Electronic Structure Research Articles

Atomic‐Level Synergistic Catalysts: Single‐Atom Site Integrated with Atom, Cluster and Nanoparticle

AbstractThe emerging atomic‐level synergistic catalysts based on the single‐atom sites and other valuable components, such as atom, cluster, nanoparticle and other nano‐matter, shine in various catalytic fields. They can integrate the advantages of individual catalytic sites and other valuable components to enhance the activity, selectivity and stability of many chemical reactions via activating their key rate‐determining steps and multistep transformations. In addition, because of the ultrahigh atom utilization (~100 %) and adjustable microenvironment of metal centers, the single‐atom sites can intelligently construct with other useful large size sites to strengthening in tandem a typical catalytic process. Herein, the structure and mechanism of atomic‐level synergistic catalysts with controllable electronic structures and regulatory reaction processes are presented. We particularly emphasize the interactions between active components of atomic‐level synergistic catalysts and catalytic reaction processes, which are essential for understanding how these catalysts are cooperatively working. It is anticipated that this minireview can make the promotion of advanced atomic‐level synergistic catalysts based on single‐atom sites.

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.

Threefold Impact on Reaction Coordinate Mapping of Zirconium Based Tri‐Chalcogenide Pseudo‐Monolayers as Emerging Ultrathin Catalysts for Water Splitting

AbstractThe continuous quest of finding optimum catalysts for photo‐electrocatalytic (PEC) water splitting has been revolving around 2D ultrathin materials because of the fact of exploiting both the surface area. In this work, a threefold impact is envisaged route to enhance the activity both in terms of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in the emerging Zirconium Tri‐sulfides (ZrS3) based pseudo‐monolayers. Due to the unique and distinct electronic properties of the tri‐chalcogenide systems as compared to the di‐chalcogenide counterpart of Zirconium, one could afford to explore the implications of not only single‐atom functionalization and vacancy defect, but also the external strain to expedite the bifunctional catalytic activity in this promising material. Rigorous electronic structure calculations have been performed for the mentioned threefold effect on not only the band‐edge alignment, but going beyond to it by further constructing the reaction coordinate mapping corresponding to HER and OER mechanism. The repercussion of external strain in addition to the single atom functionalization and vacancy defect on the adsorption free energies of the prime intermediates of HER and OER reaction has been further correlated with the work function variation in this pseudo‐monolayer system.

Double exchange interaction in Mn-based topological kagome ferrimagnet

Recently discovered Mn-based kagome materials, such as RMn6Sn6 (R = rare-earth element), exhibit the coexistence of topological electronic states and long-range magnetic order, offering a platform for studying quantum phenomena. However, understanding the electronic and magnetic properties of these materials remains incomplete. Here, we investigate the electronic structure and magnetic properties of GdMn6Sn6 using x-ray magnetic circular dichroism, photoemission spectroscopy, and theoretical calculations. We observe localized electronic states from spin frustration in the Mn-based kagome lattice and induced magnetic moments in the nonmagnetic element Sn experimentally, which originate from the Sn-p\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$p$$\\end{document} and Mn-d\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d$$\\end{document} orbital hybridization. Our calculations also reveal ferromagnetic coupling within the kagome Mn-Mn layer, driven by double exchange interaction. This work provides insights into the mechanisms of magnetic interaction and magnetic tuning in the exploration of topological quantum materials.

Strong Metal-Support Interactions in Heterogeneous Oxygen Electrocatalysis.

Molecular oxygen redox electrocatalysis involves oxygen reduction and evolution as core reactions in various energy conversion and environmental technology fields. Strong metal-support interactions (SMSIs) based nanomaterials are regarded as desirable and state-of-the-art heterogeneous electrocatalysts due to their exceptional physicochemical properties. Over the past decades, considerable advancements in theory and experiment have been achieved in related studies, especially in modulating the electronic structure and geometrical configuration of SMSIs to enable activity, selectivity, and stability. In this focuses on the concept of SMSI, explore their various manifestations and mechanisms of action, and summarizes recent advances in SMSIs for efficient energy conversion in oxygen redox electrocatalysis applications. Additionally, the correlation between the physicochemical properties of different metals and supports is systematically elucidated, and the potential mechanisms of the structure-activity relationships between SMSIs and catalytic performance are outlined through theoretical models. Finally, the obstacles confronting this burgeoning field are comprehensively concluded, targeted recommendations and coping strategies are proposed, and future research perspectives are outlined.

