Unique Electronic Structure Research Articles

Origin of unique electronic structures of single-atom alloys unraveled by interpretable deep learning.

We uncover the origin of unique electronic structures of single-atom alloys (SAAs) by interpretable deep learning. The approach integrates tight-binding moment theory with graph neural networks to accurately describe the local electronic structure of transition and noble metal sites upon perturbation. We emphasize the complex interplay of interatomic orbital coupling and on-site orbital resonance, which shapes the d-band characteristics of an active site, shedding light on the origin of free-atom-like d-states that are often observed in SAAs involving d10 metal hosts. This theory-infused neural network approach significantly enhances our understanding of the electronic properties of single-site catalytic materials beyond traditional theories.

Synthesis of Dibenzoazulene Derivatives via Pd‐Catalyzed (3+2) Alkyne Annulation of Dibenzosuberenone

AbstractNon‐benzenoid PAHs with pentagon/heptagon pairs have unique electronic structures and promising opto‐electronic properties. However, the construction of pentagon/heptagon pair units in these PAHs is challenging. Herein, we developed a Pd‐catalyzed (3+2) alkyne annulation reaction of heptagons, and constructed heptagon/pentagon pairs. The substrate scope is wide and the yield is good to moderate. A series of dibenzoauzlene derivatives were synthesized and their opto‐electronic properties were systematically studied by UV‐vis absorption and cyclic voltammetry. In addition, the dibenzoazulene derivative was further transformed to tropylium cation and tropyl radical, which showed bathochromic shifted absorption and switched aromaticity.

Recent Progress in Non-Noble Metal Catalysts for Oxygen Evolution Reaction: A Focus on Transition and Rare-Earth Elements.

The demand for renewable energy sources has become more urgent due to climate change and environmental pollution. The oxygen evolution reaction (OER) plays a crucial role in green energy sources. This article primarily explores the potential of using non-noble metals, such as transition and rare earth metals, to enhance the efficiency of the OER process. Due to their cost-effectiveness and unique electronic structure, these non-noble metals could be a game-changer in the field. 'Doping,' which is the process of adding a small amount of impurity to a material to alter its properties, and 'synergistic effects,' which refer to the combined effect of two or more elements that is greater than the sum of their individual effects, are two key concepts in this field. Transition and rare earth metals can reduce the overpotential, a measure of the excess potential required to drive a reaction, thus enhancing the OER process by engineering the electronic and surface molecular structure. This article summarizes the roles of various non-noble metals in the OER process and highlights opportunities for researchers to propose innovative ways to optimize the OER process.

Regulatory Mechanisms and Applications of Rare Earth Elements‐Based Electrocatalysts†

Comprehensive SummaryAmidst the pressing environmental challenges posed by the prevalent reliance on fossil fuels, it becomes imperative to seek sustainable alternatives and prioritize energy efficiency. Electrocatalysis, which is renowned for its high efficiency and environmental friendliness, has garnered significant attention. Rare earth elements (REEs), distinguished by their unique electronic and orbital structures, play a crucial role in electrocatalysis. The strategic integration of REEs into catalysts allows for the fine‐tuning of atomic structures, which in turn, significantly boosts catalytic performance. Despite substantial advancements in rare earth‐based materials for electrocatalysis, a comprehensive overview of the regulatory mechanisms involving REEs is lacking. In this mini‐review, we systematically explore the regulatory mechanisms of REEs within electrocatalysts and their pivotal roles in essential electrocatalytic processes such as the CO2 reduction reaction, oxygen reduction reaction, and hydrogen evolution reaction. We commence with an elucidation of REEs, proceed to delineate their regulatory impacts on electrocatalysts and delve into their applications in key electroreduction reactions. We conclude with discussions on current limitations and prospects for further advancements in this burgeoning field of research. Key Scientists

Designing Robust Single Atom Catalysts by Three-in-One Strategy: Sub-1-nm Space Confining, Bimetallic Bonding and Reaction-Induced Forming Active Sites.

