Atoms, molecules, solids, and surfaces: Applications of the generalized gradient approximation for exchange and correlation

Nitrogen-doping-induced electron spin polarization activates scandium oxide as high-performance zinc-air battery cathode

Platinum (Pt) is the most active catalyst for the oxygen reduction reaction (ORR). However, the scarcity, high cost, and susceptibility to deactivation of Pt constrain its large-scale applications. Transition metal oxide (TMO) materials have emerged as promising alternatives due to their abundant availability and catalytic potential. Herein, we report a dissolution-and-carbonization strategy to synthesize a carbon-supported nitrogen-doped Sc2O3 catalyst (N-Sc2O3/C). Nitrogen doping significantly enhances the conductivity of the otherwise poor-conductivity Sc2O3, transforming it into a superior ORR catalyst. The synthesized N-Sc2O3/C exhibits remarkable ORR performance in 0.1 M KOH, achieving a half-wave potential of 0.92 V, which is 55 mV higher than the state-of-the-art commercial Pt/C (0.87 V). Moreover, as a cathode for a zinc-air battery, N-Sc2O3/C achieves a peak power density of 150.7 mW cm-2 and a specific capacity of 766.4 mAh gZn-1. Density functional theory calculations reveal that nitrogen doping induces electron spin polarization within Sc2O3, narrowing the bandgap. This enhanced electronic structure improves conductivity and optimizes the adsorption of oxygen intermediates, thereby facilitating the ORR process. Our study demonstrates that nitrogen doping activates the wide-bandgap Sc2O3 semiconductor, converting it into a highly efficient ORR electrocatalyst and highlighting the potential of wide-bandgap TMO materials in energy applications.

Boosting selective chlorine evolution reaction: Impact of Ag doping in RuO2 electrocatalysts

The chlor-alkali process is critical to the modern chemical industry because of the wide utilization of chlorine gas (Cl2). More than 95 % of global Cl2 production relies on electrocatalytic chlorine evolution reaction (CER) through chlor-alkali electrolysis. The RuO2 electrocatalyst serves as the main active component widely used in commercial applications. However, oxygen evolution reaction (OER) generally competes with CER electrocatalysts at RuO2 electrocatalyst owing to the intrinsically scaling reaction energy barrier of *OCl and *OOH intermediates, leading to decreased CER selectivity, high energy consumption, and increased cost. Here, the effect of Ag doping on selective CER over RuO2 electrocatalysts prepared by a sol-gel method has been systematically studied. We found that Ag-doping can effectively improve the Faradaic efficiency of RuO2 electrocatalyst for CER. Furthermore, the improved CER selectivity of Ag-doped RuO2 electrocatalysts is highly dependent on the Ag-doping concentration. The optimized Ag0.15Ru0.85O2 electrocatalyst displays an overpotential of 105 mV along with a selectivity of 84.64 ± 1.84 % in 5.0 M NaCl electrolyte (pH = 2.0 ± 0.05), significantly outperforming undoped one (142 mV, 72.75 ± 1.52 %). Our experiments and density functional theory (DFT) calculations show electron transfer from Ag+ to Ru4+ suppresses *OOH intermediates desorption on Ag-doped RuO2, enabling improved CER selectivity. Such designs of Ag-doped RuO2 electrocatalysts are expected to be favorable for practical chlor-alkali applications.

Two-in-one strategy to enhance the stability of Ti3C2Tx in transition metal ion solutions

Although MXenes have attracted significant attention across diverse fields, they exhibit a pronounced susceptibility to oxidation in aqueous environments, with oxidation significantly accelerated in the presence of transition metal ions (TMI) such as Fe3+ and Cu2+. This limitation impedes the synthesis of transition metal compounds/MXene-based composites and their potential for functional applications. In this study, we elucidate the mechanism of accelerated oxidation of Ti3C2Tx is that Fe3+ promotes the electron loss in Ti3C2Tx, thus leading to an increased production of hydroxyl radicals (OH) to oxidize Ti3C2Tx. Furthermore, a rational two-in-one strategy is provided with adding electron-rich ethylenediaminetetraacetic acid disodium zinc salt (ZnNa2EDTA) to enhance the stability of Ti3C2Tx by defect filling and electron donation. Consequently, the production of OH is significantly reduced and thus Ti3C2Tx remains well-preserved in the presence of Fe3+, which has also effectively enhanced the oxidation stability of Ti3C2Tx in the presence of Cu2+. This work is expected to pave a new pathway for targeted applications with coexisting Ti3C2Tx and TMI.

Proposing lithium pump mechanism for observing Ag-Li two-phase interface reaction of in-situ Li-O2 battery by two-step method

Silver (Ag) plays an important role as a cathode catalyst in lithium-oxygen batteries (Li-O2 batteries). However, the catalytic mechanism of Ag remains unclear. Despite efforts dedicated to studying interfacial reactions, observing efficient reactions and ion transport at the Ag-Li solid-solid interface continues to be a challenge. Here, we used Ag nanowires (Ag NWs) as working electrodes, creating a lithiation-oxidation microenvironment within spherical aberration-corrected transmission electron microscopy (ETEM) through a two-step method to investigate the reaction mechanisms at the Ag-Li interface. The lithiation process generates Ag3Li10, while the oxidation process precipitates Ag nanoparticles (Ag NPs). The alternating reactions of Ag-Ag3Li10-Ag form a cycle process, elucidating the transport pathway of Li+ at the Ag-Li solid-solid interface during discharge process and demonstrating a typical lithium pump effect. Density Functional Theory (DFT) calculations also confirm these results. This work provides novel insights into the interfacial mechanisms of Ag catalysts in Li-O2 batteries, offering valuable guidance for strategies to monitor and control complex, multi-step interfacial reactions.

Spontaneous immobilization of single atom in Nb2CTx MXene as excellent nanozyme for detecting and preventing gastric mucosal injury

Early diagnosis and treatment of gastric mucosal injury is crucial to prevent further gastritis and even canceration. As an efficient biocatalyst, single-atom nanozyme (SAzyme) is proposed to be an ideal candidate for the construction of multifunctional platforms. Nevertheless, SAzyme still faces challenges in detecting and treating diseases due to the complexity of preparation methods, limitations of enzyme activity, and undesirable biocompatibility. Specifically, the Nb2CTx MXene with abundant Nb-deficit vacancy defects and high reductive capability can potentially be recognized as an effective support for stabilizing single atoms. Single-atom Pt-immobilized Nb2CTx nanosheet (SA Pt-Nb2CTx) possessing significant glutathione peroxidase (GPx)-like and superoxide dismutase (SOD)-like activities have been synthesized by a simple spontaneous reduction method. Based on the GPx-like activity of SA Pt-Nb2CTx, a simple Fe2+ fluorescence sensor is developed with a detection limit of 1.02 μM. Furthermore, the in vitro experiments reveal the excellent antioxidation capacity of this nanozyme, which effectively alleviates the inflammatory response. Importantly, the self-assembled SA Pt-Nb2CTx possesses a superior protective effect against ethanol-induced gastric mucosal damage, which is mainly related to the enhanced antioxidant and anti-inflammatory effects. Overall, engineered single-atom modified MXene as a multienzyme mimetic provides new insights for the manufacture of single-atom nanozyme and its application in protecting gastrointestinal health.

Synthesis of a biphenylene nanoribbon by compressing biphenylene under extreme conditions

Nonbenzenoid graphene nanoribbons such as biphenylene networks have gained increasing attention owing to their promising electronic and transport properties, but their scalable synthesis is still a huge challenge. Pressure-induced topochemical polymerization is an effective method to assemble molecular units into extended carbon materials, and the structure and properties of the carbon material can be tuned by modifying its molecular precursors. Herein, by directly compressing biphenylene at room temperature, we successfully synthesized crystalline biphenylene nanoribbons in milligram scale. By combining the spectroscopy and single crystal X-ray diffraction methods as well as theoretical calculation, we found that biphenylene experiences a minor phase transition above 3 GPa, and two phenyls in biphenylene undergo sequential para-polymerization along the a-axis to form a ribbon structure at 14 GPa. Our work provides an important reference for the high-pressure reaction of aromatics and the synthesis of complex nanoribbons.

