mechanisms during reaction conditions. Herein, we demonstrate a "ship-in-a-bottle and pyrolysis" strategy that utilizes Fe2(CO)9 dinuclear-cluster to precisely construct Fe2 site, consisting of two Fe1-N3 units connected by Fe-Fe bonds and firmly bonded to N-doped carbon. Systematic characterizations and theoretical modeling reveal that the Fe-Fe coordination motif markedly reduced the devotion of the antibonding state in the Fe-O bond because of the strong orbital coupling interaction of dual Fe d-d orbitals. This facilitates O-O covalent bond cleavage of O3 and enhances binding strength with reaction intermediates (atomic oxygen species; *O and *OO), thus boosting catalytic ozonation performance. As a result, Fe dinuclear site catalyst exhibits 100% ozonation efficiency for CH3SH elimination, outperforming commercial MnO2 catalysts by 1,200-fold. This research provides insights into the atomic-level structure-activity relationship of ozonation catalysts and extends the use of dinuclear catalysts in catalytic ozonation and beyond.

Orbital Coupling of PbO7 Node in Single-Crystal Metal-Organic Framework Enhances Li-O2 Battery Electrocatalysis.

Optimizing the local coordination environment of metal centers in metal-organic frameworks (MOFs) is crucial yet challenging for regulating the overpotential of lithium-oxygen (Li-O2) batteries. Herein, we report the synthesis of a class of PbO7 nodes in a single crystal MOF (naphthalene-lead-MOF, known as Na-Pb-MOF) to significantly enhance the kinetics of both discharge and charge processes. Compared to the PbO6 node in the single-crystal tetramethoxy-lead-MOF (4OMe-Pb-MOF), the bond length between Pb and O in the PbO7 node of Na-Pb-MOF increases, resulting in weaker Pb 5d-O 2p orbital coupling, which optimizes the adsorption interaction toward intermediates, and thereby promotes the rate-determining steps of both the reduction of LiO2 to Li2O2 and the oxidation of LiO2 to O2 for reducing the activation energy of the overall reaction. Consequently, Li-O2 batteries based on Na-Pb-MOF electrocatalysts exhibit a low total charge-discharge overpotential of 0.52 V and an excellent cycle life of 140 cycles.

Manipulating the Spin State of Spinel Octahedral Sites via a π-π Type Orbital Coupling to Boost Water Oxidation.

Spin state is often regarded as the crucial valve to release the reactivity of energy-related catalysts, yet it is also challenging to precisely manipulate, especially for the active center ions occupied at the specific geometric sites. Herein, a π-π type orbital coupling of 3d (Co)-2p (O)-4f (Ce) was employed to regulate the spin state of octahedral cobalt sites (CoOh) in the composite of Co3O4/CeO2. More specifically, the equivalent high-spin ratio of CoOh can reach to 54.7 % via tuning the CeO2 content, thereby triggering the average eg filling (1.094) close to the theoretical optimum value. The corresponding catalyst exhibits a superior water oxidation performance with an overpotential of 251 mV at 10 mA cm-2, rivaling most cobalt-based oxides state-of-the-art. The π-π type coupling corroborated by the matched energy levels between Ce t1u/t2u-O and CoOh t2g-O π type bond in the calculated crystal orbital Hamilton population and partial density of states profiles, stimulates a π-donation between O 2p and π-symmetric Ce 4fyz 2 orbital, consequently facilitating the electrons hopping from t2g to eg orbital of CoOh. This work offers an in-depth insight into understanding the 4f and 3d orbital coupling for spin state optimization in composite oxides.

Efficient Removal of Antibiotic Resistance Genes through 4f-2p-3d Gradient Orbital Coupling Mediated Fenton-Like Redox Processes.

