Generalized Gradient Approximation Made Simple

Signature of Topological Surface Bands in Altermagnetic Weyl Semimetal CrSb

As a special type of collinear antiferromagnetism (AFM), altermagnetism has garnered significant research interest recently. Altermagnets exhibit broken parity-time symmetry and zero net magnetization, leading to substantial band splitting in the momentum space. Meanwhile, parity-time symmetry breaking is a prerequisite for nontrivial band topology in Weyl physics. When there is band crossing, it is usually easy to generate Weyl nodes. Weyl semimetal states have been theoretically proposed in altermagnets; rare reports of experimental observation have been made up to this point. Using angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations, we systematically studied the electronic structure of room-temperature altermagnet candidate CrSb. We clearly observed the band spin splitting and signature of topological surface states on the (100) cleaved side surface close to the Fermi level originating from bulk band topology. Our results imply that CrSb contains interesting nontrivial topological Weyl physics, in addition to being an excellent room temperature altermagnet.

Structural Dynamic Evolution of Pt Nanoclusters in Ultra-Low-Temperature Methane Combustion with Nitrous Oxide

Tailoring and stabilizing the active sites of supported noble-metal catalysts to a semioxidized state with unsaturated coordination remain a long-standing challenge in heterogeneous catalysis. Herein, we develop a reaction-atmosphere-driven evolution approach for dynamic structural tuning of semioxidized metal sites in supported Pt catalysts. N2O as an alternative oxidant is used over Pt/TiO2 in CH4 combustion to dynamically prompt the transformation of Pt0 nanoclusters into Ptδ+ (0 < δ < 2) nanoclusters. Compared to CH4 combustion with O2 that inclines to overoxidize Pt0, the catalytic activity of CH4-N2O combustion is distinctly boosted, achieving complete CH4 combustion at only 200 °C, outperforming the state-of-the-art catalysts using O2 as the oxidant. Computational and experimental studies validate that N2O triggers less electron transfer from Pt than from O2, thereby facilitating the formation and preservation of Ptδ+ species during CH4 combustion. The newly emerged semioxidized Ptδ+ species with oxygen-deficient coordination structures simultaneously enhance lattice oxygen activation and the first C-H bond dissociation of CH4, contributing to ultralow temperature activity. Our work demonstrates that modulating the reaction atmosphere to achieve the structural dynamic evolution of semioxidized metal sites can provide new strategies for designing highly efficient catalysts for low-temperature CH4 combustion.

Novel two dimensional B2C3 monolayer as a high theoretical capacity anode material for Li or Na ion batteries

In this study, we utilized first-principles calculations to design a novel class of two-dimensional (2D) polycyclic materials composed of carbon and boron atoms, termed k-B2C3, which hold significant promise as high-capacity, fast-diffusing anode materials for Li/Na-ion batteries. We investigated the thermodynamic stability, mechanical properties, electronic structure, and energy storage characteristics of k-B2C3. The results reveal that k-B2C3 exhibits a density of states at the Fermi level of 0.18 states/eV, a Young's modulus of [Formula: see text], and a Poisson's ratio of 0.43, indicating excellent metallic conductivity and mechanical ductility, which are crucial for stability during charge/discharge cycles. Furthermore, the Li/Na diffusion barriers for k-B2C3 are 0.55 eV and 0.17 eV, respectively, which are vital for efficient charge/discharge processes. Most notably, k-B2C3 demonstrates a high theoretical storage capacity of 930 mAhg-1 for both Li and Na, coupled with low open-circuit voltages (1.30-0.54 V for Li and 1.17-0.34 V for Na). These findings suggest that 2D k-B2C3 is a promising candidate for use as an anode material in Li/Na-ion batteries and provides valuable insights for the development of advanced 2D electrode materials.

Efficient capture and detoxification of gaseous arsenic trioxide from flue gas using silicomanganese alloy dust

This study aims to develop efficient capture materials for gaseous arsenic trioxide (As2O3(g)) that can prevent arsenic poisoning in selective catalytic reduction (SCR) systems and reduce atmospheric arsenic emissions from coal-fired power plants. One kind of metallurgical dust from a silicomanganese alloy plant (named as SiMnD) was found to be cost-effective and environmentally friendly for As2O3(g) removal from flue gas for the first time. The sorbent showed excellent performance for gaseous arsenic trioxides capture with a good capacity of 13.82 mg/g at 450 °C in 60 min, which was better than the other reported metal oxides at high temperature. The As2O3(g) capture capacity in 12-h continuous test reached as high as 118.16 mg/g without penetration, and the sorbent showed good long-term durability and pretty good resistance to high concentrations of nitric oxide (NO), sulfur dioxide (SO2) and carbon dioxide (CO2). The sorbent also exhibited good recyclability even after five regeneration cycles. Nearly 92% of As2O3(g) was transformed into manganese (II) pyroarsenate (Mn2As2O7), manganese arsenate (MnAsO4) and diarsenic pentoxide (As2O5) after capture with lower toxicity. The results of Toxicity Characteristic Leaching Procedure (TCLP) and five-step sequential extraction demonstrated that spent SiMnD exhibited low arsenic bioavailability, indicating reduced environmental mobility of arsenic species. Trimanganese tetroxide (Mn3O4) and blythite (Mn3Mn2(SiO4)3) were the most essential active component for As2O3(g) removal and detoxification. The optimal As2O3(g) capture temperature of SiMnD was 450 °C which was suitable to be applied before SCR with little operating cost. SiMnD was proved to be one excellent capture and detoxification agent for As2O3(g) in flue gas at a lower temperature with promising application prospects.

Layered Germanium-Selenium Compounds as Phonon-Glass Electron-Crystals: A Pathway to Enhance the Thermoelectric Performance

The early concept of a "phonon-glass electron-crystal" for enhancing the thermoelectric figure of merit (ZT) is explored theoretically in layered Ge-Se crystals, where phonon transport exhibits glass-like behavior. Ab initio lattice dynamics and the rigid electronic band method project an ultrahigh ZT = 4.04 at 1000 K along the a axis in the high-temperature GeSe2 phase at an electron doping concentration of 1020 cm-3. Meanwhile, the low-temperature Ge4Se9 phase achieves a high ZT = 2.19 at 600 K along the a axis with an electron doping concentration of 6 × 1019 cm-3. These maximal values reflect the ultralow lattice thermal conductivity, 0.168 W m-1 K-1 (GeSe2, 1000 K) and 0.289 W m-1 K-1 (Ge4Se9, 600 K), and high power factor at optimized carrier concentrations along the a axis. Our calculations indicate a promising pathway for approaching the early concept of maximizing ZT, by tailoring carrier doping in layered crystals with glass-like phononic transport.

An iterative and automatic collective variable optimization scheme via unsupervised feature selection with CUR matrix decomposition

Phase transitions frequently involve surmounting significant energy barriers, necessitating the construction of collective variables (CVs) to facilitate enhanced sampling of high-energy structures in molecular dynamics simulations. However, optimizing CVs remains a formidable challenge, particularly when limited prior knowledge about the transition process is available. This study presents an unsupervised approach for optimizing the CVs by iteratively applying the principal component analysis algorithm on the representative feature variables generated with the CUR method (an efficient feature space contraction algorithm that can be employed to seek the representative feature variables). The approach is validated using a hypothetical three-phase model of ultra-high-pressure hydrogen derived at the density functional theory level of theory to characterize transition pathways. CVs are constructed using feature variables extracted from simulated x-ray diffraction intensity spectra. Our fully unsupervised approach demonstrated self-correction capabilities in discovering probable phase-transition pathways. By relying solely on unbiased molecular dynamics simulations of metastable structures to construct the initial dataset, the free energy profile can be properly reproduced for the phase transitions among them, which suggests the potential for developing a highly autonomous approach to exploring complex systems with elusive physical mechanisms.