Single-Atom Saturation: A Fundamental Principle for Single-Atom-Site Catalyst Design

Single-atom alloys (SAAs), with twin advantages of alloys and single-atom catalysts, have emerged as an innovative class of electrocatalysts. This uniqueness is expected to achieve unattainable catalytic performance but simultaneously gives rise to the absence of guidelines for designing desired SAAs. Herein, we proposed a fundamental principle, single-atom saturation (SSA), to quantify the binding strength of different intermediates on SAAs, enabling the rapid and qualitative evaluation of the catalytic activity across various reactions. SSA is rationalized by combining the variation of electronic structure (d electron occupancy saturation) and geometrical structure (coordination saturation) of the single guest atom as well as the effect of the host atom type and the intermediate adsorption configuration. Based on the insights given by SSA, Pd1Cu(111), Ru1Cu(111), Ir1Ag(111), Pt1Ag(111), and Pt1Cu(111) are predicted to possess excellent activity for CO2 reduction, N2 reduction, O2 evolution, O2 reduction, and H2 evolution reactions, respectively, most of which are supported by reported experiments. Moreover, SSA is also applicable to nitrogen-doped graphene-supported single-atom catalysts (SACs) with ultrahigh accuracy. In general, single-atom saturation is a concise, interpretable, and universal descriptor that deciphers the structure-activity relation of SAAs across various reactions, where the insights revealed also offer a simple and fundamental principle for the design of excellent single-atom-site catalysts.

Boosting Amino Acid Synthesis with WOx Sub-Nanoclusters

The conversion of nitrate-rich wastewater and biomass-derived blocks into high-value products using renewably generated electricity is a promising approach to modulate the artificial carbon and nitrogen cycle. Here, a new synthetic strategy of WOx sub-nanoclusters is reported and supported on carbon materials as novel efficient electrocatalysts for nitrate reduction and its coupling with α-keto acids. In acidic solutions, the NH3-NH2OH selectivity can also optimized by adjusting the potential, with the total FE exceeding 80% over a wide potential range. After introducing α-keto acids, the WOx/D-CB electrode achieves remarkable activity and selectivity toward C2-C6 amino acids. For glycine and alanine, impressive FEs of 49.34% and 38.22% based on transitional metal oxides can be obtained, surpassing those of WOx nanoclusters with larger size. In situ analysis and mechanistic studies reveal the critical role of WOx sub-nanoclusters in reducing the energy barriers of key steps in alanine synthesis. This work opens up new insights into the rational design of cluster catalysts to promote electrochemical amino acid synthesis.

Unveiling Aqueous Potassium-Ion Batteries with Prussian Blue Analogue Cathodes

Aqueous rechargeable potassium-ion batteries have considerable advantages and potentials in the application of large-scale energy storage systems, owing to its high safety, abundant potassium resources, and environmental friendliness. However, the practical applications are fraught with numerous challenges. Identification of suitable cathode materials and potassium storage mechanisms are of great significance. Herein, an aqueous potassium-ion battery comprising Prussian blue analogs cathode (K1.15Fe[Fe(CN)6]·1.36H2O) and perylene-3,4,9,10-tetracarboxylic anode is designed, which delivers a high energy density of 52.0 Wh kg-1 and excellent cycling stability with high capacity retention of 84.5% after 4000 cycles. Importantly, a synergistic study of the relationships among crystal structure, spin state, kinetics, and electrochemical performances is thoroughly conducted. By employing in situ and ex situ characterizations, the potassium storage mechanism is comprehensively elucidated from multiple perspectives.

Prediction of Redox Potentials for Different Oxidation States of U, Np, Pu, and Am in Alkaline Aqueous Solution

The redox potentials for U, Np, Pu, and Am for oxidation states +III up to +VIII in alkaline aqueous solutions were predicted using density functional theory (DFT) and small-core pseudopotentials and their basis sets, with a hybrid explicit/implicit solvent model using SHE = 4.28 V. For each oxidation state, various oxo/hydroxo complexes were evaluated, resulting in a variety of one-electron redox pathways. For An(VIII/VII) couples, the predicted redox potentials for the [An(VIII)O5(OH)]-3/[An(VII)O4(OH)2]-3 or [An(VIII)O4(OH)2]-2/[An(VII)O4(OH)2]-3 couples are in good agreement with existing estimates. For An(VII/VI) redox couples, all couples, particularly [An(VII)O4(OH)2]-3/[An(VI)O2(OH)4]-2, were in agreement with experimental values for U, Np, and Pu, but the results for Am showed larger differences from the estimated potentials. The An(VI/V) couples were consistent with experiments for dioxo/tetrahydroxo couples, and the An(V/IV) couples showed acceptable agreement based on actinide-specific couples, with neutral hydroxides often favored in the +IV state. The An(IV/III) couples were consistent with the literature values when modeled as soluble neutral hydroxides. The use of our approach yielded calculated redox potentials that were within ±0.2 V of experimental or estimated values consistent with our prior calculations on redox potentials of actinides from Ac to Am in acidic aqueous solutions. This supports the robustness of our DFT-based methodology for predicting actinide redox potentials, offering valuable insights into actinide chemistry in aqueous solutions.

Highly Symmetrical Palladium Cluster Complexes with Either Anticuboctahedral or Cuboctahedral Pd13 Core: Theoretical Insight into Factors Determining Symmetrical Structure

One of the important open questions is what factor(s) determines the symmetry of the structure of the metal nanocluster complex. [Pd13(μ-Cl)3(μ4-C16H16)6]+ (Anti-μ4; C16H16 = [2.2]paracyclophane) has an anticuboctahedral Pd13 core unlike [Pd13(μ4-C7H7)6]2+ with cuboctahedral Pd13 core. DFT calculations show that Anti-μ4 is more stable than isomers, [Pd13(μ-Cl)3(μ3-C16H16)3(μ4-C16H16)3]+ and [Pd13(μ-Cl)3(μ2-C16H16)3(μ4-C16H16)3]+ with cuboctahedral Pd13 core (Cubo-μ3,μ4 and Cubo-μ2,μ4, respectively) and [Pd13(μ-Cl)3(μ3-C16H16)6]+ with distorted icosahedral Pd13 core (dis-Ih-μ3). Not the stabilities of [Pd13(μ-Cl)3]+ core and (C16H16)6 ligand-shell but rather the interaction energy (Eint) between [Pd13(μ-Cl)3]+ and (C16H16)6 ligand-shell determines stabilities of these complexes. μ4-C16H16 coordination bond is stronger than μ2- and μ3-coordination bonds, leading to a larger Eint value in Anti-μ4 than in isomers bearing μ2- or μ3-coordination bond. An icosahedral Pd13 core is not favorable for these Pd13 complexes because of the absence of a Pd4 plane. [Pd13(μ-Cl)3(μ4-C16H16)6]+ with cuboctahedral Pd13 (Cubo-μ4) is not stable despite the presence of six Pd4 planes, because its three Pd4 planes with μ-Cl ligand cannot form μ4-C16H16 coordination bond due to steric repulsion of C16H16 with the μ-Cl ligand. In contrast, Anti-μ4 is stable because it has six Pd4 planes with no Cl ligand to form strong μ4-C16H16 coordination bonds without steric repulsion. Also, discussion is presented on the difference in symmetry between [Pd13(μ-Cl)3(μ4-C16H16)6]+ and [Pd13(μ4-C7H7)6]2+.

