In this study, we investigated the catalytic properties of mono- and bimetallic palladium (Pd) and platinum (Pt) nanoparticles deposited via supercritical fluid reactive deposition (SFRD) on titanium ...dioxide (TiOsub.2) powder. Transmission electron microscopy analyses verified that SFRD experiments performed at 353 K and 15.6 MPa enabled the deposition of uniform mono- and bimetallic nanoparticles smaller than 3 nm on TiOsub.2. Electron-dispersive X-ray spectroscopy demonstrated the formation of alloy-type structures for the bimetallic PdPt nanoparticles. Hsub.2Osub.2 is an excellent oxidizing reagent for the production of fine and bulk chemicals. However, until today, the design and preparation of catalysts with high Hsub.2Osub.2 selectivity and productivity remain a great challenge. The focus of this study was on answering the questions of (a) whether the catalysts produced are suitable for the direct synthesis of hydrogen peroxide (Hsub.2Osub.2) in the liquid phase and (b) how the metal type affects the catalytic properties. It was found that the metal type (Pd or Pt) influenced the catalytic performance strongly; the mean productivity of the mono- and bimetallic catalysts decreased in the following order: Pd > PdPt > Pt. Furthermore, all catalysts prepared by SFRD showed a significantly higher mean productivity compared to the catalyst prepared by incipient wetness impregnation.
Ammonia (NHsub.3) is a critical chemical for fertilizer production and a potential future energy carrier within a sustainable hydrogen economy. The industrial Haber–Bosch process, though effective, ...operates under harsh conditions due to the high thermodynamic stability of the nitrogen molecule (Nsub.2). This motivates the search for alternative catalysts that facilitate ammonia synthesis at milder temperatures and pressures. Theoretical and experimental studies suggest that circumventing the trade-off between N–N activation and subsequent NHx hydrogenation, governed by the Brønsted–Evans–Polanyi (BEP) relationship, is key to achieving this goal. Recent studies indicate metal phosphides as promising catalyst materials. In this work, a comprehensive density functional theory (DFT) study comparing the mechanisms and potential reaction pathways for ammonia synthesis on Fe(110) and Fesub.2P(001) is presented. The results reveal substantial differences in the adsorption strengths of NHx intermediates, with Fesub.2P(001) exhibiting weaker binding compared to Fe(110). For N–N bond cleavage, multiple competing pathways become viable on Fesub.2P(001), including routes involving the pre-hydrogenation of adsorbed Nsub.2 (e.g., through *NNH*). Analysis of DFT-derived turnover rates as a function of hydrogen pressure (Hsub.2) highlights the increased importance of these hydrogenated intermediates on Fesub.2P(001) compared to Fe(110) where direct Nsub.2 dissociation dominates. These findings suggest that phosphorus incorporation modifies the ammonia synthesis mechanism, offering alternative pathways that may circumvent the limitations of traditional transition metal catalysts. This work provides theoretical insights for the rational design of Fe-based catalysts and motivates further exploration of phosphide-based materials for sustainable ammonia production.
Cation-anion co-doping has proven to be an effective method of improving the photocatalytic performances of CaTiOsub.3 perovskites. In this regard, (La/Ce-N/S) co-doped CaTiOsub.3 models were ...investigated for the first time using first-principles calculations based on a supercell of 2 × 2 × 2 with La/Ce concentrations of 0.125, 0.25, and 0.375. The energy band structure, density of states, charge differential density, electron-hole effective masses, optical properties, and the water redox potential were calculated for various models. According to our results, (La-S)-doped CaTiOsub.3 with a doping ratio of 0.25 (LCOS1-0.25) has superior photocatalytic hydrolysis properties due to the synergistic performances of its narrow band gap, fast carrier mobility, and superb ability to absorb visible light. Apart from the reduction of the band gap, the introduction of intermediate energy levels by La and Ce within the band gap also facilitates the transition of excited electrons from valence to the conduction band. Our calculations and findings provide theoretical insights and solid predictions for discovering CaTiOsub.3 perovskites with excellent photocatalysis performances.
CeOsub.2 is an important rare earth (RE) oxide and has served as a typical oxygen storage material in practical applications. In the present study, the oxygen storage capacity (OSC) of CeOsub.2 was ...enhanced by doping with other rare earth ions (RE, RE = Yb, Y, Sm and La). A series of Undoped and RE–doped CeOsub.2 with different doping levels were synthesized using a solvothermal method following a subsequent calcination process, in which just Ce(NOsub.3)sub.3∙6Hsub.2O, RE(NOsub.3)sub.3∙nHsub.2O, ethylene glycol and water were used as raw materials. Surprisingly, the Undoped CeOsub.2 was proved to be a porous material with a multilayered special morphology without any additional templates in this work. The lattice parameters of CeOsub.2 were refined by the least–squares method with highly pure NaCl as the internal standard for peak position calibrations, and the solubility limits of RE ions into CeOsub.2 were determined; the amounts of reducible–reoxidizable Cesup.n+ ions were estimated by fitting the Ce 3d core–levels XPS spectra; the non–stoichiometric oxygen vacancy (Vsub.O) defects of CeOsub.2 were analyzed qualitatively and quantitatively by O 1s XPS fitting and Raman scattering; and the OSC was quantified by the amount of Hsub.2 consumption per gram of CeOsub.2 based on hydrogen temperature programmed reduction (Hsub.2–TPR) measurements. The maximum OSC of CeOsub.2 appeared at 5 mol.% Yb–, 4 mol.% Y–, 4 mol.% Sm– and 7 mol.% La–doping with the values of 0.444, 0.387, 0.352 and 0.380 mmol Hsub.2/g by an increase of 93.04, 68.26, 53.04 and 65.22%. Moreover, the dominant factor for promoting the OSC of RE–doped CeOsub.2 was analyzed.
