Xiubing Huang

Synthesis of confined Ag nanowires within mesoporous silica via double solvent technique and their catalytic properties.

Ag nanowires within the channels of mesoporous silica have been successfully synthesized via a double solvent technique, in which n-hexane is used as a hydrophobic solvent to disperse mesoporous silica and an AgNO(3) aqueous solution is used as a hydrophilic solvent to fill mesochannels. The morphology of the obtained Ag (nanowires, nanoparticles or nanorods) can be controlled by adjusting the concentration of AgNO(3) solution and the template pore size. HRTEM images demonstrate extensive Ag nanowires with several to tens of hundreds nanometers in length are deposited along the long axis of mesochannels when the atomic AgNO(3)/Si ratio is 0.090. When the atomic AgNO(3)/Si ratio is 0.068 or 0.11, there is a combination of Ag nanoparticles and nanowires; nanoparticles are mainly formed when the atomic AgNO(3)/Si ratio is higher than 0.14. Further, the catalytic results of the oxidation of styrene show that styrene oxide and benzaldehyde are the main products of the reaction, and the morphology and diversity of Ag in Ag/mesoporous silica composites have an effect on the conversion of styrene and selectivity of styrene oxide.

Hierarchically nanostructured MnCo2O4 as active catalysts for the synthesis of N-benzylideneaniline from benzyl alcohol and aniline

A facile and scaled-up synthesis route to hierarchically nanostructured transition metal oxides with desirable properties is of great practical importance because of their excellent performance as heterogeneous catalysts in organic synthesis. In this work, hierarchically nanostructured MnCo2O4 nanorods with multi-nanopores have been prepared by a facile co-precipitation method using oxalic acid as a precipitant and through their consequent removal by calcination. When evaluated as catalysts for the synthesis of N-benzylideneaniline from benzyl alcohol and aniline, the as-prepared hierarchically nanostructured MnCo2O4-500 nanorods possessed high conversion (90.9%) of benzyl alcohol and selectivity (95.4%) of N-benzylideneaniline at 60 °C even under air for 15 h, which can be attributed to the appropriate and similar ratios of Mn2+/Mn3+ (1.36:1) and Co2+/Co3+ (1.35:1) with excellent synergistic effects. The proposed mechanism reveals that the benzyl alcohol is initially dehydrogenated to benzaldehyde which then reacts with another molecule of aniline to form N-benzylideneaniline. The MnCo2O4-500 nanorods can also be easily recycled without significant loss in catalytic activity for at least 4 cycles. Our findings could provide some guidance on the design of nanostructured spinel-type metal oxide catalysts with better synergistic effects in organic synthesis.

A sustainable method toward melamine-based conjugated polymer semiconductors for efficient photocatalytic hydrogen production under visible light

The search for conjugated polymer photocatalysts for H2 production under visible light remains a key challenge. Reported herein is a conjugated polymer (i.e., melamine-terephthalaldehyde polymer (PMTPA)) derived from melamine and terephthalaldehyde precursors without an external solvent through a Schiff-base reaction. By adjusting the polymerization temperature, PMTPA with different sample colors and band gaps was obtained, which was further applied as a photocatalyst to investigate its activity in H2 evolution. A photocatalytic H2 evolution efficiency up to 58.1 μmol h−1 was observed over PMTPA polymerized at 250 °C under visible light (λ > 420 nm), which was about two times as high as that of C3N4. The Schiff-base reaction without external solvent conditions provides a facile strategy for the synthesis of conjugated polymeric semiconductors with better molecular engineering for advanced applications in the fields of catalysis, energy, and environmental remediation.

