Catalysis beyond frontier molecular orbitals: Selectivity in partial hydrogenation of multi-unsaturated hydrocarbons on metal catalysts

Density Functional Theory-Based Indicators to Estimate the Corrosion Potentials of Zinc Alloys in Chlorine-, Oxidizing-, and Sulfur-Harsh Environments

Nowadays, biodegradable metals and alloys, as well as their corrosion behavior, are of particular interest. The corrosion process of metals and alloys under various harsh conditions can be studied via the investigation of corrosion atom adsorption on metal surfaces. This can be performed using density functional theory-based simulations. Importantly, comprehensive analytical data obtained in simulations including parameters such as adsorption energy, the amount of charge transferred, atomic coordinates, etc., can be utilized in machine learning models to predict corrosion behavior, adsorption ability, catalytic activity, etc., of metals and alloys. In this work, data on the corrosion indicators of Zn surfaces in Cl-, S-, and O-rich harsh environments are collected. A dataset containing adsorption height, adsorption energy, partial density of states, work function values, and electronic charges of individual atoms is presented. In addition, based on these corrosion descriptors, it is found that a Cl-rich environment is less harmful for different Zn surfaces compared to an O-rich environment, and more harmful compared to a S-rich environment.

In Silico Drug Design and Analysis of Dual Amyloid-Beta and Tau Protein-Aggregation Inhibitors for Alzheimer's Disease Treatment

Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disorder that gradually leads to the state of dementia. The main features of AD include the deposition of amyloid-beta peptides (Aβ), forming senile plaques, and the development of neurofibrillary tangles due to the accumulation of hyperphosphorylated Tau protein (p-tau) within the brain cells. In this report, seven dual-inhibitor molecules (L_1-7) that can prevent the aggregation of both Aβ and p-tau are suggested. The drug-like features and identification of the target proteins are analyzed by the in silico method. L_1-7 show positive results in both Blood-Brain Barrier (BBB) crossing and gastrointestinal absorption, rendering to the results of the permeation method. The molecular docking test performed for L_1-7 shows binding energies in the range of -4.9 to -6.0 kcal/mol towards Aβ, and -4.6 to -5.6 kcal/mol for p-tau. The drug's effectiveness under physiological conditions is assessed by the use of solvation models on the investigated systems. Further, the photophysical properties of L_1-3 are predicted using TD-DFT studies.

Homogeneity of Supported Single-Atom Active Sites Boosting the Selective Catalytic Transformations

Selective conversion of specific functional groups to desired products is highly important but still challenging in industrial catalytic processes. The adsorption state of surface species is the key factor in modulating the conversion of functional groups, which is correspondingly determined by the uniformity of active sites. However, the non-identical number of metal atoms, geometric shape, and morphology of conventional nanometer-sized metal particles/clusters normally lead to the non-uniform active sites with diverse geometric configurations and local coordination environments, which causes the distinct adsorption states of surface species. Hence, it is highly desired to modulate the homogeneity of the active sites so that the catalytic transformations can be better confined to the desired direction. In this review, the construction strategies and characterization techniques of the uniform active sites that are atomically dispersed on various supports are examined. In particular, their unique behavior in boosting the catalytic performance in various chemical transformations is discussed, including selective hydrogenation, selective oxidation, Suzuki coupling, and other catalytic reactions. In addition, the dynamic evolution of the active sites under reaction conditions and the industrial utilization of the single-atom catalysts are highlighted. Finally, the current challenges and frontiers are identified, and the perspectives on this flourishing field is provided.

Ti3AlC2/Pd Composites for Efficient Hydrogen Production from Alkaline Formaldehyde Solutions

Research on catalytic oxidation in a promising but mild manner to remove formaldehyde and produce hydrogen is rarely reported. Here, the use of the Ti3AlC2 MAX phase as support for palladium nanoparticles was explored for the hydrogen generation from alkaline formaldehyde solution at room temperature. The results showed that Ti3AlC2/Pd catalyst with 3 wt% Pd loading had a much higher capability for hydrogen production than conventional Pd nanoparticles. In addition, by further optimizing the formaldehyde concentration, NaOH concentration, and the reaction temperature, the hydrogen production rate could be further increased to 291.6 mL min-1g-1. Moreover, the obtained apparent activation energy of the Ti3AlC2/Pd catalyzed hydrogen production reaction is 39.48 kJ mol-1, which is much lower than that of the literature results (65 kJ mol-1). The prepared Ti3AlC2/Pd catalysts as well as the catalytic process could act as a "two birds with one stone" effect, that is, they not only eliminate noxious formaldehyde but also generate clean hydrogen.