Peroxymonosulfate (PMS) mediated radical and nonradical active substances can synergistically achieve the efficient elimination of antibiotic resistance genes (ARGs). However, enhancing interface electron cycling and optimizing the coupling of the oxygen-containing intermediates to improve PMS activation kinetics remains a major challenge. Here, Co doped CeVO4 catalyst (Co-CVO) with asymmetric sites was constructed based on Ce 4f-O 2p-Co 3d gradient orbital coupling. The catalyst achieved approximately 2.51×105 copies/mL of extracellular ARGs (eARGs) removal within 15 minutes, exhibited ultrahigh degradation rate (k=1.24 min-1 ). The effective gradient 4f-2p-3d orbital coupling precisely regulates the electron distribution of Ce-O-Co active center microenvironment, while optimizing the electronic structure of Co 3d states (especially the occupancy of eg ), promoting the adsorption of oxygen-containing intermediates. The generated radical and nonradical generated by interfacial electron cycling enhanced by the reduction reaction of PMS at the Ce site and the oxidation reaction at the Co site achieved a significant mineralization rate of ARGs (83.4 %). The efficient removal of ARGs by a continuous flow reactor for 10 hours significantly reduces the ecological risk of ARGs in actual wastewater treatment.

Electronic Modulation of Ru Nanosheet by d-d Orbital Coupling for Enhanced Hydrogen Oxidation Reaction in Alkaline Electrolytes.

The alkaline polymer electrolyte fuel cells (APEFCs) hold great promise for using nonnoble metal-based electrocatalysts toward the cathodic oxygen reduction reaction (ORR), but are hindered by the sluggish anodic hydrogen oxidation reaction (HOR) in alkaline electrolytes. Here, a strategy is reported to promote the alkaline HOR performance of Ru by incorporating 3d-transition metals (V, Fe, Co, and Ni), where the conduction band minimum (CBM) level of Ru can be rationally tailored through strong d-d orbital coupling. As expected, the obtained RuFe nanosheet exhibits outstanding HOR performance with the mass activity of 233.46 A gPGM -1 and 23-fold higher than the Ru catalyst, even threefold higher than the commercial Pt/C. APEFC employing this RuFe as anodic catalyst gives a peak power density of 1.2 W cm-2 , outperforming the documented Pt-free anodic catalyst-based APEFCs. Experimental results and density functional theory calculations suggest the enhanced OH-binding energy and reduced formation energy of water derived from the downshifted CBM level of Ru contribute to the enhanced HOR activity.

Unraveling the Function of Metal-Amorphous Support Interactions in Single-Atom Electrocatalytic Hydrogen Evolution.

Amorphization of the support in single-atom catalysts is a less researched concept for promoting catalytic kinetics through modulating the metal-support interaction (MSI). We modeled single-atom ruthenium (RuSAs ) supported on amorphous cobalt/nickel (oxy)hydroxide (Ru-a-CoNi) to explore the favorable MSI between RuSAs and the amorphous skeleton for the alkaline hydrogen evolution reaction (HER). Differing from the usual crystal counterpart (Ru-c-CoNi), the electrons on RuSAs are facilitated to exchange among local configurations (Ru-O-Co/Ni) of Ru-a-CoNi since the flexibly amorphous configuration induces the possible d-d electron transfer and medium-to-long range p-π orbital coupling, further intensifying the MSI. This embodies Ru-a-CoNi with enhanced water dissociation, alleviated oxophilicity, and rapid hydrogen migration, which results in superior durability and HER activity of Ru-a-CoNi, wherein only 15 mV can deliver 10 mA cm-2 , significantly lower than the 58 mV required by Ru-c-CoNi.

Highly Efficient Asymmetric Multiple Resonance Thermally Activated Delayed Fluorescence Emitter with EQE of 32.8 % and Extremely Low Efficiency Roll-Off.

Multiple resonance thermally activated delayed fluorescence (MR-TADF) emitters show great potentials for high color purity organic light-emitting diodes (OLEDs). However, the simultaneous realization of high photoluminescence quantum yield (PLQY) and high reverse intersystem crossing rate (kRISC ) is still a formidable challenge. Herein, a novel asymmetric MR-TADF emitter (2Cz-PTZ-BN) is designed that fully inherits the high PLQY and large kRISC values of the properly selected parent molecules. The resonating extended π-skeleton with peripheral protection can achieve a high PLQY of 96 % and a fast kRISC of above 1.0×105  s-1 , and boost the performance of corresponding pure green devices with an outstanding external quantum efficiency (EQE) of up to 32.8 % without utilizing any sensitizing hosts. Remarkably, the device sufficiently maintains a high EQE exceeding 23 % at a high luminance of 1000 cd m-2 , representing the highest value for reported green MR-TADF materials at the same luminescence.

