Oxide Clusters Research Articles

Boron oxide B5O6 and B5O6− clusters with a hexagonal B3O3 ring: Overturn of potential energy landscapes by one electron

Boron oxide clusters feature novel structures and nonclassical chemical bonding, owing to the electron deficiency of boron. We report on a quantum chemical study on structural, electronic, and bonding properties of B5O6 and B5O6− clusters through global-minimum (GM) searches and electronic structure calculations. The neutral B5O6 cluster is shown to assume a GM structure composed of a boroxol core, a terminal boronyl, and a terminal BO2 group, which differs distinctly from anion GM B5O6− cluster. The latter has a boroxol core and three terminal ligands: two boronyls and one O− unit. One electron completely overturns the potential energy surfaces of the present system, which is governed by the nature of frontier molecular orbitals in two types of structures. As a consequence, one electron can make a difference by as much as 2 − 3 eV. The structural transformation is also elucidated using a proposed possible mechanism of boronyl ligand migration.

Inverse catalysts: tuning the composition and structure of oxide clusters through the metal support

Computational modeling of metal–oxide interfaces is challenging due to the large search space of compositions and structures and the complexity of catalyst materials under operating conditions in general. In this work, we develop an efficient structure search workflow to discover chemically unique and relevant nanocluster geometries of inverse catalysts and apply it to ZnyOx and InyOx on Cu(111), Pd(111), and Au(111). We show that the workflow is successful in obtaining a large range of chemically distinct structures. Structural geometry trends are identified, including stable motifs such as tripod, rhombus, and pyramidal motifs. Using ab initio thermodynamics, we explore the in situ stability of the structures, including single-atom alloys, at a range of oxygen availabilities. This approach allows us to find trends such as the susceptibility to oxidation of the different systems and the range of stability of different cluster motifs. Our analysis highlights the importance of taking the diversity of sites exposed by metal–oxide interfaces into account in catalyst design studies.

Rapid one-pot microwave-assisted synthesis and defect engineering of UiO-66 for enhanced CO2 capture

UiO-66 and its derivative consisting of zirconium oxide clusters and terephthalate-based linkers stand out as some of the most extensively studied MOFs for various applications owing to their exceptional stability.

A Highly Hydroxylated 6-Tin Oxide Cluster Serves as An Efficient E-beam and EUV-Photoresist to Reach High-Resolution Patterns

A Highly Hydroxylated 6-Tin Oxide Cluster Serves as An Efficient E-beam and EUV-Photoresist to Reach High-Resolution Patterns

Metal-Core-Specific Screening with Machine Learning: Accelerating the Discovery of Metal Oxide Clusters for Enhanced EUV Lithography Resolution.

Obtaining effective extreme ultraviolet lithography (EUVL) materials for pragmatic applications remains challenging. The experimental design and conventional theoretical prediction are time-consuming and costly and hardly affordable to accelerate the discovery of commercial EUVL materials. In this work, we employed the machine learning (ML) technique to predict the ionization potential of promising EUVL materials, which is closely related to the photoresists' solubility switch. The developed ML model presents a strong generalization ability and can predict new EUVL materials containing different metals (i.e., Mg, Cu, Ca, Cd, Ni). Furthermore, feature analysis indicates that the number of hydrogen bond donors in a compound plays a vital role in determining the ionization potential of EUVL materials. The work provides not only an effective ML model to predict EUVL materials but also crucial insights into the correlation between the structure and properties. Finally, the developed ML model has been integrated into an online platform (https://zinc-oxo-cluster-predictor.streamlit.app/), allowing users to quickly evaluate their designed materials and develop a comprehensive scheme for discovering promising EUVL compounds based on our platform.

Polymer Films' Residual Stress Attenuation from the Supramolecular Complexation with Ultra-Small Nanoparticles for High Resolution Nanoimprint Lithography.

