Transition Metal Clusters Research Articles

Exploring Nonlinear Correlations Among Transition Metal Nanocluster Properties Using Deep Learning: A Comparative Analysis with LOO-CV Method and Cosine Similarity.

A novel approach is introduced for the rapid and accurate correlation analysis of nonlinear properties in Transition Metal (TM) clusters utilizing the Deep Leave-One-Out Cross-Validation (LOO-CV) echnique.This investigation demonstrates that the Deep Neural Network (DNN)-based approach offers a more efficient predictive method for various properties of fourth-row TM nanoclusters compared to conventional Density Functional Theory (DFT) methods, which are computationally intensive and time-consuming.The feature space, also known as descriptors, is established based on a broad spectrum of electronic and physical characteristics. Leveraging the similarities among these clusters, the DNN-based model is employed to explore the correlations among TM cluster properties.The proposed method, in conjunction with cosine similarity, achieves remarkable accuracy up to 10-9 for predicting total energy, lowest vibrational mode, binding energy, and HOMO-LUMO energy gap of TM2, TM3, and TM4 nanoclusters. By analyzing corre lation errors, the most closely coupled TM clusters are identified. Notably, Mn and Ni clusters exhibit the highest and lowest levels of energy coupling with other transition metals, respectively. Generally, energy prediction for TM2, TM3, and TM4 clusters exhibit similar trends, while an alternating behavior is observed for vibrational modes and binding energies. Furthermore, Ti, V, and Co demonstrate the highest binding energy correlations with TM2, TM3, and TM4 sets, respectively. Regarding energy gap predictions, Ni ex hibits the strongest correlation in the smallest TM2 clusters, while Cr shows the highest dependence in TM3 and TM4 sets. Lastly, Zn displays the largest error in HOMO-LUMO energy gap across all sets, indicating distinctive independent energy gap characteristics.

Theoretical investigation of graphdiyne-supported single-cluster catalysts for electroreduction of nitric oxide

The electrochemical NO reduction reaction (NORR) to NH3 offers an efficient, environmentally friendly strategy for NO removal and NH3 production, but developing effective catalysts to facilitate the conversion of NO into NH3 remains a challenge. Single-cluster catalysts (SCCs) with multi-metallic sites show promise due to the synergistic interactions among the active atoms. Herein, utilizing density functional theory (DFT) and grand-canonical DFT (GC-DFT), we systematically investigated the potential of late transition metal (TM = Fe, Co, Ni, Cu, Ru, Rh, Pd, Pt) clusters on graphdiyne (TMx/GDY, x = 1–5) for NORR. Ni3/GDY, Pd3/GDY, and Pt3/GDY emerged as the most promising candidates, demonstrating stability, excellent NORR activity, and HER suppression. Their outstanding performance is attributed to the moderate adsorption of NO, with the dxz/dyz orbitals playing a key role in NO activation. GC-DFT results highlight nonlinear variation of intermediate grand free energies with the applied potential. Detailed electronic property analyses were conducted to reveal the charge effects induced by the applied chemical potential. This study provides valuable insights into SCC-catalyzed NO reduction and highlights the significance of potential effects in theoretical simulations of electrochemical systems.

EPR spectroscopy: A versatile tool for exploring transition metal complexes in organometallic and bioinorganic chemistry

AbstractParamagnetic molecules, such as main‐group radicals and transition metal complexes, play crucial roles in catalytic and enzymatic reactions in organometallic and bioinorganic chemistry. Electron paramagnetic resonance (EPR) spectroscopy emerges as a powerful tool for probing the intricate electronic and geometric structures of these molecules. The application of EPR spectroscopy spans a wide spectrum of chemical entities, from simple radicals to transition metal complexes, metalloproteins, and metal clusters, emphasizing its versatility across various fields of chemistry. This review introduces the EPR spectra of transition metal complexes, offering a comprehensive theoretical foundation along with illustrative examples from both bioinorganic and organometallic chemistry. These examples highlight the effectiveness of EPR spectroscopy in characterizing transition metal complexes, reinforcing our understanding of their structure and reactivity.