Controlled Synthesis of 3D Flower‐like Ni2P Composed of Mesoporous Nanoplates for Overall Water Splitting

Developing efficient non-noble metal and earth-abundant electrocatalysts with tunable microstructures for overall water splitting is critical to promote clean energy technologies for a hydrogen economy. Herein, novel three-dimensional (3D) flower-like Ni2 P composed of mesoporous nanoplates with controllable morphology and high surface area was prepared by a hydrothermal method and low-temperature phosphidation as efficient electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Compared with the urchin-like Nix Py , the 3D flower-like Ni2 P with a diameter of 5 μm presented an efficient and stable catalytic performance in 0.5 m H2 SO4 , with a small Tafel slope of 79 mV dec-1 and an overpotential of about 240 mV at a current density of 10 mA cm-2 with a mass loading density of 0.283 mg cm-2 . In addition, the catalyst also exhibited a remarkable performance for the OER in 1.0 m KOH electrolyte, with an overpotential of 320 mV to reach a current density of 10 mA cm-2 and a small Tafel slope of 72 mV dec-1 . The excellent catalytic performance of the as-prepared Ni2 P may be ascribed to its novel 3D morphology with unique mesoporous structure.

Ce1−x Cr x O2−δ Nanocrystals as Efficient Catalysts for the Selective Oxidation of Cyclohexane to KA Oil at Low Temperature under Ambient Pressure

The selective oxidation of C−H bonds in saturated hydrocarbons at low temperature with noble‐metal‐free heterogeneous catalysts is a profound challenge for the catalysis community. Here we report the facile synthesis of Ce1−xCrxO2−δ (x=0, 0.1, 0.2, 0.3, and 0.4) nanocrystals through a low‐temperature hydrothermal method. The catalytic activity of the as‐prepared catalysts was evaluated in the selective oxidation of cyclohexane to cyclohexanone/cyclohexanol using H2O2 as an oxidant at room temperature and 45 °C. The activity results were correlated with their phase structure, composition, surface areas, and surface element states with the help of X‐ray diffraction, N2 adsorption, transmission electron microscopy, X‐ray photoelectron spectroscopy, and UV/Vis spectroscopy. It was found that these Ce0.7Cr0.3O2−δ nanocrystals are highly active for the selective oxidation of cyclohexane to cyclohexanone/cyclohexanol using H2O2 as an oxidant at low temperature. In the presence of H2O2 at 45 °C for 5 h using Ce0.7Cr0.3O2−δ as a catalyst, the conversion of cyclohexane reaches 50.3 % and the total selectivity of cyclohexanol/cyclohexanone is 94.4 % with relative good reversibility for at least four cycles. Mechanistic investigation results show that the high activity can be attributed to the high Cr6+ content in the Ce1−xCrxO2−δ solid solutions and the formation of highly oxidative intermediates with H2O2.

Facile synthesis of Cu3(BTC)2/cellulose acetate mixed matrix membranes and their catalytic applications in continuous flow process

Metal–organic framework (MOF)-based mixed matrix membranes (MMMs) were fabricated by a combination of Cu3(BTC)2 MOF and polymer cellulose acetate. The cellulose acetate in the MMMs served as the matrix and the Cu3(BTC)2 MOF as the filler. The as-synthesized MMMs were utilized as a heterogeneous catalyst for aldehyde acetalization. The characterization techniques indicated that the Cu3(BTC)2 crystals were uniformly dispersed in the MMMs. The BET surface area of the Cu3(BTC)2-based MMM was measured to be 459 m2 g−1 at 60 wt% Cu3(BTC)2 loading. Furthermore, the MMMs served as an excellent catalyst under our continuous flow catalytic reaction conditions. The optimal catalytic result of benzaldehyde yield reached 94% with 60 wt% Cu3(BTC)2 loading of the MMMs at room temperature and the benzaldehyde diethyl acetal reached 0.59 mmol min−1 gCu-BTC−1.

Sub-nano CoOx attached onto WO3 for efficient photocatalytic and photoelectrochemical water oxidation

Here, a facile strategy is reported for attaching a sub-nano cobalt oxide catalyst onto a WO3 surface using Co-EDTA as precursor, which greatly improved the WO3 performance in OER to give a photocatalytic O2 evolution rate of 314.3 μmol h−1 and a photocurrent density of around 2.07 mA cm−2 at 1.3 V vs. Ag/AgCl in photoelectrochemical water oxidation.