Resonant Electron Spectroscopy: Identification of Atomic Contributions to Valence States

Valence electronic structure is crucial for understanding and predicting reactivity. Valence non-resonant X-ray photoelectron spectroscopy (NRXPS) provides a direct method for probing the overall valence electronic structure. However, it is...

Selective Interactions between Free-Atom-like d-States in Single-Atom Alloy Catalysts and Near-Frontier Molecular Orbitals

In the limit of dilute alloying-the so-called "single-atom alloy" (SAA) regime-certain bimetallic systems exhibit weak mixing between constituent metal wave functions, resulting in sharp, single-atom-like electronic states localized on the dilute component of the alloy. This work shows that when these sharp states are appropriately positioned relative to given molecular orbitals, selective hybridization is enhanced, in accordance with intuitive principles of molecular orbital theory. We demonstrate the phenomenon for activation pathways of crotonaldehyde, a model α,β-unsaturated aldehyde relevant to a wide range of chemical manufacturing. This analysis suggests new possible strategies for selectivity control in heterogeneous catalysis.

Facilitating hydrogen atom migration via a dense phase on palladium islands to a surrounding silver surface

The migration of species across interfaces can crucially affect the performance of heterogeneous catalysts. A key concept in using bimetallic catalysts for hydrogenation is that the active metal supplies hydrogen atoms to the host metal, where selective hydrogenation can then occur. Herein, we demonstrate that, following dihydrogen dissociation on palladium islands, hydrogen atoms migrate from palladium to silver, to which they are generally less strongly bound. This migration is driven by the population of weakly bound states on the palladium at high hydrogen atom coverages which are nearly isoenergetic with binding sites on the silver. The rate of hydrogen atom migration depends on the palladium-silver interface length, with smaller palladium islands more efficiently supplying hydrogen atoms to the silver. This study demonstrates that hydrogen atoms can migrate from a more strongly binding metal to a more weakly binding surface under special conditions, such as high dihydrogen pressure.

Symmetrical Graph Neural Network for Quantum Chemistry with Dual Real and Momenta Space

Most of the current neural network models in quantum chemistry (QC) exclude the molecular symmetry and separate the well-correlated real space (R space) and momenta space (K space) into two individuals, which lack the essential physics in molecular chemistry. In this work, by endorsing the molecular symmetry and elementals of group theory, we propose a comprehendible method to apply symmetry in the graph neural network (SY-GNN), which extends the property-predicting coverage to orbital symmetry for both ground and excited states. SY-GNN is an end-to-end model that can predict multiple properties in both K and R space within a single model, and it shows excellent performance in predicting both the absolute and relative R and K space quantities. Besides the numerical properties, SY-GNN can also predict orbital properties, providing the active regions of chemical reactions. We believe the symmetry-endorsed deep learning scheme covers the significant physics inside and is essential for the application of neural networks in QC and many other research fields in the future.

Feasibility of N2 Reduction on the V Anchored 1T-MoS2 Monolayer: A Density Functional Theory Study

Developing efficient electrocatalysts for nitrogen reduction reaction (NRR) at ambient conditions is crucial for NH₃ synthesis. In this manuscript, the NRR performance of the transition metal anchored MoS₂ monolayer with 1T atomic structure (1T-MoS₂ ) is systematically evaluated by density functional theory computations. Our results reveal that the V decorated 1T-MoS₂ exhibits the outstanding catalytic activity toward NRR via distal mechanism where the corresponding onset potential is 0.66 V, being superior to the commercial Ru material. Furthermore, the powerful binding energy between the V atom and the 1T-MoS₂ provides the good resistance against clustering of the V dopant, indicating its stability. Overall, this work provides a potential alternative for the application of NH₃ synthesis.

