Ab initio molecular-dynamics simulation of the liquid-metal-amorphous-semiconductor transition in germanium

Self-activated oxophilic surface of porous molybdenum carbide nanosheets promotes hydrogen evolution activity in alkaline environment

Molybdenum carbides are promising alternatives to Pt-based catalysts for the hydrogen evolution reaction (HER) due to their similar d-band electronic configuration. Notably, MoxC exhibits superior HER kinetics in alkaline media compared to acidic conditions, contrasting with Pt-based catalysts. Herein, we present 3D porous β-Mo2C nanosheets, achieving an overpotential of 111 mV at 10 mA cm-2 in 1 M KOH, significantly lower than in acidic environments. Simulations on pristine Mo2C surface reveal that water dissociation poses a higher energy barrier in alkaline media, suggesting that crystal structure alone does not dictate kinetics. Operando attenuated total reflection surface-enhanced infrared absorption spectroscopy shows that Mo2C activates interfacial water, generating liquid-like and free water, and facilitates hydroxyl species adsorption, reducing activation energy to below 38.43 ± 0.19 kJ/mol. Our findings on the self-activation effect offer insights into the HER mechanism of Mo-based electrocatalysts and guide the design of highly active HER catalysts.

Ameliorating water splitting by entropy regulation and electronic structure engineering on pristine Prussian blue analog

Electrochemical water splitting is the most promising green method for hydrogen production. In this work, the traditional Prussian blue analogs were endowed with the new concept of high entropy to bring a breakthrough in electrocatalytic performance. A classic two-step synthetic strategy was employed to fabricate the high-entropy FeCoNiCr6P nanoparticle via phosphating the FeCoNiCr6, which was prefabricated using a facile coprecipitation method. The phosphides can trap protons by acting as bases to promote the discharge step faster. FeCoNiCr6P requires a lower overpotential of only 268.3 mV at a current density of 100 mA cm-2 for OER. The FeCoNiCr6P//FeCoNiCr6P electrochemical water splitting couple can realize a low voltage of 1.58 V to at 10 mA cm-2 current density. Furthermore, the electronic states and coordination environment of catalyst active sites were investigated to get deeper insight into material design.

Fabricating stable protective layer on orthorhombic tungsten oxide anode for long-lifespan pseudocapacitors by trace of aluminum ion electrolyte additives

Orthorhombic tungsten oxide (WO3·H2O) has been considered as a promising anode material due to its layered crystal structure and high capacity. However, the instability of its crystal structure usually results in poor cyclic stability of the battery/capacitor. Herein, a novel strategy of introducing aluminum ion (Al3+) additives for designing hybrid electrolyte is demonstrated to enhance the cycling stability of WO3·H2O. Aluminum ions may participate in the redox reaction and contribute extra capacitance. More importantly, the Al3+ ions can facilitate fast phase transformation of metastable orthorhombic tungsten oxides to stable monoclinic phase, but also participate in the construction of stable protective layer during the long-term cycling, forming a protective layer at the surface of tungsten oxide for alleviating the dissolution and structural damage. The WO3·H2O is electrodeposited on the exfoliated graphite foil (Ex-GF) and shows a specific capacitance of 395 mF cm-2 at 2 mA cm-2 in the LiCl + AlCl3 hybrid electrolyte (pH = 2.93), and the capacitance remains 91.8 % after 10,000 charge/discharge cycles, indicating that the WO3·H2O/Ex-GF electrode material exhibits excellent stability in supercapacitors. The density functional theory (DFT) calculations further demonstrate whether the adsorption energy or intercalation energy of Li+ at the monoclinic WO3 is lower than the orthorhombic WO3·H2O. This result suggests that the electrochemical performance of WO3·H2O, which operates on a pseudocapacitive reaction mechanism, can be enhanced through the phase transformation from the orthorhombic phase to the monoclinic phase during the cycling. Hence, this ion additive approach can adjust the interface composition and protect internal active material, and can be extended to the stability improvement of other metal oxide electrodes.

Gating Single Molecules with Counterions

We report atomic-scale gating and visualization of local charge distribution within individual rare-earth-based molecular complexes on a metallic surface. The complexes are formed by a positively charged lanthanum ion coordinated to a (pcam)3 molecule and a negatively charged counterion trapped underneath via electrostatic interactions on a Au(111) surface. Local gating is performed by adding an additional negatively charged counterion to one side of the complex, which results in the redistribution of charges within the complex and a positive shift of the frontier orbitals. This is caused by the internal Stark effect induced by the added counterion. This effect is directly captured using tunneling spectroscopy and spectroscopic mapping at 5 K substrate temperature. The polarizability of the complex is corroborated by density functional theory and analytical calculations based on experimental findings. Furthermore, the influence of charge polarization on nearby complexes is investigated in a cluster purposely assembled using three complexes, which reveals maintaining the charge states as in single complexes. These findings will enable the design of robust charged rare-earth complexes to be tailored for potential solid-state applications.

A Monoclinic Variant of ThCr2Si2-Type BaAg2Sb2: Electronic Structure and Physical Properties

A monoclinic variant of the ThCr2Si2-type structure of BaAg2Sb2, with the Pearson symbol mC10, has been discovered. Its crystal structure was determined by single-crystal X-ray diffraction, with space group C2/m (No. 12), and lattice parameters a = 12.441(4) Å, b = 4.790(2) Å, c = 4.876(2) Å, β = 112.88(1)°, and V = 268.8(6) Å3. It features tetragonally coordinated Ag2Sb2 layers that are distorted and stacked along the crystallographic a-axis, with a strong interlayer Sb-Sb bond. Transport measurements reveal a non-negligible magnetoresistivity of up to 18%, with cusp-like behavior. Electron-dominated charge carriers over a broad temperature range are also verified by Hall measurements. Moreover, temperature-dependent resistivity behavior exhibits a small deviation from the conventional Bloch-Grüneisen model, which is likely due to the brink of a possible Lifshitz transition, as revealed by first-principles calculations.

Polyoxometalated metal-organic framework superstructure for stable water oxidation

Stable, nonprecious catalysts are vital for large-scale alkaline water electrolysis. Here, we report a grafted superstructure, MOF@POM, formed by self-assembling a metal-organic framework (MOF) with polyoxometalate (POM). In situ electrochemical transformation converts MOF into active metal (oxy)hydroxides to produce a catalyst with a low overpotential of 178 millivolts at 10 milliamperes per square centimeter in alkaline electrolyte. An anion exchange membrane water electrolyzer incorporating this catalyst achieves 3 amperes per square centimeter at 1.78 volts at 80°C and stable operation at 2 amperes per square centimeter for 5140 hours at room temperature. In situ electrochemical spectroscopy and theoretical studies reveal that the synergistic interactions between metal atoms create a fast electron-transfer channel from catalytic iron and cobalt sites, nickel, and tungsten in the polyoxometalate to the electrode, stabilizing the metal sites and preventing dissolution.

Synergistic Computational and Experimental Investigation of Covalent Organic Frameworks for Efficient Alcohol Dehydration

Covalent organic frameworks (COFs), a promising class of nanoporous materials, have received significant attention for membrane separation. Currently, several COFs are reported for alcohol dehydration, but they are not efficient owing to the pervasive challenge to separate small-sized molecular mixture. Herein, first we have computationally explored a series of COFs with different functionality and aperture size as pervaporation (PV) membrane and identified a novel COF for efficient dehydration of water/alcohol mixtures (90 wt % IPA, 90 wt % n-butanol and 90 wt % t-butanol). Subsequently, the best-performing COF was experimentally synthesized and characterized, and its sorption properties were correlated with computational results. Molecular dynamics (MD) simulations revealed that solvent permeation fluxes are predominantly influenced by the pore aperture of COFs, and larger pore aperture exhibits higher flux. Conversely, the separation factor is primarily determined by the polarity of the pore functional groups. Among the tested COF membranes, TpPa-1-OC3H6OCH3 demonstrated superior performance, surpassing the current state-of-the-art membranes. The activation energy (Ea) for water permeation in alcohol mixtures through TpPa-1-OC3H6OCH3 is mostly governed by water-alcohol interactions. Furthermore, experimental evaluation of the COFs indicated a plate-like morphology for TpPa-1-OC3H6OCH3 which ascertained a 2D-sheet-like structure. TpPa-1 showed greater sorption than TpPa-1-OC3H6OCH3 with all of the solvents tested owing to the inability of the solvent molecules to enter the relatively small pores in the later COF. This is in accordance with the MD simulation predictions, which indicated that the solvent molecules cannot penetrate the small pores of TpPa-1-OC3H6OCH3. This work synergistically integrates computational and experimental approaches to develop novel COFs with superior performance compared to previously reported PV membranes, paving the way for advanced membranes for sustainable solvent recovery.