Nanoimprint lithography (NIL) has been broadly applied in the fabrication of nano-patterned polymer films for cost-efficiency and high through-put; however, the intrinsic tradeoff between mechanical strength and residual stress of polymer films significantly limits the NIL resolution while the harsh processing conditions limit its versatile applications to different substrates. Herein, 1 nm metal oxide cluster, phosphotungstic acid (PTA), is used to complexed with polyvinyl alcohol (PVA) for high-resolution NIL that can be operated at large-scale and mild conditions. The ultra-small size of PTA enables dense supramolecular interaction with PVA for the diminished crystallinity and accelerated chain dynamics that help relax the residual stress during film casting. Meanwhile, the PTAs serve as supramolecular crosslinkers for the increased modulus of the films (ca. 2 GPa), providing promising dimensional stability required for high-resolution NIL. Simple casting the aqueous blend on a master mold successfully gives a residual stress-free film with sub-2 nm resolution at wafer scale (> 100 cm2). The mild processing at ambient condition permits broad NIL applications to diverse substrates, e.g., integrated circuit chips, compact disc, PET nano grating and even delicate bio-surfaces.

Directed Electron Modulation Stabilizes Iridium Oxide Clusters for High‐Current‐Density Oxygen Evolution

AbstractThe rapid advancement of the green hydrogen industry has driven a surge in demand for devices that operate over a broad range of current density. Despite this, the development of stable iridium‐based catalysts for high‐current‐density applications in oxygen evolution reactions remains a significant challenge. In this study, directed electron modulation (DEM) of iridium oxide clusters on cobalt hydroxide nanosheets is achieved using a cyclic Joule heating strategy in pure water. The strategy achieves a rapid change of environmental energy during electronic modulation through Joule heating, which ensures strong electronic coupling between IrO2 and Co(OH)2 without significant changes in initial catalyst nanostructure and cluster size. Directed electron modulation optimizes the reactant adsorption ability of the active center (IrO2 cluster) and corresponding reaction kinetics are improved, resulting in the catalyst (DEM‐IrO2@Co(OH)2‐NF) showing excellent performance. The DEM‐IrO2@Co(OH)2‐NF exhibits excellent catalytic activity in alkaline electrolytes with only 296 mV overpotential up to 1 A cm−2 and no significant degradation in 1000 h stability test at 1 A cm−2. Additionally, the anion exchange membrane electrolyzer using DEM‐IrO2@Co(OH)2‐NF||Pt/C requires only 1.68 V at 1 A cm−2 and remains stable for 200 h. This work will provide new directions for optimization of active centers.

Vanadium Oxide Clusters Mediated Bismuth‐Tin Alloy for Accelerated Dynamics of Electrocatalytic CO2 Conversion

AbstractThe electrocatalytic conversion of carbon dioxide (CO2) to formate is significant for carbon neutrality. How to improve the reaction kinetics of electrocatalysts is one of the important challenges. An innovative electrodeposition strategy is presented herein to rationally synthesize the vanadium oxide (VOx) clusters decorated Bi‐Sn alloy (BiSn(VOx)) catalyst. Theoretical and in situ spectral studies confirm the simultaneously improved kinetics of CO2 activation and subsequent protonation via VOx clusters mediated water dissociation process, thereby optimizing the electrocatalytic activity and selectivity of CO2 to formate. Remarkably, this BiSn(VOx) catalyst achieves high Faradic efficiency (FE) of formate over 90% within wide potential window of 800 mV and excellent stability over 100 h at −0.6 V versus RHE. Moreover, the BiSn(VOx) cathode integrated rechargeable Zn‐CO2 battery realizes the largest power density of 3.8 mW cm−2, while the assembled co‐electrolysis electrolyzer delivers a total FE of formate over 182% at a cell voltage of 0.6 V, outperforming the highest value so far. The work provides a promising way to develop advanced electrocatalysts for electrolysis.

Molecularly tailorable metal oxide clusters ensured robust interfacial connection in inverted perovskite solar cells.

Interfacial recombination and ion migration between perovskite and electron-transporting materials have been the persisting challenges in further improving the efficiency and stability of perovskite solar cells (PVSCs). Here, we design a series of molecularly tailorable clusters as an interlayer that can simultaneously enhance the interaction with C60 and perovskite. These clusters have precisely controlled structures, decent charge carrier mobility, considerable solubility, suitable energy levels, and functional ligands, which can help passivate perovskite surface defects, form a uniform capping net to immobilize C60, and build a robust coupling between perovskite and C60. The target inverted PVSCs achieve an impressive power conversion efficiency (PCE) of 25.6% without the need for additional surface passivation. Crucially, the unencapsulated device displays excellent stability under light, heat, and bias, maintaining 98% of its initial PCE after 1500 hours of maximum power point tracking. These results show great promise in the development of advanced interfacial materials for highly efficient perovskite photovoltaics.