PyPWDFT: A Lightweight Python Software for Single-Node 10K Atom Plane-Wave Density Functional Theory Calculations

PyPWDFT is a Python software designed for performing plane-wave density functional theory (DFT) calculations. It can perform large-scale DFT calculations using only a single process on a single node, including local density functional for 10,000 atoms and nonlocal hybrid functional for 4096 atoms. Our benchmark test results demonstrate that PyPWDFT achieves performance comparable to that of Fortran/C++ codes, despite being developed in a native Python environment. In addition, it requires only NumPy, SciPy, and CuPy, enabling CPU-GPU heterogeneous computing, achieving a two-order-of-magnitude speedup compared to single-threaded CPU execution. Due to its excellent cross-platform compatibility, medium-scale DFT calculations can be performed through a graphical user interface on personal computers and Windows systems using consumer-grade GPUs, such as the NVIDIA GeForce RTX 4090. The computational efficiency is comparable to that of professional-grade GPUs such as the NVIDIA V100. The efficient performance, scalability to handle large-scale systems, high numerical accuracy, and different interfaces for molecular dynamics collectively underscore the considerable potential of PyPWDFT to develop into versatile DFT software.

Electron doping in non-magnetic YH3 leads to room temperature ferromagnetism and a flat band: insights from density functional theory

Herein, we investigated the origin of induced room temperature d0 ferromagnetism in YH3 doped with B (2μB per defect magnetic moment) using density functional theory (DFT) simulations. The prediction of d0 ferromagnetism in non-magnetic YH3 using the generalized gradient approximation functional was further confirmed using the hybrid HSE06 functional. Interestingly, B doping in the system led to the appearance of a flat band, which may be due to electron doping in the system. The presence of a flat band at the Fermi level may lead to stable ferromagnetism in the system. We found that YH3 attained 2.0μB magnetic moment per defect using a single B atom with an impurity concentration of 1.04 at%. The partial density of states along with the spin-density plot implied that the induced magnetic moment was the result of the interaction between the localized 2p and 4d orbitals of the impurity B and host Y atoms, respectively, within the doped system, satisfying the Stoner criteria for induced ferromagnetism. Ferromagnetism in the system at room temperature was estimated by calculating the Curie temperature, which was around Tc = 510 K, using the mean field approximation. The thermodynamic and dynamic stabilities of the system at 25 GPa were confirmed using ab initio MD simulation and phonon dispersion, respectively. All these results indicate the experimental feasibility of the system as a spintronic device, and we propose that electron doping may be a possible route for designing materials with interesting properties.

Tandem reductive amination and deuteration over a phosphorus-modified iron center

Deuterated amines are key building blocks for drug synthesis and the identification of metabolites of new pharmaceuticals, which drives the search for general, efficient, and widely applicable methods for the selective synthesis of such compounds. Here, we describe a multifunctional phosphorus-doped carbon-supported Fe catalyst with highly dispersed isolated metal sites that allow for tandem reductive amination-deuteration sequences. The optimal phosphorus-modified Fe-based catalyst shows excellent performance in terms of both reactivity and regioselectivity for a wide range of deuterated anilines, amines, bioactive complexes, and drugs (>50 examples). Experiments on the gram scale and on catalyst recycling show the application potential of this method. Beyond the direct applicability of the developed method, the described approach opens a perspective for the development of multifunctional single-atom catalysts in other value-adding organic syntheses.

Kinetic cation effect in alkaline hydrogen electrocatalysis and double layer proton transfer

Unveiling the so far ambiguous mechanism of the significant dependence on the identity of alkali metal cation would prompt opportunities to solve the more than two orders of magnitude slowdown of hydrogen electrocatalytic kinetics in base relative to acid, which has hampered the effort to reduce the precious metal usage in fuel cells by using the hydroxide exchange membrane. Herein, we present atomic-scale evidences from ab-initio molecular dynamics simulation and in-situ surface-enhanced infrared absorption spectroscopy which show that it is the apparent discrepancies in the electric double-layer structures induced by differently sized cations that lead to largely different interfacial proton transfer barriers and therefore hydrogen electrocatalytic kinetics in base. Concretely, severe accumulation of larger cation in electric double-layer causes more discontinuous interfacial water distribution and H-bond network, thus rendering the proton transfer from bulk to interface more obstructed. Such notion is strikingly different from the previously envisioned impact of cation-intermediate interactions on the energetics of surface steps, providing a unique interfacial perspective for understanding the ubiquitous cation specificity in electrocatalysis.

Capturing Copper Single Atom in Proton Donor Stimulated O-End Nitrate Reduction

Ammonia (NH3) is vital in global production and energy cycles. Electrocatalytic nitrate reduction (e-NO3RR) offers a promising route for nitrogen (N) conversion and NH3 synthesis, yet it faces challenges like competing reactions and low catalyst activity. This study proposes a synergistic mechanism incorporating a proton donor to mediate O-end e-NO3RR, addressing these limitations. A novel method combining ultraviolet radiation reduction, confined synthesis, and microwave treatment was developed to create a model catalyst embedding Cu single atoms on La-based nanoparticles (p-CNCusLan-m). DFT analysis emphasizes the critical role of La-based clusters as proton donors in e-NO3RR, while in situ characterization reveals an O-end adsorption reduction mechanism. The catalyst achieves a remarkable Faraday efficiency (FENH3) of 97.7%, producing 10.6 mol gmetal -1 h-1 of NH3, surpassing most prior studies. In a flow cell, it demonstrated exceptional stability, with only a 9% decrease in current density after 111 hours and a NH3 production rate of 1.57 mgNH3/h/cm-2. The proton donor mechanism's effectiveness highlights its potential for advancing electrocatalyst design. Beyond NH3 production, the O-end mechanism opens avenues for exploring molecular-oriented coupling reactions in e-NO3RR, paving the way for innovative electrochemical synthesis applications.

Mapping of the full polarization switching pathways for HfO2 and its implications

The discovery of ferroelectric phases in HfO2 offers insights into ferroelectricity. Its unique fluorite structure and complex polarization switching pathways exhibit distinct characteristics, challenging conventional analysis methods. Combining group theory and first-principles calculations, we identify numerous unconventional electric polarization switching pathways in HfO2 with energy barriers of 0.32 to 0.57 eV as a function of the different shift in the suboxygen lattices. In total, we identify 47 switching pathways for the orthorhombic phase, corresponding to the left cosets of the [Formula: see text] group with [Formula: see text] group. Contrary to the conception that the tetracoordinated oxygen (OIV) layers are inactive, our result demonstrates that both the tricoordinated oxygen (OIII) and OIV can be displaced, leading to polarization switching along any axial direction. The multiple switching pathways in HfO2 result in both 180° polarization reversal and the formation of 90° domains observed experimentally. Calculations show that specific switching pathways depend on the orientation of the applied electric field relative to the HfO2 growth surface. This allows HfO2 to automatically adjust the in-plane polarization direction under an out-of-plane electric field, thereby maximizing the out-of-plane component and contributing to the wake-up process. These findings redefine the roles of OIII and OIV layers, clarify unconventional switching pathways, and enhance our understanding of electric field response mechanisms, wake-up, and fatigue in ferroelectrics.