Nitrogen-Functionalized p-Type Graphene Window and Silicon Nanowire Heterostructure with High-Performing NIR Light Detection

In recent development, the type of dopants, strain, vacancies, and band alignment in reduced graphene oxide, namely, graphene window, can be a promising candidate to exhibit high near-infrared light detection. In this work, we delineate structural effects, in-plane hopping defects, and vacancies that enhance p-type behavior of nitrogen/oxygen functionalized reduced graphene oxide (NORG). The NORG-6/30 has been prepared from pyrazole at different time intervals (6-30 h). A combined spectroscopic approach and ab initio calculation imply pyrazole-based 4-pyrrole unit complex macrocyclic unit formation, i.e., in-plane hopping defect and vacancies are maximum for NORG-30. Thus, the structural effect in NORG-30 opens the band gap and work function, shifts the Fermi level position toward the valence band, and increases the hole doping concentrations. The suitable band alignment between different layered NORG-30 and Silicon nanowire substrate shows remarkable NIR-based photodetector devices having maximum responsivity and detectivity as high as 50 mA W -1 and 2.2 × 1011 Jones at -2 V. The temperature-dependent Thermionic and Cheung's models are introduced to estimate the Schottky barrier height of 0.98 eV and the diode ideality factor of 2.92, which are well corroborated with UPS analysis. The high photocurrent from photoexcited high charge carrier formation of the NORG-30/SiNW device is 2 orders higher in magnitude than other NORG/SiNW and ORG/SiNW (without using any nitrogen precursors) devices. Finally, the hybrid NORG-30/SiNW device rapidly quantifies the alcohol content and has excellent potential for application in the food industry.

Layer-by-Layer Interdigitated CuS/Au2S Heteronanoplates by Selectively Blocking the Pathway of Cation Exchange Reaction

Cation exchange reactions (CERs), recognized as a promising postsynthetic modification strategy, have garnered significant interest for generating thermodynamically unfavorable structural features, such as heterointerfaces. The formation of these heterointerfaces, which exhibit physicochemical properties distinct from those of their individual components, relies on precise control over the diffusion pathways of externally introduced cations as they migrate from the surface into the crystal interior. However, achieving regiospecific modulation of cation diffusion to rationally design heterointerfaces remains a formidable challenge. Herein, we synthesized layer-by-layer interdigitated {CuS/Au2S}@IrS2 heteronanoplates (L-Au2S HNPs), in which Au2S and CuS are alternately stacked at the atomic scale, using Cu1.81S@IrS2 nanoplates (CSIS NPs) as a starting template. This distinct structural arrangement was realized through a two-step CER with Au cations and a phase transformation process from Cu2-xS to CuS. Experimental results indicate that S-S bonds within phase-converted CuS crystals act as diffusion barriers during subsequent CER, restricting the migration of Au cations into specific CuS layers. Furthermore, theoretical calculations suggest that the expansion of the anion sublattice within channels containing diffused Au cations induces compressive strain in adjacent CuS layers, thereby impeding further Au incorporation. Expanding this synthetic strategy to construct atomic-layer-level stacked heteronanostructures across a broader range of materials could unlock new opportunities for developing advanced materials with unprecedented optical and catalytic properties.

One-dimensional molecular nanostructures interacting with two-dimensional metals

Electrons confined within the 2D layer of metals grown on silicon substrates exhibit exotic properties due to strong correlation effects. Their properties, such as their 2D superconductivity, have been frequently subjected to possible tuning by doping using charge transfer from adsorbed layers. Doping relies on adding electrons or holes to the system and the resulting shift of the Fermi level EF in the otherwise robust surface electronic structure. This strategy has not been sufficiently controlled in the case of an indium double layer grown on the Si(111) surface. This study provides an alternative approach relying on spatially periodic modification of the surface electronic structure of the 2D metal. Derivatives of diketopyrrolopyrroles (DPP) are used for the growth of perfectly ordered 1D-like molecular superstructures on top of the In double layer, imaged by scanning tunneling microscopy. The integral changes of electronic structure are measured by angle-resolved photoelectron spectroscopy and density functional theory calculations show local modification of the surface states near EF by the adsorbed molecules. This study demonstrates that the surface electronic states can be controllably patterned, using a proper bonding scheme. It is anticipated that the combination of the original 2D superconductor and the 1D-like patterning will motivate further research.

Insight into the role of tunable nitrogen vacancies in transition metal nitrides for ammonia synthesis

The thermally catalyzed nitrogen reduction reaction (NRR) is significant in the fertilizer industry and basic catalytic science. This study employs density-functional theory (DFT) calculations to explore the performance of 12 metal nitrides in thermocatalytic NRR by focusing on them. The surface incompleteness in the catalytic environment is simulated by constructing nitrogen vacancies on the metal nitride surfaces. Then the catalytic activity of these surfaces is evaluated in the thermally catalyzed ammonia synthesis process under specific experimental conditions (temperatures of 573, 673, and 773 K, and a pressure of 1 bar), as well as the effect on the activation of N2 and H2 molecules. It was found that the NRR performance can be optimized by considering the relationship between the N coordination structure on the catalyst surface and the NRR activity, thus identifying LaN(110)-V(N) and NbN(110) as two highly promising catalysts with notable stability and kinetic activity. It is also found that for metal nitride catalysts, a surface with lattice nitrogen as tetra-coordinated exhibits better NRR activity with lower reaction energy, and the distal pathway is more favorable for all catalyst surfaces studied. The present results provide new ideas for developing efficient metal nitride catalysts for ammonia synthesis and enrich the basic knowledge of metal nitride-catalyzed NRR.

Fast-Track to Catalyst Stability: Machine Learning Optimized Predictions for M1/M2-N6-Gra Catalysts

Graphene-based dual-atom catalysts M1/M2-N6-Gra have shown significant potential in various reactions, although their stabilities are debated. Therefore, developing an efficient and accurate approach to screen thermodynamically stable M1/M2-N6-Gra is significant. Herein, we designed a rational machine learning (ML) scheme based on 143 DFT calculated samples to predict the formation energies (Ef) of 1134 possible M1/M2-N6-Gra. A well performing multilayer perceptron model with test set R2 = 0.98 was obtained after feature engineering, model training, data supplementation, and transfer learning. This model successfully screened 604 thermodynamic stable M1/M2-N6-Gra with Ef < 0 eV. Feature importance, predictions distribution, and energy decomposition revealed that the coordination number significantly influences Ef, with cohesive energy dominating low-coordination catalysts and binding energy between metal and substrate being more critical in higher-coordination catalysts. This work highlights the potential of ML and developed effective approaches to screen thermodynamically stable catalysts and reveals the laws of stability for various materials.

