Transition Metal Group Research Articles

Machine Learning-Enhanced Screening of Single-Atom Alloy Clusters for Nitrogen Reduction Reaction.

The electrochemical nitrogen reduction reaction (eNRR) under ambient conditions is a promising method to generate ammonia (NH3), a crucial precursor for fertilizers and chemicals, without carbon emissions. Single-atom alloy catalysts (SAACs) have reinvigorated catalytic processes due to their high activity, selectivity, and efficient use of active atoms. Here, we employed density functional theory (DFT) calculations integrated with machine learning (ML) to investigate dodecahedral nanocluster-based SAACs for analyzing structure-activity relationships in eNRR. Over 300 nanocluster-based SAACs were screened with all the transition metals as dopants to develop an ML model predicting stability and catalytic performance. Facet sites were identified as optimal doping positions, particularly with late group transition metals showing superior stability and activity. Utilizing DFT+ML, we identified 8 highly suitable SAACs for eNRR. Interestingly, the number of valence d-electrons in dopants proved crucial in screening for eNRR activity. These catalysts exhibited low activity in hydrogen evolution reaction, further enhancing their suitability for eNRR. This successful ML-driven approach accelerates catalyst design and discovery, holding significant practical implications.

Elemental tellurium in organoelement synthesis of tellurium-containing organometallics and telluracycles

An overview presents the known methods of using elemental tellurium in the synthesis of various acyclic and cyclic, saturated and unsaturated compounds containing Te–E bonds (E = main group atom or transition metal atom). These methods include the insertion of tellurium into the C–E (E = halogen, Al, Ga, Sn, Zr) and P–E (E = Li, P, Si, Ge and Sn) and Sn–Sn single bonds and the addition to the E=E (E = Si, Ge and Sn) double bond, and PC triple bond, as well as the breakdown of the C=C double bond and the exchange of metal (Hg, Ag) and non-metal (B, I) for Te. Reactions with carbenes, their heavier (Si, Ge, Sn) analogs and free radicals are also discussed, as are the oxidation of organophosphorous (III) compounds, silanes and germanes with Te and the direct cyclisation of alkanes, arenes and heteroarenes containing two halogenomethyl fragments with elemental Te. Three-component heterocyclizations involving elemental tellurium and leading to telluracycles are also discussed. The reactions mentioned above are compared to those involving lighter chalcogens.

Catalytic engineering of transition metal (TM: Ni, Pd, Pt)-coordinated Ge-doped graphitic carbon nitride (Ge@g-c3n4) nanostructures for petroleum hydrocarbon separation: An outlook from theoretical calculations

The extraction, processing, and utilization of petroleum often results in the release of diverse hydrocarbon pollutants into the environment, leading to severe ecological and health implications. Herein, the adsorption and separation of ethane (EAN), ethene (EEN), ethyne (EYN), and benzene (BZN) fractions of paraffin, olefin, acetylene, and aromatic petroleum hydrocarbons were investigated via the catalytically engineered nickel group transition metals; nickel (Ni), palladium (Pd), and platinum (Pt). These transition metals were coordinated on Germanium-doped graphitic carbon nitride (Ge@g-C3N4) nanostructures, and the behavior of the systems was studied through Kohn–Sham density functional theory (KS-DFT) with the B3LYP–D3(BJ)/Def2-SVP computational method. The adsorption of petroleum hydrocarbons decreased in the order Ge_Ni@C3N4 > Ge_Pd@C3N4 > Ge_Pt@C3N4>Ge_Pt@C3N4. These results showed that the coordination of Ni, Pd, and Pt within Ge@C3N4 improved the separation of petroleum hydrocarbons.

Small Ring Molecules Comprising 3-6 Boron Atoms: An Account on Synthesis, Structure, and Orbital Engineering.