Strong valley splitting ind0two-dimensional SnO induced by magnetic proximity effect.

Strong magnetic interfacial coupling in van der Waals heterostructures is important for designing novel electronic devices. Besides the most studied transition metal dichalcogenides (TMDCs) materials, we demonstrate that the valley splitting can be activated in two-dimensional tetragonald0metal oxide, SnO, via the magnetic proximity effect by EuBrO. In SnO/EuBrO, the valley splitting of SnO can reach ∼46 meV, which is comparable to many TMDCs and equivalent to an external magnetic field of 800 T. In addition, the valley splitting can be further enhanced by adjusting interlayer distance and applying uniaxial strains. A design principle of new spintronic device based on this unique electronic structure of SnO/EuBrO has been proposed. Our findings indicate that SnO is a promising material for future valleytronics applications.

Experimental Realization of Two-Dimensional Buckled Lieb Lattice.

Two-dimensional (2D) materials with a Lieb lattice host exotic electronic band structures. Such a system does not exist in nature, and it is also difficult to obtain in the laboratory due to its structural instability. Here, we experimentally realized a 2D system composed of a tin overlayer on an aluminum substrate by molecular beam epitaxy. The specific arrangement of Sn atoms on the Al(100) surface, which benefits from favorable interface interactions, forms a stabilized buckled Lieb lattice. Theoretical calculations indicate a partially broken nodal line loop and a topologically nontrivial insulating state with a spin-orbital coupling effect in the band structure of this Lieb lattice. The electronic structure of this system is experimentally characterized by angle-resolved photoemission spectroscopy, in which the hybridized states between topmost Al atoms and Sn atoms are revealed. Our work provides an appealing method for constructing 2D quantum materials based on the Lieb lattice.

Electron-Lattice Coupling in Correlated Materials of Low Electron Occupancy.

In correlated materials including transition metal oxides, electronic properties and functionalities are modulated and enriched by couplings between the electron and lattice degrees of freedom. These couplings are controlled by external parameters such as chemical doping, pressure, magnetic and electric fields, and light irradiation. However, the electron-lattice coupling relies on orbital characters, i.e., symmetry and occupancy, of t2g and eg orbitals, so that a large electron-lattice coupling is limited to eg electron system, whereas t2g electron system exhibits an inherently weak coupling. Here, we design and demonstrate a strongly enhanced electron-lattice coupling in electron-doped SrTiO3, that is, the t2g electron system. In ultrathin films of electron-doped SrTiO3 [i.e., (La0.25Sr0.75)TiO3], we reveal the strong electron-lattice-orbital coupling, which is manifested by extremely increased tetragonality and the corresponding metal-to-insulator transition. Our findings open the way of an active tuning of the charge-lattice-orbital coupling to obtain new functionalities relevant to emerging nanoelectronic devices.

Giant Tunability of the Two-Dimensional Electron Gas at the Interface of γ-Al2O3/SrTiO3.

Two-dimensional electron gases (2DEGs) formed at the interface between two oxide insulators provide a rich platform for the next generation of electronic devices. However, their high carrier density makes it rather challenging to control the interface properties under a low electric field through a dielectric solid insulator, that is, in the configuration of conventional field-effect transistors. To surpass this long-standing limit, we used ionic liquids as the dielectric layer for electrostatic gating of oxide interfaces in an electric double layer transistor (EDLT) configuration. Herein, we reported giant tunability of the physical properties of 2DEGs at the spinel/perovskite interface of γ-Al2O3/SrTiO3 (GAO/STO). By modulating the carrier density thus the band filling with ionic-liquid gating, the system experiences a Lifshitz transition at a critical carrier density of 3.0 × 1013 cm-2, where a remarkably strong enhancement of Rashba spin-orbit interaction and an emergence of Kondo effect at low temperatures are observed. Moreover, as the carrier concentration depletes with decreasing gating voltage, the electron mobility is enhanced by more than 6 times in magnitude, leading to the observation of clear quantum oscillations. The great tunability of GAO/STO interface by EDLT gating not only shows promise for design of oxide devices with on-demand properties but also sheds new light on the electronic structure of 2DEG at the nonisostructural spinel/perovskite interface.