A Pulsed Tandem Electrocatalysis Strategy for CO2 Reduction

Electroreduction of CO2 to value-added C2 products remains hindered by sluggish C-C coupling kinetics and competing side reactions. Inspired by the tandem catalytic mechanisms of multienzyme systems, we designed a dual-site single-atom nanozyme (DSAN) comprising FeN4 and FeO4 sites (FeN4-FeO4). Density functional theory (DFT) calculations under constant potential reveal that the FeN4 site functions as a CO generator, while the FeO4 site facilitates CO migration, C-C coupling, and subsequent C2 product formation. To further optimize the catalytic efficiency, we introduced a pulsed electrocatalysis strategy by alternating between zero potential and -0.7 V. This approach dynamically modulates active-site functions: at -0.70 V, CO2 adsorption and *CH3CH2OH formation are facilitated, while at 0 V, CO migration and C-C coupling are enhanced due to the spin-state transitions during potential switching. Additionally, the zero potential suppresses excessive hydrogenation of key intermediates, thereby improving CH3CH2OH selectivity. These findings highlight the synergistic strategy integrating tandem catalysis and pulsed potential control, offering a novel and effective approach for CO2-to-C2 conversion using SAN catalysts.

Engineering Lattice Strain in Co-Doped NiMoO4 for boosting Methanol Oxidation Reaction

Nickel-based molybdates have attracted considerable attention owing to their distinctive isomorphous structure. In this study, pristine NiMoO4 and Co-doped Ni1-xCoxMoO4 were synthesized and investigated for their electrocatalytic activity in methanol oxidation and methanol-assisted water splitting reactions. Through a comprehensive exploration of the structure-property relationship, it was found that the optimal coexistence of α and β molybdate phases, induced by Co doping, led to lattice strain and facilitated the presence of essential catalytic descriptors such as higher oxidation states of Ni and surface oxygen vacancies within the lattice. These factors contributed to the enhanced electrocatalytic activity of Ni0.7Co0.3MoO4 in methanol oxidation and hydrogen evolution reaction. Detailed kinetic studies were conducted to further elucidate the mechanisms involved. Overall, these findings highlight the promising potential of Ni0.7Co0.3MoO4 as an effective catalyst for electrochemical methanol upgrading in conjunction with water splitting, with implications for sustainable energy conversion technologies.

Vacancy Ordering in Fe-Deficient Iron Sulfide with the NiAs-Type Structure

An Fe-deficient iron sulfide thin film with a nickeline (NiAs) type structure has been reported with a stoichiometry close to greigite (Fe3S4) [Davis E. M.; Phys. Chem. Chem. Phys.2019, 21, 20204-20210]. We have investigated the Fe-vacancy ordering in the nonstoichiometric iron sulfide with the NiAs-like structure using density functional theory calculations with a Hubbard Hamiltonian and long-range dispersion corrections [DFT + U - D3(BJ)]. We applied canonical statistical mechanics to study the thermodynamics of ordering and in the most stable configuration we found the same concentration of Fe deficiencies in each layer along the c axis. We discuss the probabilities of the configurations and the averages of observables, such as lattice parameters and magnetic moments, as a function of temperature. At equilibrium, the Fe-deficient iron sulfide is expected to be fully ordered. The predicted electronic properties of the most stable configuration suggest that this material is antiferromagnetic. The simulated electronic structure shows that the most stable configuration of the Fe-deficient iron sulfide has semimetallic properties.

High throughput screening of Ohmic contacts in 2D metal-semiconductor van der Waals heterojunctions

High-throughput DFT calculations have been employed to investigate the contact formation of 1297 semiconducting two-dimensional (2D) monolayers from the C2DB as channel materials with three 2D metal monolayers: PdTe2, NbSe2, and ScS2. van der Waals heterojunctions (vdWHs), consisting of a single-layer semiconductor and a metal monolayer, constitute metal-semiconductor 2D contacts. A total of 760, 362, and 148 monolayers were found to form n-type Ohmic contacts, while 53, 14, and 999 formed p-type Ohmic contacts with these metal monolayers, respectively, in the Anderson limit (i.e., without forming the actual vdWH). Hexagonal monolayers with minimal lattice mismatch were selected to form vdWHs, ensuring stable interfaces while preserving electronic properties. HSE06-based DFT calculations confirm both the retention and type (p or n) of Ohmic contact. The electrostatic potential difference at the interface, interfacial charge transfer, and interfacial dipole moment are identified as critical factors in determining the contact type (n-type or p-type) and the corresponding Schottky barrier height. These findings provide valuable insights for selecting 2D materials to achieve Ohmic contacts in nanodevices, enabling the development of more efficient and reliable electronic components.

Structure and thermal boundary resistance of basal plane twin boundaries in Bi2Te3

The nanostructuring of thermoelectric materials is a well-established method of suppressing lattice thermal conductivity. However, our understanding of the interfaces that form as a result of nanostructure engineering is still limited. In this work, we utilise a simple two-body pair potential to calculate the thermal boundary resistance of basal plane twin boundaries in Bi2Te3 at 300 K using reverse non-equilibrium molecular dynamics simulations. The considered interatomic potential gives an excellent description of the twin boundary formation energies and the lattice thermal conductivity of bulk Bi2Te3. Using this potential, we find that the twin boundary located at the Bi layer is not thermally stable (unlike those located at the Te layers), and undergoes a phase transition into two distinct structures. We compare the thermal boundary resistance across these different twin boundaries and link the observed trends to overall geometry, van der Waals gap sizes and degree of structural disorder in atomic layers near the boundary.

Valence activity of SO-coupled atomic core shells in solid compounds of heavy elements

A close inspection reveals chemically relevant changes from light to heavy elements of the atomic orbital-energy patterns, relevant for both chemical theory and material applications. We have quantum-chemically investigated the geometric and electronic structures of solid [ThO2] and a series of [UO3] phases at a realistic relativistic level, both with and without spin-orbit (SO) coupling. The observable band gap between the occupied O(2p) bonding valence band and the empty U(5f6d) conduction band is smallest for δ-[UO3], with medium short U-O distances and high O h symmetry. Both Pauli-repulsion of O(2p) by the strongly SO-split U(6p) core and additional covalent U(6p)-O(2p) mixing cause a "pushing up from below" (PFB) and a large SO splitting of the valence band of the light element. PFB has been observed in molecular chemistry, but PFB and PFB-induced SO splitting have so far not been considered in solid-state science. Our findings open up new possibilities for electronic material applications.

Unravelling the cleavage-rate relationship from both the experimental and theoretical standpoint: The instance of fluorite dissolution

The phenomenon of solid dissolution into a solution constitutes a fundamental aspect in both natural and industrial contexts. Nevertheless, its intricate nature at the microscale poses a significant challenge for precise quantitative characterization at a foundational level. In this work, the influence across three specific cleavage planes, namely (100), (111), and (110) on the dissolution kinetics of fluorite in aqueous environments was examined from both experimental and theoretical standpoints. For the very first time, the surface potential of fluorite planes during dissolution was measured by means of a fluorite single-crystal electrode. Experimental results indicate that the dissolution of fluorite leads to a marked increase in surface roughness as well as an augmentation in the surface area of all analyzed surfaces. The most significant alteration in roughness is observed on the (111) plane, whereas the most substantial increase in surface area occurs on the (110) plane. In comparison to the (100) crystallographic plane, which demonstrates the slowest dissolution kinetics, the (111) and (110) planes display dissolution at a comparatively expedited rate. Theoretical simulations corroborate this trend, concurrently facilitating an effective examination of the system's free-energy landscape to analyze the dynamics and rates associated with the attachment and detachment of ions to the fluorite surface. Notably, the presence of interfacial defects has the potential to influence the free energy landscape, thereby altering the transition of ions into the bulk solution. Ultimately, the interplay of correlations and discrepancies between experimental findings and theoretical predictions is critically examined.

Screening of single-atomic catalysts loaded on two-dimensional transition metal dichalcogenides for electrocatalytic oxygen reduction via high throughput ab initio calculations

The design and screening of low cost and high efficiency oxygen reduction reaction (ORR) electrocatalysts is vital in the realms of fuel cells and metal-air batteries. Existing studies largely rely on the calculation of absorption free energy, a method established 20 years ago by Jens K. Nørskov. However, the study of electrocatalysts grounded solely on free energy calculation often lacks in-depth analysis, particularly overlooking the influence of solvent and electrode potential. In this regard, we here present a novel approach using constant-potential and ab initio molecular dynamics (AIMD) simulation to screen single-atom catalysts loaded on transition metal dichalcogenides (SA@TMDs) for ORR. An extensive investigation of 1584 SA@TMDs results in 20 high performing ORR catalysts with overpotential less than 0.33 V and high working stability. In addition, our study shows that the electrode potential has different effects on the adsorption energy of *OOH, *O and *OH, which leads to a reversal of the rate-determining step (RDS) of the ORR. This work presents not only credible, high-performance catalyst candidates for experimental exploration, but also significantly improves our understanding on the reaction mechanism of ORR under realistic reaction conditions.