CrSe2 based single-cluster catalysts with controllable charge states for the oxygen reduction and hydrogen evolution reactions

Development of affordable catalysts for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) represents a central task for advancing electrochemical systems such as fuel cells and metal-air batteries. This study reported the ORR and HER performance of a set of single cluster catalysts (SCCs) with atomically dispersed 3d/4d/5d transition metal cluster (TM3) embedded in a two-dimensional (2D) defective CrSe2 substrate. Distinguishing from the conventional SCCs with positive charge active center, the unique electronegativity discrepancy between the metal clusters and the substrate renders the active center controllable charge states from negative to positive. Our investigations indicate that the TM3 cluster helps tuning the adsorption performance of the intermediates, and therefore enhancing the electrocatalytic activity of the SCCs. Among all the candidates, we demonstrated that the less reported elements of Ir and Ag exhibit the best performance of HER and ORR with low overpotentials of −0.059 and 0.61 V, respectively. Our work provides a prototype to rationally regulate the charge states of catalysts, which could potentially contribute to the development of new kinds of catalysts and serve as a valuable theoretical reference for the experimental rationalization of SCCs.

Structure search for molecular clusters. Towards a rational understanding of their size-dependent properties

Prediction of the lowest energy structure for transition metal clusters and related systems is fundamental in cluster science. Advances in the structure search methods have reduced the computer time for structure prediction, standing on the performance of density functional theory (DFT) calculations. This perspective summarizes recent advances in the employed strategies to tackle geometrical determination of small and large metallic clusters via structure identification and rationalization of the resulting properties. Particularly, we pay attention to coinage metal clusters and noble metals due to their potential technological applications. The basics and recent achievements in structure search methods and related challenges are summarized, towards determining structural evolution accounting contributing to further development on efficient catalytic materials among other applications of technological interest.

Strategies for rational design and applications of transition metal clusters

Strategies for rational design and applications of transition metal clusters

Graphene-supported MN4 single-atom catalysts for multifunctional electrocatalysis enabled by axial Fe tetramer coordination

Multifunctional electrocatalysts for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) are crucial for development of the key electrochemical energy storage and conversion devices, for which single-atom catalyst (SAC) has present great promises. Very recently, some experimental works showed that structurally well-defined ultra-small transition-metal clusters (such as Fe and Co tetramers, denoted as Fe4 and Co4, respectively), can efficiently modulate the catalytic behavior of SACs by axial coordination. Herein, taking the graphene-supported MN4 SACs as representatives, we theoretically explored the feasibility of realizing multifunctional SACs for ORR, OER and HER by this novel axial coordination engineering. Through extensive first-principles calculations, from 23 candidates, IrN4 decorated with Fe4 (IrN4/Fe4) is identified as the promising trifunctional catalyst with the theoretical overpotential of 0.43, 0.51 and 0.30 V for OER, ORR and HER, respectively. RhN4/Fe4 and CoN4/Fe4 are recognized as potential OER and ORR bifunctional catalysts. In addition, NiN4/Fe4 exhibits the best ORR activity with an overpotential of 0.30 V, far superior to the pristine NiN4 SAC (0.88 V). Electronic structure analyses reveal that the significantly enhanced ORR/OER activity can be ascribed to the orbital and charge redistribution of Ni/Ir active center, resulting from its electronic interaction with Fe4 cluster. This work could stimulate and guide the rational design of graphene-based multifunctional SACs realized by axial coordination of small TM clusters, and provide insights into the modulation mechanism.

Density Functional Theory Study of Triple Transition Metal Cluster Anchored on the C2N Monolayer for Nitrogen Reduction Reactions.

