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A mesoporous molybdenum tungsten mixed metal oxide with high surface area (173 m

We report an aerobic partial oxidation of isobutylene into isoprene, acetone, and para-xylene using a mesoporous Ni TiOx catalytic material. In this work, two catalysts were found to synthesize two of these three valuable products with high selectivity, with p-xylene being synthesized with a selectivity of 46.0% and isoprene being synthesized with a selectivity of 64.7%, with overall conversions of isobutylene being 34.0% and 11.9% respectively. These reactions were done at relatively low temperatures (300 °C or below) and are conducted at flow rates of 10 sccm oxygen and isobutylene. The nickel titania catalysts were studied extensively using various characterization methodologies such as TEM, Raman, XRD, and XRF.

Electrocatalysis of water is a scalable and easily available source of the production of hydrogen (H2), the future energy carrier. This drive for clean energy inspired us to develop an inexpensive, readily producible, highly active, and stable catalyst to replace current state of the art platinum catalysts. Building on the promising hydrogen evolution reaction (HER) activity of many pyrites, their structural tuning by different metals and nonmetals has been found to be effective in several instances. We present here one such effort by partial surface selenization of mesoporous cobalt sulfide material, which displayed long-term operational stability (for at least 25 h) besides attaining a current density of 100 mA cm–2 at an overpotential of 160 mV versus the reversible hydrogen electrode (RHE) (in acidic media). A low Tafel slope (of 52 mV dec–1) and high exchange current density (j0) (of 70 μA cm–2) make our catalyst better to most existing systems. More importantly, using a variety of analytical techniq...

We report a general bottom-up synthetic methodology to epitaxially grow 3-nm-thick single-crystalline PdPt bimetallic nanowires using amphiphilic dioctadecyldimethylammonium chloride as the surfactant template. Mechanistic studies show that the existence of Pd element is critical in the synthesis of bimetallic PdPt nanowires with controllable atomic ratios. Due to synergistic effect of anisotropic single-crystalline ultrathin one-dimensional nanostructures and bimetallic elemental compositions, the resulting PdPt nanowires exhibit superior electrocatalytic activity and stability towards the hydrogen evolution reaction (HER). Among them, bimetallic Pd86Pt14 nanowires show the best HER activity with a small overpotential of only 0.8 mV in acidic media at a current density of 10 mA/cm2 (12.8 mV positive than that of commercial Pt nanoparticles), and excellent stability with only 4.6% loss in activity after current-time chronoamperometric responses for 26 h. This surfactant template-directing approach opens a general method for precise control of anisotropic nanostructures in diverse bimetallic nanomaterials for the high-performance electrocatalysts.

In this work, amorphous copper-chromium catalysts with different Cu/Cr molar ratios have been prepared by a sol-gel method and were used in the oxidation of cyclohexane to KA-oil. The catalysts have been characterized by a variety of analytical techniques including XRD, XPS, Raman, FT-IR, BET, TEM and SEM. XRD results confirmed that the formation of amorphous structure. The XPS and Raman results indicated that most of Cu species existed in well-dispersed tetrahedral coordination before calcination. After calcination, the tetrahedrally coordinated Cu ions are transformed into octahedral coordination and the activity of catalyst is significantly reduced. The results show that the tetrahedrally coordinated Cu ions play the synergistic catalytic role with Cr ions. Interestingly, oxidation of cyclohexane is more inclined to produce cyclohexanol with uncalcined catalyst due to the presence of the tetrahedrally coordinated Cu ions; however, the appearance of surface lattice oxygen makes the reaction more conducive to cyclohexanone after calcination. After optimizing conditions, Cu-Cr oxide catalyst with the molar ratio 1:1 shows the highest activity, which obtains 62.2% yield and 92.4% selectivity for KA-oil using H2O2 as oxygen source.

The surface properties, chemical compositions, and crystal structures of manganese oxides can be altered by redox reactions, which affect their heavy metal ion adsorption capacities. Here, birnessite nanosheets (δ-MnO2) were synthesized from the photochemical reaction of Mn2+aq and nitrate under solar irradiation, and Zn2+ was electrochemically adsorbed using the as-obtained birnessite nanosheets by galvanostatic charge–discharge. The effects of current density and electrochemical techniques (symmetric electrode and three-electrode systems) on Zn2+ adsorption capacity were also investigated. The results showed that the maximum Zn2+ adsorption capacity of the birnessite in the presence of electrochemical redox reactions could reach 383.2 mg g–1 (589.0 mmol mol–1) and 442.6 mg g–1 (680.3 mmol mol–1) in the symmetric electrode and three-electrode system, respectively; however, the Mn2+ release capacity in the three-electrode system was higher than that in the symmetric electrode system. With increasing curre...

