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Bridging Structural and Chemical Insights: Integrating In Situ Electron Microscopy and X-ray Spectroscopy for Catalysis Research
Environmental transmission electron microscopy probes the local structure, composition, and chemistry of materials under gas environments, while ambient-pressure X-ray photoelectron spectroscopy provides ensemble chemical and electronic structure information in gaseous conditions. Both techniques utilize similar differential pumping schemes to mitigate electron scattering by the gas phase, allowing for unique opportunities to correlate gas–surface interactions across comparable pressure ranges. Their integration has advanced the understanding of various catalytic reactions, including the water–gas-shift reaction, CO oxidation, and surface passivation dynamics. In conclusion, this Mini-Review discusses their methodological advancements, challenges, and potential for further integration with other in situ techniques to address complex catalytic phenomena and guide catalyst design.
Tracking Rh Atoms in Zeolite HY: First Steps of Metal Cluster Formation and Influence of Metal Nuclearity on Catalysis of Ethylene Hydrogenation and Ethylene Dimerization
The initial steps of rhodium cluster formation from zeolite-supported mononuclear Rh(C2H4)2 complexes in H2 at 373 K and 1 bar were investigated by infrared and extended X-ray absorption fine structure spectroscopies and scanning transmission electron microscopy (STEM). The data show that ethylene ligands on the rhodium react with H2 to give supported rhodium hydrides and trigger the formation of rhodium clusters. STEM provided the first images of the smallest rhodium clusters (Rh2) and their further conversion into larger clusters. The samples were investigated in a plug-flow reactor as catalysts for the conversion of ethylene + H2 in a molar ratio of 4:1 at 1 bar and 298 K, with the results showing how the changes in catalyst structure affect the activity and selectivity; the rhodium clusters are more active for hydrogenation of ethylene than the single-site complexes, which are more selective for dimerization of ethylene to give butenes
Resolving the Iron Phthalocyanine Redox Transitions for ORR Catalysis in Aqueous Media
Metal macrocycles are among the most important catalytic systems in electrocatalysis and biocatalysis owing to their rich redox chemistry. Precise understanding of the redox behavior of metal macrocycles in operando is essential for fundamental studies and practical applications of this catalytic system. Here we present electrochemical data for the representative iron phthalocyanine (FePc) in both aqueous and nonaqueous media coupled with in situ Raman and X-ray absorption analyses to challenge the traditional notion of the redox transition of FePc at the low potential end in aqueous media by showing that it arises from the redox transition of the ring. Our data unequivocally demonstrate that the electron is shuttled to the Pc ring via the Fe(II)/Fe(I) redox center. The Fe(II)/Fe(I) redox transition of FePc in aqueous media is indiscernible by normal spectroscopic methods owing to the lack of a suitable axial ligand to stabilize the Fe(I) state.
Miniemulsion SI-ATRP by Interfacial and Ion-Pair Catalysis for the Synthesis of Nanoparticle Brushes
Not provided.
Atomic-Scale Structure and Catalysis on Positively Charged Bimetallic Sites for Generation of H 2
In this paper, we report that a cationic bimetallic site consisting of one Pd and three Zn atoms (Pd 1 Zn 3 ) supported on ZnO (Pd 1 Zn 3 /ZnO) exhibits an extraordinarily high catalytic activity for the generation of H 2 through methanol partial oxidation (MPO) that is 2–3 orders of magnitude higher than that of a metallic Pd–Zn site on Pd–Zn nanoalloy (Pd–Zn/ZnO). Computational studies uncovered that the positively charged Pd atom of the subnanometer Pd 1 Zn 3 bimetallic site largely decreases the activation barrier for dehydrogenation of methanol as compared to a metallic Pd atom of Pd–Zn alloy, thus switching the rate-determining step of MPO from methanol dehydrogenation over a Pd–Zn alloy with high barrier to the O 2 dissociation step on a cationic Pd 1 Zn 3 site with a low barrier, which is supported by our kinetics studies. The significantly higher catalytic activity and selectivity for H 2 production over a cationic bimetallic site suggest a new approach to design bimetallic catalysts.