Free energy profiles for chemical reactions in solution from high-dimensional neural network potentials: The case of the Strecker synthesis

Machine learning potentials (MLPs) have become a popular tool in chemistry and materials science as they combine the accuracy of electronic structure calculations with the high computational efficiency of analytic potentials. MLPs are particularly useful for computationally demanding simulations such as the determination of free energy profiles governing chemical reactions in solution, but to date, such applications are still rare. In this work, we show how umbrella sampling simulations can be combined with active learning of high-dimensional neural network potentials (HDNNPs) to construct free energy profiles in a systematic way. For the example of the first step of Strecker synthesis of glycine in aqueous solution, we provide a detailed analysis of the improving quality of HDNNPs for datasets of increasing size. We find that, in addition to the typical quantification of energy and force errors with respect to the underlying density functional theory data, the long-term stability of the simulations and the convergence of physical properties should be rigorously monitored to obtain reliable and converged free energy profiles of chemical reactions in solution.

Ferroelectrically Switchable Half-Quantized Hall Effect

Integrating ferroelectricity, antiferromagnetism, and topological quantum transport within a single material is rare but crucial for developing next-generation quantum devices. Here, we propose a multiferroic heterostructure consisting of an antiferromagnetic MnBi2Te4 bilayer and an Sb2Te3 film is able to harbor the half-quantized Hall (HQH) effect with a ferroelectrically switchable Hall conductivity of ± e2/2h. We first show that, in the energetically stable configuration, the antiferromagnetic MnBi2Te4 bilayer opens a gap in the top surface bands of Sb2Te3 through the proximity effect, while its bottom surface bands remain gapless; consequently, an HQH conductivity of e2/2h can be sustained clockwise or counterclockwise, depending on the antiferromagnetic configuration of the MnBi2Te4. Remarkably, when interlayer sliding is applied within the MnBi2Te4 bilayer, its electric polarization direction associated with parity-time reversal symmetry breaking is reversed, accompanied by a reversal of the HQH conductivity. The proposed approach offers a powerful route to control topological quantum transport in antiferromagnetic materials by ferroelectricity.

Noncentrosymmetric Mixed Chalcogenide Semiconductors La3Ga1.67(S1-xSex)7

The mixed chalcogenides La3Ga1.67(S1-xSex)7 form a complete solid solution, with members at increments of x = 0.14 prepared as phase-pure samples. Based on their powder X-ray diffraction (XRD) patterns, the cell volume increases with greater Se substitution, but the cell parameters vary in a nonmonotonic way. Single-crystal XRD studies at room temperature indicated that they adopt noncentrosymmetric hexagonal structures (in space group P63) containing stacks of Ga-centered tetrahedra and stacks of octahedra with partially occupied Ga sites. Strong preferences of S vs Se atoms within three types of chalcogen sites lead to unusual structural changes in the intermediate members of the solid solution and can be understood in terms of the need to satisfy optimum bonding requirements. Structure determination of the selenide end-member La3Ga1.67Se7 at low temperature (100 K) revealed a supercell (in space group P61) with a tripled c-axis characterized by distortions of the partially occupied Ga sites and the coordinating Se atoms, which help relieve bond strain. Two Ga sites in tetrahedral and roughly octahedral geometry were assigned by 71Ga solid-state nuclear magnetic resonance spectroscopy. The experimental optical band gaps vary from 2.6 eV for La3Ga1.67S7 to 2.0 eV for La3Ga1.67Se7.

Emissive or Nonemissive? Molecular Insight into Luminescence Properties of Tin(II) Metal Halides

In addition to the easy oxidation of tin(II) (Sn2+), the poor repeatability in synthesizing luminescent Sn2+-based halide perovskites can be attributed to the structural diversity among Sn compositions, with many structures failing to exhibit luminescence. Furthermore, compared to luminescent compounds, there is insufficient attention on the photophysical properties of these nonluminescent compositions, which impedes a deeper understanding of the relationship between their structures and optical properties. In this work, we report two Sn2+-based halide compounds, (DFPD)6SnBr8 and (DFPD)2SnBr4 (DFPD+ = 4,4-difluoropiperidinium). Both exhibit excellent air stability, with the former demonstrating a high luminescence efficiency of ∼92%, while the latter is essentially nonluminescent. Theoretical calculations suggest that the nonluminescence of (DFPD)2SnBr4 arises from charge transfer between two adjacent [SnBr4]2- units in the first excited state. In contrast, significant structural distortion and localization of excitons in (DFPD)6SnBr8 indicate that its emission originates from self-trapped excitons. As a demonstration, we prepared an X-ray scintillator based on (DFPD)6SnBr8 with a high light yield up to 27,600 ph/MeV and a low detection limit of 84.7 nGy/s, which is significantly better than the commercial LuAG/Ce scintillator (22,000 ph/MeV, 2.32 μGy/s).

Insight into the atomic-level structure of γ-alumina using a multinuclear NMR crystallographic approach

The combination of multinuclear NMR spectroscopy with 17O isotopic enrichment and DFT calculations provided detailed insight into both the bulk and surface structure of γ-Al2O3. Comparison of experimental 17O NMR spectra to computational predictions confirmed that bulk γ-Al2O3 contains Al cations primarily in "spinel-like" sites, with roughly equal numbers of alternating AlVI and AlIV vacancies in disordered "chains". The work showed that overlap of signals from OIV and OIII species complicates detailed spectral analysis and highlighted potential problems with previous work where structural conclusions are based on an unambiguous assignment (and quantification) of these signals. There was no evidence for the presence of H, or for any significant levels of O vacancies, in the bulk structure of γ-Al2O3. Computational predictions from structural models for different surfaces showed a wide variety of protonated and non-protonated O species occur. Assignment of signals for two types of protonated O species was achieved using variable temperature CP and TRAPDOR experiments, with the sharper and broader resonances attributed to more accessible surface sites that interact more strongly with water and less accessible aluminols, respectively. DFT-predicted 1H NMR parameters confirmed the 1H shift increases with denticity but is also dependent on the coordination number of the next nearest neighbour Al species. Spectral assignments were also supported by 1H-27Al RESPDOR experiments, which identified spectral components resulting from μ1, μ2 and μ3 aluminols. Combining these with 1H-27Al D-HMQC experiments showed that (i) μ1 aluminols are more likely to be bound to AlIV, (ii) μ2 aluminols are coordinated to all three types of Al, but with a higher proportion bound to similar types of Al and (iii) μ3 aluminols are most likely bound to higher coordinated Al species. 1H DQ MAS spectroscopy confirmed no aluminols exist exclusively in isolation but showed that the closest proximities are between bridging aluminols coordinated to AlIV and/or AlV species.

Defective Carbon Catalysts with Graphitic N-Modified Adjacent Pentagons as Active Sites for Boosted Oxygen Reduction Reaction in Seawater

Seawater electrocatalysis is highly desired for various energy storage and conversion systems, such as water splitting using seawater as an electrolyte and metal fuel cells. However, the adsorption of chloride ions (Cl-) on the active sites of cathodes would worsen the oxygen reduction reaction (ORR) activity and stability, thus lowering the battery performance. Herein, the coupling active sites of graphitic N-regulated adjacent pentagon defects in carbon nanosheets (GAP/CN) were first synthesized by a low-boiling-point metal-mediated partial N-removal strategy. Experimental and theoretical results affirm the advantageous cooperative effect between adjacent pentagons and graphitic N toward the ORR in a harsh seawater environment, where adjacent pentagons act as the authentic highly effective ORR active sites and surrounding graphitic N site serves as the structural regulator to weaken the binding strength of harmful Cl- to prevent catalyst poisoning. As a result, GAP/CN delivers excellent ORR activities in diverse electrolytes, including 0.1 M KOH (half-wave potential of 0.87 V), alkaline artificial seawater (half-wave potential of 0.87 V), and natural seawater (half-wave potential of 0.71 V), and also good long-term stability, which can be comparable to commercial Pt/C. This study provides valuable guidance for the rational design of ORR electrocatalysts for seawater-related energy-conversion devices.