ConspectusUnlike carbon, boron does not usually form ring compounds due to its electron-deficiency-driven affinity toward polyhedral geometries. The polyhedral boranes having closo-, nido-, arachno-, or hypho-shapes can be structurally and electronically correlated using various electron counting rules developed by Wade, Mingos, and one of us. However, in the last few decades, boron chemistry progressed significantly toward ring systems. In this regard, three of our research groups have made significant contributions to the development of boron ring molecules through different synthetic approaches. While the Ghosh group generally starts from transition metal (TM) stabilized boron species, the Himmel group typically starts from electron-deficient TM-free boron ring compounds. On the other hand, the Jemmis group studies boron rings and their analogous structures computationally and develops electron counting rules to describe them. Over the past few years, through different synthetic approaches, several boron ring molecules have been prepared by our research groups and others. Recently, the Ghosh group has reported the synthesis of an almost planar B6-ring that is stabilized by a TM template. Similarly, the B3-, B4-, and B5-rings have also been stabilized in the coordination spheres of early and late TMs. The recent work of Himmel has uncovered some remarkable diversity in the structures and bonding of B3 and B4 rings, along with their redox reactions. The well-known hydrocarbon analogues of these borane rings, i.e., two-dimensional aromatic compounds [C3H3]+, [C5H5]-, [C6H6], etc., are governed by Hückel's (4n + 2) π-electron rule. However, planar or nearly planar borane rings are not seriously thought of as achievable targets. One of the reasons for this is the influence of the Rudolph diagram in the thought process of chemists that the nido- and arachno-structures generated from closo-polyhedral boranes must also be three-dimensional (3D) fragments. However, this is not the only possibility. Flat arachno- and nido-boranes reminiscent of their organic counterparts follow from an equivalent of the Rudolph diagram. Therefore, this Account is very much necessary for the boron community, in particular, to design and synthesize 3-6 membered boron rings or beyond. This Account aims to highlight significant ongoing experimental and theoretical results in this area from our groups, in addition to relevant works from other groups wherever appropriate. This will also bring into focus various ways in which the flat Bn-systems can be stabilized, such as the utilization of TM or main group caps, utilization of various Lewis bases, edge-condensation of small rings, control over the electron count, and orbital engineering.

Roles of Impurity Levels in 3d Transition Metal-Doped Two-Dimensional Ga2O3.

Doping engineering is crucial for both fundamental science and emerging applications. While transition metal (TM) dopants exhibit considerable advantages in the tuning of magnetism and conductivity in bulk Ga2O3, investigations on TM-doped two-dimensional (2D) Ga2O3 are scarce, both theoretically and experimentally. In this study, the detailed variations in impurity levels within 3d TM-doped 2D Ga2O3 systems have been explored via first-principles calculations using the generalized gradient approximation (GGA) +U method. Our results show that the Co impurity tends to incorporate on the tetrahedral GaII site, while the other dopants favor square pyramidal GaI sites in 2D Ga2O3. Moreover, Sc3+, Ti4+, V4+, Cr3+, Mn3+, Fe3+, Co3+, Ni3+, Cu2+, and Zn2+ are the energetically favorable charge states. Importantly, a transition from n-type to p-type conductivity occurs at the threshold Cu element as determined by the defect formation energies and partial density of states (PDOS), which can be ascribed to the shift from electron doping to hole doping with respect to the increase in the atomic number in the 3d TM group. Moreover, the spin configurations in the presence of the square pyramidal and tetrahedral coordinated crystal field effects are investigated in detail, and a transition from high-spin to low-spin arrangement is observed. As the atomic number of the 3d TM dopant increases, the percentage contribution of O ions to the total magnetic moment significantly increases due to the electronegativity effect. Additionally, the formed 3d bands for most TM dopants are located near the Fermi level, which can be of significant benefit to the transformation of the absorbing region from ultraviolet to visible/infrared light. Our results provide theoretical guidance for designing 2D Ga2O3 towards optoelectronic and spintronic applications.