Chemically Surface-Engineered Mesoporous Silica for the Toxic Metal Ions Uptake: Insights from Experiment and Density Functional Calculations

Robust chemical modification of mesoporous silica was conducted using 3-mercaptopropyltriethoxysilane via a chemical surface-engineered postgrafting of mesoporous silica KIT-6 with acidic propylsulfonate groups to obtain mesoporous KIT-6-SO3H. A fabricated meso-KIT-6-SO3H-modified quartz crystal microbalance sensor with KIT-6-SO3H layers coating on a QCM electrode is utilized to detect Pb2+, Cd2+, and Cs+ ions with high sensing affinity. The functionalized KIT-SO3H exhibits adsorption capacities (Qe) of 123.5 mg g-1, 117.5 mg g-1, and 90.6 mg g-1 for Pb2+, Cd2+, and Cs+, respectively, as determined by UV-vis measurements. These values coincide well with those obtained from the QCM sensor and ICP-OES measurements. The remarkable ability to adsorb metal ions is achieved by the synergistic cooperation of the large pore volume, high surface area, and abundant acidic -SO3H groups within the mesoporous structure of KIT-6-SO3H. A comprehensive study was carried out to investigate the influence of pH on the adsorption uptake of metal ions. Kinetic and isotherm studies demonstrate that the adsorptive removal of metal ions by KIT-6-SO3H follows a second-order kinetic model and is well described by the Langmuir isotherm, reflecting monolayer adsorption behavior. Density functional calculations reveal that the adsorption of these metals is highly exothermic from a thermodynamic perspective, which aligns with and supports the experimental findings. All metals were exothermically adsorbed with binding energies of -1.790 eV for Pb2+, -0.181 eV for Cd2+, and -3.113 eV for Cs+, confirming the exergonic adsorption of the investigated metals on KIT-6-SO3H.

Understanding the Growth Mechanism of Thiol-Conjugated Au25 Cluster

The synthesis of ligand-conjugated gold nanoclusters has attracted significant attention due to its ability to achieve precise control over cluster size selectivity. Among these, Au25(SR)18 -, where R represents an alkyl group, is one of the earliest being synthesized with a very high yield, although its growth mechanism is yet to be fully understood. Using density functional theory, we present the results of a theoretical investigation on the growth process of Au25(SR)18 -, beginning from Au13(SR)12 -. Our findings indicate that the sulfur atoms in the core structure of Au13(SR)12 - preferentially bond with Au-thiol monomers. Monomers attached to two adjacent triangular faces form a staple motif of the gold-sulfur chain, releasing a single linear thiol radical. These reactions occur along the six mutually perpendicular ridges of the Au13 core. The remaining eight triangular faces, linked with linear alkyl parts, cannot bind additional Au-thiol monomers, stopping cluster growth. Furthermore, the capping gold-sulfur chains play a protective role for the core, facilitating the stable formation of the Au25(SR)18 -cluster, as confirmed experimentally.

A multi-site Ru-Cu/CeO2 photocatalyst for boosting C-N coupling toward urea synthesis

Photocatalytic urea production from nitrogen (N2) and carbon dioxide (CO2) is a sustainable and eco-friendly alternative to the Bosch-Meiser route. However, it remains a significant challenge in developing highly efficient photocatalysts for enhancing C-N coupling to high-yield urea synthesis. Herein, we propose a multi-site photocatalyst concept to address the concern of low yield by simultaneously improving photogenerated carrier separation and reactant activation. As a proof of concept, a well-defined multi-site photocatalyst, Ru nanoparticles and Cu single atoms decorated CeO2 nanorods (Ru-Cu/CeO2), is developed for efficient urea production. The incorporation of Ru and Cu sites is crucial not only to generate high-density photogenerated electrons, but also to facilitate N2 and CO2 adsorption and conversion. The in situ formed local nitrogen-rich area at Ru sites increases the encounter possibility with the carbon-containing species generated from Cu sites, substantially promoting C-N coupling. The Ru-Cu/CeO2 photocatalyst exhibits an impressive urea yield rate of 16.7 μmol g-1 h-1, which ranks among the best performance reported to date. This work emphasizes the importance of multi-site catalyst design concept in guaranteeing rapid C-N coupling in photocatalytic urea synthesis and beyond.

Investigating the stable structures of yttrium oxide clusters: Yn clusters as promising candidates for O2 dissociation

This study presents threshold photoionization (PI) spectra for a series of yttrium oxide clusters (YnOm, n = 2-8, m = 2-4) in the photon energy range of 192 to 300 nm (6.46 to 4.13 eV). Density functional theory (DFT) is employed to explore the stable structures of these clusters. For YnO2 clusters, experimental PI spectra are compared with calculated spectra for the lowest-energy and near-lowest-energy structural isomers. Stable structures contributing to the experimental PI spectra are identified. Experimentally corrected adiabatic ionization energies for YmO2 clusters are determined. The newly identified lowest-energy structure for Y2O2 differs from those in previous literature studies, while larger clusters show better agreement, primarily varying in oxygen binding sites. Molecular oxygen-absorbed configurations of yttrium oxide clusters are generally unstable or energetically unfavorable, with O2 activation occurring via charge transfer from yttrium to oxygen. Climbing image nudged elastic band (CI-NEB) calculations indicate that YnO2 forms in the ground state when an O2 molecule is absorbed onto low- or under-coordinated sites such as corners or edges of Yn clusters. This process involves the dissociation of the O-O bond, followed by the adsorption of individual O atoms at different sites on the Yn clusters. Analysis of the total density of states (TDOS) and partial density of states (PDOS) reveals an increased orbital density near the Fermi level, indicating a strong reaction affinity between Y and O atoms.

Unlocking the sensing and scavenging potential of Sc2CO2 and Sc2CO2/TMD heterostructures for phosgene detection

The detection of phosgene is critically important owing to its extreme toxicity and potential use as a chemical warfare agent to ensure public safety and security. Two-dimensional (2D) scandium carbide MXenes (Sc2CTx; T = O-, x = 2) stand out as promising materials for gas sensing applications owing to their unique electronic and adsorption properties. In this study, first-principles calculations based on the GGA-PBE functional were employed to investigate the structural, electronic, and mechanical characteristics of Sc2CO2 with different surface termination positions. The adsorption behavior of Sc2CO2 was systematically explored for various gas molecules, including N2, O2, CO, NO, CH4, H2S, and, notably, phosgene (COCl2). Specifically, phosgene exhibited a high adsorption energy, highlighting the selectivity of Sc2CO2 towards this toxic gas. Furthermore, the impact of gas adsorption on the electronic structure of Sc2CO2 was investigated. Strategies such as increasing the operating temperatures and forming heterostructures with transition metal di-chalcogenides (MoSe2 and WSe2) proved to be highly effective to mitigate the challenges related to slow recovery time. Thus, this work underscores the potential of Sc2CO2 MXenes as highly sensitive and selective gas sensors, particularly for phosgene sensing.