Insights into the Roles of Different Iron Species on Zeolites for N2O Selective Catalytic Reduction by CO.

Iron zeolites are promising candidates for mitigating nitrous oxide (N2O), a potent greenhouse gas and contributor to stratospheric ozone destruction. However, the atomic-level mechanisms by which different iron species, including isolated sites, clusters, and particles, participate in N2O decomposition in the presence of CO still remain poorly understood, which hinders the application of the reaction in practical technology. Herein, through experiments and density functional theory (DFT) calculations, we identified that isolated iron sites were active for N2O activation to generate adsorbed O* species, which readily reacted with CO following the Eley-Rideal (E-R) mechanism. In contrast, Fe2O3 particles exhibited a different reaction pathway, directly reacting with CO to generate oxygen vacancies (Ov), which could efficiently dissociate N2O following the Mars-van Krevelen (MvK) mechanism. Moreover, the transformation of iron oxide clusters into undercoordinated FeOx species by CO was also revealed through various techniques, such as CO-temperature-programmed reduction (TPR), and ab initio molecular dynamics (AIMD) simulations. Our study provides deeper insights into the roles of different iron species in N2O-SCR by CO, and is anticipated to facilitate the understanding of multicomponent catalysis and the design of efficient iron-containing catalysts for practical applications.

Preparation of Alumina Oxo-Cluster/Cellulose Polymers and Dye Adsorption Application.

Aluminum oxide clusters (AlOCs) possess high surface areas and customizable pore structures, making them applicable in the field of environmental remediation. However, their practical use is hindered by stability issues, aggregation tendencies, and recycling challenges. This study presents an in -situ synthesis of AlOCs on cellulose using a solvent thermal method. The resulting adsorbent's structural and property profiles were thoroughly characterized using multiple analytical techniques. Batch adsorption experiments were performed to assess the adsorbent's capacity and kinetics in removing selected dyes from aqueous solutions. Additionally, both real-environment simulation and regeneration experiments have been conducted to thoroughly assess the adsorbent's reliability, stability, and practical applicability. The aim was to engineer an effective and recyclable adsorbent specifically tailored for dye-contaminated wastewater treatment.

Heteroatom Effect on Site-Selective Oxygen-Sulfur Substitution Reactions of Keggin-Type Polyoxotungstates.

Sulfur, a group 16 element, can substitute the oxygen sites of metal oxides, potentially providing them with unique properties and enabling new applications. Polyoxometalates (POMs) are anionic metal oxide clusters with wide structural diversity owing to arbitrary selection of their constituting metal atoms. However, substitution of the oxygen sites of POMs with sulfur atoms has been rarely explored. Recently, we reacted a Keggin-type POM [XW12O40]4- (IX; X = Si and Ge) with a sulfurizing reagent (Lawesson's reagent), synthesizing Keggin-type polyoxothiometalates (POTMs) [XW12O28S12]4- (IIX, X = Si and Ge) in which all 12 terminal oxygen atoms of IX were site-selectively substituted with sulfur atoms. Although the selected heteroatoms (X) and anion charges substantially influence the properties and reactivities of POMs, oxygen-sulfur substitution of Keggin-type POMs with other heteroatoms and anion charges has not been attempted. Herein, we report the oxygen-sulfur substitution reaction of Keggin-type POMs [XW12O40]n- (IX; X = Al, Si, and P; n = 5, 4, and 3, respectively) with various heteroatoms, yielding the corresponding Keggin-type POTMs [XW12O28S12]n- (IIX). The oxygen-sulfur substitution reaction depended on the heteroatom: POMs with higher anion charges reacted more strongly with the sulfurizing reagents. We also investigated the reaction mechanism of POMs and sulfurizing reagents.

Atomically Precise Metal-Metal Oxide Interface in Polyoxometalate-Noble Metal Hybrid Clusters.

Metal-metal oxide hybrid materials, typically composed of metal nanoparticles anchored on metal oxides matrix, are devoted enormous attentions as famous heterogeneous catalysts. The interactions between noble metals and metal oxides as well as their interfaces have been proven to be the origin of their excellent catalytic performance. Deep understandings on the interactions between noble metals and metal oxides at atomic precision, thus to precisely assess their contributions to catalysis, can serve as basic principles for catalyst design. In recent years, polyoxometalates (POMs), which in principle can be regarded as atomically precise metal oxide clusters, have been shown to have strong affinity to noble metals, thus forming diverse kinds of POM-noble metal hybrid clusters. Their well-resolved atomically precise structures and hybrid nature promise them as ideal platforms to understand the interfaces and interactions between noble metals and metal oxides. In this review, metal-metal oxide interface is classified into different categories based on the different configurations of hybrid clusters, and aims to understand the interface structures and electronic correlations between POMs and noble metals at the atomic precision. Based on these basic understandings, the study provides the perspectives on the challenges and research efforts to be paid in the future.

