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Molybdenum oxide-based catalysts are promising catalysts for the gas-phase hydrodeoxygenation (HDO) of lignocellulosic pyrolysis oils with high selectivities to arenes. The gas-phase HDO is conducted at temperatures between 300 °C and 400 °C at ambient pressure, resulting in a low hydrogen consumption and high energy efficiency. The loading of nickel forming a binary structure consisting of MoO3and nickel molybdate (NiMoO4) during calcination results in a significant increase of the catalytic activity connected with a drastic shortening of the induction period observed for the unpromoted catalyst system. The promotional effect of nickel seems to be related to its enhanced reduction behaviour and hydrogen dissociation leading eventually to an improved formation of a molybdenum oxycarbohydride phase (MoOxCyHz). The MoOxCyHzphase plays an important role in stabilizing active Mo5+sites and prevents over-reduction to inactive MoO2. The activity and benzene selectivity are maximal when pure NiMoO4is used as a catalyst. However, the selectivity towards undesired methane increases significantly indicating the decomposition of arenes. This effect is considerably reduced for catalysts with lower nickel contents (3–5%) which still exhibit a highly improved activity compared to MoO3. In situXRD studies revealed that the population of the MoOxCyHzphase is strongly affected by the nickel content, the structure of the hydrocarbon substrate and the hydrogen content during pre-reduction and catalysis.

The hydrogenation of amides is an important but highly challenging reaction, which usually is applied under drastic conditions (temperature >160 °C). Here, we report a heterogeneous Pt–MoOx/TiO2catalyst for amide and imide hydrogenation under milder conditions. The catalytic reactivity is proposed to originate from the synergistic effect between surface active species. Pt promotes formation of partially reduced MoOxthat is responsible for CO activation, and MoOx-modified Pt can more efficiently generate surface species from gas-phase H2. This catalyst system enables the selective hydrogenation of several 2° and 3° amides as well as imides.

Low-dimensional materials have unique optical, electronic, mechanical, and chemical properties that make them desirable for a wide range of applications. Nano-scaling materials to confine transport in at least one direction is a common method of designing materials with low-dimensional electronic structures. However, bulk materials give rise to low-dimensional electronic structures when bonding is highly anisotropic. Layered Zintl phases are excellent candidates for investigation due to their directional bonding, structural variety, and tunability. However, the complexity of the structure and composition of many layered Zintl phases poses a challenge for producing phase-pure bulk samples to characterize. Eu11Zn4Sn2As12is a layered Zintl phase of significant complexity that is of interest for its magnetic, electronic, and thermoelectric properties. To prepare phase-pure Eu11–xNaxZn4Sn2As12, a binary EuAs phase was employed as a precursor, along with NaH. Experimental measurements reveal low thermal conductivity and a high Seebeck coefficient, while theoretical electronic structure calculations reveal a transition from a 3D to 2D electronic structure with increasing carrier concentration. Simulated thermoelectric properties also indicate anisotropic transport, and thermoelectric property measurements confirm the nonparabolicity of the relevant bands near the Fermi energy. Thermoelectric efficiency is known to improve as the dimensionality of the electronic structure is decreased, making this a promising material for further optimization and opening the door to further exploitation of layered Zintl phases with low-dimensional electronic structures for thermoelectric applications.

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Isotope labelling, particularly deuteration, is an important tool for the development of new drugs, specifically for identification and quantification of metabolites. For this purpose, many efficient methodologies have been developed that allow for the small-scale synthesis of selectively deuterated compounds. Due to the development of deuterated compounds as active drug ingredients, there is a growing interest in scalable methods for deuteration. The development of methodologies for large-scale deuterium labelling in industrial settings requires technologies that are reliable, robust and scalable. Here we show that a nanostructured iron catalyst, prepared by combining cellulose with abundant iron salts, permits the selective deuteration of (hetero)arenes including anilines, phenols, indoles and other heterocycles, using inexpensive D2O under hydrogen pressure. This methodology represents an easily scalable deuteration (demonstrated by the synthesis of deuterium-containing products on the kilogram scale) and the air- and water-stable catalyst enables efficient labelling in a straightforward manner with high quality control.