The electrochemical nitrogen reduction reaction (NRR) is an attractive pathway for producing ammonia under ambient conditions. The development of efficient catalysts for nitrogen fixation in electrochemical NRRs has become increasingly important, but it remains challenging due to the need to address the issues of activity and selectivity. Herein, using density functional theory (DFT), we explore ten kinds of triple transition metal atoms (M3 = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) anchored on the C2N monolayer (M3-C2N) as NRR electrocatalysts. The negative binding energies of M3 clusters on C2N mean that the triple transition metal clusters can be stably anchored on the N6 cavity of the C2N structure. As the first step of the NRR, the adsorption configurations of N2 show that the N2 on M3-C2N catalysts can be stably adsorbed in a side-on mode, except for Zn3-C2N. Moreover, the extended N-N bond length and electronic structure indicate that the N2 molecule has been fully activated on the M3-C2N surface. The results of limiting potential screen out the four M3-C2N catalysts (Co3-C2N, Cr3-C2N, Fe3-C2N, and Ni3-C2N) that have a superior electrochemical NRR performance, and the corresponding values are -0.61 V, -0.67 V, -0.63 V, and -0.66 V, respectively, which are smaller than those on Ru(0001). In addition, the detailed NRR mechanism studied shows that the alternating and enzymatic mechanisms of association pathways on Co3-C2N, Cr3-C2N, Fe3-C2N, and Ni3-C2N are more energetically favorable. In the end, the catalytic selectivity for NRR on M3-C2N is investigated through the performance of a hydrogen evolution reaction (HER) on them. We find that Co3-C2N, Cr3-C2N, Fe3-C2N, and Ni3-C2N catalysts possess a high catalytic activity for NRR and exhibit a strong capability of suppressing the competitive HER. Our findings provide a new strategy for designing NRR catalysts with high catalytic activity and selectivity.

Formation of Delocalized Linear M-B-M Covalent Bonds: A Combined Experimental and Theoretical Study of BM2(CO)8+ (M = Co, Rh, Ir) Complexes.

Investigations of transition-metal boride clusters not only lead to novel structures but also provide important information about the metal-boron bonds that are critical to understanding the properties of boride materials. The geometric structures and bonding features of heteronuclear boron-containing transition metal carbonyl cluster cations BM(CO)6+ and BM2(CO)8+ (M = Co, Rh, and Ir) are studied by a combination of the infrared photodissociation spectroscopy and density functional calculations at B3LYP/def2-TZVP level. The completely coordinated BM2(CO)8+ complexes are characterized as a sandwich structure composed of two staggered M(CO)4 fragments and a boron cation, featuring a D3d symmetry and 1Eg electronic ground state as well as metal-anchored carbonyls in an end-on manner. In conjunction with theoretical calculations, multifold metal-boron-metal bonding interactions in BM2(CO)8+ complexes involving the filled d orbitals of the metals and the empty p orbitals of the boron cation were unveiled, namely, one σ-type M-B-M bond and two π-type M-B-M bonds. Accordingly, the BM2(CO)8+ complexes can be described as a linear conjugated (OC)4M═B═M(CO)4 skeleton with a formal B-M bond index of 1.5. The three delocalized d-p-d covalent bonds render compensation for the electron deficiency of the cationic boron center and endow both metal centers with the favorable 18-electron structure, thus contributing much to the overall structural stability of the BM2(CO)8+ cations. As a comparison, the saturated BRh(CO)6+ and BIr(CO)6+ complexes are determined to be a doublet Cs-symmetry structure with an unbridged (OC)2B-M(CO)4 pattern, involving a two-center σ-type (OC)2B → M(CO)4+ dative single bond along with a weak covalent B-M half bond. This work offers important insight into the structure and bonding of late transition metal boride carbonyl cluster cations.

A Common Bottleneck for Metal Oxidation by Molecular Oxygen Across Size Regimes: Kinetics of Atomic Lanthanide Cations (La+-Lu+) with O2.

Kinetics of the lanthanide cations (Ln+ = La+-Lu+ excluding Pm+) reacting with molecular oxygen were measured in a selected-ion flow tube apparatus from 300 to 600 K. Where exothermic, these reactions occur efficiently, producing LnO+ + O. The reactions display positive temperature dependences consistent with Arrhenius equation behavior and show small activation energies (0-2 kJ mol-1) that are strongly correlated to promotion energies of the Ln+ atoms. Reanalysis of literature data on neutral Ln + O2 reactions show a similar correlation with slightly larger activation energies (0-10 kJ mol-1). The data are explained by a common mechanism controlling oxidation by molecular oxygen in these systems, as well as in gas-phase reactions of transition metal and posttransition metal cluster anions, neutral clusters deposited on surfaces, and for oxygen incident on metal surfaces. It is posited that across these systems, the height of an early barrier along the reaction coordinate is predictable based on knowledge of the electronic states of the reactants and may be used to either promote or inhibit oxygen activation.