It is imperative to design robust single atom catalysts (SACs) that maintain the stability of the active component under diverse reaction conditions and prevent aggregation or deactivation. Confining the single atom active site within sub-nanometer (sub-1-nm) spaces has proven effective in enhancing the stability and activity of the catalyst, owing to the strong constraints and regulations imposed on atomic behavior at this scale. Bimetallic bond atomic sites, comprising two distinct metal compositions, often exhibit unique electronic structures and catalytic properties. Designing SACs under reaction-induced conditions, such as varying temperatures, pressures, and atmospheres, can facilitate a deeper understanding of the formation and migration behavior of active sites in real reactions, as well as the optimization mechanisms for performance enhancement. The objective of this review is to promote a robust SAC design strategy that encapsulates bimetallic bonding active sites within sub-1-nm spaces and investigates catalyst preparation and performance under reaction-induced conditions. This design strategy is anticipated to bolster the catalytic activity and stability of the catalyst while also offering fresh perspectives and optimization avenues for the catalytic processes involved in practical chemical reactions.

Rare-Earth Metal-Based Materials for Hydrogen Storage: Progress, Challenges, and Future Perspectives.

Rare-earth-metal-based materials have emerged as frontrunners in the quest for high-performance hydrogen storage solutions, offering a paradigm shift in clean energy technologies. This comprehensive review delves into the cutting-edge advancements, challenges, and future prospects of these materials, providing a roadmap for their development and implementation. By elucidating the fundamental principles, synthesis methods, characterization techniques, and performance enhancement strategies, we unveil the immense potential of rare-earth metals in revolutionizing hydrogen storage. The unique electronic structure and hydrogen affinity of these elements enable diverse storage mechanisms, including chemisorption, physisorption, and hydride formation. Through rational design, nanostructuring, surface modification, and catalytic doping, the hydrogen storage capacity, kinetics, and thermodynamics of rare-earth-metal-based materials can be significantly enhanced. However, challenges such as cost, scalability, and long-term stability need to be addressed for their widespread adoption. This review not only presents a critical analysis of the state-of-the-art but also highlights the opportunities for multidisciplinary research and innovation. By harnessing the synergies between materials science, nanotechnology, and computational modeling, rare-earth-metal-based hydrogen storage materials are poised to accelerate the transition towards a sustainable hydrogen economy, ushering in a new era of clean energy solutions.

Antiaromatic 2-Azaboroles with π4σ2 Electronic Configuration.

Similar to pyridine, which is a structural analog of benzene, 2-azaborole can be viewed as a structural analog of borole, in which the CH group at the 2-position is replaced by an N atom. Due to its unique π4σ2 electronic configuration, it should exhibit Lewis acidity, antiaromaticity, as well as Lewis basicity simultaneously. However, this uniqueness also makes its synthesis and isolation particularly challenging. One anticipated issue is its readiness for self-dimerization. This work proposes 2-azaborole and targets the synthesis and characterization of its derivatives for the first time. By reacting benzoborirene C6H4{BN(SiMe3)2} with bulky nitriles, crystalline benzo-fused 2-azaboroles have been successfully achieved and fully characterized. The importance of steric hindrance has been experimentally verified, showing that insufficient kinetic protection results in the dimerization of benzo-fused 2-azaboroles to form BN-allenophanes, a class of 10-membered macrocyclic compounds featuring two BN-allene units. The unique electronic structure of 2-azaborole as well as the mechanism of dimerization has been corroborated by theoretical calculations. In addition, its ability to act both as a Lewis acid and a Lewis base is demonstrated through its reaction with 1,3-diisopropyl-4,5-dimethylimidazolin-2-ylidene (MeIiPr) and AlCl3, respectively, which also implies the potential of the 2-azaborole motif as a σ-donor ligand for main group and organometallic chemistry.