Acentric Order-Disorder Zn3Sb4CO6F6: Crystal Structure, Dye Degradation, Cr(VI) Removal, Antibacterial Activity, and Catalytic C-C Bond Formation

Acentric Zn3Sb4CO6F6 has been synthesized by a hydrothermal technique. Single crystal X-ray diffraction study reveals that it crystallizes in cubic symmetry with a = 8.1480 (5) Å and Z = 2 (I4̅3 m). The carbon atom has tetrahedral coordination by Sb, either as an ordered structure at the center of the tetrahedron or as a disordered structure with carbon displaced toward three Sb atoms; the latter model leads to more acceptable Sb-C interatomic distances. Zn3Sb4CO6F6 has been established as the first multifunctional [M-L-C-O-F] compound, with exceptional properties, i.e., photocatalyst, adsorbent, catalyst for organic reactions, and antibacterial agent. This compound successfully degraded 89.5% of 50 mg/L methylene blue dye under solar illumination. It was also proved to be a proficient adsorbent toward Cr(VI) removal with qmax of 47.18 mg/g. The antibacterial activity was investigated by "agar cup assay" against both Gram-positive and Gram-negative bacterial strains. Zn3Sb4CO6F6 also functions as an excellent catalyst for the solvent-free Knoevenagel condensation reaction, with more than 90% yield. Theoretical investigations further proved that Zn3Sb4CO6F6 exhibits a direct band gap energy of 1.76 eV, which is consistent with the experimental findings. The synthesized compound was also characterized through fourier transform infrared spectroscopy, powder X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction study.

Structural Snapshots on Stepwise Anionic Oxoborane Formation: Access to an Acyclic BO Ketone Analogue and Its Metathesis Chemistry with CO2 and CS2

In this work, we disclose the synthesis and characterization of non-acid/base-stabilized anionic oxoboranes [MesTer2BO][K(L)] (MesTer = -C6H3-2,6-(2,4,6-Me3-C6H2)2, L = [2.2.2]-cryptand or 18-crown-6), which are isoelectronic and isostructural with aryl-substituted ketones. The stepwise synthetic formation of these ion-separated oxoboranes is demonstrated on the one hand by the treatment of the parent borinic acid MesTer2BOH with N-heterocyclic carbenes (NHCs) to give [MesTer2BO][HNHC] derivatives, and on the other hand by a deprotonation-sequestration sequence. Bearing polarized boron-oxygen moieties, their inherent reactivity toward both carbon disulfide and carbon dioxide reveals a unique π-bond metathesis reactivity to yield [(MesTer)2B-μ-E2C=E][K(L)] (E = O, S) derivatives.

Quantum Chemical Evaluation and QSAR Modeling of N-Nitrosamine Carcinogenicity

N-Nitrosamine compounds in pharmaceuticals are a major concern due to their carcinogenic potential. However, not all nitrosamines are strong carcinogens, and understanding the structure-activity relationships of this compound group is a major challenge. The determination of the acceptable intake limits for this compound group is determined by applying either a simple carcinogenic potency categorization approach (CPCA) or read-across analysis from simple nitrosamines where experimental data exist. However, the emergence of structurally complex nitrosamines makes quantitative models desirable. Here, we present a two-step modeling approach based on a linear discriminant analysis of a set of quantum mechanical and classical descriptors followed by a 3D-QSAR PLS regression model to predict the logTD50 of nitrosamine compounds.

Planar chlorination engineering induced symmetry-broken single-atom site catalyst for enhanced CO2 electroreduction

Breaking the geometric symmetry of traditional metal-N4 sites and further boosting catalytic activity are significant but challenging. Herein, planar chlorination engineering is proposed for successfully converting the traditional Zn-N4 site with low activity and selectivity for CO2 reduction reaction (CO2RR) into highly active Zn-N3 site with broken symmetry. The optimal catalyst Zn-SA/CNCl-1000 displays a highest faradaic efficiency for CO (FECO) around 97 ± 3% and good stability during 50 h test at high current density of 200 mA/cm2 in zero-gap membrane electrode assembly (MEA) electrolyzer, with promising application in industrial catalysis. At -0.93 V vs. RHE, the partial current density of CO (JCO) and the turnover frequency (TOF) value catalyzed by Zn-SA/CNCl-1000 are 271.7 ± 1.4 mA/cm2 and 29325 ± 151 h-1, as high as 29 times and 83 times those of Zn-SA/CN-1000 without planar chlorination engineering. The in-situ extended X-ray absorption fine structure (EXAFS) measurements and density functional theory (DFT) calculation reveal the adjacent C-Cl bond induces the self-reconstruction of Zn-N4 site into the highly active Zn-N3 sites with broken symmetry, strengthening the adsorption of *COOH intermediate, and thus remarkably improving CO2RR activity.

Dual action of non-metal doped C2N and Ti3C2T2 heterojunction enhances the catalytic activity of electrochemical simultaneous oxidation of hydrogen peroxide and peroxymonosulfate:A theoretical study

Electrochemical advanced oxidation processes (EAOPs) are energy-efficient methods for generating activated radicals like HO• and SO4•-, which enable the degradation of difficult-to-mineralize chlorinated organic compounds. This study explored the catalytic activity and reaction mechanism of EAOPs under a dual strategy involving non-metal doped C2N (X@C2N (X = O, F, Si)) and a heterostructured build (X@C2N/Ti3C2T2) using first principles calculation. The non-metal doping and the heterojunction construction can make H2O2 and PMS spontaneously adsorb (Eads < 0), with negative Gibbs free energy for their oxidation to HO• and SO4•-, significantly enhancing catalytic activity. The catalytic activity of the X@C2N catalysts was in the order of O@, F@, and Si@C2N. The loading of Ti3C2T2 improved the stability and activity of the material, while Ti3C2F2 and Ti3C2O2 proved superior as heterojunction carriers compared to Ti3C2(OH)2. Notably, O@C2N/Ti3C2F2 is proved to be an appropriate catalyst for simultaneous hydrogen peroxide (ΔGmax = -0.90 eV) and peroxymonosulfate (ΔGmax = -0.99 eV) oxidation reactions, achieving non-selective generation of oxidants in electrochemistry. 2,4-D can be effectively degraded by surface-generated HO• and SO4•-, with the reactivity of SO4•- towards 2,4-D greater than that of HO•. This research highlights the potential of combining heteroatom doping with heterojunction catalyst formation to enhance EAOPs for environmental remediation.

Computational Analysis of Diastereoselectivity and Carbene Reactivity in Pt- and Au-Catalyzed 1,5-Enyne Cycloisomerization to Bicyclo[3.1.0]hexane

Bicyclo[3.1.0]hexane is a structural motif of the bioactive, naturally occurring cryptotrione and could be realized via a Pt- or Au-catalyzed reaction on 1,5-enyne with good control of the diastereoselectivity. In this work, we perform a density functional theory (DFT) study that provides mechanistic insight into this intriguing reaction and discloses the origin of the diastereoselectivity and reactivity. Distortion/interaction analyses and computational models reveal that the diastereoselective cyclization of the [Pt]-catalyzed β-enyne favors a transition state with stronger hydrogen bonding, CH···π interactions, and less steric repulsion. The degree of back donation of the platinum carbene determines the activation barrier of the rate-determining hydride migration step. In the diastereoselective transition states of the [Au]-catalyzed reaction of α-enyne, the degree of out-of-plane distortion of the alkenyl moiety and the bending of the alkynyl group determine the preference. DFT calculations provided insight into transition states and intermediates that are difficult to detect experimentally, revealing structural factors that control the selectivity and reactivity.

Cation effects on CO2 reduction catalyzed by single-crystal and polycrystalline gold under well-defined mass transport conditions

The presence of alkali metal cations in the electrolyte substantially affects the reactivity and selectivity of electrochemical carbon dioxide (CO2) reduction (CO2R). This study examines the role of cations in CO2R on single-crystal and polycrystalline Au under controlled mass-transport conditions. It establishes that CO2 adsorption is the rate-determining step regardless of cation type or surface structure. Density functional theory calculations show that electron transfer occurs to a solvated CO2-cation complex. A more positive potential of zero charge enhances CO2R activity only on Au with similar surface coordination. The symmetry factor (β) of the rate-determining step varies with surface structure and cation identity, with density functional theory calculations indicating β's sensitivity to surface and double-layer structures. These findings emphasize the importance of both surface and double-layer structures in understanding cation effects on CO2R.