Getting insights into the edge effect of FeN4C catalysts on the electroreduction of CO to methane by density functional theory calculations

Isolated FeN4 atomically dispersed on graphene (FeN4C) has emerged as a versatile catalyst for the electrochemical carbon monoxide reduction reaction (CORR). However, there is still a lack of underlying understanding of the impact of the local coordination environment of FeN4 on CORR performance, particularly the intrinsic activity differences among various FeN4 sites. Herein, by using density functional theory, we investigated the electrocatalytic performance of FeN4 embedded in the interior, armchair- and zigzag-edges of carbon sheets for converting CO to valuable C1 products. The Gibbs free energy profile analyses along the possible reaction pathways identify that the armchair-edge FeN4 site (FeN4@A) exhibits the best catalytic activity and the highest CH4-selectivity through the *CHO key intermediate with the lowest free energy change of 0.31 eV. The corresponding kinetic analyses also confirm that FeN4@A possesses the fastest kinetic CORR activity with an activation barrier of 1.31 eV for the rate-determining step. In addition, the d-band center calculations suggest that the local environment of the FeN4 site can regulate the overlap of the d-orbitals of the center Fe and the p-orbitals of coordination N atoms to change the position of the d-band center relative to the Fermi level, which significantly affects the catalytic activity of the FeN4 site. The d-band center of FeN4@A is very close to the Fermi level in energy, indicating that the armchair-edge of graphene favors the FeN4 site to achieve the high CORR performance. These results provide insight into the relationship of electronic structure-catalytic activity of different-type FeN4C catalysts, which may guide the design of novel electrode materials with improved performances for achieving efficient multi-intermediate electrocatalysis.

Synergistic Effect of Topological Semimetal TiSi and Plasmonic Cu for Enhanced Photoelectrocatalytic Water Splitting of TiO2 Nanorod Array

Developing high-efficiency and low-cost catalysts for PEC water splitting is vital for solving the issues of energy consumption, environmental pollution, and global warming. In this study, we designed and prepared a composite photoanode TiO2/TiSi/Cu by depositing a topological semimetal TiSi film and plasmonic Cu nanoparticles onto a TiO2 nanorod array. Due to the synergistic effect of the topological bands of TiSi and the SPR effect of Cu, TiO2/TiSi/Cu exhibits significantly enhanced optical absorption in the visible-light region. Under wavelength (λ) > 420 nm light irradiation, the photocurrent density of TiO2/TiSi/Cu reaches 4.46 mA cm-2 at 1.9 V vs RHE, about 17.84 times that of pure TiO2. The carrier lifetime is prolonged from 25.04 ns for pure TiO2 to 31.13 ns for TiO2/TiSi/Cu. Furthermore, the TiO2/TiSi/Cu photoanode demonstrates good long-term cyclic stability, with an average hydrogen production rate of 8.12 μmol cm-2 h-1. Our results indicate that the synergistic effect of topological semimetal TiSi and plasmonic Cu is an effective strategy to enhance the PEC performance of TiO2. This approach could be applied to other topological catalysts, providing new opportunities for developing novel and efficient catalysts.

Revealing the structure-activity relationship of Pt1/CeO2 with 17O solid-state NMR spectroscopy and DFT calculations

Single-atom catalysts (SACs) have attracted significant interest due to their exceptional and tunable performance, enabled by diverse coordination environments achieved through innovative synthetic strategies. However, various local structures of active sites pose significant challenges for precise characterization, a prerequisite for developing structure-activity relationships. Here, we combine 17O solid-state NMR spectroscopy and DFT calculations to elucidate the detailed structural information of Pt/CeO2 SACs and their catalytic behaviors. The NMR data reveal that single Pt atoms, dispersed from clusters with water vapor, exhibit a square planar geometry embedded in CeO2 (111) surface, distinct from the original clusters and other conventionally generated Pt single atoms. The square planar Pt/CeO2 SAC demonstrates improved CO oxidation performance compared to Pt/CeO2 SAC with octahedral coordination, due to moderately strong CO adsorption and low energy barriers. This approach can be extended to other oxide-supported SACs, enabling spatially resolved characterization and offering comprehensive insights into their structure-activity relationships.

Intramolecular Double Activation by Biligands Sharing a Single Metal Atom for Preferred Two-Electron Oxygen Reduction

It is challenging to selectively promote the two-electron oxygen reduction reaction (2e-ORR) since highly ORR-active electrocatalysts are not satisfied with 2e-ORR and are most likely to go all the way to 4e-ORR, completely reducing dioxygen to water. Recently, however, the possibility of a 2e-ORR preference over 4e-ORR was raised by extensively considering multiple ORR mechanisms and employing a potential-dependent activity measure for constructing volcano plots. Here, we realized the preferred 2e-ORR via an intramolecular double activation of the peroxide intermediate (*OOH) by allowing the intermediate to be easily desorbed before proceeding to 4e-ORR. Dioxygen was transformed to *OOH on a carbon atom of the imidazole ligand of zeolitic imidazolate framework-8 (ZIF-8). When an amine group was introduced via ligand exchange, the selectivity of 2e-ORR was enhanced by 11%. The added amine attracted the oxygen atom of *OOH via a hydrogen bond to weaken the binding strength of *OOH to the carbon active site (double activation). The amine-decorated ZIF-8 exhibited H2O2 faradaic efficiency at 98.5% at ultrahigh-rate production at 625 mg cm-2 h-1 by 1 A cm-2 in a flow cell.

When carbon monoxide goes "upside down": vibrational signatures of CO at NaCl(100) from ab initio molecular dynamics

CO adsorbed on NaCl(100) is a model system for surface science showing a rich variety of interesting phenomena. It features several adsorption phases like tilted/antiparallel or perpendicular/upright, very long vibrational lifetimes of the CO internal stretch (IS) mode, anharmonicity-driven vibrational energy pooling, "C-bound" vs. "O-bound" adsorption, and heavy-atom gateway tunneling during CO inversion at low temperatures. Typically, these features and phenomena are experimentally probed by stationary and time-resolved vibrational spectra, exhibiting characteristic differences between the various adsorption modes and phases. To gain atom- and time-resolved insight into vibrational response of CO molecules on NaCl(100), vibrational density of states (VDOS), infrared (IR) and vibrational sum frequency (VSF) spectra are computed from velocity velocity correlation functions (VVCFs) by ab initio molecular dynamics (AIMD) for various coverages, temperatures and phases. In agreement with experiments, we find that increasing CO ("C-bound") coverages as well as CO inversion lead to redshifts of the CO IS mode. We predict more diffuse spectra at T = 300 K compared to 30 K, reflecting the disorder of adsorbates and monolayer instability at room temperature. Analyzing molecularly decomposed and internal VDOS curves as well as computed non-linear correlation matrices give further insight into the complex molecular dynamics underlying the vibrational spectra, notably for the low-frequency regime where frustrated rotations, translations and intermolecular motions come into play. On a methodological side, we also test and discuss some intricate details of how to compute IR and VSF response using a modified formulation of the VVCF methods [Ohto et al., J. Chem. Phys., 2015, 143, 124702], by including time and angle-dependent dipole and polarizability derivatives as well as intermolecular couplings by cross correlations. Their effect on computed vibrational spectra is studied. These findings provide a detailed, microscopic insight into the picosecond vibrational spectra and dynamics of CO on NaCl(100), highlighting the effects of temperature, coverage, and changes in adsorbate orientation.

Modeling the subsurface adsorption of atomic oxygen in silver from high vacuum to high pressure

Coadsorption of atoms or molecules on a solid can modulate adsorption energies, adsorbate geometries, surface reconstructions, and surface reactions. Interactions between atomic adsorbates at higher coverages can even promote percolation of some atoms beneath the surface into the subsurface or deeper into the bulk of the solid. The evolution of surface phenomena and the emergence of subsurface adsorption with increasing coadsorption effects are less understood at the atomic level due to the experimental and theoretical challenges of studying larger surface coverages. Yet, important practical applications, such as metal oxidation, corrosion, and industrial heterogeneous catalysis occur at high adsorbate concentrations and require a fundamental understanding of adsorption and reactivity over a wide range of coverages. Here, we develop an all-site, ab initio, lattice-gas model that describes surface and subsurface adsorption in a crystalline solid and apply it to study the adsorption of atomic oxygen on the Ag(111) surface at varying oxygen concentrations and O2 pressures ranging from high vacuum to high pressure. The coadsorbate interactions in the model are treated in a pairwise manner and all parameters of the model are calculated using density functional theory. This study demonstrates that three-dimensional lattice-gas models can be powerful theoretical tools to predict the conditions for subsurface adsorption and elucidate the underlying inter-adsorbate interactions.