We present here the correlation of picomolar affinities between surface-plasmon and electrochemical immunoassays for the binding of serum glutamic acid decarboxylase 65 autoantibody (GADA), a biomarker of type 1 diabetes (T1D), to its antigen GAD-65. Carboxylated (∼5.0%)-graphene-modified immunoassembly on a gold surface-plasmon chip or on an electrochemical array provided significantly larger binding affinity, higher sensitivity, and lower detection limits than a self-assembled monolayer surface of mercaptopropionic acid (MPA). Estimation of the relative surface -COOH groups by covalent tagging of an electroactive aminoferrocene showed that the graphenyl surface displayed a greater number of -COOH groups (9-fold) than the MPA surface. X-ray-photoelectron-spectroscopy analysis showed more C-O and C═O functionalities on the graphene-COOH surface than on the MPA surface. The graphene-COOH coating on gold exhibited ∼5.5-fold enhancement of plasmon signals compared with a similar coating on a plain glass surface. In summary, this article provides a quantitative comparison of carboxylated graphene with a mercapto-monolayer immunoassembly. Additionally, we propose that the binding-constant value can be useful as a quality-control checkpoint for reproducible and reliable production of large-scale biosensors for clinical bioassays.

The inexpensive and abundant material, palygorskite, was used as a promising catalyst support to prepare Fe-Ni/Pal catalysts. Catalytic steam reforming of toluene as a biomass tar model compound over these catalysts was investigated in a fixed-bed reactor under different parameters, including reaction temperatures and S/C molar ratios. The stability and lifetime of Fe3Ni8/Palygorskite catalyst was evaluated under optimal conditions and its kinetic parameters were determined as well. The fresh and used catalysts were characterized using X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), transmission electron microscopy (TEM), and Raman spectra. The results showed that the Fe3Ni8/Palygorskite catalyst with high dispersion was successfully prepared and exhibited superior catalytic performance compared with those of the monometallic catalysts (Fe3/Palygorskite and Ni8/Palygorskite) and the bare Palygorskite. Increasing the reaction temperature from 500 °C to 700 °C was beneficial for the toluene conversion and gaseous yields. The catalytic activity of Fe3Ni8/Palygorskite varied distinctly with the increase of S/C molar ratio and reached maximum at the the S/C molar ratio of 1.0. The apparent activation energy of 41.55 kJ mol−1 and the pre-exponential factor of 1.35 × 103 m3 kg−1 h−1 were obtained for Fe3Ni8/Palygorskite in kinetic studies under optimal reaction conditions, respectively. The carbon deposition analysis of the used catalysts revealed that the formation of graphitic carbon rather than amorphous carbon was the main reason for the deactivation of Fe3Ni8/Palygorskite catalysts. When ceased the injection of steam into the reaction system, the graphitic carbon would be accelerating formed on the surface of the Fe3Ni8/Palygorskite and decreased its catalytic activity for toluene conversion. But owing to the water gas shift reaction, the catalytic activity of Fe3Ni8/Palygorskite seemed to recover gradually to its optimum.

Toughening a ceramic in a ceramic matrix composite (CMC) depends on an ability of the composite to tolerate an accumulation of matrix cracks. When the reinforcement phase is carbon fiber, these cracks leave the fiber susceptible to destructive oxidation by ingress of air during high temperature exposure. Generally, a graphitic carbon interface coating is applied to carbon fibers because it provides for a weak bond between fiber and matrix that is required to promote toughening. This investigation seeks to utilize a BN coating instead of a C coating in order to promote oxidation resistance. Like graphitic carbon, BN is soft and easily cleavable. Preliminary observations that C/BN/SiC CMC's using Toray T300 carbon fibers were highly brittle and of low strength lead to a requirement of heat treating the fibers prior to the CVD of BN for toughened composites to be fabricated. It is likely heat treating removed reactive functionalities from the fiber surface to yield a weakly adhered and compliant interface.

A facile carbothermal route was adopted to obtain niobium carbide nanoparticles (NPs) embedded in carbon network from Nb2O5 to study photocatalytic behavior. Optimization of synthesis parameters to obtain single phase NbC NPs has been successfully done. The phase identification, morphology and nature of carbon were determined with the help of X-ray diffraction, transmission electron microscopy (TEM) and Raman spectroscopy. X-ray photoelectron spectroscopy (XPS) suggested the presence of multiple oxidation states of Nb associated to NbC and NbCxOy centers on the surface of NPs. Due to the presence of NbCxOy on the surface of NPs, absorption under visible region of EM spectrum has been observed by UV-visible spectroscopy. Different organic dyes (RhB, MB and MO) were used to study the effect of holding time on the photocatalytic performance of as-synthesized samples. RhB dye was found to be the most sensitive organic molecule among all the considered dyes and degraded 78% in 120 min.

In this study polymer, metal oxide and polymer-PZT composite microsphere materials were prepared by either hydrothermal or microwave assisted methods. Materials were subjected to microwave and ultrasound irradiation under specific conditions in order to understand their mechanical stability and morphological changes in dimensions. Scanning electron microscopy imaging was carried out before and after each irradiation and clear differences were observed depending on irradiation method and sample composition.

M1 phase MoVTeNb mixed oxides exhibit unique catalytic properties that lead to high C2H4 yields in oxidative conversion of C2H6 at moderate temperatures. The role of the heptagonal channel micropores of the M1 phase in regulating reactivity and selectivity is assessed here using reactant size-dependent kinetic probes and density functional theory (DFT) treatments for C2H6 and cyclohexane (C6H12) activations inside and outside the micropores. The sizes of C2H6 and the micropores suggest a tight guest–host fit, but C6H12 cannot access intrapore sites. Measured C2H6 to C6H12 activation rate ratios on MoVTeNbO are much higher than those measured on nonmicroporous vanadium oxides (VOx/SiO2) and estimated by DFT on external surfaces, suggesting that most C2H6 activations on MoVTeNbO occur inside the micropores under typical conditions. C2H6 exhibits higher activation energy than C6H12 on VOx/SiO2, consistent with the corresponding C–H bond strengths; the activation energy difference between C2H6 and C6H12 is lo...