Uncertainty Based Machine Learning-DFT Hybrid Framework for Accelerating Geometry Optimization.

Geometry optimization is an important tool used for computational simulations in the fields of chemistry, physics, and material science. Developing more efficient and reliable algorithms to reduce the number of force evaluations would lead to accelerated computational modeling and materials discovery. Here, we present a delta method-based neural network-density functional theory (DFT) hybrid optimizer to improve the computational efficiency of geometry optimization. Compared to previous active learning approaches, our algorithm adds two key features: a modified delta method incorporating force information to enhance efficiency in uncertainty estimation, and a quasi-Newton approach based upon a Hessian matrix calculated from the neural network; the later improving stability of optimization near critical points. We benchmarked our optimizer against commonly used optimization algorithms using systems including bulk metal, metal surface, metal hydride, and an oxide cluster. The results demonstrate that our optimizer effectively reduces the number of DFT force calls by 2-3 times in all test systems.

Iron Oxide Clusters as Electron Donors Under Light Enhance Oxygen Reduction Kinetics at Atomically Dispersed Fe for Photocatalytic CH4 Partial Oxidation

AbstractPhotocatalytic CH4 oxidation to CH3OH emerges as a promising strategy to sustainably utilize natural gas and mitigate the greenhouse effect. However, there remains a significant challenge for the synthesis of methanol by using O2 at low temperature. Inspired by the catalytic structure in soluble methane monooxygenase (MMO) and the corresponding reaction mechanism, we prepared a biomimetic photocatalyst with the decoration of Fe2O3 nanoclusters and satellite Fe single atoms immobilized on carbon nitride. The catalyst demonstrates an excellent CH3OH productivity of 5.02 mmol ⋅ gcat−1 ⋅ h−1 with CH3OH selectivity of 98.5 %. Mechanism studies reveal that the synergy between Fe2O3 nanoclusters and Fe single atoms establishes a dual‐Fe site as MMO for O2 activation and subsequent CH4 partial oxidation. Moreover, the light excitation of Fe2O3 nanoclusters with a relative narrow band gap could deliver the electrons and protons to atomic Fe that facilitating the oxygen reduction kinetics for the robust of CH3OH synthesis.

Iron Oxide Clusters as Electron Donors Under Light Enhance Oxygen Reduction Kinetics at Atomically Dispersed Fe for Photocatalytic CH4 Partial Oxidation.

Photocatalytic CH4 oxidation to CH3OH emerges as a promising strategy to sustainably utilize natural gas and mitigate the greenhouse effect. However, there remains a significant challenge for the synthesis of methanol by using O2 at low temperature. Inspired by the catalytic structure in soluble methane monooxygenase (MMO) and the corresponding reaction mechanism, we prepared a biomimetic photocatalyst with the decoration of Fe2O3 nanoclusters and satellite Fe single atoms immobilized on carbon nitride. The catalyst demonstrates an excellent CH3OH productivity of 5.02 mmol ⋅ gcat -1 ⋅ h-1 with CH3OH selectivity of 98.5 %. Mechanism studies reveal that the synergy between Fe2O3 nanoclusters and Fe single atoms establishes a dual-Fe site as MMO for O2 activation and subsequent CH4 partial oxidation. Moreover, the light excitation of Fe2O3 nanoclusters with a relative narrow band gap could deliver the electrons and protons to atomic Fe that facilitating the oxygen reduction kinetics for the robust of CH3OH synthesis.

Factors Determining the Selectivity of NO Reduction Catalyzed by Copper-Vanadium Oxide Cluster Anions Cu2VO3-5.