Electrocatalytic reduction of nitrogen to ammonia on metal nanoclusters: insights and trends from d- and p-block metals

The electrocatalytic reduction of nitrogen (NRR) to ammonia on metal nanoclusters represents a transformative approach to sustainable ammonia synthesis, offering a greener alternative to the highly energy-intensive Haber-Bosch process, which is a significant contributor to global CO2 emissions. By harnessing renewable electricity under ambient conditions, electrocatalytic NRR could dramatically lower the carbon footprint and enable decentralized, on-demand ammonia production. However, the inherent stability of N2 presents a major obstacle to its efficient activation. Metal nanoclusters, with their distinctive electronic and structural characteristics, have emerged as highly promising catalysts to overcome this challenge. This study systematically investigates the NRR catalytic performance of a broad spectrum of d-block and p-block metal nanoclusters. Through the use of Genetic Algorithms (GA) for global minimum structure optimization and comprehensive mechanistic pathway analysis, we uncover key trends in N2 activation, NRR reaction pathways, selectivity, and efficiency across various nanoclusters. Our findings provide critical insights into the design of advanced NRR electrocatalysts, paving the way for more sustainable and efficient technologies for ammonia production.

Regulating the Ligand N-Heterocyclic Coordination in Bismuth-Based MOFs for Efficient CO2 Photoreduction

The increasing global concern over environmental degradation and resource depletion has driven the search for sustainable technologies to mitigate CO2 emissions. Recently, bismuth-based metal organic frameworks (Bi-MOFs) have garnered significant attention due to their high stability, adjustable porosity, and excellent light absorption properties. However, weak visible light absorption and charge recombination are still obstacles to wide application. In this study, a new class of Bi-MOFs based on tribenzoic acid with different ligand N-atom number was synthesized by solvothermal method. Experimental and computational results indicated that the introduction of one N-heterocyclic pyridine group within the ligand led to an enhanced localized internal electric field (LIEF), which could promote efficient charge separation and enhance the interaction with CO2 molecules, thus improving photocatalytic activity. This study highlights the potential of pyridine-functionalized ligands for the design of high-performance MOFs for CO2 reduction, providing valuable insights for the development of advanced materials in environmental sustainability efforts.

Enhancing the Activity and Stability of Pt Nanoparticles Supported on Multiscale Porous Antimony Tin Oxide for Oxygen Reduction Reaction

Pt nanoparticles dispersed on carbon supports (Pt/C) are the benchmark oxygen reduction reaction (ORR) catalysts in proton exchange membrane fuel cells (PEMFCs). However, their widespread application is hindered by severe stability degradation under high potentials and acidic environments, primarily due to carbon support corrosion. To address this challenge, a multiscale template-assisted method is proposed, combined with ethylene glycol reduction, to fabricate Pt nanoparticles supported onto multiscale porous conductive antimony tin oxides (Pt/PT-SSO). Both theoretical and experimental approaches have shown that the strong interaction between Pt and support markedly accelerates electron transfer and optimizes the adsorption strength of key intermediates on the Pt surface. Furthermore, the unique multiscale porous structure of support not only provides an ideal platform for the uniform dispersion of Pt nanoparticles but also greatly enhances confinement effect, effectively preventing Pt aggregation. As a result, the Pt/PT-SSO exhibits superior ORR activity and durability compared to commercial Pt/C catalysts. Specifically, its mass activity at 0.9 V (vs RHE) reaches 0.617 A mgPt⁻¹, which is twice that of Pt/C, while maintaining outstanding stability over 50 h. Notably, PEMFCs utilizing Pt/PT-SSO achieve a high power density of 1.173 W cm⁻2 and retain 94.9% after 30,000 cycles of accelerated durability testing.

Point defect formation at finite temperatures with machine learning force fields

Point defects dictate the properties of many functional materials. The standard approach to modelling the thermodynamics of defects relies on a static description, where the change in Gibbs free energy is approximated by the internal energy. This approach has a low computational cost, but ignores contributions from atomic vibrations and structural configurations that can be accessed at finite temperatures. We train a machine learning force field (MLFF) to explore dynamic defect behaviour using Te+1 i and V +2 Te in CdTe as exemplars. We consider the different entropic contributions (e.g., electronic, spin, vibrational, orientational, and configurational) and compare methods to compute the defect free energies, ranging from a harmonic treatment to a fully anharmonic approach based on thermodynamic integration. We find that metastable configurations are populated at room temperature and thermal effects increase the predicted concentration of Te+1 i by two orders of magnitude - and can thus significantly affect the predicted properties. Overall, our study underscores the importance of finite-temperature effects and the potential of MLFFs to model defect dynamics at both synthesis and device operating temperatures.

Ordered Cationic Mixing in a 1D Organic-Inorganic Hybrid

Hybrid metal halides are a remarkably dynamic family of materials that offer a flexible platform for exploring the novel crystal chemistry that emerges at the intersection of organic and inorganic solids. Herein, we report the discovery of a hybrid that contains two molecules effectively adopting isostructural geometry, (1-NA)PbI3 and (1-MQ)PbI3, and our attempts to create solid solutions of the two beyond the 1:1 ratio. Single-crystal X-ray diffraction, combined with solid-state NMR measurements, clearly show that despite having nearly identical steric geometry, the only mixed phase attained was the composition (1-MQ)(1-NA)Pb2I6, which exhibits a high degree of order between the two molecules. We propose that this ordering is primarily driven by local molecular dipoles, which ultimately creates a band structure in the blended phase that is highly characteristic of the end members, with little sign of rehybridization between the organic or inorganic components.

Tuning of anomalous magnetotransport properties in half-Heusler topological semimetal GdPtBi

Half-Heusler compounds from the REPtBi family exemplify Weyl semimetals in which an external magnetic field induces Weyl nodes. These materials exceptionally host topologically non-trivial states near the Fermi level and their manifestation can be clearly seen in the magnetotransport properties. In this study, we tune the Fermi level of the archetypal half-Heusler Weyl semimetal GdPtBi through high-energy electron irradiation, moving it away from the Weyl nodes to investigate the resilience of the contribution of topologically non-trivial states to magnetotransport properties. Remarkably, we observe that the negative longitudinal magnetoresistance, which is a definitive indicator of the chiral magnetic anomaly occurring in topological semimetals, persists even when the Fermi level is shifted by 100 meV from its original position in the pristine sample. Additionally, the anomalous Hall effect shows complex variations as the Fermi level is altered, attributed to the energy-dependent nature of the Berry curvature, which arises from avoided band crossing. Our findings show the robust influence of Weyl nodes on the magneto-transport properties of GdPtBi, irrespective of the Fermi level position, a behaviour likely applicable to many half-Heusler Weyl semimetals.

Femtosecond Laser Manipulation of Multistage Phase Switching in Two-Dimensional In2Se3 Visualized via an In Situ Transmission Electron Microscope

Phase transitions critically determine material properties for applications, making them central to material science. The two-dimensional (2D) van der Waals material In2Se3 has been extensively studied as a model system for multiphase switching due to its intricate phase transition behaviors and outstanding ferroelectric properties for device applications. However, the lack of an efficient method for precise phase control and the poorly defined conditions for multiphase transitions have severely hindered its practical use. Here, we report that the femtosecond (fs) laser can serve as a potent tool for fast and precisely manipulating multiphase transitions in In2Se3 thin flakes. Using a transmission electron microscope capable of in situ fs laser irradiation, we realize controllable fast phase switching between four phases of 2D In2Se3 by controlling the laser fluence, including the transition from the ferroelectric α phase to the antiferroelectric β' or paraelectric β phase, reversible switching between antiferroelectric β' and paraelectric β phases at room temperature, as well as reversible transformation between the ferroelectric α' phase and antiferroelectric β' or paraelectric β phase at liquid nitrogen temperature. Notably, these multiphase transitions are accompanied by rapid formation and annihilation of domain structures and superlattices, resulting in fast changes in electric conductivity. Our first-principles calculations verify the multiphase transition pathways and reveal that the conductivity change stems from electronic band structure variation among the different phases. This work systematically investigates the phase transition behaviors in In2Se3 through spatially and temporally resolved characterization methods, providing foundational insights into memory device optimization.

