Morphology-dependent performance of Zr-CeVO4/TiO2 for selective catalytic reduction of NO with NH3

A novel Zr–CeVO4/TiO2 catalyst was developed for the selective catalytic reduction (SCR) of NO with NH3. Both TiO2 nanosheets (TiO2-NS) and nanoparticles (TiO2-NP) with different crystal facets were used as supports for the catalyst. It was found that the TiO2-NS-supported catalyst showed much better activity, stability and H2O/SO2 durability than the TiO2-NP-supported catalyst. In particular, the catalyst loading amount was much lower than those of previously reported vanadate-based SCR catalysts. The crystal structures and morphologies were analysed by X-ray diffraction (XRD), Raman spectroscopy and (high-resolution) transmission electron microscopy ((HR)TEM). The redox properties, surface active species and acid sites of the catalysts were investigated through hydrogen temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), ammonia and nitrogen oxide temperature-programmed desorption (NH3-TPD and NOx-TPD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTs) experiments. The improved activity at lower temperature was due to the presence of more active oxygen species and Brønsted acid sites, as well as the formation of NO2 on the surface of the TiO2 nanosheets which have exposed (001) facets. The enhanced stability and H2O/SO2 durability of Zr–CeVO4/TiO2-NS was due to the limited formation of NH4NO3 and (NH4)2SO4/NH4HSO4. The excellent low operation temperature, low vanadium content and absence of WO3(MoO3) in this catalyst indicated that it has promising potential as a SCR catalyst for practical applications

The Screening of Homo‐ and Hetero‐Dual Atoms Anchored Graphdiyne for Boosting Electrochemical CO2 Reduction

Abstract Developing electrocatalysts with high catalytic performance and selectivity is crucial for electrochemical CO2 reduction reaction (CRR). There are many catalyst studies of transition metal (TM) atom doping to sp2 carbon material, such as graphene or carbon nanotubes. On the other hand, graphdiyne (GDY) has both sp and sp2 hybridization and stable pores, so we can tune its interaction with TM. Following the successful experimental synthesis of Ni atom doping to GDY monolayer, the CRR activity of double–atom catalysts was evaluated, including homo and hetero metal‐Ni doped on the GDY monolayer (MNi@GDY where M is Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) using the density functional theory calculations. The valence‐electron number of the catalytic center shows a strong positive correlation to the limiting potentials in the volcano plot. NiNi@GDY is the most promising candidate for converting CO2 to produce CH4 with a remarkable low limiting potential of −0.28 V, which is better than Ni@GDY and Ni3@GDY counterparts. NiNi@GDY shows excellent thermal stability and ability to suppress the competing hydrogen evolution reaction, showing its high selectivity to CH4

Co-solvation effect on the binding mode of the α-mangostin/β-cyclodextrin inclusion complex

Cyclodextrins (CDs) have been extensively utilized as host molecules to enhance the solubility, stability and bioavailability of hydrophobic drug molecules through the formation of inclusion complexes. It was previously reported that the use of co-solvents in such studies may result in ternary (host:guest:co-solvent) complex formation. The objective of this work was to investigate the effect of ethanol as a co-solvent on the inclusion complex formation between α-mangostin (α-MGS) and β-CD, using both experimental and theoretical studies. Experimental phase-solubility studies were carried out in order to assess complex formation, with the mechanism of association being probed using a mathematical model. It was found that α-MGS was poorly soluble at low ethanol concentrations (0–10% v/v), but higher concentrations (10–40% v/v) resulted in better α-MGS solubility at all β-CD concentrations studied (0–10 mM). From the equilibrium constant calculation, the inclusion complex is still a binary complex (1:1), even in the presence of ethanol. The results from our theoretical study confirm that the binding mode is binary complex and the presence of ethanol as co-solvent enhances the solubility of α-MGS with some effects on the binding affinity with β-CD, depending on the concentration employed

In Situ Synthesis of Sn-Beta Zeolite Nanocrystals for Glucose to Hydroxymethylfurfural (HMF)

The Sn substituted Beta nanocrystals have been successfully synthesized by in-situ hydrothermal process with the aid of cyclic diquaternary ammonium (CDM) as the structure-directing agent (SDA). This catalyst exhibits a bifunctional catalytic capability for the conversion of glucose to hydroxymethylfurfural (HMF). The incorporated Sn acting as Lewis acid sites can catalyze the isomerization of glucose to fructose. Subsequently, the Brønsted acid function can convert fructose to HMF via dehydration. The effects of Sn amount, zeolite type, reaction time, reaction temperature, and solvent on the catalytic performances of glucose to HMF, were also investigated in the detail. Interestingly, the conversion of glucose and the HMF yield over 0.4 wt% Sn-Beta zeolite nanocrystals using dioxane/water as a solvent at 120 °C for 24 h are 98.4% and 42.0%, respectively. This example illustrates the benefit of the in-situ synthesized Sn-Beta zeolite nanocrystals in the potential application in the field of biomass conversion

Theoretical Insight into Catalytic Propane Dehydrogenation on Ni(111)

Here, propane dehydrogenation (PDH) to propylene and side reactions, namely, cracking and deep dehydrogenation on Ni(111) surface, have been theoretically investigated by density functional theory calculation. On the basis of adsorption energies, propane is physisorbed on Ni(111) surface, whereas propylene exhibits chemisorption supported by electronic charge results. In the PDH reaction, possible pathways can occur via two possible intermediates, i.e., 1-propyl and 2-propyl. Our results suggest that PDH reaction through 1-propyl intermediate is both kinetically and thermodynamically more favorable than another pathway. The C–C bond cracking during PDH process is more difficult to occur than the C–H activation reaction because of higher energy barrier of the C–C bond cracking. However, deep dehydrogenation is the preferable process after PDH, owing to the strong adsorption of propylene on Ni(111) surface, resulting in low selectivity of propylene production. This work suggests that Ni(111) has superior activity toward PDH; however, the enhancement of propylene desorption is required to improve its selectivity. The understanding in molecular level from this work is useful for designing and developing better Ni-based catalysts in terms of activity and selectivity for propane conversion to propylene

Effect of Water Microsolvation on the Excited-State Proton Transfer of 3-Hydroxyflavone Enclosed in γ-Cyclodextrin

The effect of microsolvation on excited-state proton transfer (ESPT) reaction of 3-hydroxyflavone (3HF) and its inclusion complex with γ-cyclodextrin (γ-CD) was studied using computational approaches. From molecular dynamics simulations, two possible inclusion complexes formed by the chromone ring (C-ring, Form I) and the phenyl ring (P-ring, Form II) of 3HF insertion to γ-CD were observed. Form II is likely more stable because of lower fluctuation of 3HF inside the hydrophobic cavity and lower water accessibility to the encapsulated 3HF. Next, the conformation analysis of these models in the ground (S0) and the first excited (S1) states was carried out by density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations, respectively, to reveal the photophysical properties of 3HF influenced by the γ-CD. The results show that the intermolecular hydrogen bonding (interHB) between 3HF and γ-CD, and intramolecular hydrogen bonding (intraHB) within 3HF are strengthened in the S1 state confirmed by the shorter interHB and intraHB distances and the red-shift of O–H vibrational modes involving in the ESPT process. The simulated absorption and emission spectra are in good agreement with the experimental data. Significantly, in the S1 state, the keto form of 3HF is stabilized by γ-CD, explaining the increased quantum yield of keto emission of 3HF when complexing with γ-CD in the experiment. In the other word, ESPT of 3HF is more favorable in the γ-CD hydrophobic cavity than in aqueous solution