Graphene quantum dots/Mn-N-TiO2/g-C3N4 (GQDs/TCN) composite photocatalysts have been designed, synthesized and characterized by XRD, SEM, TEM, Raman, BET, and XPS. The photodegradation of organic pollutants (p-nitrophenol, diethyl phthalate and ciprofloxacin, called as 4-NP, CIP and DEP, respectively) coupled with simultaneous photocatalytic production of hydrogen was successfully achieved using the GQDs/TCN catalysts. The 5%GQDs/TCN-0.4 sample shows the best photocatalytic hydrogen production and organic pollutant degradation rate under simulated solar irradiation in the simultaneous photocatalytic oxidation and reduction system. Furthermore, the photocatalytic H2 evolution rates in the solution of 4-NP, CIP and DEP are all larger than that in pure water system over the 5%GQDs/TCN-0.4 catalyst. And the H2 evolution rate in the solution of 4-NP is smaller than that in the solutions of CIP and DEP. Accordingly, the photodegradation rate of 4-NP is larger than that of CIP and DEP. The analyses of density functional theory and liquid chromatography mass spectrometry indicate that some photogenerated electrons were used in the photodegradation process of 4-NP but not in that of CIP and DEP. And it leads to the photocatalytic rate of H2 evolution in the 4-NP solution smaller than that in the solution of CIP and DEP. For the first time, the present work illuminates the photocatalytic enhancement of the GQDs/TCN-0.4 catalyst and the mechanism of the effect of different organic pollutants on photocatalytic H2 evolution.

The controlled synthesis of mixed crystallographic phase Mn2O3/Mn3O4 sponge material by varying heating rates and isothermal segments provides valuable information about the morphological and physical properties of the obtained sample. The well-characterized Mn2O3/Mn3O4 sponge and applicability of difference in reactivity of H2 and CO2 desorbed during the synthesis provide new developments in the synthesis of metal oxide materials with unique morphological and surface properties. We report the preparation of a Mn2O3/Mn3O4 sponge using a metal nitrate salt, water, and Dextran, a biopolymer consisting of glucose monomers. The Mn2O3/Mn3O4 sponge prepared at 1 °C·min-1 heating rate to 500 °C and held isothermally for 1 h consisted of large mesopores-macropores (25.5 nm, pore diameter) and a pore volume of 0.413 mL/g. Furthermore, the prepared Mn2O3/Mn3O4 and 5 mol %-Fe-Mn2O3/Mn3O4 sponges provide potential avenues in the development of solid-state catalyst materials for alcohol and amine oxidation reactions.

As important components with excellent oxidation and adsorption activity in soils and sediments, manganese oxides affect the transportation and fate of nutrients and pollutants in natural environments. In this work, birnessite was formed by photocatalytic oxidation of Mn2+aq in the presence of nitrate under solar irradiation. The effects of concentrations and species of interlayer cations (Na+, Mg2+, and K+) on birnessite crystal structure and micromorphology were investigated. The roles of adsorbed Mn2+ and pH in the transformation of the photosynthetic birnessite were further studied. The results indicated that Mn2+aq was oxidized to birnessite by superoxide radicals (O2•-) generated from the photolysis of NO3- under UV irradiation. The particle size and thickness of birnessite decreased with increasing cation concentration. The birnessite showed a plate-like morphology in the presence of K+, while exhibited a rumpled sheet-like morphology when Na+ or Mg2+ was used. The different micromorphologies of birnessites could be ascribed to the position of cations in the interlayer. The adsorbed Mn2+ and high pH facilitated the reduction of birnessite to low-valence manganese oxides including hausmannite, feitknechtite, and manganite. This study suggests that interlayer cations and Mn2+ play essential roles in the photochemical formation and transformation of birnessite in aqueous environments.

Hausmannite is the most widely distributed spinel-structured manganese oxide in soils and sediments. The transformation of this metastable manganese oxide to Mn(IV) oxides with higher adsorption capacity has attracted much research interest, while the transformation mechanisms and influencing factors still remain largely unknown, especially under acidic condition. In this work, the transformation processes of hausmannite at different pH values and the influence of cations were studied. Results indicated that hausmannite was transformed into manganite at pH 5.0–9.0. The dissolution of hausmannite was initiated and promoted by protons (≤ 7.0), and the decrease of pH accelerated its conversion to Mn(IV) oxides. The tunnel-structured Mn(IV) oxide was generated via two steps during the dissolution process of hausmannite at pH ≤ 3.0. Hausmannite was disproportionated to δ-MnO2 at first, which was then transformed to nsutite in the presence of Na+ and H+ through the transfer of electrons from adsorbed Mn(II) to structural Mn(IV). The disproportionation of hausmannite to δ-MnO2 was not affected by other cations, while the presence of K+ promoted the further transformation of δ-MnO2 to cryptomelane. The structural rearrangement process of δ-MnO2 was the rate-determining step for the formation of final products. This work expands the understanding of the formation, transformation and geochemical processes of manganese oxides in supergene environments.