Engineering of in-plane SnS2–SnO2 nanosheets heterostructures for enhanced H2S sensing

In-plane heterostructures has attracted considerable interest due to exceptional electron transport properties, high specific surface area, and abundant active sites. However, synthesis of in-plane SnS2–SnO2 heterostructures are rarely reported, and the deep investigation of the fine structure on reactivity is of great significance. Here, we propose partial in-situ oxidation strategy to construct the in-plane SnS2–SnO2 heterostructures and the surface properties, the ratio of two components can be finely tuned by precisely adjusting the treatment temperature. In particular, the SnS2–SnO2 heterostructures formed after annealing of SnS2 nanosheets at 350 °C exhibits a unique electronic structure and surface properties due to rich grain boundaries, which exhibits excellent gas sensing performance to H2S (Ra/Rg = 169.81 for 5 ppm H2S at 160 °C, fast response and recovery dynamic (41/101 s), excellent reliability (σ = 0.01) and sensing stability (φ = 0.11 %)). Notably, the in-plane heterostructures endow the material with abundant grain boundaries and effectively regulates the electronic structure of the Sn p-orbital, which facilitate the formation of active oxygen species (O−(ad)), thus contributing to the sensing performance. Our work provides a promising platform to design in-plane heterostructures for various advanced applications.

Embedding Reverse Electron Transfer Between Stably Bare Cu Nanoparticles and Cation-Vacancy CuWO4.

Cu nanoparticles (NPs) have attracted widespread attention in electronics, energy, and catalysis. However, conventionally synthesized Cu NPs face some challenges such as surface passivation and agglomeration in applications, which impairs their functionalities in the physicochemical properties. Here, the issues above by engineering an embedded interface of stably bare Cu NPs on the cation-vacancy CuWO4 support is addressed, which induces the strong metal-support interactions and reverse electron transfer. Various atomic-scale analyses directly demonstrate the unique electronic structure of the embedded Cu NPs with negative charge and anion oxygen protective layer, which mitigates the typical degradation pathways such as oxidation in ambient air, high-temperature agglomeration, and CO poisoning adsorption. Kinetics and in situ spectroscopic studies unveil that the embedded electron-enriched Cu NPs follow the typical Eley-Rideal mechanism in CO oxidation, contrasting the Langmuir-Hinshelwood mechanism on the traditional Cu NPs. This mechanistic shift is driven by the Coulombic repulsion in anion oxygen layer, enabling its direct reaction with gaseous CO to form the easily desorbed monodentate carbonate.

Research Progress of Deep-Red to Near-Infrared Electroluminescent Materials Based on Organic Cyclometallated Platinum(II) Complexes.

In recent years, the near-infrared (NIR) light-emitting materials have attracted increasing attention due to the broad application prospects in the fields of military industry, aerospace, lighting, display and wearable devices. As the transition metal complexes, platinum(II) complexes have been shown to emit luminescence efficiently in NIR organic light-emitting diodes because of the unique d8 electron structure. This structure ensures that the platinum(II) complex molecules exhibit a high planarity, variety of excited states, and strong intermolecular interactions. This review summarizes the research progress of deep red to NIR organic light-emitting materials based on platinum(II) complexes in recent years and provides a certain reference for the further design and synthesis of NIR platinum(II) complex luminescent materials with superior performance.

S-Modified Graphitic Carbon Nitride with Double Defect Sites For Efficient Photocatalytic Hydrogen Evolution.

Graphitic carbon nitride (gC3N4) is an attractive photocatalyst for solar energy conversion due to its unique electronic structure and chemical stability. However, gC3N4 generally suffers from insufficient light absorption and rapid compounding of photogenerated charges. The introduction of defects and atomic doping can optimize the electronic structure of gC3N4 and improve the light absorption and carrier separation efficiency. Herein, the high efficiency of carbon nitride photocatalysis for hydrogen evolution in visible light is achieved by an S-modified double-deficient site strategy. Defect engineering forms abundant unsaturated sites and cyano (─C≡N), which promotes strong interlayer C─N bonding interactions and accelerates charge transport in gC3N4. S doping tunes the electronic structure of the semiconductors, and the formation of C─S─C bonds optimizes the electron-transfer paths of the C─N bonding, which enhances the absorption of visible light. Meanwhile,C≡N acts as an electron trap to capture photoexcited electrons, providing the active site for the reduction of H+ to hydrogen. The photocatalytic hydrogen evolution efficiency of SDCN (1613.5µmolg-1h-1) is 31.5 times higher than that of pristine MCN (51.2µmolg-1h-1). The charge separation situation and charge transfer mechanism of the photocatalysts are investigated in detail by a combination of experimental and theoretical calculations.