Developing orbital-dependent corrections for the non-additive kinetic energy in subsystem density functional theory

We present a novel route to constructing cost-efficient semi-empirical approximations for the non-additive kinetic energy in subsystem density functional theory. The developed methodology is based on the use of Slater determinants composed of non-orthogonal Kohn-Sham-like orbitals for the evaluation of kinetic energy expectation values and the expansion of the inverse molecular-orbital overlap matrix into a Neumann series. By applying these techniques, we derived and implemented a series of orbital-dependent approximations for the non-additive kinetic energy, which are employed self-consistently. Our proof-of-principle computations demonstrated quantitatively correct results for potential energy curves and electron densities and hinted on the applicability of the introduced empirical parameters to different types of molecular systems and intermolecular interactions. Therefore, we conclude that the presented study is an important step toward constructing accurate and efficient orbital-dependent approximations for the non-additive kinetic energy applicable to large molecular systems.

Surface-Dependent Role of Oxygen Vacancies in Dimethyl Carbonate Synthesis from CO2 and Methanol over CeO2 Catalysts

The conversion of CO2 into value-added commodity chemicals, such as dimethyl carbonate (DMC), represents an environmentally friendly approach to CO2 utilization. This study exhaustively investigates the influence of oxygen vacancies (Ov) on CeO2 catalysts and, in particular, the role of surface structure. By integrating density functional theory calculations with experimental synthesis, we analyze the complex reaction mechanisms involved in DMC synthesis over both oxidized (Sto-(111), Sto-(110), and Sto-(100)) and nonoxidized (Ovsub-(111), Ovsur-(110), and Ovsur-(100)) CeO2 catalysts. Our findings indicate that Ov on the (111) surface inhibits DMC formation, whereas Ov on the (110) and (100) surfaces promotes it. This differential behavior is primarily attributed to Ov's modulation of the microscopic coordination environment on distinct surfaces, which impacts the rate-limiting step of C-O bond formation: CO2 + OCH3 → CH3OCOO (monodentate methyl carbonate, MMC) and CH3OCO + OCH3 → DMC. Additionally, analysis of the highly active Sto-(111) and Ovsur-(110) catalysts shows that their unique surface coordination microenvironments mitigate steric hindrance and facilitate an optimal arrangement of Lewis acid sites in proximity to Lewis base sites, thereby enhancing the DMC activity. This work underscores the pivotal role of surface structure in determining the effects of Ov, paving the way for the rational design of CeO2-based catalysts for the direct synthesis of DMC from CO2 and methanol.

Understanding the mechanism of water splitting on (111) and (001) surfaces of CsPbI2Br: time-domain ab initio analysis and DFT study

Photochemical splitting of water is a promising source of clean and sustainable energy. Perovskites are increasingly being used as photocatalysts. In this paper, we have presented nonadiabatic quantum dynamics simulations (NAMD) and ab initio simulation studies of photocatalytic splitting of water on the (111) and (001) surfaces of CsPbI2Br. The simulations not only helped identify the surface on which splitting occurred but also provided atomistic insights into this behavior. We proposed a three-step reaction mechanism, comprising photogeneration of charge carriers, followed by hole transfer from the iodine atom to water and splitting of water at the interface. Subsequent to water splitting, a hydrogen bond was formed between H and I. The splitting occurred due to the shifting of p-orbitals of the oxygen atom in the presence of light. We have computed the charge carrier lifetime on the (111) and (001) surfaces. The overlap integral between the conduction band minima (CBM) and valence band maxima (VBM) was suppressed on the (111) surface compared to that on the (001) surface. As a result, charge carriers remained separated for a longer time on the (111) surface and could participate in the water splitting process.

Interfacial Polarization Enhanced Ultrafast Carrier Dynamics in Ferroelectric CuInP2S6

Two-dimensional (2D) ferroelectric materials hold great potential for various electronic applications, including nonvolatile memory, ferroelectric field-effect transistors, and functional sensors. Cooperative phenomena associated with ferroelectricity-modulated carrier dynamics in the 2D context have primarily remained unexplored. To address this gap, we investigate the photoinduced dynamics in CuInP2S6 (CIPS) and elucidate the relationship between photoexcited carrier dynamics and interfacial polarizations. The intrinsic polarization substantially prolongs the carrier lifetime assisted by the mitigation of Cu+ ions. Additionally, the intralayer carrier recombination within CIPS is significantly accelerated by 2 orders of magnitude upon the formation of heterojunctions with graphene. The carrier dynamics exhibit clear dependence on interfacial polarizations, thereby facilitating the spatial separation of photoinduced carriers. The findings lay the groundwork for future investigation of 2D ferroelectric materials, paving the way for ferroelectric memory and computing technology for industrial applications.

Two-dimensional polyaniline crystal with metallic out-of-plane conductivity

Linear conducting polymers show ballistic transport, imposed by mobile carriers moving along the polymer chains1,2, whereas conductance in the extended dimension, that is, between polymer strands or layers, remains weak due to the lack of intermolecular ordering and electronic coupling3-5. Here we report a multilayer-stacked two-dimensional polyaniline (2DPANI) crystal, which shows metallic out-of-plane charge transport with high electrical conductivity. The material comprises columnar π arrays with an interlayer distance of 3.59 Å and periodic rhombohedral lattices formed by interwoven polyaniline chains. Electron spin resonance spectroscopy reveals significant electron delocalization in the 2DPANI lattices. First-principles calculations indicate the in-plane 2D conjugation and strong interlayer electronic coupling in 2DPANI facilitated by the Cl-bridged layer stacking. To assess the local optical conductivity, we used terahertz and infrared nanospectroscopy to unravel a Drude-type conductivity with an infrared plasma frequency and an extrapolated local d.c. conductivity of around 200 S cm-1. Conductive scanning probe microscopy showed an unusually high out-of-plane conductivity of roughly 15 S cm-1. Transport measurements through vertical and lateral micro-devices revealed comparable high out-of-plane (roughly 7 S cm-1) and in-plane conductivity (roughly 16 S cm-1). The vertical micro-devices further showed increasing conductivity with decreasing temperature, demonstrating unique out-of-plane metallic transport behaviour. By using this multilayer-stacked 2D conducting polymer design, we predict the achievement of strong electronic coupling beyond in-plane interactions, potentially reaching three-dimensional metallic conductivity6,7.

Post-CCSD(T) Thermochemistry of Chlorine Fluorides as a Challenging Test Case for Evaluating Density Functional Theory and Composite Ab Initio Methods

Quantum chemistry plays a key role in exploring the chemical properties of highly reactive chlorine polyfluoride compounds (ClFn). Here, we investigate the thermochemical properties of ClFn species (n=2-6) by means of high-level thermochemical procedures approximating the CCSDT(Q) and CCSDTQ5 energies at the complete basis set limit. We consider total atomization energies (TAEs), Cl-F bond dissociation energies (BDEs), F2 elimination energies (F2 elim.), ionization potentials (IPs), and electron affinities (EAs). The TAEs have significant contributions from post-CCSD(T) correlation effects. The higher-order triple excitations, CCSDT-CCSD(T), are negative and amount to -0.338 (ClF2), -0.727 (ClF3), -0.903 (ClF4), -1.335 (ClF5), and -1.946 (ClF6) kcal/mol. However, the contributions from quadruple (and, where available, also quintuple) excitations are much larger and positive and amount to +1.335 (ClF2), +1.387 (ClF3), +2.367 (ClF4), +2.399 (ClF5), and +3.432 (ClF6) kcal/mol. Thus, the contributions from post-CCSD(T) excitations exceed the threshold of chemical accuracy in nearly all cases. Due to their increasing hyper-valency and multireference character, the ClFn series provides an interesting and challenging test case for both density functional theory and low-level composite ab initio procedures. Here, we highlight the limitations in achieving overall chemical accuracy across all DFT and most composite ab initio procedures.