Controlling the Activity and Selectivity of Cu Catalysts toward Industrially Relevant Ethanol Electrosynthesis via High-Index Step Density Engineering

Electrochemical CO2 reduction reaction on Cu catalysts can generate high-value multicarbon (C2+) products, making it a significant research area of growing commercial interest. However, the production rate of ethanol remains low owing to the trade-off between the activity and selectivity of Cu catalysts. Here, we develop a defect-rich Cu catalyst with abundant high-index step sites by chemically etching commercially available Cu nanoparticles. This catalyst exhibits a high Faradaic efficiency of ∼50% and a partial current density of ∼416 mA cm-2 for ethanol production. Furthermore, it shows good stability at a high total current density of ∼800 mA cm-2, without obvious decay in ethanol selectivity. Control experiments indicate that the impressive ethanol selectivity is closely associated with the high density of high-index steps present on the defect-rich Cu catalyst. In situ Raman spectroscopy and density functional theory calculations further verify that the optimal high-index step sites enable balanced adsorption of *CO, *OH, and *H, and facilitate the hydrogenation of *CHCOH to *CHCHOH, thereby improving ethanol selectivity. This work underscores the importance of step density control for steering the reaction pathway and selectivity toward ethanol.

Investigation of a Few Noble Metal Oxides with 17O Solid-State NMR Spectroscopy

Noble metal oxides are highly valuable and act as a key component of metal-oxide interfaces in oxide-supported noble metal catalysts, which play a crucial role in modern industrial society. Here, we investigate the structure of four common and stable noble metal oxides using 17O solid-state NMR. The optimal isotopic labeling temperature ensures the highest labeling efficiency while preserving the structure of the oxides. The variation in characteristic signals for each noble metal oxide reveals oxygen species in different chemical environments, while the NMR parameters related to chemical shift anisotropy and quadrupolar interaction obtained from spectral fitting indicate more structural information. DFT calculations are used to assist spectral assignments for various oxygen species. This work serves as a prerequisite for studying solid-state NMR of oxide-supported noble metal catalysts.

Direct Carbonate Reduction on Sn Oxide Surface

Direct reduction of carbonate (CO3 2-) to value-added chemicals presents several advantages for integrating CO2 capture from air with electrochemical conversion at near-unity efficiency. However, a critical challenge lies in effectively adsorbing CO3 2- as a reactive intermediate for sequential reduction. Density functional theory calculations indicate that the presence of oxygen vacancies (VO) on a SnO2 surface significantly enhances its reactivity toward CO3 2- adsorption, with the resulting adsorbed species (*CO3) detectable by Raman spectroscopy. Operando electrochemical Raman spectra have confirmed the formation of *CO3 on the partially reduced SnO2-xVO surface. Pulsed electrolysis has successfully converted CO3 2- to CO at a constant flow rate in an electrolyzer featuring a gas diffusion electrode configuration. A reaction cycle, encompassing SnO2 partial reduction, CO3 2- adsorption and reduction, and SnO2 regeneration, has been proposed as a viable approach for continuous direct CO3 2- reduction.

Tracking Charge Dynamics in a Silver Single-Atom Catalyst During the Light-Driven Oxidation of Benzyl Alcohol to Benzaldehyde

Understanding charge transfer in light-driven processes is crucial for optimizing the efficiency and performance of a photocatalyst, as charge transfer directly influences the separation and migration of photogenerated charge carriers and determines the overall reaction rate and product formation. However, achieving this understanding remains challenging in the context of single-atom photocatalysis. This study addresses this gap and investigates an Ag-based single-atom catalyst (Ag1@CN x ) in the photocatalytic oxidation of benzyl alcohol to benzaldehyde. Comprehensive characterization was conducted using a battery of diffractive, textural, spectroscopic, and microscopic methods, confirming the catalyst crystallinity, porosity, elemental composition, and atomic dispersion of silver atoms. This material displayed efficient performance in the selective oxidation of benzyl alcohol to benzaldehyde. Density functional theory calculations were used to rationalize the catalyst structure and elucidate the reaction mechanism, unveiling the role of the photogenerated holes in lowering the reaction energy barriers. Time-resolved transient spectroscopic studies were used to monitor the dynamics of photogenerated charges in the reaction, revealing the lifetimes and behaviors of excited states within the catalyst. Specifically, the introduction of silver atoms led to a significant enhancement in the excited state lifetime, which favors the hole-transfer in the presence of the benzyl alcohol. This indicated that the photoexcited carriers were effectively transferred to the reactant, thereby driving the oxidation process in the presence of oxygen. These mechanistic insights are pivotal in spectroscopically elucidating the reaction mechanism and can be practically applied to design single-atom photocatalysts more rationally, targeting materials that combine both rapid reductive quenching and efficient charge transfer to the metal.

Intentional Formation of Persistent Surface Redox Mediators by Adsorption of Polyconjugated Carbonyl Complexes to Pd Nanoparticles

Adsorbing polyconjugated carbonyl and aromatic species to Pd nanoparticles forms persistent intermediates that mediate reactions between hydrogen and oxygen-derived species. These surface redox mediators form in situ and increase selectivities toward H2O2 formation (∼65-85%) compared to unmodified Pd nanoparticles (∼45%). Infrared spectroscopy, temperature-programmed oxidation measurements, and ab initio calculations show that these species adsorb irreversibly to Pd surfaces and persist over extended periods of catalysis. Combined rates and kinetic isotope effect measurements and simulations suggest that carbonyl groups of bound organics react heterolytically with hydrogen to form partially hydrogenated oxygenated complexes. Subsequently, these organic species transfer proton-electron pairs to O2-derived surface species via pathways that favor H2O2 over H2O formation on Pd nanoparticles. Computational and experimental measurements show redox pathways mediated by partially hydrogenated carbonyl species form H2O2 with lower barriers than competing processes while also obstructing O-O bond dissociation during H2O formation. For example, adsorption and hydrogenation of hexaketocyclohexane on Pd forms species that react with oxygen with high H2O2 selectivities (85 ± 8%) for 130 h on stream in flowing water without additional promoters or cosolvents. These paths resemble the anthraquinone auto-oxidation process (AAOP) used for industrial H2O2 production. These surface-bound species form partially hydrogenated intermediates that mediate H2O2 formation with high rates and selectivities, comparable to AAOP but on a single catalytic nanoparticle in pure water without organic solvents or multiunit reaction-separation chains. The molecular insights developed herein provide strategies to avoid organic solvents in selective processes and circumvent their associated process costs and environmental impacts.

Exploring the potential of 2D beryllonitrene as a lithium-ion battery anode: a theoretical study

The development of new and high-capacity anode materials for Li-ion batteries (LIBs) can lead to significant improvements in energy storage technology, promoting sustainable practices, and enabling a wider adoption of clean energy solutions. Herein, the recently synthesized 2D beryllonitrene has been studied computationally to evaluate its Li+ capacity and feasibility as an anode material in LIBs. 2D BeN4 can load a single layer of Li above and below the plane giving a theoretical capacity of 824 mA h g-1. Upon binding with BeN4, the Li become monocationic and the average adsorption energy per Li+ is -1.522 eV, lesser than the cohesive energy of bulk Li. The Li+ diffusion in BeN4 is facilitated by low barrier energies of ∼0.4-0.8 eV and is consistent when an implicit solvent model is applied for ethylene carbonate. Ab initio molecular dynamics simulations reveal that Li+ have high diffusivity (4.5 × 10-12 m2 s-1) in BeN4, comparable to commercially available anodes. The surface intercalation density of BeN4 is higher (1.00) compared to that calculated for graphite and single-walled carbon nanotubes. Thus, BeN4 shows promising Li+ loading and diffusivity behaviour, is thermally and mechanically stable, and is predicted to be a high-capacity anode material for LIBs.