Porous and highly flexible OMS-2 membranes have successfully been obtained via side-by-side and end-to-end alignment of the short OMS-2 nanorods into 1D microyarn superarchitectures and interweaving the resultant microyarn superarchitectures under ambient pressure. The side-by-side and end-to-end alignment of the short OMS-2 nanorods into 1D microyarn superarchitectures is effected by the use of cheap, abundant, and bioavailable cellulose linters as a sacrificial template that is completely digested within the course of the reaction and thus no post-synthesis treatment to remove it is required. The as-prepared OMS-2 membrane, without the use of conductive carbon, shows specific capacitance of 104 F/g at current density of 0.5 A/g and excellent electrochemical cycling. Scanning and transmission electron microscopy reveals the remarkable alignment of the short nanorods into microyarn superarchitectures and interweaving of the microyarns. In addition, transmission electron microscopy shows that the primary building blocks, the nanorods, are singly crystalline while cross-sectional imaging by tomography shows stratified and porous internal structure of the membrane.

To understand the effect of porous parameters and chemical components on CO2 capturing performance of solid state amine absorbents and their kinetic parameters, a clay mineral-based CO2 absorbent was prepared by impregnating five different liquid amines onto SiO2 nanowire clusters from fibrous sepiolite (Sep). Characterization was conducted by XRD, SEM, FTIR, and N2 adsorption–desorption isotherm, CO2 adsorption performances were measured by TGA. After acid treatment, the raw Sep mineral changed into amorphous silica nanowires, and the largest SBET of the obtained SiO2 nanowires reached 320 m2/g, which was 8 times larger than the pristine mineral. Amongst the adapted amines, tetraethylenepentamine (TEPA) showed superiority in the CO2 adsorption capacity. The optimized adsorption capacity reached 3.7 mmol/g at 75 °C from a CO2 + N2 mixture on a ∼50 wt% TEPA loaded SiO2 sample, and the capacity remained 3.6 mmol/g after ten circles of adsorption/desorption tests. The pore size and pore structure of the matrix, rather than the surface area, will obviously affect the adsorption ability of the product. Kinetic parameters for the CO2 adsorption process fitted well with a fractional-order model, confirming that the CO2 adsorption process by the solid absorbent should be a combination of both physical and chemical reactions. Results in this article provide detailed parameters for preparing and understanding these clay mineral based solid state CO2 absorbents.

The CO and H2 (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 °C), compared to supported Au catalyst (TONH2 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 °C.

Electroless deposition of aluminum using room temperature ionic liquids (RTIL) and liquid reducing agents is extremely water sensitive and has only been successful in glove boxes with deposition on copper or glass substrates. We have successfully brought the deposition out of the glove box using Schlenk techniques. We also have reported the first electroless aluminum deposition onto a nickel nanowire substrate. The nanowire synthesis and subsequent aluminum deposition were confirmed with measurements of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), small angle neutron scattering (SANS), and a superconducting quantum interference device (SQUID) magnetometer. Aluminum plating reached a deposition rate of 1.14 × 10−4 mol/hr. Results indicate a smooth and pure aluminum coating with thin surface oxidation on the nanowires.

Electrocatalytic decomposition of urea for the production of hydrogen, H2, for clean energy applications, such as in fuel cells, has several potential advantages such as reducing carbon emissions in the energy sector and environmental applications to remove urea from animal and human waste facilities. The study and development of new catalyst materials containing nickel metal, the active site for urea decomposition, is a critical aspect of research in inorganic and materials chemistry. We report the synthesis and application of [NH4]NiPO4·6H2O and β-Ni2P2O7 using in situ prepared [NH4]2HPO4. The [NH4]NiPO4·6H2O is calcined at varying temperatures and tested for electrocatalytic decomposition of urea. Our results indicate that [NH4]NiPO4·6H2O calcined at 300 °C with an amorphous crystal structure and, for the first time applied for urea electrocatalytic decomposition, had the greatest reported electroactive surface area (ESA) of 142 cm2/mg and an onset potential of 0.33 V (SCE) and was stable over a 24-h test period.

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 °C–450 °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.

Magnetic behavior of nanostructured mesoporous manganese oxide materials, designated UCT-1 and UCT-18, were studied using a combination of superconducting quantum interference device (SQUID) magnetometry and 55Mn zero-field spin–echo nuclear magnetic resonance (NMR). Curie–Weiss fits to the magnetic susceptibility for the UCT-1 and UCT-18 samples calcined at 550 °C yielded paramagnetic moment values consistent with spin-only Mn3+ ions in the α-Mn2O3 phase (S = 2, 4.90 μB). However, the magnetization and NMR results reported here clearly identify a small amount of the Mn3O4 second phase (ferrimagnetic with TC ≈ 43 K) that does not appear in X-ray diffraction (XRD). The study resulted in the observation of fascinating magnetic behavior: (1) exchange bias, which occurs in cases where a ferromagnetic (or ferrimagnetic) phase forms a boundary with an antiferromagnetic phase and (2) a magnetic contribution attributed to uncompensated spins on the surfaces of the α-Mn2O3 nanoparticles. The presence of Mn3O4 and ...