0.1–3 wt % Ce-promoted MCM-41-supported nickel catalysts were prepared for dry reforming of CH4(DRM) and characterized by surface area and pore analyses, powder X-ray diffraction , temperature-programed reduction with H2, temperature-programed CO2desorption, X-ray photoelectron spectroscopy, thermogravimetric analysis, and scanning transmission electron microscopy using a high-angle annular dark field. Notably, 5Ni0.5Ce/MCM-41 has a bimodal distribution of NiO crystallites inside and outside the pores of MCM-41, the highest number of basic sites inducing profound CO2interactions with the surface, and metallic nickel particles interacting with the support for facilitating CH4dissociation. In addition, a thin surface layer of ceria provides surface oxygen species for carbon deposit oxidation. All these physiochemical properties ensured >90% conversion (H2/CO ∼ 1) over 330 min on stream and >80% conversion over 75 h of time on stream (H2/CO = 0.98) over the 5Ni0.5Ce/MCM-41 catalyst. A higher ceria loading than 0.5 wt % masked the active Ni sites with a ceria layer, which diminished the number of basic sites and deteriorated the catalytic performance.

Photocatalytic transformation of organics is a promising alternative to conventional synthetic methodologies. ZnIn2S4is active in photocatalytic redox reactions, but its performance is hindered by fast charge recombination, and optimizing its properties through synthesis or modification is complicated. Herein, Zn-In-S based composites were prepared via a facile solvothermal method by varying the ratio of sulfide precursor (TAA) with a fixed Zn/ In molar ratio of 1: 2. The phase composition of the obtained materials depends on the amount of TAA. At lower ratios, composites consisting of crystalline In(OH)3and unknown ZnxInySzphase were formed. Pure-phase ZnIn2S4was obtained when the feed molar ratio of zinc and TAA was 1: 6 or higher. The photocatalytic oxidation of benzyl alcohol (BA) and reduction of nitrobenzene (NB) in a coupled system were applied to evaluate the activity of Zn-In-S-based composites. Under visible light irradiation, the ZnxInySz/ In(OH)3composite (ZIS14) synthesized with a molar ratio of Zn to TAA of 1: 4 exhibited boosted and optimal performance compared to the bare ZnIn2S4and other samples. After 5hours of irradiation, the BA conversion and benzaldehyde (BAD) yield were 57% and 55%, respectively, and the NB conversion and aniline (AN) yield were 70% and 35%, individually, outperforming previous studies under similar experimental conditions. This work not only elucidates the photoredox process of BA and NB in one system, but also has significant implications for understanding the complex hydro/solvothermal processes involved in the fabrication of multicomponent sulfides.

Alkyl cyclohexanes were synthesized in high selectivity viaa combined hydrogenation/hydrodeoxygenation of aromatic ketones using ligand-free RhCl3as pre-catalyst in trifluoroethanol as solvent. The true catalyst consists of rhodium nanoparticles (Rh NPs), generated in situduring the reaction. A range of conjugated as well as non-conjugated aromatic ketones were directly hydrodeoxygenated to the corresponding saturated cyclohexane derivatives at relatively mild conditions. The solvent was found to be the determining factor to switch the selectivity of the ketone hydrogenation. Cyclohexyl alkyl-alcohols were the products using water as a solvent.

To date, a great number of various materials have been tested for the oxidative coupling of methane (OCM). On the basis of previous statistical analysis of OCM-related literature data, we developed novel catalysts based on K2MnO4or KMnO4supported on SiO2showing selectivity to C2-hydrocarbons (C2H4and C2H6) up to 68 or 66%. The analysis of catalysts containing the single components (Mn/SiO2, K2O/SiO2or SiO2) demonstrates that the co-existence of K and Mn is essential for achieving high selectivity to the desired products. The selectivity can be additionally improved when the OCM reaction is performed in the presence of water. The positive effect of water is attributed to the suppressed direct oxidation of CH4to CO2. Water also enhances the rates of methane conversion into C2-hydrocarbons and CO. Besides, the effects of water are more pronounced for samples based on crystalline SiO2rather than amorphous SiO2. Transient experiments with isotopically labelled oxygen suggest that the accelerating effect should be of heterogenous nature. As the positive influence of water on the selective methane oxidation to C2-hydrocarbons has been established over different catalysts, it may be advantageous to consider it when developing novel materials for the OCM reaction and even for other oxidation reactions.

A convenient methodology for perfluoroalkylation including trifluoromethylation of (hetero)arenes with perfluoroalkyl bromides was developed. Key for the success is the use of a specific cobalt-based nanocatalyst, which can be recycled at least up to 4 times. The scope of this first cobalt-catalyzed perfluoroalkylation is presented and detailed catalyst characterization (e.g.analytical STEM, XPS, and XRD) has been carried out.