A first-principles study of Hoffmann-type ultra-wide bandgap semiconductor material

A novel Hoffmann-type metal-organic framework ultra-wide bandgap semiconductor material, {Ni(DMA)2[Ni(CN)4]}(DMA denotes dimethylamine), has been predicted. The material has been named Ni-DMA-Ni, and its structure, stability, electronic, mechanical, optical, and transport properties have been investigated by first-principles simulations. The calculation results demonstrate that Ni-DMA-Ni exhibits excellent thermal and dynamics stability at room temperature, with a bandgap value as high as 4.89 eV and the light absorption capacity reaches 105cm-1level in the deep ultraviolet region. The Young's modulus is 27.94 GPa, and the shear modulus is 10.82 GPa, indicating mechanical anisotropy. In addition, the construction of a two-probe device utilizing Ni-DMA-Ni to evaluate its transport properties revealed a negative differential resistance effect in itsI-Vcharacteristic curve. These unique properties highlight the potential application of the Ni-DMA-Ni material in the deep ultraviolet optoelectronic field. This study provides novel concepts and contributes significant insights to the research of Hoffmann-type semiconductor materials in the field of optoelectronic devices.

DFT Investigation of a Direct Z-Scheme Photocatalyst for Overall Water Splitting: Janus Ga2SSe/Bi2O3 Van Der Waals Heterojunction

Constructing van der Waals heterojunctions with excellent properties has attracted considerable attention in the field of photocatalytic water splitting. In this study, four patterns, coined A, B, C, and D of Janus Ga2SSe/Bi2O3 van der Waals (vdW) heterojunctions with different stacking modes, were investigated using first-principles calculations. Their stability, electronic structure, and optical properties were analyzed in detail. Among these, patterns A and C heterojunctions demonstrate stable behavior and operate as direct Z-scheme photocatalysts, exhibiting band gaps of 1.83 eV and 1.62 eV. In addition, the suitable band edge positions make them effective for photocatalytic water decomposition. The built-in electric field across the heterojunction interface effectively inhibits electron-hole recombination, thereby improving the photocatalytic efficiency. The optical absorption coefficients show that patterns A and C heterojunctions exhibit higher light absorption intensity than Ga2SSe and Bi2O3 monolayers, spanning from the ultraviolet to visible range. Their corrected solar-to-hydrogen (STH) efficiencies are 13.60% and 12.08%, respectively. The application of hydrostatic pressure and biaxial tensile strain demonstrate distinct effects on photocatalytic performance: hydrostatic pressure preferentially enhances the hydrogen evolution reaction (HER), while biaxial tensile strain primarily improves the oxygen evolution reaction (OER). Furthermore, the heterojunctions exhibited enhanced optical absorption across the UV-visible spectrum with increasing hydrostatic pressure. Notably, a 1% tensile strain results in an improvement in visible light absorption efficiency. These results demonstrate that Ga2SSe/Bi2O3 heterojunctions hold great promise as direct Z-scheme photocatalysts for overall water splitting.

Optimizing Excited Charge Dynamics in Layered Halide Perovskites through Compositional Engineering

Dion-Jacobson phase multilayered halide perovskites (MLHPs) improve carrier transport and optoelectronic performance thanks to their shorter interlayer distance, long carrier lifetimes, and minimized nonradiative losses. However, limited atomistic insights into dynamic structure-property relationships hinder rational design efforts to further boost their performance. Here, we employ nonadiabatic molecular dynamics, time-domain density functional theory, and unsupervised machine learning to uncover the impact of A-cation mixing on controlling the excited carrier dynamics and recombination processes in MLHPs. Mixing smaller-sized Cs with methylammonium in MLHP weakens electron-phonon interactions, suppresses the nonradiative losses, and slows down intraband hot electron relaxations. On the contrary, larger-sized guanidinium incorporation accelerates nonradiative relaxations. The mutual information analyses reveal the importance of interlayer distances, intra- and interoctahedral angle dynamics, and A-cation motion in extending the excited carrier lifetime by mitigating nonradiative losses in MLHPs. Our work provides a guideline for strategically choosing A-cations to boost the optoelectronic performance of layered halide perovskites.

Polybenzimidazole Composite Separators Engineered from MOFs-HNTs Composites Applicated in Lithium-Ion Batteries

Incorporating inorganic nanostructured materials into polymeric separators for lithium-ion batteries (LIBs) enhances properties such as ionic conductivity, electrolyte wettability, and thermal resistance. However, poor interfacial compatibility between inorganic materials and the polymeric matrix remains a significant challenge. In this study, Zr-based UiO-66 metal-organic frameworks (MOFs) is employed as an interfacial binder between halloysite nanotubes (HNTs) and a poly-(arylene ether benzimidazole) (OPBI) matrix, preparing porous separators using the non-solvent phase separation (NIPS) method. The UiO-66 MOFs promote strong adhesion of HNTs to the OPBI chains, creating a more cohesive inorganic-organic system, as confirmed by molecular dynamics (MD) simulations of binding energy. The resulting OPBI@M-H10 composite separator exhibits high porosity (80%), an electrolyte absorption capacity of 377%, and an ionic conductivity of 1.59 mS·cm⁻¹. Furthermore, LiFePO4 half-cells assembled with this composite separator show a discharge capacity of 161 mAh·g⁻¹ and a retention rate of 97.96% after 200 charge-discharge cycles. The separator also demonstrates excellent electrode stability in the plating/stripping test of Li symmetric cells, lasting up to 1600 hours and effectively inhibiting dendrite growth on the Li anode. This approach provides a promising solution for high-performance LIBs separators and paves the way for advancements in LIBs technology and energy storage applications.

Pyrrolation of Melem: A Facile Gateway into the Field of Monomeric s-Heptazine Chemistry

Monomeric s-heptazines are an intriguing class of compounds with many attractive properties for various areas of application such as photocatalysis or organic light-emitting diodes. However, research into these properties has so far been challenging, as only a few synthetic routes for the preparation of monomeric s-heptazines are known in the literature. Furthermore, these few reported synthetic pathways generally require the use of specialized equipment that may not be available to all laboratories interested in studying monomeric s-heptazines. For this reason, a more accessible synthetic route for the preparation of monomeric s-heptazines has been developed in the course of this work. The central compound of this new approach is 2,5,8-tri(1H-pyrrol-1-yl)-s-heptazine, which could be conveniently synthesized via an acid catalyzed pyrrolation of melem with bench-stable 2,5-dimethoxytetrahydrofuran in a simple one-pot synthesis in air. This compound was shown to be a potent starting material for the synthesis of numerous other monomeric s-heptazines by reaction with both nucleophiles and electrophiles. The monomeric s-heptazines thus accessible were analyzed for their crystal structures by single crystal X-ray diffraction and for their optical properties by ultraviolet/visible and photoluminescence spectroscopy.

Glycerol Adsorption on TiO2 Surfaces: A Systematic Periodic DFT Study

Conversion of glycerol to added-value products is desirable due to its surplus during biodiesel synthesis. TiO2 has been the most explored catalyst. We performed a systematic study of glycerol adsorption on anatase (101), anatase (001), and rutile (110) TiO2 at the Density Functional Theory level. We found several adsorption modes on these surfaces, with anatase (101) being the less reactive one, leading to adsorption energies between -0.8 and -0.4 eV, with all adsorptions molecular in nature. On the contrary, anatase (001) is the most reactive surface, leading to both molecular and dissociative adsorption modes, with energies ranging from -4 to -1 eV and undergoing severe surface reconstructions in some cases. Rutile (110) also shows both molecular and dissociative adsorptions, but it is less reactive than anatase (001). Surfaces with oxygen vacancies affects the adsorbed states and energies. The electronic structure analysis reveals that glycerol adsorption mainly affects the band gap of the material and not the individual contributions to the valence and conduction band. Bader charge analysis shows that strong adsorption modes on anatase (001) and rutile (110) are associated with large charge transfer from glycerol to the surface, while weak and molecular adsorption modes involve low charge transfer.