Effect of copper cluster on reaction pathways of carbon dioxide hydrogenation on magnesium hydride surface

Understanding the reaction mechanism of CO2 hydrogenation to produce value-added chemicals is essential for the rational design of catalysts to improve reaction activity and product selectivity. In this work, the first-principles calculations based on density functional theory were employed to study the effect of copper cluster on product selectivity in CO2 hydrogenation utilizing magnesium hydride as hydrogen source. The results show that on pristine MgH2 (0 0 1), CO2 molecule adsorbs on the surface with an O atom close to Mg atom, and the hydrogenation reaction follows formate pathway to yield CH3OH with an energy barrier only 1.09 eV for the rate-limiting step; however, the production of the most accessible C2-based product (CH2OH)2 needs to overcome an energy barrier up to 1.94 eV. On MgH2 (0 0 1) with Cu7 cluster, the C atom of CO2 molecule can strongly adsorb on a Cu atom of Cu7 cluster, and the hydrogenation more likely proceeds through reverse water-gas shift pathway, in which it is easy to generate C2 product C2H4 by the coupling of intermediate H2C*, with an energy barrier only 1.53 eV for the rate-limiting step. The findings utilizing transition metal cluster to change the reaction pathway and product selectivity of CO2 hydrogenation on magnesium hydride can provide novel perspectives for the design of catalysts.

Performance of density-functional-theory and random-phase-approximation methods on the study of transition-metal clusters: the Tan clusters as an example

Recently developed density-functional-theory (DFT) and random-phase-approximation (RPA) methods are used to study competing isomers of some negatively charged Ta clusters, namely Ta12 - and Ta10 -, in an attempt to find a suitable strategy towards accurate studies of transition-metal clusters based on DFT. Also the neutral and cationic forms Ta12 (0,+) of the twelve-atom cluster are studied. The results are compared with experimental information obtained by several methods that differ in the property under study and the total electric charge of the clusters. We find that a careful choice of the density functional, the use of relativistic two-component methods, eventually in combination with all-electron basis sets, and the application of RPA-type methods, may all be necessary steps for a good assessment. Such an assessment should be made in relation to several experimental properties as much as possible.

QTAIM analysis of the bonding in anionic group 6 carbonyl selenide clusters: [Se2M3(CO)10]2- (M=Cr, Mo, W).

This research aims to offer a deeper understanding of the bonding interactions between M-Se and M-CO and how these interactions change across the group 6 transition metal series: [Se2M3(CO)10]2- (M = Cr, Mo, W). It also seeks to explore the impact of carbonyl groups on M-M interactions within the clusters. Seven criteria, which are based on QTAIM properties, have been considered and compared with the corresponding criteria in other transition metal clusters. The results confirm that no such bond critical points or bond baths occur between transition metals, which instead have 5c-7e bonding interactions delocalized over their five-membered M3(μ-Se)2 ring, as evidenced by the non-negligible nonbonding delocalization indices. The topological properties of three bond clusters, Cr-Se, Mo-Se, and W-Se, resemble those of "intermediate closed shell characters," which combine covalent and electrostatic properties. Source function calculations indicated that the bonded Se atom contributed the most to each Cr-Se and Mo-Se bcp. The OCO atoms and nonbonded Se atoms also contributed to some extent. However, metal atoms act as sinks rather than as sources of electron density. In contrast, the majority of the metal atoms, both bonded and nonbonded, contribute to Cr-W bcps. Analysis of the delocalization indices δ(M…O) in the three clusters indicates that CO significantly contributes to Cr π-back donation in cluster 1. In contrast, no π-back donation occurs from CO to Mo or W in clusters 2 or 3, respectively. The B3P86 hybrid functional was used for computations in the Gaussian 09 software. The LanL2DZ basis set was employed for Cr, Mo, and W, while the 6-31G (d, p) basis set was used for C, O, and Se atoms. We performed QTAIM analysis using the AIM2000 and Multiwfn packages, incorporating B3P86/WTBS for Cr, Mo, and W atoms. The 6-311++G(3df,3pd) basis set was used for C, O, and Se atoms. Additionally, we utilized the ELF and SF.