One-Step Scalable Synthesis of 3D Self-Supported Superaerophobic Ce-Coupled Ni3S2/NiS@NF Nanobud Catalyst for Efficient Oxygen Evolution Reaction

The elaborate design of inexpensive, high-performance electrocatalysts from earth-abundant elements toward oxygen evolution reaction (OER) is critical in various (electro)chemical processes. Herein, a novel binder-free catalyst of Ce-coupled Ni3S2/NiS supported on Ni foam (Ce-Ni3S2/NiS@NF) is successfully synthesized via a facile one-step hydrothermal method that enables practical feasibility with a significant enhancement of OER activity through anchoring Ce dopants on an Ni3S2/NiS nanobud host. Ce species coupling can modulate electronic structure, which reduces the reaction energy barrier and optimizes OER catalytic activity. More profoundly, the superhydrophilic and superaerophobic properties of the Ce-Ni3S2/NiS@NF electrode further promote mass transfer. As a result, the Ce-Ni3S2/NiS@NF electrode exhibits excellent OER activity with a low overpotential of 236 and 350 mV to achieve current densities of 10 and 100 mA cm−2, respectively, and long-term durability for 24 h in alkaline medium. These results could supply valuable guidelines for the design of other OER catalysts and beyond.

Pressure effects on the electronic structure and magnetic properties of infinite-layer nickelates

Pressure effects on the electronic structure and magnetic properties of infinite-layer nickelates

Engineering of Single-Atomic Sites for Electro- and Photo-Catalytic H2O2 Production.

Direct electro- and photo-synthesis of H2O2 through the 2e- O2 reduction reaction (ORR) and H2O oxidation reaction (WOR) offer promising alternatives for on-demand and on-site production of this chemical. Exploring robust and selective active sites is crucial for enhancing H2O2 production through these pathways. Single-atom catalysts (SACs), featuring isolated active sites on supports, possess attractive properties for promoting catalysis and unraveling catalytic mechanisms. This review first systematically summarizes significant advancements in atomic engineering of both metal and nonmetal single-atom sites for electro- and photo-catalytic 2e- ORR to H2O2, as well as the dynamic behaviors of active sites during catalytic processes. Next, the progress of single-atom sites in H2O2 production through 2e- WOR is overviewed. The effects of the local physicochemical environments on the electronic structures and catalytic behaviors of isolated sites, along with the atomic catalytic mechanism involved in these H2O2 production pathways, are discussed in detail. This work also discusses the recent applications of H2O2 in advanced chemical transformations. Finally, a perspective on the development of single-atom catalysis is highlighted, aiming to provide insights into future research on SACs for electro- and photo-synthesis of H2O2 and other advanced catalytic applications.

Unveiling the Redox Noninnocence of Metallocorroles: Exploring K-Edge X-ray Absorption Near-Edge Spectroscopy with a Multiconfigurational Wave Function Approach.

X-ray absorption near-edge spectroscopy (XANES) is an advanced technique for probing the local electronic structure of catalysts, effectively identifying the noninnocent nature of ligands in transition-metal complexes. Metallocorroles with noninnocent corrole rings exhibit unusual electronic structures that challenge traditional density functional theory (DFT) methods, necessitating more rigorous approaches to describe electron correlation accurately. We explored K-edge XANES spectra of Fe, Mn, and Co metallocorroles using TDDFT and wave function-based methods. This is the first investigation employing multireference methods, specifically RASSCF, RASPT2, and MC-PDFT, to analyze the redox noninnocent nature of metallocorroles reflected in their XANES spectra. We quantified the noninnocent character of the corrole and the oxidation states of the metals, capturing more than singly excited excitations responsible for the pre-edge peak. Our findings demonstrate the importance of these advanced computational techniques for accurately predicting XANES spectra, providing a reliable understanding of the electronic properties of such complexes. This study offers a new strategy for investigating ligand redox noninnocence via integrated experimental and computational XANES.