Self-Powered Ultraviolet Sensor Based on CsPbCl3 for Skin Safety Monitoring

Extended exposure to ultraviolet (UV) radiation significantly increases the risk of skin cancer. The World Health Organization reports that when the UV index surpasses 7, the skin becomes vulnerable to diseases like erythema. There is an urgent need for an UV photodetector capable of real-time UV intensity monitoring. In recent years, cesium lead chloride (CsPbCl3) has emerged as a superior candidate material in the field due to its wide bandgap of 2.8 eV and outstanding UV optoelectronic and ferroelectric performance. In this study, a self-powered CsPbCl3 thin-film photodetector was fabricated by a two-step spin-coating method along with a seven-level UV detection system. When the UV level reaches or exceeds level 7, the device sends a warning via Wi-Fi, enabling individuals to take prompt protective measures against harmful UV radiation. Additionally, the potential of the detector for optical imaging was demonstrated by reconstructing the image of the letters "UJS" using single-pixel imaging techniques. The findings indicate that the self-powered CsPbCl3 UV photodetector holds substantial promise for skin health management and optical imaging.

Three-Dimensional Atomic-Level Structure of an Amorphous Glucagon-Like Peptide-1 Receptor Agonist

Amorphous formulations are increasingly used in the pharmaceutical industry due to their increased solubility, but their structural characterization at atomic-level resolution remains extremely challenging. Here, we characterize the complete atomic-level structure of an amorphous glucagon-like peptide-1 receptor (GLP-1R) agonist using chemical shift driven NMR crystallography. The structure is determined from measured chemical shift distributions for 17 of the 32 carbon atoms and 16 of the 31 hydrogen atoms in the molecule. The chemical shifts are able to provide a detailed picture of the atomic-level conformations and interactions, and we identify the structural motifs that play a major role in stabilization of the amorphous form. In particular, hydrogen bonding of the carboxylic acid proton is strongly promoted, although no carboxylic acid dimer is formed. Two orientations of the benzodioxole ring are promoted in the NMR structure, corresponding to a significant stabilization mechanism. Our observation that inclusion of water leads to stabilization of the carboxylic acid group might be used as a strategy in future formulations where hydrogen bonding between neighboring molecules may otherwise be hindered by sterics.

Adsorption and reaction of 2-methylbenzimidazole molecules on a partially oxidized Cu(110) surface

N-Heterocyclic carbenes (NHCs) have emerged as a promising candidate for functionalizing and modifying metal surfaces. Despite extensive research, the influence of oxides, which frequently occur on metal surfaces, on the adsorption behavior of NHCs has received limited attention at the nanometric scale. In this study, the adsorption configurations and reactions of 2-methylbenzimidazole (MBI) molecules on a CuO/Cu(110) surface were investigated using scanning tunneling microscopy and non-contact atomic force microscopy (nc-AFM). Following the deposition of MBI molecules, Cu islands were observed, and the molecules predominantly adsorbed in a flat-lying configuration. Comparative experiments conducted on a bare Cu(110) surface indicate that the dehydrogenation of MBI molecules due to the cleavage of N-H bonds leads to CuO reduction and the release of Cu adatoms, which subsequently aggregate into islands. Upon annealing at 378 K, molecules adsorbed at the CuO strips assume a tilted flat-lying configuration, suggesting the formation of coordination bonds between nitrogen and copper atoms. On the copper regions, molecules assemble into double-chains, adopting an upright configuration. High-resolution nc-AFM images reveal a similarity between molecules in the double-chains and those at step edges, implying that Cu atoms are extracted from terraces to form slots where molecules preferentially occupy.

Discovery of a molecular adsorbent for efficient CO2/CH4 separation using a computation-ready experimental database of porous molecular materials

The development and sharing of computational databases for metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have significantly accelerated the exploration and application of these materials. Recently, molecular materials have emerged as a notable subclass of porous materials, characterized by their crystallinity, modularity, and processability. Among these, macrocycles and cages stand out as representative molecules. Experimental discovery of a target molecular material from a vast possibility of structures for defined applications is generally impractical due to high experimental costs. This study presents the most extensive Computation-ready Experimental (CoRE) database of macrocycles and cages (MCD) to date, comprising 7939 structures. Using the MCD, we conducted simulations of binary CO2/CH4 competitive adsorption under conditions relevant to industrial applications. These simulations established a structure-property-function relationship, enabling the identification of materials with potential for CO2/CH4 separation. Among them, a macrocycle, NDI-Δ, exhibited promising CO2 adsorption capacity and selectivity, as confirmed by gas sorption and breakthrough experiments.

Identification of Topological Metal g-C2N with High Activity and Selectivity for Versatile Oxygen Electrocatalysis

Two-dimensional (2D) carbon nitride materials are emerging as ideal supports for single-atom catalysts (SACs) due to their excellent physicochemical stability, abundant active sites, and ample capacity for metal loading. However, their intrinsic semiconducting properties constrain electrical conductivity, thereby hindering charge transfer during catalytic processes. Herein, we propose a graphene-like 2D carbon nitride structure, g-C2N, derived from first-principles calculations and theoretical analysis. This structure is identified as a topological metal, featuring a symmetry-protected Dirac cone. Its topologically nontrivial nature is evidenced by distinct edge states, nonzero Berry curvature, and quantized Zak phase. Remarkably, g-C2N exhibits a Fermi velocity exceeding that of graphene. Furthermore, the constructed Co@C2N2 structure is identified as a highly active and selective catalyst for hydrogen peroxide (H2O2) electrosynthesis, with a low thermodynamic overpotential of 0.08 V. Additionally, the Co@C2N2-N catalyst developed through N-doping strategies demonstrates outstanding bifunctional 4e- OER/ORR activity with low overpotentials of 0.27 and 0.32 V, respectively. These findings not only broaden the scope of 2D carbon nitride materials but also offer foundational insights for the rational design of highly active catalysts for oxygen electrocatalysis.

Study on spin-dependent thermoelectric transport properties of graphene nanoribbon molecular devices modulated by DNA bases adsorption

This study employs density functional theory and non-equilibrium Green's function methods to investigate the thermoelectric and thermal spin transport properties of four molecular devices, which are constructed by four different DNA base molecules, adenine (A), guanine (G), cytosine (C), thymine (T), adsorbing on graphene nanoribbon (GNR). The research reveals that the Device-G and Device-C adsorption turn on a spin-down electron transport channel, resulting in a strongly spin-polarized current. When a temperature difference is applied at GNR electrodes, the values of thermoelectric both charge current and spin current follows the device sequence A < T < C < G. Further analysis indicates that the adsorption of base molecules on graphene substrates effectively enhances electronic conductance, with the thermoelectric performance of adsorbed G and C significantly surpassing those of A and T. This research provides insights into the potential of thermoelectric method for DNA bases recognition.

Gold bis(dithiolene) radical with fused pyrazine and dithiine rings on dithiolene ligand turns metallic under pressure

Conducting molecular materials built on dithiolene complexes, as mixed-valence salts or single component materials, are most often based on planar structures which efficiently stack on top of each other. Herein, we report an original dithiolene ligand, namely, [1,4]dithiino[2,3-b]pyrazine-2,3-bis(thiolate) (hereafter noted as pzdtdt), which combines an electron-withdrawing pyrazine ring and a folded (by 40-50°) dithiine ring. Until now, such strong distortions from planarity have been hindering the isolation of highly conducting materials from dithiine-containing dithiolene complexes. However, in this study, we showed that the gold complex radical [Au(pzdtdt)2]˙ obtained via electrocrystallization from the 1e- oxidation of [Ph4P][Au(pzdtdt)2] organized into regular, non-dimerized chains in the solid state. Interestingly, [Au(pzdtdt)2]˙ exhibited a semi-conducting behaviour at ambient pressure and turned metallic upon application of pressures above 4 GPa. The electronic structure of [Au(pzdtdt)2]˙ was investigated in terms of electron localization effects through spin-polarized band-structure calculations.

