Direct catalytic conversion of methane to methanol with O 2 has been a fundamental challenge in unlocking abundant natural gas supplies. Metal-free methane conversion with 17% methanol yield based on the limiting reagent O 2 at 275 °C was achieved with near supercritical acetonitrile in the presence of boron nitride. Reaction temperature, catalyst loading, dwell time, methane–oxygen molar ratio, and solvent-oxygen molar ratios were identified as critical factors controlling methane activation and the methanol yield. Extension of the study to ethane (C2) showed moderate yields of methanol (3.6%) and ethanol (4.5%).

Aerobic self‐esterification of primary alcohols catalyzed by mesoporous metal oxides (manganese and cobalt oxides) is reported under base and solvent free conditions. For a range of aliphatic alcohols, up to 90 % conversions to esters was achieved. The catalytic reaction is likewise applicable to neat aldehydes as substrates with yields of up to 86 %. High pressure batch reaction for ethanol to ethyl acetate led to 22 % yield. Isotope labeling studies indicated decarboxylation on the catalyst surface. Mechanistic and kinetic experiments implicate oxygen rebound and α‐carbon removal as intermediate steps. Mesoporous cobalt oxide showed about 20 % higher catalytic activity compared to mesoporous manganese oxide.

A series of bimetallic Ga-containing materials using TiO2 and TiO2-promoted SiO2 supports have been prepared. Rhodium, palladium, and platinum have been used as additional metals in this system. The materials are characterized and used as catalysts for the partial oxidation of methane into synthesis gas (H-2 and CO). The presence of a low quantity of titanium in the form of anatase TiO2 was shown to improve the overall activity of catalytic methane oxidation and to strongly increase the selectivity of partial oxidation products over the total oxidation of methane to carbon dioxide and water. Particular attention is paid to the formation of gallium-metal alloys on the surface of the catalyst supports. Rh-Ga-Ti-SiO2 was found to be the most active and selective catalyst, giving 89% conversion of methane and 99% selectivity to synthesis gas at 750 degrees C, as well as exhibiting catalytic activity and preferential conversion to partial oxidation products at temperatures as low as 350 degrees C.

Perovskite materials have attracted much attention in heterogeneous catalysis. Here, we report a perovskite type material LaNiO3-delta (LNO) for degradation of methyl orange (MO) azo dye in aqueous solutions under dark ambient conditions (room temperature, atmospheric pressure) without additional lights or chemical stimulants. The high degradation percentage of 5 ppm MO with 1.5 g/L LNO was 94.3% after 4 h with a stirring speed of 500 rpm. Reactions under nitrogen, oxygen and carbon dioxide conditions were performed with efficiencies of 19.6%, 7.1%, and 96.8% respectively after 6 h to understand the mechanism. MO was shown to degrade under dark ambient condition via main intermediates, sulfanilic acid anion and N,N-dimethyl-p-phenylenediamine (DPD), by electrospray ionization mass spectrometry (ESI/MS) and high performance liquid chromatography (HPLC). Degradation of MO under such a mild condition is due to two synergic effects proposed by means of XRD, FTIR, TGA, SEM, and XPS. Nickel is oxidized during MO degradation; lanthanum carbonate (La-analog calkinsite) is formed on the LNO surface due to the aqueous solution environment and speeds up azo bond cleavage. This work unravels the mechanism behind MO degradation by LNO under dark ambient conditions for the first time. It is a fundamental information on perovskite for dye degradation, especially for lanthanum series of perovskite. Excellent perovskite materials should be tailorable for water remediation applications considering the large variety of perovskites in terms of constituents and composition.

The CO and H-2 (syngas) production from methane partial oxidation (MPO) using TiO2 supported Au-Pd bimetallic catalysts are discussed. The supported Au, Pd and Au-Pd bimetallic nanoparticles were prepared by an incipient wetness impregnation or co-impregnation method and were characterized. The supported Au-Pd catalyst was selective for reforming and was more active compared to bare TiO2, TiO2 supported Au only, or Pd only catalysts. The catalyst properties before and after MPO reaction were investigated, including the stability of the TiO2 support, and the stability of Au and Pd nanoparticles. The supported Au-Pd catalyst has the highest TON (TONH2 = 23 at 650 degrees C), compared to supported Au catalyst (TONH2 < 1) and supported Pd catalyst (TONH2 < 1). Based on the analysis of outlet gases from the MPO reaction in a flow reactor, synergetic effects between Au and Pd, where Pd activates C-H bonds while gold modulates the behavior of oxygen at the catalyst surface, are shown to contribute to MPO. Additionally, the Au-Pd/TiO2 material shows long-term activity (> 12 h) for the MPO reaction at 600 degrees C.