Chlorine Axial Coordination Activated Lanthanum Single Atoms for Efficient Oxygen Electroreduction with Maximum Utilization

Currently, there are still obstacles to rationally designing the ligand fields to activate rare-earth (RE) elements with satisfactory intrinsic electrocatalytic reactivity. Herein, axial coordination strategies and nanostructure design are applied for the construction of La single atoms (La-Cl SAs/NHPC) with satisfactory oxygen reduction reaction (ORR) activity. The nontrivial LaN4Cl2 motifs configuration and the hierarchical porous carbon substrate that facilitates maximized metal atom utilization ensure high half-wave potential (0.91 V) and significant robustness in alkaline media. The aqueous and flexible Zinc-air battery (ZAB) integrating La-Cl SAs/NHPC as the cathode catalyst exhibits a maximum power density of 260.7 and 68.5 mW cm-2, representing one of the most impressive RE-based ORR electrocatalysts to date. Theoretical calculations have demonstrated that the Cl coordination evidently modulate the electronic structures of La sites, which promoted electron transfer efficiency by d-p orbital couplings. With enhanced electroactivity of La sites, the adsorptions of key intermediates are optimized to alleviate the energy barriers of the potential-determining step. Importantly, this preparation strategy is also successfully applied to other REs. This work provides perspectives for near-range electronic structure modulation of RE-SAs based on a nonplanar coordination micro-environment for efficient electrocatalysis.

Light-Triggered Reversible Assembly of Halide Perovskite Nanoplatelets

Advancements in stimuli-driven nanoactuators necessitate the discovery of photo-switchable, self-contained semiconductor nanostructures capable of precise mechanical responses. The reversible assembly of 0D Cs3Bi2I9 halide perovskite nanoplatelets (NPLs) between stacked and scattered configurations are demonstrated under light and dark, respectively. This sunlight-triggered perpetual flipping of the NPLs, occurring in less than a minute, is associated with a color change between brown and red. The photomechanical response is driven by the formation and cleavage of sulfide linkages at the NPL surface. In the stacked configuration, various stacking modes create moiré superstructures, enhancing the interlayer charge distribution, and increasing the electronic conductivity and optical absorbance. This leads to a decrease in exciton binding energy from 247 meV for scattered NPLs to 162 meV for stacked NPLs, resulting in a 3.5-fold enhancement in dark current for the stacked NPL films. The switchable control over color and electric current is continuously reversible and retraceable, exhibiting a minor memory effect observed during extended cycling. The self-flipping NPL nanoactuators demonstrate reversible mechanical responses, with topographical oscillations ranging from 14 nm in scattered NPLs to 50 nm in the vertically stacked configuration. This seamless reversible nano-assembly with color interchangeability offers numerous possibilities for nanorobotics, nanoscale switches, and sensors.

Electron density distribution in bis(guanidinium) disodium hypodiphosphate heptahydrate, (CH6N3)2Na2(P2O6)·7H2O

X-ray structural analysis of bis(guanidinium) disodium hypodiphosphate heptahydrate, (CH6N3)2Na2(P2O6)·7H2O revealed close Na+...guanidinium [Na...N 3.0366 (6) Å] and water...guanidinium O-H...N [H...N 2.07 Å, O...N 3.0401 (9) Å] contacts, the nature of which is explored with the use of electron density distribution and Hirshfeld surface analysis. The crystal structure is governed by coordination interactions to Na+ cations and an extensive network of hydrogen bonds, in which guanidinium cations, hypodiphosphate ions and water molecules are involved. Na+ cations are in tetragonal pyramidal or octahedral environment, which was proved by continuous shape measures. From ∇2ρ(rc) and bond degree values, the character of P-P bonds are classified as shared shell or covalent bond types, whereas P-O bonds are of transit closed shell or polarized covalent types. Despite the lack of a lone electron pair on the N atom and positive charge of the guanidinium cation, the existence of an O-H...N hydrogen bond was confirmed by electron density studies.

Broadband Emission Induced by Band-Edge Carrier Reconfiguration in 2D Hybrid Lead Halide Perovskites

Broadband emission in hybrid lead halide perovskites (LHPs) has gained significant attention due to its potential applications in optoelectronic devices. The origin of this broadband emission is primarily attributed to the interactions between electrons and phonons. Most investigations have focused on the impact of structural characteristics of LHPs on broadband emission, while neglecting the role of electronic mobility. In this work, the study investigates the electronic origins of broadband emission in a family of 2D LHPs. Through spectroscopic experiments and density functional theory calculations, the study unveils that the electronic states of the organic ligands with conjugate effect in LHPs can extend to the band edges. These band-edge carriers are no longer localized only within the inorganic layers, leading to electronic coupling with molecular states in the barrier and giving rise to additional interactions with phonon modes, thereby resulting in broadband emission. The high-pressure photoluminescence measurements and theoretical calculations reveal that hydrostatic pressure can induce the reconfiguration of band-edge states of charge carriers, leading to different types of band alignment and achieving macroscopic control of carrier dynamics. The findings can provide valuable guidance for targeted synthesis of LHPs with broadband emission and corresponding design of state-of-the-art optoelectronic devices.

Oxidative pyrolysis of alkali lignin using nitrogen functionalized graphene oxide-cerium oxide nanocatalysts: Mechanistic insights thorough density functional theory

In this study, a functionalized graphene oxide-cerium oxide nanocatalysts (FGCe) with varying graphene oxide (GO) contents were prepared using an in-situ reflux method. The prepared nanocatalysts showcased improvement in the crystallinity and BET surface area values with increasing GO contents. The efficacies of prepared catalysts were investigated towards oxidative pyrolysis of alkali lignin in an ethanol-water system. Among various nanocatalyst samples, the best lignin conversion (93 %) and bio-oil yield (86 %) were achieved using 50 mg FGCe nanocatalyst (0.5 wt% GO) at 423 K and 60 min. GC-MS and 1HNMR analyses were used to identify significant lignin conversion products, including 2-pentanone-4-hydroxy-4-methyl, 2-methoxyphenol, nonylcyclopropane, vanillin, apocynin, homovanollic acid, and benzoic acid. Kinetic studies revealed that the activation energy for lignin conversion was 24.36 kJ/mol at 423 K. Mechanistic investigations by density functional theory analysis revealed that the lignin breakdown occurred at oxygen bonds producing aromatic.

Kinetics and Mechanism of the Thermal Isomerization of Cyclopropane to Propene: A Comprehensive Theoretical Study

The kinetics of the homogeneous gas-phase thermal isomerization of cyclopropane to propene has been studied theoretically to clarify existing discrepancies regarding the interpretation of its mechanism. High-level ab initio and density functional theory calculations were used to determine the branching ratios of the biradical and carbene reaction channels over wide temperature and pressure ranges. For this, relevant molecular and thermochemical properties of the proposed intermediates and related transition states were computed and compared with literature values. The Arrhenius equation, derived between 400 and 1400 K in the high-pressure limit at the CCSD(T)/6-311++G(3df,3pd)//CCSD/6-311++G(d,p) level of theory, is given by log10(koverall,∞/s-1) = (15.60 ± 0.06) - (65.70 ± 0.17) kcal mol-1 (2.303 RT)-1. This expression is in very good agreement with the available experimental data. According to these results, the biradical pathway is the predominant mechanism, while the carbene pathway contributes 1-2% at higher temperatures. The G4//B3LYP/6-311++G(3df,3pd) and G4//M06-L/6-311++G(3df,3pd) levels showed comparable Arrhenius parameters. Low-pressure limit rate coefficients and falloff curves were also estimated to evaluate the effect of pressure on the reaction. Additionally, the possibility of a concerted path is considered, but calculations showed unstable wave functions, suggesting that this mechanism would not be plausible.