Enhanced Electrocatalytic Carbon Dioxide Reduction Activity via Local Charge Environment Regulation of Active Sites with Rational Functionalization

Covalent organic frameworks (COFs) are a new emerging class of electrochemical catalysts for the CO2 reduction reaction (CO2RR) with fascinating structural tunability. In this work, to dig more detailed information about the effect of local charge environment regulation of active sites via structure modification on the catalytic performance of COFs for CO2RR, the Gibbs free-energy change (ΔG) of each elementary reaction step involved in the CO2RR and competitive hydrogen evolution reaction (HER) on COF366-Co and its derivatives were examined theoretically. It is observed that the valence band maximum (VBM) energy level of the COFs is increased by incorporation of electron-donating groups, and then the charge distribution on the Co center of COF366-Co is increased due to the increased charge-transfer amount from the electron-occupied N sp2 hybrid orbitals to the empty Co3d orbitals. For incorporating electron-withdrawing groups, the VBM energy level and the d-band center (ξd) of the Co atom are downshifted, and the d-band center gets closer to the occupied VBM energy level as the VBM is decreased to a larger extent than the ξd. As a result, electrosorption of the intermediate is facilitated and the CO2RR performance is enhanced by such a linker functionalization strategy, especially for electron-withdrawing groups. Our study highlights the key role that controlled local electrical environment via chemical structure modification of COFs can play in regulating the catalytic activity for its CO2RR applications.

Intelligent self-correcting growth of uniform Bernal-stacked bi-/trilayer graphene

State-of-the-art synthesis strategies of two-dimensional (2D) materials have been designed following the nucleation-dominant pattern for structure control. However, this classical methodology fails to achieve the precise layer- and stacking-resolved growth of wafer-scale few-layer 2D materials due to its intrinsically low energy resolution. Here, we present an intelligent self-correcting method for the high-resolution growth of uniform few-layer graphene. We demonstrate the layer-resolved growth of wafer-scale bilayer and trilayer graphene (BLG and TLG) with selective Bernal stacking through spontaneous correction of the single-layer graphene film with disordered multilayer graphene islands. Theoretical calculations reveal that the self-correcting growth is driven by the stepwise energy minimization of the closed system and kinetically activated by forming a low-barrier pathway for the carbon detachment-diffusion-attachment. Such uniform Bernal-stacked BLG and TLG films show high quality with distinct quantum Hall effect being observed. Our work opens an avenue for developing an intelligent methodology to realize the precise synthesis of diverse 2D materials.

Synergistic Enhancement of Hydrolysis-Oxidation Drives Efficient Catalytic Elimination of Chlorinated Aromatics over VOx/TiO2 Catalysts at Low Temperature

The efficient catalytic elimination of toxic chlorinated aromatics (i.e., dioxins, chlorobenzenes, etc.) at low temperature is still a great challenge. Based on the VOx/TiO2 catalyst, a hydrolysis-oxidation strategy (CeOx and WOx doping) was built for desirable low-temperature catalytic activity, product selectivity, H2O tolerance, and chlorine desorption. The in situ and ex situ experimental characterizations and density functional theory calculations revealed that hydrolysis sites favored molecular adsorption, C-Cl cleavage, and HCl formation; meanwhile, oxidation sites enhanced the activation of reactive oxygen species and improved oxygen mobility and redox properties. The enhanced oxygen storage/release capacity (33-53 fold) and extended redox cycle (e.g., from V5+↔V4+ to V5+↔V4+↔V3+) favored the deep oxidation. The introduction of H2O triggered the hydrolysis-oxidation process that promoted the catalytic activity and chlorine desorption due to the elevated generation of ·O2- and higher-activity ·OH. Furthermore, the water resistance of the VOx/TiO2-based catalyst was enhanced after the application of the hydrolysis-oxidation strategy. The V-Ce-W/Ti catalyst exhibited remarkable removal efficiency of dioxins (96.7-98.2%), which was reduced from 0.34-0.48 ng I-TEQ Nm-3 to 0.006-0.016 ng I-TEQ Nm-3 during pilot tests at 160-180 °C, achieving ultralow emissions. This work provides practical guidance for industry development for efficiently eliminating chlorinated organics in flue gas.

AI-Generated Ammonium Ligands for High-Efficiency and Stable 2D/3D Heterojunction Perovskite Solar Cells

The 2D/3D heterojunction perovskite solar cells (PSCs) exhibit remarkable stability, but the quantum well in the 2D perovskite capping layer hinders the carrier transport, thereby lowering the power conversion efficiency (PCE). The relationship between the transport barrier and the complex structure of ammonium ligands (ALs) is currently poorly understood, thus leading to the one-sided approach and inefficient process in the development of 2D perovskite. Here, a machine learning procedure is established to comprehensively explore the relationship and combined it with an artificial intelligence (AI) model based on reinforcement learning algorithm to accelerate the generation of ALs. Finally, the AI-designed ALs improved the carrier transport performance of the 2D perovskite capping layer, and we achieved a certified PCE of 26.12% in inverted PSCs. The devices retained 96.79% of the initial PCE after 2000 h operation in maximum power point tracking under 1-sun illumination at 85°C.

Tungsten oxide as a universal source for the synthesis of complexes with different nuclearities in WO3/chalcogen/NaCN systems

Tungsten trioxide can be used as a readily available source in the one-step preparation of a variety of cyanide and chalcocyanide mononuclear and cluster complexes of tungsten. In our study of phase formation in the system 6WO3 + 8Q + 32NaCN (Q = S, Se or Te) in the temperature range of 250-700 °C, we determined which soluble complex compounds are formed, the temperature limits of their existence and the influence of synthesis time on the composition of the products. As the temperature increases, the process begins with the formation of mononuclear and then cluster complexes and ends with the formation of tungsten dichalcogenides: [W(CN)8]4- → [WS4]2-/[WS3O]2- → [{W3Q4}(CN)9]5- (Q = S or Se), [{W3S3O}(CN)9]5- → [{W4Q4}(CN)12]6- (Q = S, Se or Te) → WQ2 (Q = S or Se). Depending on the synthesis conditions, these complexes can either coexist in a mixture or one of them becomes the main product of the reaction. The obtained trinuclear and tetranuclear cluster complexes were studied by 13C, 77Se and 183W NMR spectroscopy using DFT calculations to assign the spectral signals. The crystal structures of the salts Cs5Na3[W(CN)8]2·2H2O (1), Cs2.8Na2.2[{W3S4}(CN)9]·2.2H2O (2), Cs5[{W3S3O}(CN)9]·2H2O·0.5CsCl (3) and Cs3.5Na1.5[{W3Se4}(CN)9]·6.5H2O (4) were determined by single-crystal X-ray diffraction analysis. It was also revealed that the quantitative ratio of trinuclear complexes [{W3S3O}(CN)9]5- and [{W3S4}(CN)9]5- with different cluster core compositions formed in the 6WO3 + 8S + 32NaCN system at 300 °C depends on the synthesis time. Dynamics of the observed transformation of the initially dominant complex with a heteroleptic cluster core {W3(μ3-S)(μ-S)2μ-O} into the complex with a homoleptic core {W3(μ3-S)(μ-S)3} was studied using 13C NMR spectroscopy.

Electrical Control of the Nuclear Spin States of Rare-Earth Adatoms

Rare-earth adatoms on surfaces have been studied for potential atomic-scale magnetic storage, quantum sensing, and quantum computing applications. Despite accumulating experimental efforts, a comprehensive description of the electronic configurations of the adatoms remains elusive. Here, we investigate two charge states and several electronic configurations, including 5d and 6s valence shells, for a Sm adatom on a MgO substrate using multiconfigurational ab initio methods, for the possibility of using the Sm nuclear spin levels as qubits. For the configurations in a neutral charge state, we find that the electronic ground state is a singlet, and thus the hyperfine interaction associated with the 147Sm nucleus is absent, which may greatly enhance nuclear spin coherence time. The degeneracy of the nuclear levels is lifted by the nuclear quadrupole interaction. We show that the splitting of the nuclear levels can be controlled by a static electric field, and that Rabi oscillations between the nuclear levels can be induced by a time-dependent electric field. For the configurations in a singly charged state, electronic Kramers doublets are formed. The electronic configurations including an unpaired 6s orbital exhibit a strong hyperfine Stark effect due to a large Fermi contact contribution to the hyperfine interaction. In these configurations, electric-field-induced Rabi oscillations between the electronic-nuclear levels can occur at frequencies up to 3 orders of magnitude higher than those for the neutral charge state. The proposed system may be experimentally observed within scanning tunneling microscopy.