Four micro (nano)-sized mesoporous ferric hydroxyphosphates (FHP) are synthesized by a reverse microemulsion-solvothermal method, and then are used as supports to prepare supported Pt catalysts. The mean particle diameter of Pt nanoparticles (NPs) was 4.5–4.6 nm. When the four different Pt/FHP catalysts were used into the hydrogenation of α,β-unsaturated aldehydes (ketones) to their corresponding unsaturated alcohols, Pt/FHP (c) catalyst showed better catalytic performance than the other three partners. Under the optimal experimental conditions, several tested α,β-unsaturated aldehydes could be effectively transformed into corresponding unsaturated alcohols over Pt/FHP (c) catalyst. The catalyst could be recycled and reused several times without activity loss. We propose the stronger interaction between the Pt NPs and ferric ions of the FHP (c) are responsible for its good catalytic performance, and this stronger interaction should be rooted in its enhanced Lewis acid strength.

Herein, we discuss a heterogeneous catalytic protocol using cobalt doped mesoporous manganese oxide for amine–alcohol cross-coupling to selectively produce symmetric or asymmetric imines. Thorough investigations on the surface chemistry and physical properties of the material revealed its outstanding oxidation–reduction properties and reaction mechanism which was supported by quantum mechanical calculations done by using density functional theory (DFT).

The formation and transformation of iron oxide nanominerals in water environments control the migration and conversion of essential and toxic elements and organic pollutants. This study demonstrates the formation of iron oxide nanominerals through the oxidation of Fe2+aq by hydroxyl radicals (OH˙) and superoxide radicals (O2˙−) generated from the photolysis of nitrate. The mineral compositions were affected by the anion species and pH. In the photochemical system, schwertmannite was formed in 5.0 mmol L−1 SO42− solution with the initial pH of 6.0, and a mixture of goethite and lepidocrocite was formed when the SO42− concentration decreased to 0.1 mmol L−1. The particle size of schwertmannite increased with decreasing initial pH from 6.0 to 3.0. When Cl− was used instead of SO42−, single-phase lepidocrocite was formed with the initial pH of 6.0. When the initial pH decreased to 4.5 and 3.0, a mixture of goethite and lepidocrocite was formed, and the relative content of lepidocrocite decreased with decreasing initial pH. Under anoxic conditions, Fe2+aq promoted the transformation of the photochemically synthesized schwertmannite to goethite and lepidocrocite by dissolution–recrystallization. The present work expands our understanding of the generation and transformation of iron oxide nanominerals in nitrate-rich supergene environments.

Perovskite materials have attracted much attention in heterogeneous catalysis. Here, we report a perovskite type material LaNiO3-δ (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.

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.

Copper manganese oxide (CuMn2O4) was introduced into the nanoarray-based monolithic catalysts system for advanced exhaust after-treatment. Through scalable and cost-effective hydrothermal reactions, nanosheet layers of copper manganese oxide were uniformly coated onto the manganese oxide nanoarrays (HM-PCR), which were grown on the cordierite honeycomb monoliths. The core nanoarray support, HM-PCR, a well-defined array architecture for active material deposition, contributed to an increase of open surface area and thus enhanced catalytic oxidation performance. The CuMn2O4 coated nanoarray-based catalyst, NA-CuMn2O4, shows efficient 90% propane (C3H8) conversion at around 400 °C, which is 50 °C and 75 °C lower than CuMn2O4 wash-coated catalyst (WC-CuMn2O4) and Pd loaded catalyst (WC-Pd), respectively. Compared to monolithic catalysts with a traditional alumina support, the benefit of nanoarray morphology was demonstrated by correlating the variation of surface area to the reactivity. The incorporation of cobalt ions was found to increase the specific surface area and thus enhance C3H8 conversion of CuMn2O4. The CuMn2O4/MnO2 nanoarray-based monoliths are promising types of emission control devices.

Climate change, global warming, fossil fuel depletion and rising fuel prices have created great incentives to seek alternative fuel production technologies. CO transformation to value-added products using renewable H has proven to be an emerging solution to enable this goal. In this regard, three different promising processes, namely methane, methanol and hydrocarbon synthesis via CO hydrogenation are thoroughly discussed. In addition, the influential factors affecting process efficiencies such as catalyst design and mechanistic insight, operating conditions as well as reactor types are investigated, with key pathways that dictate catalyst activity and selectivity of the most promising materials described. Furthermore, a brief overview of the reactor configuration and its crucial role in the improving process viability is analyzed. Accordingly, fixed-bed, fluidized-bed, annular and spherical reactors along with HO/H perm-selective membrane reactors are disscussed for hydrocarbon production. In addition, different reactor configurations are compared to assess the best one that is adjustable depending on the reaction mechanism. Consequently, a corrugated-wall dual-type membrane reactor is proposed as an emerging alternative for CO hydrogenation to value-added products., This research has been supported by the NRDI Fund (TKP2020 NC, Grtant No. BME-NCS) based on the charter of bloster issued by the NRDI office under the auspices of the Ministry for Innovation and Technology. SLS acknowledges the support of the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical, Biological and Geological Sciences under grant DE-FG02-86ER13622.A000.