Discovery of ketene/acetyl as a potential receptor for hydrogen-transfer reactions in zeolites

Hydrogen-transfer is the primary process responsible for elevating the degree of unsaturation of intermediates in zeolite-catalyzed methanol-to-hydrocarbon reactions, with olefins serving as the typical receptor and alkanes being produced as the by-product. Intriguingly, the introduction of CO was shown to suppress the selectivity of alkanes and enhance the production of aromatics, yet microscopic understanding of this phenomenon remains elusive. Here, based on ab initio molecular dynamics simulations and free energy sampling methods, we discover a non-olefin-induced hydrogen-transfer reaction in the presence of CO, with ketene/acetyl emerging as a more suitable hydrogen-transfer receptor than olefins. This predominant route enhances the degree of unsaturation of olefins without generating additional alkanes, and the produced dienes and acetaldehyde could further contribute to the formation of aromatics. Moreover, we construct a general mechanism applicable to a series of CO-coupled aromatics synthesis reactions, offering distinctive insights and strategies for the optimization of efficiency.

Deciphering the direct heterometallic interaction in κ3-bis(donor)ferrocenyl-transition-metal complexes

Ligands featuring a 1,1'-bis(donor)ferrocene motif can adopt various binding modes. Among them, the κ3 binding mode, which involves interaction between the iron center of the ferrocene unit and the transition metal is the most unique. Although various examples highlight the interaction itself, the exact quantification of its strength remains uncertain. In our computational study, we systematically investigate the nature of this unique heterometallic bond, demonstrating that the electron density at the transition metal primarily governs the heterobimetallic interaction. On the other hand, the contribution of the ipso-carbon atoms of the cyclopentadiene ring is not negligible. We demonstrated that isodesmic reactions provide the most quantifiable data regarding the interaction. If the transition metal center is complexed with good electron-donor ligands or its positive charge is compensated by the negative charge of the ligands, the interaction with the electron-rich iron center recedes into the background. Finally, we highlighted the importance of the accurate computational description of these systems.

Tunable Magnetic Order in Fe-Mg Codoped Montmorillonite Nanoclay Interfaced with Amino Acids

This study elucidates the sensitivity of the spin magnetic moment of the Fe-Mg codoped montmorillonite (MMT) nanoclay to its interactions with three unnatural amino acids (AAs): 5-aminovaleric acid, 2-aminopimelic acid, and DL-2-aminocaprylic acid, in the presence and absence of an aqueous environment. These AAs are known as intercalating agents for MMT clay, providing the formation of the nanoplates. Using spin-polarized density functional theory (SP-DFT), the magnetic moment and its tunability to the position of Fe and Mg impurities in the MMT nanoclay crystal lattice, along with the alignment of AA molecules on the nanoclay surface, have been investigated. There is substantial charge transfer between the AA molecule (a donor) and the MMT nanoclay (an acceptor), indicating their strong electrostatic interaction. Moreover, it is found that AA molecules stabilize Fe(II) and prevent its oxidation to Fe(III) through strong interactions with the nanoclay, highlighting the significance of clay-amino acid interactions. The calculations predict the possible transition in magnetic orders (ferromagnetic, antiferromagnetic, and ferrimagnetic) governed by interactions between the MMT nanoclay and the AA molecules in the vacuum and aqueous medium. The significant magnetic exchange coupling observed in some of the nanoclay models, in the presence of an aqueous medium, suggests a unique property of quantum ferrofluids. These findings indicate promising applications of these materials in biomedicine and bioengineering, particularly in the areas requiring an electromagnetic response, such as magnetic resonance and magneto-optical imaging, magnetic drug targeting, hyperthermia cancer treatment, magnetic separation, and magneto-mechanical sensors.

Influence of Ni on carbon nanotube production with Fe-based catalysts

This study investigates the role of Ni in CNT production using Fe-based catalysts. Among the various catalysts used, such as 40Fe-0Ni, 40Fe-1Ni, 40Fe-3Ni, 40Fe-5Ni, 40Fe-7Ni, and 40Fe-10Ni, the 40Fe-5Ni catalyst achieved a notable yield of 5.80 gC per g metal, which is higher than the 1.03 gC per g metal obtained with the pure Fe catalyst. DFT study reveals that Fe3Ni exhibits stronger carbon binding, enabling more efficient CNT production and supporting our experimental results.

Mixed Resolution-of-the-Identity Compressed Exchange for Hybrid Mixed Deterministic-Stochastic Density Functional Theory from Low to Extreme Temperatures

Exact exchange contributions included in density functional theory calculations have rendered excellent electronic structure results on both cold and extremely hot matter. In this work, we develop a mixed deterministic-stochastic resolution-of-the-identity compressed exchange (mRICE) method for efficient calculation of exact and hybrid electron exchange, suitable for applications alongside mixed stochastic-deterministic density functional theory. mRICE offers accurate calculations of the electronic structure at a largely reduced computation time compared to other compression algorithms, such as Lin's adaptive compressed exchange, for the warm dense matter. mRICE grants flexibility in the number of exchange compression vectors used to resolve the approximated exchange operator kernel, reducing the computation time of the application of the exchange operator to the vectors by up to 40% while maintaining accuracy in electronic structure predictions. We demonstrate mRICE by computing the density of states of warm dense carbon and neon between temperatures of 10 and 50 eV (116,045 and 580,226 K) and comparing timing and accuracy at varying levels of compression. Finally, we carry out mRICE on the difference between the Fock exchange operator and the semilocal exchange potential kernels and show an enhanced convergence of electronic structure calculations at reduced stochastic sampling.

Metal-Translocation-Coupled Ligand-Binding/Release by Dinuclear Rhodium Sandwich Complexes

Switching the location of metal atoms or ions in a molecule has been of great interest as a behavior of molecular machines. We describe herein that the reversible metal translocation can be coupled with the ligand-binding/release of organometallic complexes. The two rhodium moieties sandwiched between arylpolyene ligands exhibit metal-assembly and disassembly through reversible migration between the arene site and the olefin site, in response to the association and dissociation of additional ligands. This occurs either with bridging or even non-bridging ligands, where the latter involves oxidative π-addition of the unsaturated hydrocarbon binder to the metal moieties. The assembling- and disassembling states were characterized by NMR and X-ray diffraction analysis.

Surface-hydrogenated CrMnOx coupled with GaN nanowires for light-driven bioethanol dehydration to ethylene

Light-driven bioethanol dehydration offers attractive outlooks for the sustainable production of ethylene. Herein, a surface-hydrogenated CrMnOx is coupled with GaN nanowires (GaN@CMO-H) for light-driven ethanol dehydration to ethylene. Through combined experimental and computational investigations, a surface hydrogen-replenishment mechanism is proposed to disclose the ethanol dehydration pathway over GaN@CMO-H. Moreover, the surface-hydrogenated GaN@CMO-H can significantly lower the reaction energy barrier of the C2H5OH-to-C2H4 conversion by switching the rate-determining reaction step compared to both GaN and GaN@CMO. Consequently, the surface-hydrogenated GaN@CMO-H illustrates a considerable ethylene production activity of 1.78 mol·gcat-1·h-1 with a high turnover number of 94,769 mole ethylene per mole CrMnOx. This work illustrates a new route for sustainable ethylene production with the only use of bioethanol and sunlight beyond fossil fuels.