Coordinated assembly of alkali and alkaline earth metals with the perfluorinated [AlF6] group to design deep-ultraviolet zero-order waveplate materials

The capability of zero-order waveplates to manipulate the polarization of fundamental-frequency light has garnered significant attention in light of the rapid advancements in laser technology. In particular, zero-order waveplate materials in the deep-ultraviolet range (DUV; λ < 200 nm) are in urgent and short supply. In this study, three new aluminum fluorides, AlF3 (P6/mmm), BaAlF5 (I4/m), and Li2KAl2F9 (C2/m), have been successfully designed and synthesized through a strategy that combines the perfluorinated [AlF6] group with alkali and alkaline-earth metals. The results of experimental and theoretical calculations indicate that three new aluminum fluorides have a short cutoff edge (λ < 200 nm) and small birefringence (0.0006-0.0056@1064 nm). In addition, the AlF3 (P6/mmm) has the shortest wavelength of 125 nm based on theoretical calculations, which is comparable to the shortest wavelength of the commercially available MgF2. However, its birefringence of 0.0006@1064 nm is about 20 times lower than that of the MgF2 (0.012@546 nm), making it highly advantageous for fabricating deep-ultraviolet zero-order waveplate materials. Further microscopic analysis reveals that the [AlF6] group exhibits a substantial band gap of 9.17 eV and small polarizability anisotropy, indicating that the aluminum fluorides are potential candidates for designing suitable compounds for DUV zero-order waveplate materials.

Strain-Induced Charge Density Waves with Emergent Topological States in Monolayer NbSe2

Emergence of topological states in strongly correlated systems, particularly two-dimensional (2D) transition-metal dichalcogenides, offers a platform for manipulating electronic properties in quantum materials. However, a comprehensive understanding of the intricate interplay between correlations and topology remains elusive. Here we employ first-principles modeling to reveal two distinct 2 × 2 charge density wave (CDW) phases in monolayer 1H-NbSe2, which become energetically favorable over the conventional 3 × 3 CDWs under modest biaxial tensile strain of about 1%. These strain-induced CDW phases coexist with numerous topological states characterized by Z 2 topology, high mirror Chern numbers, topological nodal lines, and higher-order topological states, which we have verified rigorously by computing the topological indices and the presence of robust edge states and localized corner states. Remarkably, these topological properties emerge because of the CDW rather than a pre-existing topology in the pristine phase. These results elucidate the interplay between correlations, topology, and geometry in 2D materials and indicate that strain-induced correlation effects can be used to engineer topological states in materials with initially trivial topology. Our findings may be applied in electronics, spintronics, and other advanced quantum devices that require robust and tunable topological states.

First-Principles Molecular Dynamics with Potential and Charge Fluctuations Applied to Au(111) in Alkaline Solutions

Electrified solid-liquid interfaces play a crucial role in energy conversion, storage, photoconversion, sensors, and corrosion processes. While computational chemistry simulations can provide detailed insights into reaction mechanisms, aligning experimental and simulation results remains a significant challenge. In this work, we introduce the FDT-SJM method for ab initio molecular dynamics simulations under potential control, where the electrode charge fluctuates around an average value following the fluctuation-dissipation theorem (FDT), and electrode charges are screened by the solvated jellium method (SJM). The FDT-SJM is developed in GPAW, a Python-based open-source DFT code. We validate this approach by simulating the Au(111) interface in pure water, KOH, LiOH, Li, and K solutions at several electrode potentials. We analyze water reorientation in response to changes in the electrode surface charge and demonstrate that the method enables the estimation of interface capacitance and the potential of zero charge, yielding values consistent with experimental data.

In situ activation-induced surface reconstruction on Cr-incorporated Ni3S2 for enhanced alkaline hydrogen evolution reaction

Ni3S2 has emerged as one of the most promising hydrogen evolution reaction (HER) catalysts due to its moderate activity, exceptional electrical conductivity, and scalable synthesis methods. However, the high energy barrier for H2O dissociation and weak desorption of the H* intermediate severely hinder its HER kinetics. In this study, a novel Cr-incorporated Ni3S2 was grown on a Ni mesh substrate (denoted as Cr-Ni3S2/NM) using a one-step electrodeposition approach, resulting in a large surface area with abundant Ni3S2/Cr2S3 heterojunctions. Subsequently, it underwent surface reconstruction after in situ activation (denoted as A-Cr-Ni3S2/NM), which not only enhanced charge and mass transfer but also altered the electronic structure by introducing more oxygen species on the catalyst surface and creating S vacancies. Using theoretical calculations, this in situ activation was shown to not only promote charge transport but also boost HER kinetics by strengthening OH* desorption for H2O dissociation and facilitating the desorption of H* intermediates. As a result, the fabricated A-Cr-Ni3S2/NM demonstrated exceptional HER performance with a small overpotential of 78 mV to deliver a current density of -10 mA cm-2, along with stability for over 200 h at 100 mA cm-2. While surface reconstruction has been intensively studied in catalysts for the oxygen evolution reaction, we illustrate that it also plays a significant and positive role in Cr-Ni3S2 HER catalysts in this study, thus providing a pathway for achieving high-performance HER catalysts.

Isomerization of Organometallic Polymers on Ag(111): Revealing the Intermolecular Hydrogen Transfer Mechanism

Dehalogenation plays a crucial role in on-surface synthesis, but the bond-forming sites in dehalogenation occasionally differ from the original halogen-substituted sites, leading to unexpected products. Revealing its mechanism is essential for the atomically precise fabrication of low-dimensional nanomaterials, although it remains elusive. Herein, we report an isomerization of organometallic polymers derived from debromination on Ag(111) and elucidate the mechanism involving intermolecular hydrogen transfer via combining scanning tunneling microscopy, noncontact atomic force microscopy, and density functional theory calculations. At room temperature, the precursor 1,4-bis(3-bromothiophen-2-yl)benzene undergoes surface-assisted debromination on Ag(111), forming two organometallic polymers where the bond-forming sites correspond to the original debromination sites. Upon annealing to 393 K, the isomerization of organometallic polymers generates a linear organometallic polymer, where the bond-forming sites mismatched with the original debromination sites. Control experiments combined with theoretical calculations demonstrate that the unexpected isomerization proceeds through the dissociation of polymer chains into surface-stabilized diradical monomers or oligomers, intermolecular hydrogen transfer, and the final recombination of surface-stabilized radicals with Ag adatoms.

Experimental and Theoretical Studies on Photocatalytic CO2 Reduction to HCOOH by Biomass-Derived Carbon Dots Embedded Phytochemical-Based CdS Quantum Dots

Photocatalytic CO2 reduction provides a sustainable route to combat climate change by converting CO2 into valuable chemicals by using sunlight. This study presents both experimental and theoretical insights into the reduction of CO2 to HCOOH using biomass-derived carbon dots embedded onto phytochemical-based CdS quantum dots. The 0D CDs/CdS QDs(bio) composites exhibit rich sulfur vacancies and a more negative conduction band, effectively inhibiting CdS photocorrosion (SO42-) while enhancing the CO2 adsorption and photocurrent response. Additionally, it reduced PL intensity and increased decay time, suggesting the enhancement of charge separation and suppression of charge recombination. The optimal 0.4CDs/CdS QDs(bio) composite exhibited a remarkable CO2 reduction to HCOOH formation yield of 439.51 μmol g-1 h-1 (apparent quantum yield of 3.81%) while retaining its structural and morphological stability. Density functional theory calculations reveal HCOO* as a key intermediate, confirming the thermodynamic preference for HCOOH formation over CO with a free energy change of -0.71 eV. This study introduces a novel bio-based CdS QDs composite modified with biomass-derived CDs, providing mechanistic insights into photocatalytic CO2 reduction for sustainable fuel production.