Hierarchically Ordered Pore Engineering of Carbon Supports with High-Density Edge-Type Single-Atom Sites to Boost Electrochemical CO2 Reduction.

Metal sites at the edge of the carbon matrix possess unique geometric and electronic structures, exhibiting higher intrinsic activity than in-plane sites. However, creating single-atom catalysts with high-density edge sites remains challenging. Herein, the hierarchically ordered pore engineering of metal-organic framework-based materials to construct high-density edge-type single-atomic Ni sites for electrochemical CO2 reduction reaction (CO2RR) is reported. The created ordered macroporous structure can expose enriched edges, further increased by hollowing the pore walls, which overcomes the low edge percentage in the traditional microporous substrates. The prepared single-atomic Ni sites on the ordered macroporous carbon with ultra-thin hollow walls (Ni/H-OMC) exhibit Faraday efficiencies of CO above 90% in an ultra-wide potential window of 600mV and a turnover frequency of 3.4×104h-1, much superior than that of the microporous material with dominant plane-type sites. Theory calculations reveal that NiN4 sites at the edges have a significantly disrupted charge distribution, forming electron-rich Ni centers with enhanced adsorption ability with *COOH, thereby boosting CO2RR efficiency. Furthermore, a Zn-CO2 battery using the Ni/H-OMC cathode shows an unprecedentedly high power density of 15.9mW cm-2 and maintains an exceptionally stable charge-discharge performance over 100h.

Alkali-Stable Metal-Organic Frameworks with Enhanced Electroconductivity for Black-Brown Electrochromic Energy Storage Smart Window.

Metal-organic frameworks (MOFs) deliver potential applications in electrochromism and energy storage. However, the poor intrinsic conductivity of MOFs in electrolytes seriously hampers the development of the above-mentioned electrochemical applications, especially in one MOF electrode. Herein, a new Ni-based MOF (denoted Ni-DPNDI) is proposed with enhanced conductivity by π-delocalized DPNDI connectors. Predictably, the obtained Ni-DPNDI MOF achieves a conductivity of up to 4.63 S∙m-1 at 300 K. Profiting from its unique electronic structure, the Ni-DPNDI MOF delivers excellent electrochromic and energy storage performance with a great optical modulation (60.8%), a fast switching speed (tc = 7.9 s and tb = 6.4 s), a moderate specific capacitance (25.3 mAh·g-1) and good cycle stability over 2000 times. Meanwhile, energy storage capacity is visual by the coloration states of Ni-DPNDI film. As a proof of the potential application, a large-area (100 cm2) electrochromic energy storage smart window is further designed and displayed. The strategy provides an interesting alternative to porous multifunctional materials for the new generation of electronic devices with diverse applications.

Anion substitution strategy for constructing abundant oxygen vacancies in perovskites enables efficient nitrate electroreduction

Perovskite oxides have emerged as promising candidates for electrocatalytic nitrate reduction (ERN) catalysts due to their unique electronic structures and tunable chemical compositions. In this work, we employed a fluorine ion substitution strategy to modulate the oxygen site of LaCoO3 (LCO), resulting in the construction of F-substituted LaCoO3 (LCOF0.5) catalyst for efficient ERN. The incorporation of fluorine ions leads to a weakening of the hybridization between the O 1 s orbital and Co 3d orbital of the catalyst, thereby inducing an increase in oxygen vacancies. The abundant oxygen vacancies can facilitate the electron transfer and surface adsorption energy of the ERN reaction intermediates. This leads to a reduction in the energy barriers for both the reduction of *HNO3 to *NO2 and the reduction of *HNO2 to *NO, thereby enhancing the performance of ERN. As excepted, LCOF0.5 exhibits a rapid reaction rate of k = 5.48 × 10−3 min−1, which is 1.70 times faster than that of pristine LCO, and its catalytic activity approaches that of the state-of-the-art electrocatalysts for ERN. Applying this strategy to LaFeO3 and LaMnO3 also yields similar results, demonstrating its general applicability. The F-anion substitution strategy offers new opportunities for significantly enhancing ERN performance.