We report on the new facile synthesis of mesoporous NiO/MnO2 in one step by modifying inverse micelle templated UCT (University of Connecticut) methods. The catalyst shows excellent electrocatalytic activity and stability for both the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) in alkaline media after further coating with polyaniline (PANI). For electrochemical performance, the optimized catalyst exhibits a potential gap, ΔE, of 0.75 V to achieve a current of 10 mA cm–2 for the OER and −3 mA cm–2 for the ORR in 0.1 M KOH solution. Extensive characterization methods were applied to investigate the structure–property of the catalyst for correlations with activity (e.g., XRD, BET, SEM, HRTEM, FIB-TEM, XPS, TGA, and Raman). The high electrocatalytic activity of the catalyst closely relates to the good electrical conductivity of PANI, accessible mesoporous structure, high surface area, as well as the synergistic effect of the specific core–shell structure. This work opens a new aven...

In this study, metal organic chemical vapor deposition (MOCVD) was used to deposit zinc oxide (ZnO) for use as a ceramic matrix composite (CMC) interphase. ZnO coatings (400–500 nm) were deposited on 3 M Nextel™ 610 fabric by thermal decomposition of zinc acetate dihydrate in a low pressure hot wall CVD reactor. An α-alumina matrix was applied to the 8 ply fabric lay up for a total CMC porosity of 30% with 32% fiber volume. The morphology, structure and strength of the resulting continuous fiber CMC were characterized in conjunction with a control CMC with no interphase. The results show that when a zinc acetate dihydrate precursor is used, a functional interphase can be obtained. Flexural strength of the Oxide-Oxide CMC could be increased up to 30% upon addition of this oxide interphase with corresponding toughening mechanisms.

Manganese oxides have been widely used as deionization capacitor electrode materials to remove heavy metal ions from aqueous solutions. However, the effect of pseudocapacitive properties of manganese oxides on the removal processes remains elusive. In this work, synthesized nanostructured birnessite-type manganese oxide and birnessite/carbon nanotubes (HB/CNTs) nanocomposites were used as deionization pseudocapacitor electrode materials for Zn 2+ and Ni 2+ removal from aqueous solution by constant potential electrolysis. The effects of operation potential and introduction of carbon nanotubes (CNTs) on Zn 2+ and Ni 2+ removal capacities were further investigated. The results demonstrated a significant enhancement of electrochemical removal capacities for Zn 2+ and Ni 2+ by the pseudocapacitive properties of birnessite and the introduction of CNTs. The Zn 2+ and Ni 2+ removal capacities of birnessite electrode increased first and then decreased with the decrease of potential from 0.2 to −0.2 V ( vs . SCE), and the highest removal capacities for Zn 2+ and Ni 2+ respectively reached 89.5 and 96.6 mg g −1 when the potential was controlled at 0 V. The HB/CNTs nanocomposite showed higher removal capacities (155.6 mg g −1 for Zn 2+ and 158.4 mg g −1 for Ni 2+ when the relative content of manganese oxide was 45.6%) and a better cycling stability (about 90% and 88% of the initial Zn 2+ and Ni 2+ removal capacity were retained after 5 cycles) than birnessite electrode. The present study makes clear the pseudocapacitive mechanism of heavy metal ion removal using birnessite, and proposes a facile method to remove heavy metal ions from aqueous solution.

The construction of macroscopic 3D sponges is of great technological importance for various applications. An outstanding challenge is the facile fabrication of sponges with the desirable combination of good stability, high electrical conductivity, and absorption ability. Here free-standing 3D OMS-2 sponges are demonstrated, with various densities, which possess a combination of desirable physical properties including high porosity, robustness, permeability, recyclability, high electrical conductivity, and selective water absorption in preference to oil. Some of these properties have systematic trends with various densities. The stress of the OMS-2 sponge, made by nanowire-based freeze-drying process, is four orders of magnitude higher than that made by calcination-related process. These new materials should find practical applications in environmental, catalysis, sensing, absorption, and energy storage, particularly in the removal of water spill cleanup, and beyond.

Manganese oxides are metastable phases due to oxygen loss at high temperature. Conventional ceramic routes need high temperature and thus are unsuitable for making MnOx foams. A mild templating route at 300–400 °C was developed to construct metastable MnOx foams. Interwoven OMS-2 (cryptomelane) nanofibers with a length-diameter ratio of ca. 3000 over a template may create an OMS-2 foam at 400 °C with an atmosphere of 21% O2 content, a MnO/C foam at 400 °C with an atmosphere of 0% O2 content, OMS-2/Mn3O4 foams at 400 °C with an atmosphere of 1–5% O2 content, or Mn3O4/MnO2 foams at 300–350 °C in an atmosphere of 1% O2 content. Three foam materials are materials with ductility while others belong to brittle materials.

Adsorbents of mesoporous polymeric networks of divinylbenzene (PDVB) with different functionalities were synthesized by simple hydrothermal treatment of divinylbenzene (DVB) with co-monomers of vinylimidazole (VI) and 3-((3-(cyclohexylamino)propyl)thio)propyl methacrylate (ACAM) which resulted in P(DVB-VI) and P(DVB-ACAM) respectively. The CO2 adsorptive properties of PDVB were compared with the functionalized polymers. Although incorporation of ACAM monomer leads to loss of surface area, the functional groups of amine, thiol, and ester on P(DVB-ACAM) provide favorable sites for CO2 molecules to be adsorbed more efficiently in comparison with non-functionalized PDVB. The amine/thiol functionalized adsorbent, P(DVB-ACAM), also showed high selectivity and regenerability with the heat of adsorption of >70 kJ/mol indicating chemical interactions of active sites with CO2 at low adsorption limit and physical adsorption at higher adsorptions.