Crystal Structure and Low-Dimensional Magnetism in CsNiV2O6Cl

Single crystals of CsNiV2O6Cl were grown hydrothermally. Its crystal structure (space group I2̅/a) is based on vertex-sharing twisted chains of Ni2+O4Cl2 octahedra and edge-sharing chains of V5+O5 tetragonal pyramids. These chains running along the c- and a-axes, respectively, link, forming an open framework with Cs ions in the voids. At elevated temperatures, the temperature dependence of dc magnetic susceptibility evidences a Haldane-type behavior with estimated intrachain exchange interaction J = 267 ± 16.5 K followed by the strong upturn at lower temperatures. Both dc and ac magnetic susceptibilities exhibit a sharp peak at low temperatures; the latter is independent of frequency. The position of the peak in Fisher's specific heat d(χT)/dT coincides with that in specific heat Cp, which defines the Neel temperature TN = 5.6 ± 0.2 K. While the values of the calculated interchain exchange interaction J' and single-ion anisotropy D place this system into the Haldane sector of the Sakai-Takahashi phase diagram, the long-range antiferromagnetic order at low temperatures is induced by the defects/impurities.

Photo-Fenton degradation on Mo-doped NiFe2O4 photocatalyst

The poor photo-Fenton properties of NiFe2O4, a magnetic material, can be altered by appropriate metal ion doping. We carried out preliminary DFT and TD-DFT calculations and found that the photoexcited molybdenum doped NiFe2O4 interacts effectively with H2O2 for hydroxyl radical generation. Based on this prediction, we prepared Mo-doped NiFe2O4 and tested its photo-Fenton activity for tetracycline (TC) degradation. The Mo-doped NiFe2O4 nanoparticles were significantly finer in size and superparamagnetic, enabling easy after-use separation. Experimental and DFT calculation results showed that the Mo-dopant substitutes the Fe3+ occupying the octahedral site in NiFe2O4. Mo-doping extended the absorption edge and decreased the interfacial charge transfer resistance of NiFe2O4. The Mo-doped NiFe2O4 nanoparticles demonstrated excellent TC photo-Fenton degradation activity, along with appropriate recyclability. A combination of experimental and DFT calculation results indicated the possible photo-Fenton mechanism.

Atomic insights into the electrocatalytic properties of LaBO3 perovskite oxides for lithium-sulfur battery performance

The intricate shuttle effect and sluggish conversion kinetics of lithium polysulfides (Li2Sn, n = 1, 2, 4, 6, and 8) present significant challenges for the practical applications of lithium-sulfur batteries (LSBs). Introducing electrocatalysts to enhance the anchoring ability for Li2Sn and accelerate its conversion is an effective strategy. To gain a deeper understanding of the underlying mechanisms of the anchoring effect and to identify optimal electrocatalytic materials for enhancing the performance of LSBs, the interactions between Li2Sn and electrocatalysts should be studied at the atomic level. In this study, density functional theory calculations were performed to explore cubic LaBO3 (B = Cr, Mn, Fe, Co, and Ni) perovskite oxides as potential electrocatalysts for boosting the electrochemical performance of LSBs. The results show that LaFeO3 exhibits the lowest energy barrier (0.37 eV) for the rate-determining step of the sulfur reduction reaction, while LaCoO3 achieves the lowest decomposition energy barrier for Li2S (1.67 eV) during sulfur oxidation, effectively facilitating Li2S dissociation. Further structural deformation and charge transfer analyses demonstrate that LaBO3 (B = Cr, Mn, Fe, and Co) effectively activates the O and B sites by enabling O to capture electrons initially transferred from Li to S. This process promotes the formation of Li-O and B-S bonds, thereby mitigating the shuttle effect, weakening the Li-S bonds, and enhancing the redox kinetics of LSBs. These findings offer valuable insights for the future design of more efficient perovskite-based electrocatalysts.

Rational design of mixed-valence cobalt-based nanowires via simultaneous vanadium and iron modulations for enhanced alkaline electrochemical water splitting

Strategic modulation of the electronic structure and surface chemistry of electrocatalysts is crucial for achieving highly efficient and cost-effective bifunctional catalysts for water splitting. This study demonstrated the strategic incorporation of redox-active elements (vanadium (V) and iron (Fe)) to optimize the catalytic interface of mixed-valence cobalt-based nanowires (Co5.47N and CoP), which enhanced their hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalytic activity. Experimental and theoretical analyses revealed that the dual-cation doping increased the surface area and optimized the electronic structure of the nanowires, which promoted rapid water dissociation, favoured hydrogen adsorption kinetics, and stabilized the oxygen intermediates. Consequently, the V,Fe-Co5.47N and V,Fe-CoP nanowire electrocatalysts achieved low overpotentials of 55/251 and 63/265 mV for HER/OER at 10 mA cm-2 in 1 M KOH electrolyte, respectively, outperforming their pristine and single-cation-doped counterparts. The alkaline overall water-splitting devices assembled based on these bifunctional catalysts required an overall voltage of only 1.64 V and 1.66 V at 100 mA cm-2 and also demonstrated excellent durability. This work provides valuable insights into enhancing transition metal-based catalysts through the incorporation of redox-active elements for efficient water splitting.

Oleic acid rearrangement enables facile transfer of red-emitting quantum dots from hexane into water with enhanced fluorescence

There is significant demand for the conversion of hydrophobic nanoparticles (NPs) into water-soluble NPs, particularly for the transfer of photoluminescent quantum dots (QDs) synthesized in organic solvents into water-based settings. However, these transfer processes are often inefficient, with only a fraction of the QDs transferred into water, and typically result in decreases in photoluminescence quantum yield (PLQY). Here, we demonstrate a straightforward technique to efficiently transfer oleic acid (OA)-coated CdSe/CdS core-shell QDs into water without the addition of any new reagents. In contrast to the decrease in PLQY that is usually observed when QDs are transferred into water, this process in fact leads to an increase of the PLQY after transfer in basic water (pH 8). The process is highly reproducible and can be applied to other oleic acid-coated NPs. Density-functional-theory (DFT) calculations indicate that the QD transfer into water is enabled by the rearrangement of OA ligands at the surface of the QDs. This discovery allows for widely available, hydrophobic OA-coated QDs to be used in water media without any further modification and with enhanced fluorescence.

Vetting molecular candidates posited for the first diffuse interstellar bands (5780 and 5797 Å): a quantum chemical study

Diffuse interstellar bands (DIBs) comprise over 550 celestial absorption features whose molecular carriers remain largely unidentified or contested. In this study, we present a statistical analysis that identifies two previously overlooked families of strongly correlated lines associated with the original Heger features at 5780 and 5797 Å. Comprehensive UV-vis spectra were computed at several levels of theory (mainly TD-PBE0 and EOM-CCSD with an aug-cc-pVTZ basis set) for the following candidates posited as diffuse interstellar band carriers (in both their neutral and cationic forms): 2-cyclopenten-1-one, 3(2H)-thiophenone, 2(5H)-furanone, 3(2H)-selenophenone, 3-hydroxypropanamide, oxamic acid, lactamide, and glycolamide. Glycolamide is of particular interest since it has recently been detected in microwave (rotational) spectra of the comparatively dense molecular cloud G+0.693-0027. Importantly, the computations reveal that the anions exhibit marginal electron affinities despite producing improbable lines (i.e., with excitations to levels above the ionization threshold) overlapping DIBs, whereas the neutral molecules yield lines shortward of DIBs and possibly linked to the broad 220 nm interstellar feature, and their cations produced too few lines in the DIB domain inspected. Further vetting of candidates awaits the construction of an expansive optical-infrared molecular ion database, which will facilitate concurrent matching to DIBs in the optical (electronic) and their energy differences in the mid-infrared (vibrational), thereby narrowing the parameter space.