We synthesized a series of new antimony(III) compounds by reaction of Sb(OEt)sub.3 with organic ligands of the type E(CHsub.2-CHsub.2-OH)sub.2, with E = NH, NMe, O, S, Se, and Te. The synthesized ...compounds have the general composition E(CHsub.2-CHsub.2-O)sub.2Sb(OEt). For comparison, the compound (O-CHsub.2-CHsub.2-S)Sb(OEt) was prepared. All compounds are characterized using NMR, IR, and Raman spectroscopy. The molecular structures of the products reveal the formation of chelate complexes, wherein the ligand molecules coordinate as tridentate O,E,O-ligands to the antimony atom. Dimer formation in the solid state allows the antimony atoms to reach pentacoordination. Quantum chemical calculations including topological analysis of electron density reveal that there are polar shared bonds between antimony and the oxygen atoms bound to antimony. The interactions between the donor atom E and the Sb atom and the interactions in the dimers can be characterized as Van der Waals interactions. The reactivity of MeN(CHsub.2-CHsub.2-O)sub.2Sb(OEt) was investigated as an example. For this purpose, the compound reacted with a range of organic compounds such as carboxylic acids and carboxylic anhydrides and small molecules like COsub.2 and NHsub.3. This study establishes a new and easy accessible class of antimony(III) compounds, provides new insights into the chemistry of antimony compounds and opens up new opportunities for further research in this field.
Regioselective C-H alkenylation of
-dialkylanilines with ynamides was developed using AgNTf
as a catalyst. This approach represents a facile hydroarylation of ynamides, allowing for the introduction ...of an alkenyl group exclusively at the
position of aniline derivatives. As a result, a series of 4-alkenyl
-dialkylanilines were synthesized with excellent regioselectivities.
Understanding the processes that occur during the redox transformations of complexes coordinated by redox-active apical ligands is important for the design of electrochemically active compounds with ...functional properties. In this work, a detailed analysis of the interaction energy and electronic structure was performed for cluster complexes trans-Resub.6Ssub.8bipysub.4Clsub.2sup.n (n = 2–, 4–, 6–, 8–), which can be obtained by stepwise electrochemical reduction of a neutral cluster trans-Resub.6Ssub.8bipysub.4Clsub.2 in DMSO solution. It was shown that the formation of open-shell paramagnetic ions with S = 1, 2 and 1 is the most energetically favorable for n = 2–, 4– and 6–, respectively.
ReSsub.2-based heterostructures, which involve the coupling of a narrow band-gap semiconductor ReSsub.2 with other wide band-gap semiconductors, have shown promising performance in energy conversion ...and environmental pollution protection in recent years. This review focuses on the preparation methods, encompassing hydrothermal, chemical vapor deposition, and exfoliation techniques, as well as achievements in correlated applications of ReSsub.2-based heterostructures, including type-I, type-II heterostructures, and Z-scheme heterostructures for hydrogen evolution, reduction of COsub.2, and degradation of pollutants. We believe that this review provides an overview of the most recent advances to guide further research and development of ReSsub.2-based heterostructures for photocatalysis.
There has been a great focus on halogen-bonding as a unique interaction between electron-deficient halogen atoms with Lewis basic moieties. Although the application of halogen-bonded atoms in organic ...chemistry has been eagerly researched in these decades, the development of chiral molecules with halogen-bonding functionalities and their utilization in asymmetric catalysis are still in the\ir infancy. We have previously developed chiral halonium salts with amide functionalities, which behaved as excellent catalysts albeit in only two reactions due to the lack of substrate activation abilities. In this manuscript, we have developed chiral halonium salts with an N-nitrosamine moiety and applied them to the Mannich reaction of isatin-derived ketimines with malonic esters. The study focused on our novel bromonium salt catalyst which provided the corresponding products in high yields with up to 80% ee. DFT calculations of the chiral catalyst structure suggested that the high asymmetric induction abilities of this catalyst are due to the Lewis basic role of the N-nitrosamine part. To the best of our knowledge, this is the first catalytic application of N-nitrosamines.
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