Rare Earth Oxide Anchored Platinum Catalytic Site Coated Zeolitic Imidazolate Frameworks toward Enhancing Selective Hydrogenation

Controlling and manipulating the self-assembly technology at the nanoscale has become a powerful strategy for improving chemical processes and further developing the conception of atom efficiency. Herein, an unexpected core-shell structured Gd₂O₃@Pt@ZIF-8 nanoreactor has been fabricated using the self-assembly strategy in which the firm Gd₂O₃ nanosupport anchored the highly active Pt nanoparticle coated porous zeolitic imidazolate framework (ZIF-8). The well-designed Gd₂O₃@Pt@ZIF-8 structure shows good performance in selective hydrogenation of aldehyde-, keto-, and nitro-compounds with full conversion (>99.9%) and superior selectivity (>95%). It showed the channel sieving effect of the ZIF-8 channels toward enhancing the catalytic selectivity. After being recycled eight times, their activity remains unchanged and their core-shell structure is kept intact. So, the outer ZIF-8 membranes not only prevent Pt nanoparticles from agglomeration and slipping during a catalytic reaction but also maintain the original activity and long-term stability compared to the Gd₂O₃@Pt catalyst. The self-assembly strategy demonstrated here will allow the development of other highly active, stable, and selective catalysts for important but challenging transformations.

First-principles study on the selective hydrogenation of the CO and CC bonds of acrolein on Pt–M–Pt (M = Pt, Cu, Ni, Co) surfaces

Selective hydrogenation of the CO and CC bonds of acrolein on Pt–M–Pt (M = Pt, Cu, Ni, Co) surfaces has been investigated with first-principles calculations to understand the trends of the activity and selectivity of the reaction.

Ni/NiO Nanocomposites with Rich Oxygen Vacancies as High-Performance Catalysts for Nitrophenol Hydrogenation

Heterogeneous catalysis often involves charge transfer between adsorbed molecules and the surface of catalyst, and thus their activity depends on the surface charge density. The efficiency of charge transfer could be optimized by adjusting the concentration of oxygen vacancies (Ov). In this work, hexagonal Ni(OH)2 nanoparticles were initially synthesized by a hydrothermal process using aluminum powder as the sacrificial agent, and were then converted into 2D Ni/NiO nanocomposites through in situ reduction in hydrogen flow. The oxygen vacancy concentration in the NiO nanosheet could be well-controlled by adjusting the reduction temperature. This resulted in strikingly high activities for hydrogenation of nitrophenol. The Ni/NiO nanocomposite could easily be recovered by a magnetic field for reuse. The present finding is beneficial for producing better hydrogenation catalysts and paves the way for the design of highly efficient catalysts.

Deep Molecular Orbital Driven High-Temperature Hydrogen Tautomerization Switching

Hydrogen tautomerization molecular switches, a promising class of molecular components for the construction of complex nanocircuits, have been extensively studied using low-temperature scanning tunneling microscopy. However, these molecules are generally only reliably controllable in cryogenic environments, obstructing their utility in real devices. Here, we use dispersion-inclusive density functional theory and systematically investigate the adsorption and tautomerization behaviors of porphycene on six transition-metal surfaces. Among these surfaces, we found that hydrogen tautomerization on the Pt(110) surface corresponds to the largest switching barrier, allowing a controllable transition at high temperature. The switching behavior is closely related to the exceptional degree of charge transfer in the HOMO-2 orbital, illustrating the important role of deep orbital-surface interactions in porphycene molecular switching. Our work provides an in-depth understanding of the porphycene tautomerization mechanism and highlights new research avenues toward the practical application of molecular switches.

External strain-enhanced cysteine enantiomeric separation ability on alloyed stepped surfaces

Using density functional theory with an accurate treatment of van der Waals interactions, we investigate the enantioselective recognition and separation of chiral molecules on stepped metal surfaces. Our calculations demonstrate that the separation ability of metal substrates can be significantly enhanced by surface decoration and external strain. For example, applying 2% tensile strain to the Ag-alloyed Au(532) surface leads to a dramatic increase (by 89%) in cysteine enantioselectivity as compared to that of pristine Au(532). Analysis on the computed binding energies shows that the interaction energy is the predominant factor that affects the separation efficiency in strongly bound systems. Our study presents a new strategy to modify the enantioselectivity of stepped metal surfaces and paves the way for exploring high efficiency chiral separation technology in pharmaceutical industry.

Understanding electro-catalysis by using density functional theory

DFT calculations are indispensable for understanding the electro-catalysis through explanation of the experimental phenomena, prediction of experimental results, and guiding of the experimental investigation.