Effect of Chlorine Inclusion in Wide Band Gap FAPbBr3 Perovskites

AbstractWide bandgap perovskites have recently gained attention owing to their physical properties, versatility, and potential in various optoelectronic devices including LEDs, detectors, and building‐integrated photovoltaics (BIPV). However, BIPV materials must meet conflicting requirements, necessitating high performance, high transparency in the visible spectrum and color neutrality. This study investigates the controlled addition of chlorine in FAPb(Br1‐xClx)3 perovskites to achieve band gaps exceeding 2.4 eV. Increasing chlorine content from xCl = 0.00 to xCl = 0.25 widens the band gap from 2.37 to 2.52 eV, effectively improving the visible light transparency. Advanced characterization techniques including X‐ray diffraction, synchrotron radiation photoelectron spectroscopy, photoluminescence imaging, and fast transient absorption spectroscopy, complemented by density functional theory, reveal insights into absorption properties, electronic structure, and ultrafast recombination dynamics as a function of the thin film chemical composition. Furthermore, this study evaluates energetic disorder, carrier recombination rates, and non‐radiative losses for different compositions by extracting quantitative parameters such as Urbach energy and quasi‐Fermi level splitting, offering novel insights and guidelines for the design and optimization of emerging photovoltaic (PV) materials. Optimal PV performance metrics are achieved with a wide bandgap bromine perovskite containing 14% chlorine, striking a balance between morphology, transparency, and voltage losses.

Effect of Vacancy Defects on the Electronic Structure and Optical Properties of Bi4O5Br2: First-Principles Calculations

First-principles calculations based on density functional theory are employed to investigate the impact of vacancy defects on the optoelectronic properties of Bi4O5Br2. The results indicate that vacancy defects induce minimal lattice distortion in Bi4O5Br2 without compromising its structural stability. Oxygen or bromine vacancies are more likely to occur than bismuth vacancies. The introduction of a bismuth vacancy leads to n-type semiconductor behavior in the Bi4O5Br2 system, while the creation of an oxygen vacancy reduces the bandgap and enhances the light absorption capacity. Bi4O5Br2 with three coordinated oxygen vacancies exhibits a higher effective electron–hole pair mass ratio, which is advantageous for the efficient separation of electron–hole pairs. Bi4O5Br2 with three coordinated oxygen vacancies exhibits enhanced absorption and reflection coefficients in the visible-light region compared to other systems, indicating that oxygen vacancy defects significantly promote visible-light absorption and electron–hole separation. This research provides new theoretical insights for understanding and optimizing the performance of photocatalysts based on Bi4O5Br2.

Isomer-Specific, Cryogenic Ion Vibrational Spectroscopy Investigation of D2- and N2-Tagged, Protonated Formic Acid Complexes Using Two-Color, IR-IR Photobleaching.

Here we analyze cryogenic ion vibrational spectra of tagged protonated formic acid (PFA) with electronic structure and anharmonic vibrational calculations to establish the isomers generated by electrospray ionization (ESI) followed by buffer gas cooling to ∼25 K. Two isomers are identified (the trans form (E,Z) and the cis form (E,E)) and generated in comparable abundance despite the fact that the calculated E,E structure lies 6.40 kJ mol-1 above the E,Z form. A large (∼60 kJ mol-1) barrier separates them such that the E,E form can be kinetically trapped upon cooling in the ion trap. The anticooperativity between the H-bonds of the OH groups is explored by measuring the shift in the D2-bound OH fundamental when a second D2 is attached. Both isomers are observed in the N2-tagged counterparts, displaying the expected red-shifted OH bands. These results indicate that ESI generates both isomers and both must be considered when analyzing cluster spectra based on the PFA core ion.