Rational Design of Highly Stable and Active Single-Atom Modified S-MXene as Cathode Catalysts for Li-S Batteries

The practical application of Li-S batteries is hindered by the shuttle effect and sluggish sulfur conversion kinetics. To address these challenges, this work proposes an efficient strategy by introducing single atoms (SAs) into sulfur-functionalized MXenes (S-MXenes) catalysts and evaluate their potential in Li-S batteries through first-principles calculations. Using high-throughput screening of various SA-modified S-MXenes, this work identifies 73 promising candidates that exhibit exceptional thermodynamic and kinetic stability, along with the effective immobilization of polysulfides. Notably, the incorporation of Ni, Cu, or Zn as SAs into S-MXenes results in a significant Gibbs free energy barrier reduction by 51%-75%, outperforming graphene-based catalysts. This reduction arises from SA-induced surface electron density that influences the adsorption energies of intermediates and thereby disrupts the scaling relations between Li₂S₂ and other key intermediates. Further enhancement in catalytic performance is achieved through strain engineering by shifting the d-band center of metal atoms to higher energy levels, increasing the chemical affinity for intermediates. To elucidate the intrinsic adsorption properties of intermediates, this work develops a machine learning model with high accuracy (R2 = 0.88), which underscores the pivotal roles of SA electronegativity and local coordination environment in determining adsorption strength, offering valuable insights for the rational design of catalysts.

Impact of alkyl-substituted auxiliary acceptor positioning on dyes for DSSCs with Hagfeldt donor

The introduction of an auxiliary acceptor into donor/acceptor dye systems is one of the most widely used strategies to enhance the light-harvesting properties of dye-sensitized solar cells. However, our understanding of the effects of these auxiliary acceptors remains limited. In this study, we utilize two organic dyes that differ in the positioning of the auxiliary acceptor to explore their impacts on several important factors associated with short-circuit current density and open-circuit photovoltage. These parameters include light-harvesting ability, electron injection, conduction band energy shift and charge recombination. Contrary to common assumptions, we find that the positioning of the alkyl-substituted auxiliary acceptor affects not just the light-harvesting ability but also influences the charge recombination process by altering the dominant conformation of the Hagfeldt donor. Specifically, the auxiliary acceptor situated farther from the Hagfeldt donor is more effective in enhancing the dye's light-harvesting ability compared to those located near the donor end. Conversely, when the auxiliary acceptor is positioned near the Hagfeldt donor and introduces alkyl chains on one side, the two benzene rings substituted with alkoxy groups in the Hagfeldt donor tend to interact with the alkyl chain of the auxiliary acceptor. This interaction hinders the surface protection effect of the Hagfeldt donor and reduces its inhibitory effect on the electron recombination process. These new insights into the effects of alkyl-substituted auxiliary acceptors on inhibiting charge recombination through their influence on the dominant conformation of the Hagfeldt donor opens avenues for the systematic design of high-performance sensitizers.

Identifying In Situ Activity and Selectivity of Oxygen Reduction Catalysts at the Subparticle Level

Oxygen reduction reaction (ORR) plays a crucial role in both the chemical and energy industries. Despite substantial advancements in theoretical, computational, and experimental studies, identifying both the in situ activity and selectivity in ORR electrocatalysis remains a major challenge. Here, using a suite of correlative operando scanning electrochemical probe and electrochemiluminescence microscopy techniques, we establish a link between the morphological structure and the local ORR activity and selectivity of single Au and Au@Pt platelets at the subparticle level. It is clearly shown that the edge facets of Au and Au@Pt platelets exhibit higher activity for 4e- ORR compared to basal planes, whereas the basal planes of both Au and Au@Pt platelets demonstrate superior 2e- selectivity relative to the edge facets. These findings deepen our understanding of ORR activity and selectivity across different facets at the subparticle level, which offers valuable guidance for the rational design of highly efficient ORR electrocatalysts.

Deep photocatalytic NO oxidation on ZnTi-LDH: Pivotal role of surface hydroxyls dynamic evolution

Surface defect engineering has been regarded as an appealing strategy to improve photocatalytic performance, but defects are susceptible to inactivation and thus lose their function as active sites. In this study, we successfully tailored and identified the dynamic evolution of surface hydroxyl defects over ZnTi-layered double hydroxide (ZnTi-LDH) photocatalyst. The enrichment of surface hydroxyl electrons and the dynamic circulation of hydroxyl defects result in enhanced separation and transport capabilities of photogenerated carriers, thereby ensuring the perpetual activation of small molecules into •O2- and •OH. The optimized structure has demonstrated NO removal efficiency values as high as 70.0 %, while concurrently suppressing the emission of NO2 - a dangerous byproduct. Furthermore, ZnTi-LDH exhibits remarkable adaptability to varying environmental conditions and satisfactory durability over extended periods of reaction. This research offers valuable insights into the key role of surface hydroxyl in sustainable NOx removal technologies, and the findings contribute significantly to the advancement of environmental remediations.

Self-cleaning Spiro-OMeTAD via multimetal doping for perovskite photovoltaics

Record power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) are usually achieved using organic spiro-OMeTAD. However, conventional doping with hygroscopic dopants (LiTFSI and tBP) leads to compromised device stability. We introduce a synergistic mixed doping strategy that utilizes a combination of metal-TFSI dopants-LiTFSI, KTFSI, NaTFSI, Ca(TFSI)2, and Mg(TFSI)2-to enhance doping efficiency while effectively removing hygroscopic contaminants from the Spiro-OMeTAD solution. This approach achieves PCEs exceeding 25% and significantly improves stability under harsh environmental conditions. Notably, Ca(TFSI)2 and Mg(TFSI)2 facilitate enhanced oxidative doping, while NaTFSI promotes interstitial doping in the bulk perovskite. Additionally, KTFSI serves as a catalytic agent, lowering the reaction energy barrier for the other dopants, thereby accelerating spiro-OMeTAD ion radical production. These findings underscore the potential of synergistic doping in optimizing the performance and longevity of photovoltaic devices.

A First Principle Study to Understand the Importance of Edge-exposed and Basal Plane Defective MoS2 Towards Nitrogen Reduction Reaction

Nitrogen reduction reaction (NRR) as a promising approach to ammonia synthesis has received much attention in recent years. Molybdenum disulfides (MoS2), as one of the most potential candidates for NRR, are extensively investigated. However, the inert basal plane limits the application of MoS2. Herein, by using density functional theory (DFT) calculations, we constructed edge-exposed MoS2 and different kinds of basal plane defects, including anti-site, sulfur vacancy and pore defects, to systematically investigate their influence on the NRR performance. The thermodynamically calculated results revealed that the NRR on edge-exposed MoS2, anti-site defects, sulfur vacancy with three sulfur atoms missing (S3V) and porous defect (D) exhibit great catalytic activity with low limiting potentials. The calculated limiting potentials are -0.43 and -0.47 V at armchair and zigzag edge MoS2, -0.42 and -0.44 V at anti-site defects, -0.49 and -0.67 V at S3V and D. However, by inspecting the thermodynamic properties of the hydrogen evolution reaction, we proposed that the zigzag-end MoS2 and anti-site defects exhibit a better NRR selectivity compared to armchair-end MoS2, S3V and D. Electronic structure calculations reveals that the edge-exposed and basal plane defective MoS2 can improve the conductivity of the material by reducing the band gap. Donation-backdonation mechanism can effectively promote the activation of nitrogen molecule. Our results pave the way to understanding the defective effects of the MoS2 inertness plane for NRR and designing high-performance NRR catalysts.

CO2-Promoted Assembly of Nonplanar B12O24-Ring as a Fundamental Building Block in Lithium-Sodium Alkali Borates during Carbon Capture

The crystalline structure of Li3NaB4O8, a reaction product resulting from CO2 absorption by lithium-sodium orthoborate ((Li0.5Na0.5)3BO3), a recently developed sorbent for high-temperature carbon capture, is herein elucidated. The compound crystallizes to form a peculiar isolate borate fundamental building block consisting of six 3-membered borate rings interlinked through mutual tetrahedral borates to form a nonplanar 6-membered borate ring of chemical formula B12O24. The identification of this structure allows closing of the loop regarding the reaction mechanism characterizing CO2 capture by lithium-sodium orthoborate, sheds light on previously made observations regarding the evolution of the physicochemical properties of the melt during carbon capture, and provides valuable information for future studies and process simulations involving this promising new material for carbon capture.