Quantifying van der Waals Interactions in Layered Transition Metal Dichalcogenides from Pressure-Enhanced Valence Band Splitting.

van der Waals (vdW) forces, despite being relatively weak, hold the layers together in transition metal dichalcogenides (TMDs) and play a key role in their band structure evolution, hence profoundly affecting their physical properties. In this work, we experimentally probe the vdW interactions in MoS2 and other TMDs by measuring the valence band maximum (VBM) splitting (Δ) at K point as a function of pressure in a diamond anvil cell. As high pressure increases interlayer wave function coupling, the VBM splitting is enhanced in 2H-stacked MoS2 multilayers but, due to its specific geometry, not in 3R-stacked multilayers, hence allowing the interlayer contribution to be separated out of the total VBM splitting, as well as predicting a negative pressure (2.4 GPa) where the interlayer contribution vanishes. This negative pressure represents the threshold vdW interaction beyond which neighboring layers are electronically decoupled. This approach is compared to first-principles calculations and found to be widely applicable to other group-VI TMDs.

Large Tunable Spin-to-Charge Conversion in Ni80Fe20/Molybdenum Disulfide by Cu Insertion.

Spin-to-charge conversion at the interface between magnetic materials and transition metal dichalcogenides has drawn great interest in the research efforts to develop fast and ultralow power consumption devices for spintronic applications. Here, we report room temperature observations of spin-to-charge conversion arising from the interface of Ni80Fe20 (Py) and molybdenum disulfide (MoS2). This phenomenon can be characterized by the inverse Edelstein effect length (λIEE), which is enhanced with decreasing MoS2 thicknesses, demonstrating the dominant role of spin-orbital coupling (SOC) in MoS2. The spin-to-charge conversion can be significantly improved by inserting a Cu interlayer between Py and MoS2, suggesting that the Cu interlayer can prevent magnetic proximity effect from the Py layer and protect the SOC on the MoS2 surface from exchange interactions with Py. Furthermore, the Cu-MoS2 interface can enhance the spin current and improve electronic transport. Our results suggest that tailoring the interface of magnetic heterostructures provides an alternative strategy for the development of spintronic devices to achieve higher spin-to-charge conversion efficiencies.

Anisotropic Melting Path of Charge-Ordering Insulator in LSMO/STO Superlattice.

Multiple phases coexist in manganite with simultaneously active couplings, and the transition among them depends on the relative intensities of different interactions. However, the melting path with variable intensities is unclear. The concentration and the ordering of oxygen vacancy in previous work are found to induce ferromagnetic charge-ordering insulator phase in [(La0.7 Sr0.3 MnO3 )10 /(SrTiO3 )5 ]n superlattice, which translates into metallic phase with magnetic field H and temperature T. In the current work, the H-T phase diagram for current I//[100] and I//[110] shows a large difference with H normal to the film plane, which is ascribed to the response of a variable range of hopping process to H with the in-plane anisotropic hopping probability of charge carrier. With H rotating from the out-of-plane to the in-plane direction, the preferred occupancy of the 3 d z 2 - r 2 $3{d}_{{z}^2 - {r}^2}$ orbital causes a decrease of spin-orbital coupling and lowers the activation energy, inducing a gentler melting process of a charge-ordering insulator. This work shows that the melting path of a charge-ordering insulator phase can be largely modulated in manganite with anisotropy.

Magnetic Properties and Microstructure of FePt(BN, X, C) (X = Ag, Re) Films.