Electric arc vacuumless synthesis of IV–V group transition metal carbides

Electric arc vacuumless synthesis of IV–V group transition metal carbides

Dynamic mechanism of CO2 capture from flue gas via hydrate-based method induced by using IB group transition metal functionalized carbon nanotubes

Capturing CO2 emitted from industrial power plants is the most efficient method for reducing global carbon emissions at present. In this work, the enhanced dynamic mechanism of CO2 capture from flue gas has been investigated through IB group transition metal functionalized carbon nanotubes (CNTs) as kinetic accelerators via the hydrate-based approach in combination with theoretical calculations and experiments. The computational results revealed that the both the hydrophilic oxygen-containing group and Cu modified CNTs not only enhanced the CO2 adsorption ability but also exhibited high selectivity towards CO2. Importantly, experiments demonstrated that the multi-walled carbon nanotubes (MWCNTs) based accelerators significantly enhanced the dynamic performance of the hydrate formation, substantially increasing gas consumption and CO2 separation efficiency. Particularly, the theoretical selected Cu@FMWCNTs mixed with THF accelerators exhibited superior kinetic indexes during the hydrate formation even under relative low pressure at 1.5 MPa with the largest CO2 separation efficiency of 76.49%, which showed Cu@FMWCNTs to be a potential kinetic accelerator for CO2 capture. This study could provide valuable findings for nanomaterial design of novel hydrate accelerators and facilitate the development of the hydrate-based technology for CO2 capture from the economic perspective of low energy consumption.

Predicting the formation enthalpy and phase stability of (Ti,Al,TM)N (TM = III-VIB group transition metals) by high-throughput ab initio calculations and machine learning

The development of transition-metal-alloyed (Ti,Al)N thin films has become a common strategy to achieve optimized mechanical and thermal properties. Selection of a suitable alloying element, however, should consider the effect on Al solubility, directly influencing phase stability during the deposition. Here we use high-throughput ab initio formation enthalpy calculations to assess stability of the cubic (c) vs. hexagonal wurtzite-type (w-) phase of TM-alloyed (Ti,Al,TM)N. This compositionally-limited ab initio dataset serves to fit several machine-learning (ML) models enabling phase stability predictions over the entire compositional range. Of all the models, the linear regression using Magpie feature descriptor pre-processed by a genetic algorithm has the highest accuracy. For Ta, Nb, Mo, and W addition below ∼10 at.%, our ML model predicts enhanced stability of c-(Ti,Al,TM)N due to increased solubility of Al. Other alloying elements, especially Sc and Y from IIIB group and Hf and Zr from IVB group, decrease the cubic metastable solubility limit. In agreement with available experimental data, all transition metals except for Cr and V increase the volume of c-(Ti,Al,TM)N and w-(Ti,Al,TM)N.

Zigzag boron nitride nanotube functionalization as a sensor for the recognition of group IIA (Mg2+, Ca2+) metal ions, quasi-metal (Si2+, Ge2+) ions, and transition metal (Cu2+, Zn2+) ions: a computational study.

Boron nitride nanotubes (BNNTs) provide an exceptional and sophisticated platform for detecting metal ions with high surface area and remarkable chemical stability. Metal cations tend to bind to the surface of BNNTs, which leads to significant changes in the electrical properties of nanotubes. BNNT-based metal ion sensors have shown promising results in various applications, including water quality monitoring, biomedical research, industrial quality control, and environmental monitoring. In the present study, we have explored the electronic sensitivity of the BNNT to metal ions (Si2+, Ge2+, Cu2+, Zn2+, Mg2+, and Ca2+). The interaction between the ions with the pristine BNNT is performed in the solution phase. The results show that ion adsorption on the nanotube surface is exothermic and favorable. The density of states calculation is presented to investigate the electronic properties of the nanotube during the adsorption process. The results display that an increase in the electrical conductivity of the complexes accompanies the reduction in the energy gap. Based on the obtained data, the Si2+ and Ge2+ cations adsorbed on the BNNT with satisfactory Eg changes (%ΔE) can be promising candidates for better sensing ability. All calculations are conducted within the density functional theory (DFT) using the ωB97XD functional and 6-31G(d,p) basis set. The present approach incorporates the utilization of empirical atom-atom dispersion in conjunction with long-range correction. The calculations are performed using the quantum chemistry package GAMESS, and the obtained results are visualized by employing the GaussView 6.0.16 program.