Halogen-Driven Structural Engineering in Tellurium Oxyhalides: Enhanced SHG Response and Broad Optical Transparency

Oxyhalides are promising candidates for nonlinear optical (NLO) applications due to their unique structural and optical properties. In this study, we report the synthesis of two tellurium-based oxyhalides, Te8O15Cl2 and Te6O11Cl2, which exhibit distinct structural features and exceptional optical performance. Te8O15Cl2 crystallizes in a noncentrosymmetric 2D layered structure, while Te6O11Cl2 adopts a centrosymmetric 1D chain arrangement. Both compounds display wide optical transmission windows (0.30/0.31-25 μm), with Te8O15Cl2 achieving a large second-harmonic generation (SHG) efficiency surpassing conventional materials and a significant birefringence (Δn = 0.185 at 546 nm). The SHG response of Te8O15Cl2 is attributed to the alignment of nonlinear-active units driven by the [TeO3Cl] disphenoid and the stereochemically active lone pairs (SCALPs), facilitated by halogen-mediated structural distortion. These results highlight the potential of halogen modification for the design of advanced NLO materials with enhanced performance.

Lithiation-Driven Phase Engineering Unlocking Broadband NIR Emission in Cr-Doped Zinc Tantalate

Structural phase evolution is among the most powerful tools for tuning material properties, enabling advancements in catalysis, dielectrics, optoelectronics, and photoluminescence. Such an evolution can significantly enhance the near-infrared (NIR) emission properties of Cr3+-doped phosphors. Herein, we present, to the best of our knowledge, the first observation of lithiation-induced continuous structural phase evolution in ZnTa2O6 phosphors, driven by Li+ incorporation. This evolution proceeds systematically from orthorhombic ZnTa2O6 (Pbcn) to tetragonal ZnTa2O6 (P42/mnm) and ultimately to trigonal (Li0.5Zn0.5)TaO3 (R3c) as the Li+ content increases. When doped with Cr3+, the NIR emission peak exhibits a progressive blue shift, moving from 949 to 885 nm and eventually to 862 nm, in tandem with the phase evolution. This phase evolution also yields significant enhancements in photoluminescent intensity, internal quantum yield (IQY), and photoluminescence thermal stability. Our findings establish a new paradigm for designing highly efficient ultra-broadband NIR phosphors and offer a foundation for developing tantalate-based materials with versatile functionalities, including improved dielectric properties.

Planar Pentacoordinate Bromine in Global Minimum Br6Li5. Chemphyschem 2025;26:e202400882. [PMID: 39861969 DOI: 10.1002/cphc.202400882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Delocalized multicenter bonds play a crucial role in clusters with a planar hypercoordinate center(s), making it difficult for highly electronegative elements, especially halogen atoms, to achieve the planar hypercoordinate arrangement. Herein, we introduce a star-like cluster Br6Li5 -, whose global minimum contains a planar pentacoordinate bromine (ppBr). In this cluster, the central ppBr atom coordinates with five alkali metal Li atoms, which in turn bridge an equal number of electronegative Br atoms in the periphery, leading to the formation of the binary cluster Br6Li5 -. Remarkably, bonding analyses indicate that the planar pentacoordinate configuration of Br6Li5 - is dominated by the electrostatic interactions between the central ppBr atom and the Li5Br5 framework rather than covalent interactions. Despite the absence of delocalized bonds, Br6Li5 - is still a highly stable cluster with a wider HOMO-LUMO gap of 7.73 eV and a higher VDE of 7.55 eV. Therefore, Br6Li5 - should be a promising candidate for future gas-phase generation and spectroscopic characterization.

Tailoring Mesopores on Ultrathin Hollow Carbon Nanoarchitecture with N2O2 Coordinated Ni Single-Atom Catalysts for Hydrogen Evolution

Single-atom catalysts (SACs) offer exceptional atomic utilization and catalytic efficiency, particularly in the hydrogen evolution reaction (HER), where effective mass transport and electronic structure control are critical. However, many SACs suffer from suboptimal hydrogen adsorption energies and limited synergy with the support matrix, which restrict their intrinsic activity and durability. Overcoming these limitations requires an integrated strategy that simultaneously optimizes both the atomic coordination environment and the support architecture. Here, we present a dual-template strategy for synthesizing ultrathin mesoporous hollow carbon (MHC) with tunable mesopores, which enhances ion transport and structural accessibility. Ni single atoms are stabilized within the MHC framework via a tailored N2O2 coordination environment, which fine-tunes the electronic structure of Ni and facilitates efficient hydrogen adsorption and HER kinetics. This coordination environment and the hierarchical porous framework collectively enhance HER activity, significantly reducing the overpotential to 68 mV at 10 mA cm-2 and resulting in remarkable mass activity (5 A mgNi-1 at 50 mV) and enhanced durability over 5000 cycles. Spectroscopic analyses and density functional theory calculations reveal that the N2O2 coordination fine-tunes the electronic structure of Ni, promoting efficient hydrogen adsorption and evolution. These findings highlight the synergistic effects of atomic-level Ni dispersion and tailored support, offering a robust strategy for fabricating single-atom electrocatalysts for sustainable hydrogen production.

Highly efficient degradation of perfluoroalkyl substances (PFAS) by a novel polytetrafluoroetylene piezocatalyst

Perfluoroalkyl substances (PFAS) are environmentally persistent, bioaccumulative and toxic pollutants. However, thorough degradation of PFAS remains exceptionally difficult due to the high dissociation energy of the C-F bond. Here, we report a viable strategy to markedly degrade PFAS completely by capitalizing on a harmless polytetrafluoroetylene (PTFE) as a piezocatalyst. Remarkably, perfluorooctanoic acid (PFOA), as one of the widely used PFAS, was almost completely removed with a degradation rate of 93.4 % and a defluorination rate of 91.5 % by the ultrasound excitation of PTFE for 1 h. On the basis of the intermediate analysis, we proposed an oxidation mechanism for the piezocatalytic PFOA degradation. Furthermore, this strategy was also efficient for the degradation of perfluoroheptanoic acid (PFNA), perfluorooctane sulfonate (PFOS) and hexafluoropropylene oxide dimer acid (Gen-X), implying its effectiveness to remediate water containing multiple PFAS. Impressively, due to the diverse energy gap between HOMO and LUMO energy of various PFAS, the degradation reaction kinetics of different PFAS are of significant difference. This study provides the deep insight into the piezocatalytic technique for the remediation of persistent and disparate PFAS.

Mo4/3B2Tx boosting the electrochemical kinetics and Na2S adsorption of SnS anode in sodium ion batteries

SnS with high theoretical capacity, large lamellar spacing, and favorable voltage plateau is considered as a highly prospective anode material for sodium-ion batteries (SIBs). Nevertheless, the unsatisfied intrinsic conductivity and damaging volume variation during cycles restricted its specific capacity and potential application. In this work, a synergistic sodium storage of interfacial engineering and Na2S adsorption was proposed to boost the electrochemical kinetics of SnS by vertically growing SnS@C nanosheets on MBenes. The experimental and theoretical calculation results verified that the nanosheets, heterogeneous interface, and charge transfer between Mo4/3B2Tx and SnS offered rapid ion diffusion pathways and ameliorated the intrinsic conductivity, promoting the electrochemical kinetics. The sufficient sulfur vacancies and strong adsorption ability of Na2S on MBenes provided supplementary active sites for ion adsorption and suppressed the shuttle effect of Na2S, improving the electrochemical capacity and reversibility. Consequently, the MBenes-SnS@C anode delivered high capacities of 411 mAh g-1 at 1 A g-1 and 420 mAh g-1 after 100 cycles at 0.5 A g-1. The synergistic sodium storage mechanism arising from interfacial effects and Na2S adsorption offered novel insights for the rational design of high-performance transition metal sulfide anodes for SIBs.