A sputtered FePt(BN, Re, C) film, here boron nitride (BN), was compared to a reference sample FePt(BN, Ag, C). Intrinsically, these films illustrate a high anisotropy field (Hk) and perpendicular magnetocrystalline anisotropy (Ku),although the reference sample shows a higher value (Hk = 69.5 kOe, Ku = 1.74 × 107 erg/cm3) than the FePt(BN, Re, C) film (Hk = 66.9 kOe, Ku = 1.46 × 107 erg/cm3). However, the small difference in the anisotropy constant (K2/K1) ratio presents a close tendency in the angular dependence of the switching field. Extrinsically, the out-of-plane coercivity for the reference sample is 32 kOe, which is also higher than the FePt(BN, Re, C) film (Hc = 27 kOe), and both films present lower remanence (Mr(parallel)/Mr(perpendicular) = 0.08~0.12), that is, the index for perpendicular magnetic anisotropy. The higher perpendicular magnetization for both films was due to highly (001) textured FePt films, which was also evidenced by the tight rocking width of 4.1°/3.0° for (001)/(002) X-ray diffraction peaks, respectively, and high-enough ordering degree. The reference sample was measured to have a higher ordering degree (S = 0.84) than FePt(BN, Re, C) (S = 0.63). As a result, the Ag segregant shows stronger ability to promote the ordering of the FePt film; however, the FePt(BN, Re, C) film still has comparable magnetic properties without Ag doping. From the surface and elemental composition analysis, the metallic Re atoms found in the FePt lattice result in a strong spin-orbital coupling between transition metal Fe (3d electron) and heavy metals (Re, Pt) (5d electron) and we conducted high magnetocrystalline anisotropy (Ku). Above is the explanation that the lower-ordered FePt(BN, Re, C) film still has high-enough Ku and out-of-plane Hc. Regarding the microstructure, both the reference sample and FePt(BN, Re, C) show granular structure and columnar grains, and the respective average grain size and distributions are 6.60 nm (12.5%) and 11.2 nm (15.9%). The average widths of the grain boundaries and the aspect ratio of the columnar grain height are 2.05 nm, 1.00 nm, 2.35 nm, and 1.70 nm, respectively.

Spin-Selective Coupling in Mott-Schottky Er2 O3 -Co Boosts Electrocatalytic Oxygen Reduction.

Alkaline oxygen reduction reaction (ORR) is critical to electrochemical energy conversion technology, yet the rational breaking of thermodynamic inhibition for ORR through spin regulation remains a challenge. Herein, a Mott-Schottky catalyst consisting of Er2 O3 -Co particles uniformly implanted into carbon nanofibers (Er2 O3 -Co/CNF) is designed for enhancing ORR via spin-selective coupling. The optimized Er2 O3 -Co/CNF affords a high half-wave potential (0.835 V vs reversible hydrogen electrode, RHE) and onset potential (0.989 VRHE ) for the ORR surpassing individual Co/CNF and Er2 O3 /CNF. Theoretical calculations reveal the introduction of Er2 O3 optimizes the electronic structure of Co through Er(4f)-O(2p)-Co(3d) gradient orbital coupling, resulting in significantly enhanced ORR performance. Through gradient orbital coupling, the induced spin-up hole in Co 3d states endows the Er-O-Co unit active site with a spin-selective coupling channel for electron transition. This favors the decrease of the energy gap in the potential-limiting step, thus achieving a high theoretical limiting potential of 0.77 VRHE for the Er2 O3 -Co. Moreover, the potential practicability of Er2 O3 -Co/CNF as an air-cathode is also demonstrated in Zn-air batteries. This work is believed to provide, new perspectives for the design of efficient ORR electrocatalysts by engineering spin-selective coupling induced by rare-earth oxides.

Reinforcing CoO Covalency via Ce(4f)─O(2p)─Co(3d) Gradient Orbital Coupling for High-Efficiency Oxygen Evolution.