A facile high-efficiency preparation strategy for Al-containing multi-component boride microcrystals with superior comprehensive performance

Multi-component transition group metal borides (MMB2) have become a research hotspot due to their new composition design concepts and superior properties compared with conventional ceramics. Most of the current methods, however, are complicated and time-consuming, the mass production remains a challenge. Herein, we proposed a new high-efficiency strategy for synthesis of MMB2 using molten aluminum as the medium for the first time. The prepared Al-containing multi-component borides (TiZrHfNbTa)B2 microcrystals had a homogeneous composition with a hexagonal AlB2 structure and ultra-high hardness value of ∼35.3 GPa, which was much higher than data reported in the literature and the rule of mixture estimations. Furthermore, combined with the First-principles calculation results, we found that the Poisson's ratio (v) values exhibit a clearly ascending trend from 0.17 at VEC = 3.5 to 0.18 at VEC = 3.4, then to 0.201 at VEC = 3.2 with the increasing of Al content. This indicates that the intrinsic toughness of multi-component boride microcrystals is obviously enhanced by the trace-doped Al elements. Besides, the fabricated Al-containing multi-component boride microcrystals have superior oxidation activation energy and structural stability. The enhanced oxidation resistance is mainly attributed to the formation of a protective Al2O3 oxide layer and the lattice distortion, both of which lead to sluggish diffusion of O2. These findings propose a new unexplored avenue for the fabrication of MMB2 materials with superior comprehensive performance including ultra-hardness and intrinsically improved thermo-mechanical properties.

Cobalt group transition metals (TM: Co, Rh, Ir) coordination of S-doped porphyrins (TM_S@PPR) as sensors for molecular SO2 gas adsorption: a DFT and QTAIM study.

The intricate challenges posed by SO2 gas underscore the imperative for meticulous monitoring and detection due to its adverse effects on health, the environment, and equipment integrity. Hence, this research endeavors to delve deeply into the intricate realm of transition-metals functionalized sulfur-doped porphyrins (S@PPR) surfaces through a comprehensive computational study. The electronic properties revealed that upon adsorption, Ir_S@PPR surface reflects the least energy gap of 0.109eV at the O-site of adsorptions, indicating an increase in electrical conductivity which is a better adsorption trait. Owing to the negative adsorption energy observed, the adsorption behavior is described as chemisorption, with the greatest adsorption energy of - 10.306eV for Ir_S@PPR surface at the S-site of adsorption. Based on the mechanistic attributes, iridium-functionalized S@PPR surface is a promising detecting material towards the sensing of SO2 gas. This report will provide useful insight for experimental researchers in selecting and engineering materials to be used as detectors for SO2 gas pollutant. All theoretical investigations were carried out using density functional theory (DFT), calculated at PW6B95-D3/GenECP/Def2svp/LanL2DZ computational method.

Spectroscopic analyses and photocatalytic properties of transition group metal oxide films with different entropy values

Spectroscopic analyses and photocatalytic properties of transition group metal oxide films with different entropy values

Precisely constructing charge-asymmetric dual-atom Fe sites supported on hollow porous carbon spheres for efficient oxygen reduction

Transition group metal catalysts showing atomic dispersion are on the rise as affordable electrocatalysts for the oxygen reduction reaction (ORR) in fuel cell batteries, but their activity in acidic media remains constrained.

First-principles study on structural stability, electronic structure and mechanical properties of VB group transition metal tungsten alloys W-TM (TM=V, Nb, Ta)

The engineering design of tungsten and its alloys as plasma-oriented components has been proposed and practised as an effective solution to the key problem of the interaction between plasma and wall materials in Tokamak experiments. However, it is still worth exploring the internal mechanism and the influence of mechanical properties after the transition metals (TM) of the same group form alloy with tungsten (W). In this work, the structural stability, electronic structure, mechanical stability and Debye temperature of W-TM (TM=V, Nb, Ta) alloy were investigated by first principles based on density functional theory. The lattice constant, formation energy and cohesion energy of W-TM alloy were calculated. The W-TM alloy remains a bcc lattice, and all structures are energy stable. Using the optimized lattice, the elastic constants are calculated, and the elastic modulus and other mechanical parameters are derived. It is found that most of the mechanical properties of W-TM are lower than those of tungsten, especially W-Nb alloy, but B/G and Poisson's ratio prove that W-TM alloy has better ductility. The calculated melting point Debye temperature proves that the alloy has no significant change from pure tungsten and can still maintain good thermal stability. The metallicity of tungsten can be enhanced by doping with VB group transition metals. Among them, W-Ta alloy can effectively improve the ductility of the material without causing serious decline in other mechanical properties. The research results can provide a reference for the selection of plasma materials for fusion reactor design.