Molybdenum carbide nanosheets with iron doping as electrocatalysts for highly efficient ammonia electrosynthesis

The electrochemical reduction of nitrogen to ammonia represents a greener alternative to the Haber-Bosch process, demanding a shift towards low-cost and high-efficiency electrocatalysts. Recent advances in research have demonstrated the potential of molybdenum carbide-based catalysts to have their unique electronic structure and physicochemical properties. This study introduces ultrathin iron-doped molybdenum carbide nanosheets (Fe-MoC) as a novel catalyst for ammonia electrosynthesis. Demonstrating a remarkable ammonia production rate of 16 µg h−1 mg−1 and a Faradaic efficiency (FE) of approximately 13 % at −0.2 V, our synthesized Fe-MoC nanosheets stand out for their superior catalytic activity and selectivity towards nitrogen activation. The indophenol technique was employed to identify the generation of NH3 in our experiments, followed by UV–vis spectrometry for quantitative analysis. Additionally, various characterization techniques, including XRD, Raman, and XPS, were used to analyze the material structure and surface properties. Through comprehensive characterization and electrochemical studies, we reveal the pivotal role of iron doping in enhancing the electrocatalytic performance for nitrogen reduction reaction (NRR), offering insights into the mechanistic pathways facilitated by Fe-MoC. The future development and perspective of Fe-MoC towards high performance are proposed.

Growth and electronic structure of the nodal line semimetal in monolayer Cu2Si on Cu(111)

Cu2Si, a single-layer two-dimensional material with a honeycomb structure, has been proposed to have Dirac nodal line fermions. In this study, the synchrotron radiation X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and angle-resolved photoemission spectroscopy (SR-XPS, SR-UPS, and SR-ARPES) techniques were used to investigate the dynamic process of in situ deposition of single-layer Cu2Si on a Cu(111) crystal surface via molecular beam epitaxy (MBE). Cu2Si existed as a monolayer (ML) alloy, and there were competing mechanisms of distinct chemical states of silicon in different growth periods, according to a detailed examination of the experimental SR-XPS and SR-UPS spectra. Additionally, a weak interaction between the Cu2Si ML and Cu(111) was demonstrated via SR-ARPES and first-principles computations. The unique electronic structure of the Cu2Si ML was not destroyed by either this weak interaction or the disordered silicon produced on the surface during the growth process. The study of the Cu2Si growth kinetics provides a guarantee and a basis for the future exploration of the exotic properties of Cu2Si.

Weakening O-Intermediates Adsorption Strength Over the Pd Metallene via Lewis-Acidic Site Modulation for Enhanced Oxygen Reduction.

The reasonable design and modulation of the electronic properties of Pd metallene are acknowledged as a promising avenue for enhancing the oxygen reduction reaction (ORR) in anion exchange membrane fuel cells (AEMFCs), yet they remain a formidable challenge. Herein, a thin-sheet structure of Zr-doped Pd metallene (PdZr metallene) with abundant defects is proposed using a facile wet-chemical approach for efficient and highly durable ORR electrocatalysis. Multiple microstructural analyses uncover that orchestrated electronic and oxophilic regulation of PdZr metallene via Lewis-acidic Zr site modulation could concurrently optimize the electronic configuration of Pd, downshift the d-band center of Pd, and, thus, promote the intrinsic activity. Benefiting from the unique two-dimensional morphology and electronic structure optimization facilitated by the Zr coupling effect, the resultant PdZr metallene demonstrates significantly enhanced ORR electrocatalytic performance in basic solutions, with a high half-wave potential (E1/2) of 0.87 V and commendable stability for 30 000 s, surpassing those of Pd metallene and various advanced Pd-based catalysts reported in the literature. Encouragingly, the PdZr metallene-based AEMFC achieves an increased maximum power density (90.4 mW cm-2) and impressive robustness over 12 h in an alkaline environment, manifesting the practical application of PdZr metallene in AEMFCs. This study showcases the applicability of PdZr metallene via Lewis acid site regulation for fabricating highly active electrocatalysts for high-performance AEMFCs.