CO oxidation behavior of different manganese oxide materials was studied as a model probe reaction to benchmark catalytic activities that could be useful for other aerobic oxidations. K-OMS-2, which showed intermediate activity [Ea = 3.0 and 6.3 kcal/mol for K-OMS-2 (made in solvent free procedure or SF) and K-OMS-2 (made via hydrothermal route or REF) respectively], were chosen for metal dopant studies using microwave assisted hydrothermal synthesis. These were further characterized using X-ray diffraction (XRD), N2 sorption, Raman spectroscopy, scanning electron microscopy (SEM), and carbon monoxide temperature programmed reduction (CO-TPR). Additional characterization was carried out for Ni-K-OMS-2 materials using atomic absorption spectroscopy (AAS) and thermogravimetric analysis-mass spectroscopy (TGA-MS). Doping K-OMS-2 with Ni resulted in a large increase in oxygen mobility and re-adsorption, and the moderate activation energy for CO oxidation (13. kcal/mol) by Ni-K-OMS-2(SF) suggests that Ni-doped materials are good candidates for low temperature selective oxidation.

We report microwave assisted synthesis of a series of highly hydrophobic porous organic polymers of poly divinylbenzene (PDVB), for the first time, which were modified by amine-rich co-monomers of vinyl imidazole (VI) and vinyl triazole (VT) resulting in PDVB-VI and PDVB-VT adsorbents. There is an optimum amount of incorporated co-monomer and initiator which led to high adsorptive activity of the material towards CO2. Atmospheric CO2 adsorption was enhanced by the addition of amine moieties while maintaining an optimum surface area and pore volume. A certain amount of initiator led to better incorporation of VT monomer while surface area and pores remain accessible. A maximum CO2 adsorption of 2.65 mmolg -1 at 273 K/1 bar was achieved for triazole based adsorbent (PDVB-VT) with 0.7 g of VT and 0.07 g of initiator. In comparison with a non-functionalized material (PDVB) with 1.2 mmolg -1 CO2 uptake, the adsorption efficiency was enhanced more than twice. The adsorbent maintained its efficiency up to seven cycles. Theoretical modeling confirms the active site is nitrogen on the imidazole/triazole ring and that incorporation of VT to the polymeric networks enhanced the adsorptive properties better than vinyl imidazole (VI) due to more active sites.

There is an intense need for development in the field of hierarchically structured functional materials due to their outstanding and peculiar properties. Herein, three types of hexagonal Mn3O4 micro/nano hierarchical architectures were successfully prepared based on a self-assembly approach via a hydrothermal synthesis route at low temperature, which is sparse in the literature. These three types of hexagonal Mn3O4 micro/nano hierarchical architectures were constructed from different building block nanostructures. The formation mechanisms are discussed, and the electrochemical performances are investigated. Electrochemical studies show that Mn3O4 hierarchical architectures exhibit good specific capacitance and electrochemical stability, making them promising electrode materials for electrochemical capacitors.

The system hydrogen peroxide/sodium bicarbonate/manganese sulfate was used for the first time to epoxidize cyclopentene. Effects of parameters such as type and amount of solvent, ratio of hydrogen peroxide and manganese sulfate to cyclopentene, presence of additives, and reaction time and temperature on the selectivity to cyclopentene oxide were evaluated. Gas chromatography was used to quantify residual cyclopentene and produced cyclopentene oxide using the internal standard method. Type and amount of solvent, addition method, and temperature were important factors to increase the selectivity to cyclopentene oxide. Unlike previous reports on epoxidation of different substrates, additives like sodium acetate and salicylic acid did not improve the selectivity to cyclopentene oxide. One time, single-step addition of hydrogen peroxide/sodium bicarbonate to the solution of cyclopentene/solvent/manganese sulfate produced more cyclopentene oxide than stepwise addition. The maximum selectivity obtained was 56%, possibly due to the high reactivity of cyclopentene that causes the formation of oxidation products different to cyclopentene oxide, which were not detected in the analyzed phase.

The rational design of the Au–support electronic interaction is crucial for Au nanocatalysis. We herein report our observation of electronic perturbation at the Au–carbon interface and its application in controlling the reaction selectivity in styrene oxidation. Ultrasmall Au nanocatalysts were grown in situ on a nitrided carbon support where the nitrogen-doped carbon supports enriched the surface charge density and generated electron-rich Au surface sites. The Au–carbon interaction altered the binding behavior of C═C bonds to catalytic centers, leading to a solvent-polarity-dependent selectivity in C═C oxidation reactions. A high selectivity of 90% to benzaldehyde was achieved in an apolar solvent, and a selectivity of 95% to styrene epoxide was attained in a polar solvent. The Au–carbon electronic perturbation, originating from surface functional groups on the carbon support, may provide an alternative avenue to tune the selectivity and activity of more complex reactions in heterogeneous catalysis.