First-principles study of structure and bonding in Ni-group transition metal carbonyls with terminal tin chalcogenides [M(CO)3SnX] (M = Ni, Pd, Pt; X = O, S, Se, and Te) complexes

This analysis employs atomistic molecular modelling based on density functional theory (DFT) approach within the B3LYP/LANL2DZ/6-31G* framework to investigate the structural and bonding analysis of nickel group transition metal Carbonyls [M(CO)4] with terminal substituted tin chalcogenides Complexes [M(CO)3SnX] (M = Ni, Pd, and Pt; X = O, S, Se, and Te). The study optimises geometries, calculates vibrational frequencies, Electron localisation parameters, inherent charges, molecular orbitals, and natural bond orders (NBO) of Ni, Pd, Pt tetra carbonyl compounds (M(CO)4) and Tin chalcogenides (M(CO3(SnX)) 1–15. While the optimised structures display tetrahedral 18-electron configurations, M(CO)3(SnX) compounds depict significant dipole moments (1.47–3.03 Debye) and varied M-Sn and C–O bond lengths. Bonding analysis through NBO, WBI, and orbital contributions elucidates polarised M-Sn bonds and distinctive sigma donor behaviour of SnX. Molecular orbital analysis uncovers trends in stability based on energy gaps. Results of the energy decomposition analysis (EDA) reveals the values of ΔEelstat are higher than that of ΔEorb, thus, indicating that the bonds under study have more ionic character. The [Ni(CO)4] shows 60.13% ionic and 39.87% covalent contribution towards Ni-C bond. The findings contribute to understanding molecular structures, reactivity, and applications in diverse chemical domains.

The d‐band energy level splitting of ferric group (Fe, Co, Ni) metals drives the adsorption‐conversion of polysulfides

AbstractThe notorious lithium polysulfides (LiPSs) shuttle effect, which results in low capacity, subpar rate performance, and quick capacity deterioration, has severely restricted the practical applications of lithium sulfur (Li‐S) batteries. Therefore, it is very important for modified materials to promote thermodynamics and redox kinetics in the entrapping‐conversion process of polysulfides. Density functional theory (DFT) calculations show that ferric group (Fe, Co, Ni) transition metals not only provide moderate binding contacts with LiPSs but also act as an active catalyst in the spontaneous and sequential lithiation of S8 to Li2S by d‐band energy level splitting, and quick migration of Li ions can be operated on their surface, enhancing the utilization of LiPSs. Experimentally, felicitously‐fabricated ferric group (Fe, Co, Ni) transition metals encapsulated in nitrogen‐doped carbon nanotubes (M@NCNT) electrocatalysts were introduced into Li‐S batteries via separator functionalization. Actually, the experiments demonstrated that the excellent shuttle effect hindering was enabled. Consistent with theoretical predictions, Li‐S batteries with Ni@NCNT modified separators had significantly improved rate capacity and cycling stability. The cells with Ni@NCNT were able to achieve a high initial discharge capacity of 1035 mAh g−1 and a capacity retention rate of 70% at 500 discharges at 1.0 C with a 0.060% capacity decay each cycle, performing considerable cycle‐life with state‐of‐the‐art separators. Our work demonstrated a realistic separator‐modified strategy of d‐band energy level splitting from ferric group metals for high‐performance and long‐life Li‐S batteries, further propelling Li‐S battery commercialization.

Synthesis of High Entropy and Entropy-Stabilized Metal Sulfides and Their Evaluation as Hydrogen Evolution Electrocatalysts.

High entropy metal chalcogenides are materials containing five or more elements within a disordered sublattice. These materials exploit a high configurational entropy to stabilize their crystal structure and have recently become an area of significant interest for renewable energy applications such as electrocatalysis and thermoelectrics. Herein, we report the synthesis of bulk particulate HE zinc sulfide analogues containing four, five, and seven metals. This was achieved using a molecular precursor cocktail approach with both transition and main group metal dithiocarbamate complexes which are decomposed simultaneously in a rapid (1 h) and low-temperature (500 °C) thermolysis reaction to yield high entropy and entropy-stabilized metal sulfides. The resulting materials were characterized by powder XRD, SEM, and TEM, alongside EDX spectroscopy at both the micro- and nano-scales. The entropy-stabilized (CuAgZnCoMnInGa)S material was demonstrated to be an excellent electrocatalyst for the hydrogen evolution reaction when combined with conducting carbon black, achieving a low onset overpotential of (∼80 mV) and η10 of (∼255 mV).