Tunable spin splitting of reflected vortex-beam of Weyl semimetal metasurface with stronger optical activity

This work investigated the spin splitting of a reflected beam with a vortex beam irradiating on a metasurface. This metasurface structure is the periodically rectangular-groove array of ionic crystal, where the array is a sub-wavelength grating with its periodical direction situated in the surface plane. In the grating structure, we embedded magnetic Weyl semimetals. Consequently, a stronger optical activity can be found, which originates from the unique electronic structure of Weyl semimetals and the orientation of the grating arrangement. By controlling the separation of Weyl points and grating orientation, we observe notable asymmetric spin splitting in different frequency ranges with distinctly unique distributions. Significant spin splitting was observed to be correlated with substantial Kerr rotation angles and reflectance differences, indicating strong optical activity. Additionally, with the increasing topological charges, the spin splitting increases significantly. Our results are useful for the manipulation of infrared radiations and infrared optical detection.

Recent progress in the synthesis and electrocatalytic application of MXene‐based metal phosphide composites

AbstractIn the domain of novel catalyst design and application, metal phosphides have attracted widespread interest due to their unique electronic structure and potential catalytic activity. Various types of supports that can effectively anchor metal phosphides have been reported, among which MXene have received significant attention due to their two‐dimensional (2D) structure, adjustable composition, and composite variability. This work mainly aims to elucidate the preparation of novel MXene carriers and their unique roles in loading metal phosphides and participating in catalytic reactions. We will clarify the preparation strategy of MXene, the interaction between metal phosphides and MXene carriers, to explain the stabilization of metal phosphide active sites and the rational adjustment of electronic structure. In addition, we will comprehensively summarize recent research progress of MXene‐based metal phosphide composites, with particular emphasis on advancements in the synergistic effect of heterostructures. Regarding applications, we review the utilization of MXene‐based metal phosphide composites in electrocatalysis, including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). Finally, some fundamental challenges and prospects for the efficient electrocatalysis of MXene‐based metal phosphide composites are introduced.

INVESTIGATION OF X-RAY EMISSION FROM LASER PRODUCED ALUMINIUM ANTIMONIDE PLASMA

Lasers are integral to numerous applications in our daily lives, with one of their notable uses being the ablation of materials to generate plasma, which in turn produces X-rays with a variety of applications. This study investigates the generation of hard X-rays from Aluminum Antimonide (AlSb) plasma, induced by a Q-switched Nd: YAG laser operating at 1064[Formula: see text]nm with a pulse duration of 9–14[Formula: see text]ns and a peak power of 1.1[Formula: see text]MW. The AlSb target was selected due to its unique electronic structure and high atomic number, which are advantageous for efficient X-ray generation. At a tight focus, the laser produced a spot size of 11.8 micrometers, achieving an intensity of 1012 W/cm[Formula: see text], to study the transmission of hard X-rays both in a vacuum environment with a pressure of 10[Formula: see text] torr and in air at atmospheric pressure. A Photo Multiplier Tube (PMT) was employed to detect the transmitted hard X-rays, which were filtered using a 10 [Formula: see text]m-thick Al filter. The fundamental mechanisms behind the emission of hard X-rays from laser-induced AlSb plasma were explored. Plasma plume expansion and the energy of the emitted radiation were found to depend on the number of laser pulses and the ambient pressure. The intensity of the plasma plume was observed to be inversely proportional to the ambient pressure and directly proportional to the number of laser pulses fired. Plasma confinement under high pressures was also examined. Time-resolved studies of the hard X-ray emission contributed to the analysis. The relationship between different laser shots and the current, voltage, and energy of the hard X-rays, as well as their inverse proportionality to ambient pressure, was quantified. At an ambient pressure of 10[Formula: see text] torr, the dynamics of the AlSb plasma plume were observed. The surface morphology of the laser-irradiated AlSb target was also analyzed, revealing unique properties pertinent to X-ray emission.