Structural, electronic and optical properties of CdTiX2 (X = N and P): A first principles density functional theory investigation

In the present paper, we have proposed new ternary materials CdTiN2 and CdTiP2 with body centered tetragonal structure. We have studied the structural, electronic, and optical properties of the proposed compounds with the help of the first principles density functional theory. The calculated electronic band structure shows that these compounds show indirect band gap of 1.089 eV and 0.359 eV for the compounds CdTiN2 and CdTiP2 respectively and hence it is concluded that these compounds are semiconducting nature. The optical properties such as the reflectivity, absorption, refractive index, real and imaginary part of dielectric function, optical conductivity, electronic energy loss function shows that studied compounds CdTiN2 and CdTiP2 may be promising materials for optoelectronic devices and the photoelectric solar cells.

Magneto-optical properties of heavily Fe-doped GaAs: a density functional approach.

The magneto-optical properties of heavily iron-doped GaAs are investigated. Complex permittivity, optical conductivity and absorption coefficients are mainly discussed using spin-polarized electronic band structures close to the Fermi energy level. Furthermore, prominent magneto-optical properties in visible light and ultraviolet regions, including magnetic circular dichroism as well as complex Kerr and Faraday rotation angles, are presented and discussed. A density functional approach corroborated by some experimental results indicates that GaAs with 25% Fe dopants either in As or Ga sites is a promising ferromagnetic material and a useful platform for optoelectronic and spintronic device applications.

Na-Promoted Bimetallic Hydroxide Nanoparticles for Aerobic C-H Activation: Catalyst Design Principles and Insights into Reaction Mechanism.

A precious metal-free bimetallic FexMn1-x(OH)y hydroxide catalyst was developed that is capable of catalyzing aerobic C-H oxidation reactions at low temperatures, without the need for an initiator, relying sustainably on molecular oxygen. Through a systematic synthetic effort, we scanned a wide nanoparticle synthesis parameter space to lay out a detailed set of catalyst design principles unraveling how the Fe/Mn cation ratio, NaOH(aq) concentration used in the synthesis, catalyst washing procedures, extent of residual Na+ promoters on the catalyst surface, reaction temperature, and catalyst loading influence catalytic C-H activation performance as a function of the electronic, surface chemical, and crystal structure of FexMn1-x(OH)y bimetallic hydroxide nanostructures. Our comprehensive XRD, XPS, BET, ICP-MS, 1H NMR, and XANES structural/product characterization results as well as mechanistic kinetic isotope effect (KIE) studies provided the following valuable insights into the molecular level origins of the catalytic performance of the bimetallic FexMn1-x(OH)y hydroxide nanostructures: (i) catalytic reactivity is due to the coexistence and synergistic operation of Fe3+ and Mn3+ cationic sites (with minor contributions from Fe2+ and Mn2+ sites) on the catalyst surface, where in the absence of one of these synergistic sites (i.e., in the presence of monometallic hydroxides), catalytic activity almost entirely vanishes, (ii) residual Na+ species on the catalyst surface act as efficient electronic promoters by increasing the electron density on the Fe3+ and Mn3+ cationic sites, which in turn, presumably enhance the electrophilic adsorption of organic reactants and strengthen the interaction between molecular oxygen and the catalyst surface, (iii) in the fluorene oxidation reaction the step dictating the reaction rate likely involved the breaking of a C-H bond (kH/kD = 2.4), (iv) reactivity patterns of a variety of alkylarene substrates indicate that the C-H bond cleavage follows a stepwise PT-ET (proton transfer-electron transfer) pathway.

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

Double-pentagon silicon chains in a quasi-1D Si/Ag(001) surface alloy

Silicon surface alloys and silicide nanolayers are highly important as contact materials in integrated circuit devices. Here we demonstrate that the submonolayer Si/Ag(001) surface reconstruction, reported to exhibit interesting topological properties, comprises a quasi-one-dimensional Si-Ag surface alloy based on chains of planar double-pentagon Si moieties. This geometry is determined using a combination of density functional theory calculations, scanning tunnelling microscopy, and grazing incidence x-ray diffraction simulations, and yields an electronic structure in excellent agreement with photoemission measurements. This work provides further evidence of pentagonal geometries in 2D materials and heterostructures and elucidates the importance of surface alloying in stabilizing their formation.