Top-Down versus Bottom-Up Approaches for σ-Functionals Based on the Approximate Exchange Kernel

Recently, we investigated a number of so-called σ- and τ-functionals based on the adiabatic-connection fluctuation-dissipation theorem (ACFDT); particularly, extensions of the random phase approximation (RPA) with inclusion of an exchange kernel in the form of an antisymmetrized Hartree kernel. One of these functionals, based upon the approximate exchange kernel (AXK) of Bates and Furche, leads to a nonlinear contribution of the spline function used within σ-functionals, which we previously avoided through the introduction of a simplified "top-down" approach in which the σ-functional modification is inserted a posteriori following the analytic coupling strength integration within the framework of the ACFDT and which was shown to provide excellent performance for the GMTKN55 database when using hybrid PBE0 reference orbitals. In this work, we examine the analytic "bottom-up" approach in which the spline function is inserted a priori, i.e., before evaluation of the analytic coupling strength integral. The new bottom-up functionals, denoted σ↑AXK, considerably improve upon their top-down counterparts for problems dominated by self-interaction and delocalization errors. Despite a small loss of accuracy for noncovalent interactions, the σ↑AXK@PBE0 functionals comprehensively outperform regular σ-functionals, scaled σ-functionals, and the previously derived σ+SOSEX- and τ-functionals in the WTMAD-1 and WTMAD-2 metrics of the GMTKN55 database.

Redox Cycling with Tellurium. Si-H Bond Activation by a Lewis Superacidic Tellurenyl Cation

The C,N-chelated aryltellurenyl triflate [2-(tBuNCH)C6H4Te][OTf] (1) activates the Si-H bonds in the tertiary silanes R3SiH via umpolung of H- to H+ to give rise to the iminium salts (tBuN(H)CH)C6H4TeSiR3][OTf] (2R, R=Et, Ph (elusive) and R=Si(CH3)3 isolated; OTf=O3SCF3) comprising Te-Si bonds, which are capable of generating silyl triflates, R3SiOTf, under attack of a second equivalent of 1. The unprecedented Si-H activation was utilized in main group redox catalysis using p-quinones, which were converted into (silylated) hydroquinones.

Atomically Dispersed Fe1Mo1 Dual Sites for Enhanced Electrocatalytic Nitrogen Reduction

The electrocatalytic nitrogen reduction reaction (eNRR) is an attractive strategy for the green and distributed production of ammonia (NH3); however, it suffers from weak N2 adsorption and a high energy barrier of hydrogenation. Atomically dispersed metal dual-site catalysts with an optimized electronic structure and exceptional catalytic activity are expected to be competent for knotty hydrogenation reactions including the eNRR. Inspired by the bimetallic FeMo cofactor in biological nitrogenase, herein, an atomically dispersed Fe1Mo1 dual site anchored in nitrogen-doped carbon is proposed to induce a favorable electronic structure and binding energy. The as-prepared electrocatalyst (FeMo-NC) presents a maximum NH3 yield rate of 1.07 mg h-1 mgmetal-1 together with a Faradaic efficiency of 21.7% at -0.25 V vs RHE, outperforming many reported atomically dispersed non-noble metal electrocatalysts. Further density functional theory (DFT) calculations reveal that the Fe1Mo1 dual site activates *N2 most strongly via a side-on adsorption configuration and optimizes the binding energy of eNRR intermediates, thus lowering the limiting barrier during the overall hydrogenation and promoting NH3 generation.

Densely populated macrocyclic dicobalt sites in ladder polymers for low-overpotential oxygen reduction catalysis

Dual-atom catalysts featuring synergetic dinuclear active sites, have the potential of breaking the linear scaling relationship of the well-established single-atom catalysts for oxygen reduction reaction; however, the design of dual-atom catalysts with rationalized local microenvironment for high activity and selectivity remains a great challenge. Here we design a bisalphen ladder polymer with well-defined densely populated binuclear cobalt sites on Ketjenblack substrates. The strong electron coupling effect between the fully-conjugated ladder structure and carbon substrates enhances the electron transfer between the cobalt center and oxygen intermediates, inducing the low-to-high spin transition for the 3d electron of Co(II). In situ techniques and theoretical calculations reveal the dynamic evolution of Co2N4O2 active sites and reaction intermediates. In alkaline conditions, the catalyst exhibits impressive oxygen reduction reaction activity featuring an onset potential of 1.10 V and a half-wave potential of 1.00 V, insignificant decay after 30,000 cycles, pushing the overpotential boundaries of ORR electrocatalysis to a low level. This work provides a platform for designing efficient dual-atom catalysts with well-defined coordination and electronic structures in energy conversion technologies.

Controllable spin rectification behavior of vertical and lateral VSe2/WSe2 heterojunction Schottky diodes

Heterojunctions (HJs) based on two-dimensional (2D) transition metal dichalcogenides are considered promising candidates for next-generation electronic and optoelectronic devices. Here, vertical (V-type) and lateral (L-type) HJ diodes based on metallic 1T-VSe2 and semiconducting 2H-WSe2 with out-of-plane and in-plane contacts are designed. First-principles quantum transport simulations reveal that both V- and L-type VSe2/WSe2 HJ diodes form p-type Schottky contacts. Under zero gate voltage, V-type VSe2/WSe2 HJ Schottky diodes exhibit superior spin rectification behavior compared to L-type, with rectification ratios approaching 109 and 106, respectively. At 300 K, the ideality factor of the V-type diode is lower than that of the L-type and reaches the ideal state at 478 and 510 K, respectively. Notably, positive gate voltage can reverse the rectification direction in both diodes and weaken the rectifying effect in V-type devices. Conversely, negative gate voltage significantly increases the current in both diodes and enhances the rectification ratio of the L-type device to 109. These findings provide insights into the spin-dependent rectification behavior of V- and L-type VSe2/WSe2 HJs in Schottky diodes, offering theoretical guidance for exploring magnetic nanoscale devices based on 2D materials.

Zr4+-doped sodium manganese oxide: enhanced electrochemical performance as a cathode in sodium ion batteries

Sodium manganese oxides are regarded as a valuable class of cathode materials for sodium-ion batteries. By varying the stoichiometry of Na, Mn and O, it is possible to obtain layered, tunnel and spinel type structures, which can withstand the electrochemically-triggered sodiation-desodiation process. In this work, we report the electrochemical performance of Na4Mn2O5, a sodium-rich manganese oxide, which has been previously reported to suffer from structural instability due to the Jahn-Teller distortion of the Mn3+ ion. It was observed that the Na4Mn2-xZrxO5 (x = 0.1) cathode delivered a discharge capacity of ∼203 mA h g-1 post 250 cycles with a capacity retention rate of ∼82.8% on doping with Zr4+ ions. The improvement in cycling ability and rate capability is attributed to the enhanced structural stability and improved electronic conduction brought about by the substitution of Mn3+ by Zr4+ in Na4Mn2O5. Density functional theory-based studies were conducted, which adequately support the obtained results.

Bioinspired artificial antioxidases for efficient redox homeostasis and maxillofacial bone regeneration

Reconstructing large, inflammatory maxillofacial defects using stem cell-based therapy faces challenges from adverse microenvironments, including high levels of reactive oxygen species (ROS), inadequate oxygen, and intensive inflammation. Here, inspired by the reaction mechanisms of intracellular antioxidant defense systems, we propose the de novo design of an artificial antioxidase using Ru-doped layered double hydroxide (Ru-hydroxide) for efficient redox homeostasis and maxillofacial bone regeneration. Our studies demonstrate that Ru-hydroxide consists hydroxyls-synergistic monoatomic Ru centers, which efficiently react with oxygen species and collaborate with hydroxyls for rapid proton and electron transfer, thus exhibiting efficient, broad-spectrum, and robust ROS scavenging performance. Moreover, Ru-hydroxide can effectively sustain stem cell viability and osteogenic differentiation in elevated ROS environments, modulating the inflammatory microenvironment during bone tissue regeneration in male mice. We believe this Ru-hydroxide development offers a promising avenue for designing antioxidase-like materials to treat various inflammation-associated disorders, including arthritis, diabetic wounds, enteritis, and bone fractures.