Catalytic NO reduction by CO is imperative to satisfy the increasingly rigorous emission regulations. Identifying the structural characteristic of crucial intermediate that governs the selectivity of NO reduction is pivotal to having a fundamental understanding on real-life catalysis. Herein, benefiting from the state-of-the-art mass spectrometry, we demonstrated experimentally that the Cu2VO3-5 - clusters can mediate the catalysis of NO reduction by CO, and two competitive channels to generate N2O and N2 can co-exist. Quantum-chemical calculations were performed to rationalize this selectivity. The formation of the ONNO unit on the Cu2 dimer was demonstrated to be a precursor from which two pathways of NO reduction start to emerge. In the pathway of N2O generation, only the Cu2 dimer was oxidized and the VO3 moiety functions as a "support", while both moieties have to contribute to anchor oxygen atoms from the ONNO unit and then N2 can be generated. This finding displays a clear picture to elucidate how and why the involvement of VO3 "support" can regulate the selectivity of NO reduction.

High sodium conductive polymer electrolyte-based nanoclusters in supercapacitor

The sodium-ion polymer electrolytes (PEs) spur the development of the high safe solid batteries due to their merits of safety, flexibility, lower interfacial resistance with electrodes, and easy processing. Herein, a rational strategy is developed to construct the PE, which can integrate the excellent sodium ion conductivity with the mechanical performances. This strategy applies the nano-sized metal oxide clusters (MOCs) not only to supply the sodium ions but also to inhibit the polymer crystallization. The released polymer chains, crosslinked via physical crosslinking points (nanoclusters), form a network that provides the electrolyte film with toughness over a wide temperature range. The targeted electrolyte exhibits excellent Na-ion conductivity of 3.8 × 10−4 S cm−1 at room temperature, tensile strength up to 0.74 Mpa and breaking elongation of 23 %. In addition, this PE widens the electrochemical stability window of the aqueous Na-ion supercapacitor up to 2.0 V since the water molecules are effectively confined via the strong interactions among components. Our research on sodium polymer electrolytes combined by nanoclusters and PVA holds significant promise for advancing solid-state sodium supercapacitors— a new generation of high-performance, safe, and cost-effective energy storage solutions.

Reactions of Aluminum Oxide Cluster Cations with Ethane: A Mass-Spectrometric and Vibrational Spectroscopy Study.

The pathways for the reactions of aluminum oxide cluster ions with ethane have been measured. For selected ions (Al2O+, Al3O2 +, Al3O4 +, Al4O7 +) the structure of the collisionally-stabilized reaction intermediates were explored by measuring the photodissociation vibrational spectra from 2600 cm-1-3100 cm-1. Density functional theory was used to calculate features of the potential energy surfaces for the reactions and the vibrational spectra of intermediates. Generally, more than one isomer contributes to the observed spectrum. The oxygen-deficient clusters Al2O+ and Al3O2 + have large C-H activation barriers, so only the entrance channel complexes in which intact C2H6 binds to aluminum are observed. This interaction leads to a substantial (~200 cm-1) red shift of the C-H symmetric stretch in ethane, indicating significant weakening of the proximal C-H bonds. In Al3O4 +, the complex formed by interactions with three C2H6 is investigated and, in addition to entrance channel complexes, the C-H activation intermediate Al3O4H+(C2H5)(C2H6)2 is observed. For oxygen-rich Al4O7 +, the C2H6 is favored to bind at an aluminum site far from the reactive superoxide group, reducing the reactivity. As expected, oxygen-rich species and open-shell cluster ions have smaller barriers for C-H bond activation, except for Al3O4 + which is predicted and observed to be reactive.

Regulating Catalytic Oxidation Enantiomers Behavior by Imparting Chiral Microenvironment in Zr-Based Metal-Organic Frameworks.

Chiral inversions of enantiomers have significantly different biological activities, so it is important to develop simple and effective methods to efficiently identify optically pure compounds. Inspired by enzyme catalysis, the construction of chiral microenvironments resembling enzyme pockets in the pore space structure of metal-organic frameworks (MOFs) to achieve asymmetric enantioselective recognition and catalysis has become a new research hotspot. Here, a super-stable porphyrin-containing material PCN-224 is constructed by solvothermal method and a chiral microenvironment around the existing catalytic site of the material is created by post-synthesis modifications of the histidine (His) enantiomers. Experimental and theoretical calculations results show that the modulation of chiral ligands around Zr oxide clusters produces different spatial site resistances, which can greatly affect the adsorption and catalytic level of the enantiomeric molecules of tryptophan guests, resulting in a good enantioselective property of the material. It provides new ideas and possibilities for future chiral recognition and asymmetric catalysis.