Donor-acceptor activation of Carbon Dioxide.

The activation and functionalization of carbon dioxide entails great interest related to its abundance, low toxicity and associated environmental problems. However, the inertness of CO2 has posed a challenge towards its efficient conversion to added-value products. In this review we discuss one of the strategies that have been widely used to capture and activate carbon dioxide, namely the use of donor-acceptor interactions by partnering a Lewis acidic and a Lewis basic fragment. This type of CO2 activation resembles that found in metalloenzymes, whose outstanding performance in catalytically transforming carbon dioxide encourages further bioinspired research. We have divided this review into three general sections based on the nature of the active sites: metal-free examples (mainly formed by frustrated Lewis pairs), main group-transition metal combinations, and transition metal heterobimetallic complexes. Overall, we discuss one hundred compounds that cooperatively activate carbon dioxide by donor-acceptor interactions, revealing a wide range of structural motifs.

Energy Distribution of Sputtered Atoms Explored by SRIM Simulations

The energy of the sputtered atoms is important to control the microstructure and physical properties of thin films. In this work, we used the SRIM program to simulate the energy of sputtered atoms. We analyzed the energy distribution functions (EDFs) and the average energies of the atoms in different spatial directions for a range of target materials and Ar ion energies. The results were compared to the analytical equations for EDFs derived by Sigmund and Thompson and with experimental data from the literature. The SRIM simulations give realistic EDFs for transition metals, but not for elements lighter than Si. All EDFs show a low-energy peak positioned close to one-half of the surface binding energy and a high-energy tail decreasing as approximately E−2. We analyzed the characteristics of EDFs, specifically, the position of low- and high-energy peaks, FWHM, and the energy tail, with respect to the ion energy and position of the element in the periodic table. The low-energy peak increases with atomic number for elements within each group in the periodic table. Similar changes were observed for FWHM. For the period 5 and 6 elements, additional broad high-energy peaks were observed at emission angles above 45° when sputtered by Ar ions with 300 eV and also in some heavier elements when bombarded by 600 eV and 1200 eV ions. The transition metals in groups 4, 5, and 6 in periods 5 and 6 have the highest average energies, while the lowest average energies have elements in group 11. The results of simulations show that the average energies of sputtered atoms were inversely proportional to the sputtering yield, i.e., the higher the sputtering yield, the lower the average energy of sputtered atoms. We established an empirical equation for transition metals to estimate the average energy of sputtered atoms from the sputtering yield. The angular distribution of the average atom energy depends on the atomic number. Transition metals with 22 < Z < 72 have an anisotropic energy distribution, with the highest average energies in the 40°–70° range. For the elements in group 11, the angular distribution of the average energies is more isotropic.

Do transition metal sigma complexes of main group metal E–C bonds exist?

Starting with the first σ-H2 complex reported by Kubas in 1984, the 3-center 2-electron bonding between σ-E–H bonds of the main group elements and transition metals has become a common topic of fundamental importance in organometallic chemistry. In many cases, the E atom is a metal of the main group series, as Mg, Al, or Zn. However, despite the ubiquity of organometallic reagents with metal–carbon bonds (i.e. MgR2, AlR3 or ZnR2) that are commonly used in conjunction with transition metals, related transition metal σ-E–C complexes (E = main group metal) have not been described as such. Those would involve as the main bonding component the donation of a highly polar E–C bond, that retains some covalent character, towards an empty orbital of a transition metal. In this perspective work we question ourselves whether the definition of such σ-E–C complexes could indeed be coined to compounds that revolve around M−C−E motifs. In most of the cases we have based our analysis strictly on reported structural X-ray diffraction data, though key information extracted from spectroscopic and computational techniques is discussed when available.