We report the synthesis of mesoporous Co3O4 by an inverse micelle template self-assembly method and its catalytic activity towards selective oxidation of alkenes to epoxides. The chemical and structural properties of the materials were characterized by powder X-ray diffraction, nitrogen sorption studies, electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis. The morphology of the material exhibits flower like nanoparticle aggregates. Nanoparticles are packed closely in a random manner to form the mesoporous network via connected interparticle voids. Particle size expansion could be observed with heat treatment (250 degrees C-450 degrees C), which strongly correlates with surface area of the material. Co-250, which has the highest surface area along with highest oxygen vacancies, gave the best performance in alkene epoxidation. The catalyst was found to be efficient in selective oxidation of alkenes to epoxides with a broad substrate scope and achieved > 99% conversion with high selectivity (93%). Liquid phase batch mode reactions were carried out under atmospheric pressure and aerobic conditions, in the absence of any additives. Moreover the catalyst could be recycled several times without losing its activity, which makes this catalyst economical and environmentally benign.

A tandem experimental and theoretical investigation of a mesoporous ceria catalyst reveals the properties of the metal oxide are conducive for activity typically ascribed to metals, suggesting reduced Ce3+ and oxygen vacancies are responsible for the inherent bi-functionality of CO oxidation and dissociation of water required for facilitating the production of H-2. The degree of reduction of the ceria, specifically the (100) face, is found to significantly influence the binding of reagents, suggesting reduced surfaces harbor the necessary reactive sites. The metal-free catalysis of the reaction is significant for catalyst design considerations, and the suite of in situ analyses provides a comprehensive study of the dynamic nature of the high surface area catalyst system. This study postulates feasible improvements in catalytic activity may redirect the purpose of the water-gas shift reaction from CO purification to primary hydrogen production.

We have synthesized and tested a highly active Cu doped mesoporous CeO2 catalyst system for the low temperature water-gas shift (WGS) reaction. While typical oxide-supported copper WGS catalysts are characterized by high copper loadings (30-40%), the morphological properties of the mesoporous CeO2 material enable high catalytic activity at copper loadings as low as 1%. Operando X-ray diffraction, in situ X-ray absorption near-edge structure spectroscopy (XANES), and operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) methods were used to probe the interactions between the metal and mesoporous oxide components under reaction conditions. Copper was observed to undergo reduction from oxide to metal under WGS conditions at 150 °C, while the CeO2 lattice was observed to expand upon heating, indicating Ce3+ formation correlated with CO2 production. The active state of the catalysts was confirmed by in situ XANES to contain Cu0 and partially reduced CeO2. DRIFTS analysis revealed carboxyl species bound to copper during reduction, as well as formate and carbonate surface species on ceria. Lower concentrations of copper were observed to foster enhanced metal-support interactions.

In this study, we aim to investigate the change in photon emission statistics of single CdSe/CdS core/shell quantum dots (QDs) on dielectric modified gold nanoparticle (NP) substrates as a function of the excitation wavelength. Photons emitted from single QDs are typically "anti-bunched" and are independent of the excitation wavelength. However, when QDs are coupled to plasmonic substrates, even at the low excitation power regime, we observed a significant change in photoluminescence emission behavior of single QDs; i.e. the emission transformed from incomplete photon anti-bunched to bunched when the excitation was changed from "off" to "on" plasmon resonance. Theoretical studies based on electrodynamics modeling suggested that for the QD-Au NP system, the quantum yield of single excitons decreases while that of biexcitons increases. In addition, when excited at the "on" resonance condition, the absorption is highly enhanced, resulting in an increased population of higher order excitons of the QDs. The higher order exciton emission was directly observed as an additional peak appeared at the blue side of the exciton peak of single QDs. The combined effect of the change in quantum yield and the increase in the absorption cross-section switches the photons emitted by single QDs from anti-bunched to bunched. These results provided direct evidence that not only the plasmonic nanostructures but also the excitation wavelength can effectively control the photon emission statistics of single QDs in the hybrid metal-semiconductor system. Manipulating the multiexciton-plasmon interaction in a hybrid complex like this could possibly open up new doors for applications such as entangled photon pair generation and plasmon-enhanced optoelectronic devices.