Two ternary mixed oxides, Ru-Mn-Ce and Ru-Co-Ce, were prepared by a co-precipitation method and used in the aerobic oxidation of alcohols to corresponding aldehydes (ketones). Interestingly, different catalytic results were obtained when these compounds were calcined. The calcination temperature had an adverse effect on the catalytic performance of Ru-Mn-Ce catalysts, while being beneficial to the Ru-Co-Ce catalysts. To illustrate these effects, these materials were characterized using X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Temperature-programmed reduction (TPR), Electron paramagnetic resonance (EPR) and other techniques. The data showed that ruthenium oxides were uniformly dispersed in the mixed oxides, and phase transformations occur after calcination. Mn3O4 was transformed to MnO2 for the Ru-Mn-Ce catalyst, while CoO(OH) was transformed to Co3O4 in the Ru-Co-Ce catalyst. The interactions between ruthenium oxides and Co (Mn)-Ce mixed oxides of the former strengthened while the latter weakened. 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. Under optimal reaction conditions, various kinds of alcohols were transformed to corresponding aldehydes (ketones) in high yields over the Ru-Mn-Ce catalyst suggesting these ternary oxides are environmental friendly and economical catalytic systems.

Tandem oxidation processes enabling one-pot multistep reactions received great attention as an efficient synthetic methodology for construction of complex molecules from simple substrates by a single operation. We report here tandem oxidative transformations of seven different functional groups (imine, imidazole, cyanide, amide, lactone, ester and olefin) from a single substrate (alcohol) by a single cesium promoted mesoporous manganese oxide catalyst (meso Cs/MnOx). High conversions were obtained with a broad range of substrates including aliphatic long chain alcohols. The catalyst can be reused without any loss of catalytic activity. We also demonstrated a unique multiple esterification reaction from a single aliphatic alcohol under aerobic atmospheric conditions catalyzed by meso Cs/MnOx.

Multiferroic properties of orthorhombically distorted perovskite rare-earth chromites, such as HoCrO 3 , are being investigated extensively in recent years. In the present work, we report on the effect of Fe substitution on the magnetic properties of HoCrO 3 thin films. Thin films of HoCrO 3 and HoCr 0.7 Fe 0.3 O 3 were fabricated via a solution route on platinized silicon substrates. Structural properties of the films were evaluated by X-ray diffraction and Raman spectroscopy techniques. The surface morphology and cross-sections of the films were examined using scanning electron microscopy. Optical band gaps of pure and Fe doped HoCrO 3 films are found to be 3.45 eV and 3.39 eV, respectively. The magnetization measurements show that the Neel temperatures (where Cr 3+ orders) for the HoCrO 3 and HoCr 0.7 Fe 0.3 O 3 films are 134 and 148 K, respectively. In a magnetic field of 2 T, the maximum entropy change and relative cooling power, two parameters to evaluate the magnetocaloric properties of a material, were 0.813 J/kg K at 11 K and 21.1 J/kg for HoCrO 3 film, in comparison with 0.748 J/kg K at 15 K and 26.8 J/kg for HoCr 0.7 Fe 0.3 O 3 film. To our knowledge, this is the first work exploring the band gap and magnetocaloric properties of rare-earth chromite thin films. These findings should inspire the development of rare-earth chromite thin films for temperature control of nanoscale electronic devices and sensors in the low temperature region (

One of the most promising approaches to produce sustainable energy is hydrogen evolution by water splitting. Since water electrolysis is limited by the high overpotential required for the water oxidation reaction, electrocatalysts are applied to reduce the activation energy necessary for this reaction. However, primary catalysts may chemically convert to other compounds during the reaction. Therefore, the physicochemical and electrochemical changes of catalysts used over a long time need to be investigated in detail to understand the real operating catalyst. In this work, we have observed long-term microstructural changes and amorphization of La 0.65 Sr 0.35 MnO 3 when used as a catalyst in water-electrolysis at near neutral pH. Microscopic and electrochemical analyses show that the catalyst changed at the molecular level. This study revealed that an entirely different catalyst evolved from the original material over the course of the water oxidation reaction. This observation revealed the importance of the study of the long-term stability and reactivity of La 0.65 Sr 0.35 MnO 3 toward the water oxidation reaction.

In this work, mesoporous aluminas (MAs) with uniform and monomodal pores were fabricated via a modified inverse micelle synthesis method, using a non-polar solvent (to minimize the effect of water content) and short reaction time (for a fast evaporation process). The effects of reaction times (4–8 h), surfactant chain lengths (non-ionic surfactants), and calcination temperatures and hold times (450–600 °C; 1–4 h) on the textural properties of MA were studied. The targeted pore sizes of MA were obtained in the range of 3.1–5.4 nm by adjusting the surfactant and reaction time. The surface area and pore volume were controlled by the calcination temperature and hold time while maintaining the thermal stability of the materials. The tuned MA of the large mesopore volume achieved 168 mg/g octamethylcyclotetrasiloxane (D4 siloxane) adsorption capacity, a 32% improvement compared to commercially activated alumina. After three adsorption recycles, the synthesized MA still maintained approximate 85% of its original adsorption capacity, demonstrating a sustainable adsorption performance and high potential for related industrial applications.