Spontaneous Formation of 1D Pattern in Monolayer VSe 2 with Dispersive Adsorption of Pt Atoms for HER Catalysis
Creation of functional patterns in two-dimensional (2D) materials provides opportunities to extend their potential for applications. Transition-metal dichalcogenides (TMDCs) are suitable 2D materials for pattern generation because of properties including alterable polymorphic phases, easy chalcogen-vacancy formation, metal-atom insertion, and alloying. Such patterning can be used for selective functionalization. Here we report the spontaneous formation of long-range, well-ordered 1D patterns in monolayer vanadium diselenide (VSe 2 ) by a single annealing stage during growth. Atomic-resolution images in real space combined with density-functional-theory (DFT) calculations reveal the 1D features of patterned VSe 2 . Further experimental characterization of the intermediate states in the growth process confirm the spontaneous formation of the 1D pattern by annealing-induced Se-deficient linear defects. The 1D pattern can be reversibly transformed to homogenous VSe 2 monolayer by reintroducing Se atoms. Moreover, additional experiments demonstrate that a dispersive deposition of Pt atoms along the 1D structures of patterned VSe 2 is achieved, while DFT calculations find that their catalytic activity for hydrogen evolution reaction (HER) is as good as that of Pt surfaces. Further, the formation of long-range, well-ordered 1D patterns not only demonstrates an effective way of dimension modulation in 2D materials but also enriches the potential of intrinsically patterned 2D materials for promising catalytic activities.
Pd–Methyl Bond Energy─Property Correlations, Noncorrelations, Machine Learning Models, and Application to Polymerization Catalysis
Metal–carbon bonds are a key intermediate in a variety of homogeneous organometallic transformations and often determine the critical thermodynamics and kinetics of catalytic processes. Surprisingly, the influence of different ligands on metal–carbon bond strengths has been largely overlooked. Here, in this study, we evaluated nearly 700 experimental Pd–methyl complexes by calculating their bond dissociation energies using density functional theory (DFT) and compared these bond strengths to several fundamental molecular properties, and this revealed several surprising correlations and noncorrelations. Most surprising was that several fundamental properties, such as the bond length, bond force constant, and bond electron density, have no correlation with bond strength, despite these correlations often holding for main-group compounds. We were indeed able to identify key ligand-dependent chemical features/descriptors that provided a highly accurate machine learning model and provided insight into the general factors that control the Pd–carbon bond strength, such as radical delocalization and nucleophilicity. Insights gained from the Pd–Me bond energy analysis were then applied to CO migratory insertion steps that are part of copolymerization reactions.
Localized Orbital Excitation Drives Bond Formation in Plasmonic Catalysis
Localized surface plasmons generated on metallic nanostructures can be used to accelerate molecular transformations; however, the efficiency is limited by the challenge to control the energy/charge transfer at the interfaces. Here, we combine density functional theory (DFT) calculations and experiments to reveal the mechanism of nitrophenol reduction on Au nanoparticles under visible-light irradiation and propose a strategy to further enhance the reaction rates. DFT calculations show a reduced activation barrier under electronic excitation on Au(111), thus explaining the measured higher rates under visible-light irradiation. Furthermore, we propose a heterostructure with Au nanoparticles covered by a thin film of hexagonal boron nitride; the latter is used to decouple the molecular orbitals from the metal to enable charge localization in the molecule. DFT calculations show that, by this electronic decoupling, the activation barrier can be lowered by a factor of five. Furthermore, this work thus provides a valuable strategy for optimizing catalytic efficiency.
High Surface Area Antimony-Doped Tin Oxide Electrodes Templated by Graft Copolymerization. Applications in Electrochemical and Photoelectrochemical Catalysis
Not Available
Schottky Barrier Catalysis Mechanism in Metal-Assisted Chemical Etching of Silicon
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Interface Engineering of Gold Nanoclusters for CO Oxidation Catalysis
Not provided.