Unraveling active sites regulation and temperature-dependent thermodynamic mechanism in photothermocatalytic CO2 conversion with H2O

In the photothermal synergistic catalytic conversion of CO2 and H2O, the catalyst harnesses solar energy to accumulate heat, thereby elevating the reaction system’s temperature. The influence of this temperature effect on surface chemical reactions remains an underexplored area. Here the impact of temperature on the surface-level thermodynamic reactions and conversion of CO2 with H2O on oxide semiconductors at the atomic scale was investigated using first-principle calculations. 13 different metal oxides and 5 transition metal clusters were used to introduce surface functional sites on the TiO2 supporting catalyst. The potential metal oxide cocatalysts that could be most beneficial to the following conversion of CO2 by H2O were initially screened by calculating the degrees of promotion of CO2 adsorption and activation of surface H to provide protons. The proton donation and hydrogen evolution difficulty from H2O were further analyzed, identifying transition metal cocatalysts that promote direct CO2 hydrogenation. Upon introducing bifunctional sites to facilitate adsorption and reduction, the production of CH3OH and CH4 could be further enhanced through the facilitation of the proton donation process of H2O. The results of Gibbs free-energy calculations revealed that increasing temperature enhances the reaction thermodynamics for each C1 product formation at different surface sites to varying degrees. These findings offer valuable theoretical insights for designing and regulating active sites on oxide semiconductor surfaces for efficient photothermal catalytic CO2 reduction by H2O.

Conversion of the greenhouse gases CH4 and CO2 to CH3COOH using transition metal Clusters: Two birds with one stone

Density functional theoretical studies are performed to investigate the conversion of carbon dioxide and methane to acetic acid using group 10 transition metal clusters in their free and carbon-supported states. The adsorption of CH4 is more feasible than CO2 for most of the clusters and the reaction is initiated with the adsorption of CH4 over the catalysts. Energy barrier for the reaction is reduced significantly using the clusters compared to that in free state which is further reduced when coronene is used as a carbon support. Among various metal clusters, the barrier is found to be the lowest for Ni3.

Mechanism of adsorption and gas-sensing of hazardous gases by MoS2 monolayer decorated by Pdn (n=1–4) clusters

The adsorption behaviors of hazardous gases (NO2 and SO2) on MoS2 monolayer decorated by Pdn (n=1–4) clusters (Pdn-MoS2) are investigated by first-principles calculations, and the performance of Pdn-MoS2 gas sensors has also been studied in this work. Our results show that Pdn nanocluster can enhance the electrical conductivity of MoS2 monolayer with band gaps of Pdn-MoS2 (n=1–4) sharply decreased, and the adsorption performance of NO2 and SO2 with higher adsorption energy and larger charge transfer. Thus, Pdn-MoS2 show higher sensitive to NO2 and SO2 molecules compared with pristine MoS2. The band gaps of Pdn-MoS2 can be further decreased upon the adsorption of NO2 and SO2 (except for SO2/Pd4-MoS2), indicating Pdn-MoS2 (n=1–3) gas sensor shows improved gas-sensitive response to both NO2 and SO2, and Pd4-MoS2 shows improved gas-sensitive response only to NO2. The recovery time analysis indicates that Pdn-MoS2 (n=1–4) is applicable to be utilized as NO2 and SO2 scavenger at ambient temperature, and the recovery process can be realized simply by heating. Our results indicate that Pdn-MoS2 (n=1–4) monolayer is a favorable candidate as adsorbent for detection and removal of NO2 and SO2, and also provides guidance for further study of the MoS2 monolayer decorated by transition metal clusters.