Elucidating the Photo-Induced Electronic Structure and Mechanisms of ZnAl-Layered Double Hydroxides: A DFT Study.

Layered double hydroxides (LDHs) have been regarded as excellent catalysts for a variety of photocatalytic applications including the hydrogen production, carbon dioxide reduction, and nitrogen fixation, etal. The elucidation of the photocatalytic mechanism of LDH-based photocatalysts under light irradiation, especially at the ultraviolet (UV) and deep ultraviolet (DUV) region, at the molecular level has remained elusive. In this study, the photo-induced electronic structure of ZnAl-LDH materials were investigated, and a comprehensive understanding of its underlying mechanism, both in the UV and DUV region, was gained using density functional theory (DFT) calculations. The UV and DUV regions exhibit distinct excitation characteristics, revealing the complex interactions between electrons and holes within the system. The DUV region significantly promotes electron transfer, indicating the potential application of LDH materials as a DUV catalysis material. This study elucidates the electron transfer kinetics in LDHs upon UV and DUV irradiation, thereby offering new perspective for the development of photocatalytic materials under different light region.

Topological Band Engineering of One-Dimensional π-d Conjugated Metal-Organic Frameworks.

One-dimensional (1D) π-d conjugated metal-organic frameworks (c-MOFs) have garnered widespread research interest in chemical energy storage and conversion. In this work, we introduce a universal principle to engineer the topological bands of 1D c-MOFs. Connected by d orbitals of transition metals, two equivalent hidden molecular π orbitals in 1D c-MOFs can generate a staggered hopping within and between the organic ligands, forming Su-Schrieffer-Heeger-shaped 1D topological bands. Guided by this discovery, we investigate the electronic structures of the typical 1D c-MOF assembled from Ni atoms and 2HQDI (QDI = 2,5-diamino-1,4-benzoquinonediimine) precursors (NiQDI) by first-principles calculations, revealing 1D topological bands around the Fermi level. Due to local bonding variations at the QDI terminations, these two hidden molecular π orbitals become atomically bonded but electronically separated at the edge QDI, creating spatially localized in-gap topological edge states at the end of the NiQDI chain. This definitive signature for 1D topological bands is identified through differential conductance spectra in scanning tunneling microscopy measurements. Our results provide conclusive experimental evidence for topological bands in 1D c-MOFs, paving the way for exploring the topological physics in organic materials through frontier molecular orbitals.

Efficient and Ultrastable Seawater Electrolysis at Industrial Current Density with Strong Metal-Support Interaction and Dual Cl--Repelling Layers.

Direct seawater electrolysis is emerging as a promising renewable energy technology for large-scale hydrogen generation. The development of Os-Ni4Mo/MoO2 micropillar arrays with strong metal-support interaction (MSI) as a bifunctional electrocatalyst for seawater electrolysis is reported. The micropillar structure enhances electron and mass transfer, extending catalytic reaction steps and improving seawater electrolysis efficiency. Theoretical and experimental studies demonstrate that the strong MSI between Os and Ni4Mo/MoO2 optimizes the surface electronic structure of the catalyst, reducing the reaction barrier and thereby improving catalytic activity. Importantly, for the first time, a dual Cl- repelling layer is constructed by electrostatic force to safeguard active sites against Cl- attack during seawater oxidation. This includes a strong Os─Cl adsorption and an in situ-formed MoO4 2- layer. As a result, the Os-Ni4Mo/MoO2 catalyst exhibits an ultralow overpotential of 113 and 336mV to reach 500mA cm-2 for HER and OER in natural seawater from the South China Sea (without purification, with 1m KOH added). Notably, it demonstrates superior stability, degrading only 0.37 µV h-1 after 2500 h of seawater oxidation, significantly surpassing the technical target of 1.0 µV h-1 set by the United States Department of Energy.