Rare-earth (RE)-based transition metal oxides (TMO) are emerging as a frontier toward the oxygen evolution reaction (OER), yet the knowledge regarding their electrocatalytic mechanism and active sites is very limited. In this work, atomically dispersed Ce on CoO is successfully designed and synthesized by an effective plasma (P)-assisted strategy as a model (P-Ce SAs@CoO) to investigate the origin of OER performance in RE-TMO systems. The P-Ce SAs@CoO exhibits favorable performance with an overpotential of only 261 mV at 10 mA cm-2 and robust electrochemical stability, superior to individual CoO. X-ray absorption spectroscopy and in situ electrochemical Raman spectroscopy reveal that the Ce-induced electron redistribution inhibits CoO bond breakage in the CoOCe unit site. Theoretical analysis demonstrates that the gradient orbital coupling reinforces the CoO covalency of the Ce(4f)─O(2p)─Co(3d) unit active site with an optimized Co-3d-eg occupancy, which can balance the adsorption strength of intermediates and in turn reach the apex of the theoretical OER maximum, in excellent agreement with experimental observations. It is believed that the establishment of this Ce-CoO model can set a basis for the mechanistic understanding and structural design of high-performance RE-TMO catalysts.

Propagation Characteristics of Circular Airy Vortex Beams in a Uniaxial Crystal along the Optical Axis.

Circular airy vortex beams (CAVBs) have attracted much attention due to their "abruptly autofocusing" effect, phase singularity, and their potential applications in optical micromanipulation, communication, etc. In this paper, we numerically investigated the propagation properties of circular airy beams (CABs) imposed with different optical vortices (OVs) along the optical axis of a uniaxial crystal for the first time. Like other common beams, a left-hand circular polarized (LHCP) CAVB, propagating along the optical axis in a uniaxial crystal, can excite a right-hand circular polarized (RHCP) component superimposed with an on-axis vortex of topological charge (TC) number of 2. When the incident beam is an LHCP CAB imposed with an on-axis vortex of TC number of l = 1, both of the two components have an axisymmetric intensity distribution during propagation and form hollow beams near the focal plane because of the phase singularity. The phase pattern shows that the LHCP component carries an on-axis vortex of TC number of l = 1, while the RHCP component carries an on-axis vortex of TC number of l = 3. With a larger TC number (l = 3), the RHCP component has a larger hollow region in the focal plane compared to the LHCP component. We also studied cases of CABs imposed with one and two off-axis OVs. The off-axis OV makes the CAVB's profile remain asymmetric throughout the propagation. As the propagation distance increases, the off-axis OVs move near the center of the beam and overlap, resulting in a special intensity and phase distribution near the focal plane.

Topological properties of Xene tuned by perpendicular electric field and exchange field in the presence of Rashba spin-orbit coupling.

Xene (X=Si, Ge, Sn) is a typical and promising two-dimensional topological insulator with many novel topological properties. Here, we investigate the topological properties of Xene tuned by a perpendicularly applied electric field, exchange field, and Rashba spin-orbit coupling (RSOC) using the tight-binding (TB) method. We show that in the presence of RSOC, the system can be converted from a quantum spin Hall (QSH) insulator into a conventional band insulator (BI) by a weak perpendicular electric field or into a quantum anomalous Hall (QAH) insulator by a weak exchange field. Additionally, a suitable combination of electric and exchange fields can give rise to a valley-polarized metallic (VPM) state. Furthermore, we explore the competition between the electric field and exchange field in tuning the topological states owing to the Rashba coupling effect. When the electric field is stronger than the exchange field, the system tends to be in a topologically trivial BI state; otherwise, it will be a QAH insulator. More intriguingly, for a fixed exchange field and RSOC, as the perpendicular electric field increase continuously from zero, the system undergoes multiphase (e.g. QSH-VPM-BI) transitions. This paves the way for designing multiphase transition devices through external single-field regulation.

Highly Crowded Twisted Thienylene-Phenylene Structures: Evidence for Through-Space Orbital Coupling in a [4]Catenated Topology.

Sterically highly crowded and twisted thienylene-phenylenes are synthesized and structurally characterized. Single-crystal X-ray structure analyses and theoretical studies give evidence of through-space delocalization of π-electrons of peripheral (hetero)aromatic rings in toroidal and catenated topology.