Exploring the Impact of Active Site Structure on the Conversion of Methane to Methanol in Cu‐Exchanged Zeolites

AbstractIn the past, Cu‐oxo or ‐hydroxy clusters hosted in zeolites have been suggested to enable the selective conversion of methane to methanol, but the impact of the active site's stoichiometry and structure on methanol production is still poorly understood. Herein, we apply theoretical modeling in conjunction with experiments to study the impact of these two factors on partial methane oxidation in the Cu‐exchanged zeolite SSZ‐13. Phase diagrams developed from first‐principles suggest that Cu‐hydroxy or Cu‐oxo dimers are stabilized when O2 or N2O are used to activate the catalyst, respectively. We confirm these predictions experimentally and determine that in a stepwise conversion process, Cu‐oxo dimers can convert twice as much methane to methanol compared to Cu‐hydroxyl dimers. Our theoretical models rationalize how Cu‐di‐oxo dimers can convert up to two methane molecules to methanol, while Cu‐di‐hydroxyl dimers can convert only one methane molecule to methanol per catalytic cycle. These findings imply that in Cu clusters, at least one oxo group or two hydroxyl groups are needed to convert one methane molecule to methanol per cycle. This simple structure–activity relationship allows to intuitively understand the potential of small oxygenated or hydroxylated transition metal clusters to convert methane to methanol.

Exploring the Impact of Active Site Structure on the Conversion of Methane to Methanol in Cu-Exchanged Zeolites.

In the past, Cu-oxo or -hydroxy clusters hosted in zeolites have been suggested to enable the selective conversion of methane to methanol, but the impact of the active site's stoichiometry and structure on methanol production is still poorly understood. Herein, we apply theoretical modeling in conjunction with experiments to study the impact of these two factors on partial methane oxidation in the Cu-exchanged zeolite SSZ-13. Phase diagrams developed from first-principles suggest that Cu-hydroxy or Cu-oxo dimers are stabilized when O2 or N2O are used to activate the catalyst, respectively. We confirm these predictions experimentally and determine that in a stepwise conversion process, Cu-oxo dimers can convert twice as much methane to methanol compared to Cu-hydroxyl dimers. Our theoretical models rationalize how Cu-di-oxo dimers can convert up to two methane molecules to methanol, while Cu-di-hydroxyl dimers can convert only one methane molecule to methanol per catalytic cycle. These findings imply that in Cu clusters, at least one oxo group or two hydroxyl groups are needed to convert one methane molecule to methanol per cycle. This simple structure-activity relationship allows to intuitively understand the potential of small oxygenated or hydroxylated transition metal clusters to convert methane to methanol.

Transition metal clusters with precise numbers of atoms anchored on graphdiyne as multifunctional electrocatalysts for OER/ORR/HER: a computational study

Transition metal clusters with precise numbers of atoms anchored on graphdiyne as multifunctional electrocatalysts for OER/ORR/HER: a computational study

The Effect of Global and Local Chemical Reactivity Descriptors in the Determination of Properties of Transition Metal Clusters

Recently, research on material properties has got lots of attention because of their promising technological applications. In this paper, the author’s focus is on the global and local chemical reactivity descriptors of some transition metal clusters. In addition, the author also include findings of chemical properties with reactivity descriptors. Furthermore, according to Thomas–Fermi approximation and from the exact formulation of Density Functional Theory by Hohenberg and Kohn’s theorem, the author introduce electronegativity and the theory of hardness and softness for further investigation of chemical properties of the clusters. As a part of investigations, the author also introduce the Fukui functions with an emphasis for the determinations of chemical reactivity descriptors. All the results are obtained by theoretical investigation of electronegativity), Chemical potential (), chemical hardness (), and polarizability () of the given transition metal clusters (Cr and Mn). From the results, the author observed that the ionization potential of the clusters increases with decreasing cluster size as the clusters become more stable and tend towards chemical inertness. In conclusion, determination of the reactivity descriptors of the transition metal clusters show results that are in line with previous experimental and theoretical findings.