Non-oxidative dehydrogenation of propane is one of the most promising technologies for propene production in terms of environmental impact and sustainability. The purpose of the present study was to develop environmentally friendly and low-cost alternatives to currently applied Pt- or CrOx-based catalysts. Rutile TiO2-based catalysts with supported ZnOxand ZrOxspecies were established to show promising performance under industrially relevant conditions. The amount of propene produced within 3 h on propane stream at 550 °C over the optimized catalyst with 2 wt% Zn and 5.6 wt% Zr is close to that obtained over commercial-like K–CrOx/Al2O3and the state-of-the-art Cu/YZrOxcatalyst. The selectivity to propene over our catalyst was about 95% at a propane conversion of about 23%. The kind of active sites and the effect of ZrO2addition on catalyst performance and physicochemical properties were elucidated owing to the application of complementary characterisation techniques such as XRD, N2physisorption, HRTEM, EDX, XPS, X-ray absorption spectroscopy, NH3-TPD, CO-TPR, Raman and O2-TPO. ZnOxclusters with 1–3 Zn atoms were concluded to be the active sites. ZrO2enhances their intrinsic activity and inhibits the formation of the inactive rhombohedral ZnTiO3phase.

Supported V2O5/Ce0.5Ti0.5−xMnxO2−δ(x= 0, 0.01, 0.05, 0.1, and 0.2) catalysts and bare supports were investigated in the selective catalytic reduction (SCR) of NO by NH3between 100 and 300 °C. Incorporation of Mn into Ce0.5Ti0.5O2increased the NO removal efficiency, reaching both NO and NH3conversions above 85% between 175 to 300 °C at remarkably high N2selectivities of ≥95%. Moreover, Mn-modified supports were also much more stable against deactivation in the presence of water. Deposition of vanadia on the Ce0.5Ti0.5−xMnxO2−δsupports enhanced the N2selectivity, reaching ≥98% in the whole temperature range for Mn percentages of ≤0.1. Characterization results revealed that incorporation of Mn leads to supports with higher lattice disorder and smaller crystallite size and enhances the oxygen mobility and the reducibility of the supports. OperandoEPR studies show that the synergistic effect of VOxand MnOxsurface species in moieties containing Mn3+/Mn2+and VO3+/VO2+in close vicinity contributes to the prevention of undesired NH3oxidation, thus improving the N2selectivity of these catalysts.

It is generally accepted that optimal particle sizes are key for efficient nanocatalysis. Much less attention is paid to the role of morphology and atomic arrangement during catalytic reactions. Here, we unravel the structural, stoichiometric, and morphological evolution of gas-phase produced and partially oxidized cobalt nanoparticles in a broad size range. Particles with diameters between 1.4 and 22 nm generated in cluster sources are size selected and deposited on amorphous alumina (Al2O3) and ultrananocrystalline diamond (UNCD) films. A combination of different techniques is employed to monitor particle properties at the stages of production, exposure to ambient conditions, and catalytic reaction, in this case, the oxidative dehydrogenation of cyclohexane at elevated temperatures. A pronounced size dependence is found, naturally classifying the particles into three size regimes. While small and intermediate clusters essentially retain their compact morphology, large particles transform into hollow spheres due to the nanoscale Kirkendall effect. Depending on the substrate, an isotropic (Al2O3) or anisotropic (UNCD) Kirkendall effect is observed. The latter results in dramatic lateral size changes. Our results shed light on the interplay between chemical reactions and the catalyst’s structure and provide an approach to tailor the cobalt oxide phase composition required for specific catalytic schemes.

We report the colloidal synthesis of 2D SnTe nanosheets through precursor hot injection in a nonpolar solvent. During the reaction, an important intermediate─Sn-template─is formed which defines the confined growth of SnTe. This “flake-like” structure gives the first evidence for the possible 2D morphology formation prior to the anion precursor injection (TOP-Te). Additionally, we explore the role of each ligand in the reaction process. Thus, we explain the formation and morphology evolution of 2D SnTe nanostructures from a mechanism perspective as well as the role of each ligand on the molecular scale. The interplay of ligands provides the necessary conditions for the realization of stable low-dimensional SnTe nanomaterials with tunable size and shape.

Vertically oriented nanowires (NWs) of single-crystalline wurtzite GaN have been fabricated on sapphire substrates, via metal organic chemical vapor deposition (MOCVD). We present ex situ investigations on orientation and structure of grown GaN nanowires on GaN(0001) surface using reflection high energy electron diffraction (RHEED). Both ordered and randomly oriented GaN crystalline structures have been detected.