Series of Ru-Mn-Ce and Ru-Co-Ce catalysts are prepared and used in the aerobic oxidation of alcohols, the calcination temperature had an adverse effect on the catalytic performance of Ru-Mn-Ce catalysts, while it was beneficial to the Ru-Co-Ce catalysts, which is an interesting finding, and this is an environmental friendly and economical catalytic systems. The interactions between ruthenium oxides and Co (Mn)-Ce mixed oxides of the former strengthened while the latter weakened after calcination. Calcination decreased the content of adsorbed oxygen and restricted oxygen transfer mechanism in the manganese system, while the opposite effect was observed with the cobalt-containing catalyst.

Copper oxide supported on mesoporous manganese oxide (meso Cu/MnO,) was synthesized by an inverse micelle templated evaporation induced self-assembly procedure. Controlled aggregation of nanoparticles and a monomodal size distribution of mesopores with tunable structural properties were observed. The material possessed superior catalytic activity in the aerobic oxidative coupling of terminal alkynes. Excellent conversion (>99% in most cases) and selectivity were observed in both homocoupling and cross coupling of alkynes using the optimized reaction conditions. Use of air as the sole oxidant, avoidance of any kind of additives, ease of product separation, great functional group tolerability, wide synthetic scope, and superior reusability (up to eighth cycle) are the notable features of our catalytic protocol. While the reaction mechanism was elucidated, a synergistic cooperative effect between the copper and manganese has been established, which is responsible for the superior catalytic activity. The labile lattice oxygen of the meso Cu/MnOx played a vital role in deprotonation of the alkyne proton, as supported by TPD and TGA studies. Moreover, for the first time, we designed model complexes for the active sites of the catalyst by DFT calculations and provided a qualitative description of the coupling mechanism, which supports the experimental findings.

A unique approach for the synthesis of nonstoichiometric, mesoporous molybdenum oxide (MoO 3– x ) with nanosized crystalline walls by using a soft template (PEO‐ b ‐PS) synthesis method is introduced. The as‐synthesized mesoporous MoO 3– x is very active and stable (durability > 12 h) for the electrochemical hydrogen evolution reaction (HER) under both acidic and alkaline conditions. The intrinsic MoO 3 serves as an HER electrocatalyst without the assistance of carbon materials, noble metals, or MoS 2 materials. The results from transmission electron microscopy and N 2 sorption techniques show that the as‐synthesized mesoporous MoO 3– x has large accessible pores (20–40 nm), which are able to facilitate mass transport and charge transfer during HER. In terms of X‐ray diffraction, X‐ray photoelectron spectroscopy, temperature‐programmed oxidation, and diffusive reflectance UV–vis spectroscopy, the mesoporous MoO 3– x exhibits mixed oxidation states (Mo 5+ , Mo 6+ ) and an oxygen‐deficient structure. The as‐synthesized MoO 3– x only requires a low overpotential (≈0.14 V) to achieve a 10 mA cm −2 current density in 0.1 m KOH and the Tafel slope is as low as 56 mV dec −1 . Density functional theory calculations demonstrate a change of electronic structure and the possible reaction pathway of HER. Oxygen vacancies and mesoporosity serve as key factors for excellent performance.

Aerogels of SnO2 were synthesized by an epoxide-initiated sol–gel method.

Activated carbon templated Copper Aluminum mixed oxide (CuAl MO) catalysts have been synthesized and studied for direct imine formation by oxidative coupling of alcohols and amines under solvent free conditions. Among the catalysts, CuAl MO20%C (catalyst synthesized by adding 20% activated carbon) shows the best activity and selectivity for this reaction. Here, air is used as the oxidant which is considered as the most economical and green oxidant among different oxidizing agents. Pyridine adsorption results confirmed that the presence of higher number of Lewis acidic sites enhances the catalytic activity of the material. Various alcohol and amine substrates were readily converted into the corresponding imines in good to excellent yields. According to catalytic activity studies and TG-MS data, surface oxygen availability and facile reversibility of oxygen readsorption on the surface account for the superior activity and high durability of the CuAl MO20%C catalyst. The regenerated catalyst showed 92% conversion with 100% selectivity even after the 4th reuse. (C) 2016 Published by Elsevier B.V.