Multivalent Sulfur Vacancy-Rich NiCo2 S4 @MnO2 Urchin-Like Heterostructures for Ambient Electrochemical N2 Reduction to NH3.

Innovative advances in the exploitation of effective electrocatalytic materials for the reduction of nitrogen (N2 ) to ammonia (NH3 ) are highly required for the sustainable production of fertilizers and zero-carbon emission fuel. In order to achieve zero-carbon footprints and renewable NH3 production, electrochemical N2 reduction reaction (NRR) provides a favorable energy-saving alternative but it requires more active, efficient, and selective catalysts. In current work, sulfur vacancy (Sv)-rich NiCo2 S4 @MnO2 heterostructures are efficaciously fabricated via a facile hydrothermal approach followed by heat treatment. The urchin-like Sv-NiCo2 S4 @MnO2 heterostructures serve as cathodes, which demonstrate an optimal NH3 yield of 57.31 µg h-1  mgcat -1 and Faradaic efficiency of 20.55% at -0.2 V versus reversible hydrogen electrode (RHE) in basic electrolyte owing to the synergistic interactions between Sv-NiCo2 S4 and MnO2 . Density functional theory (DFT) simulation further verifies that Co-sites of urchin-like Sv-NiCo2 S4 @MnO2 heterostructures are beneficial to lowering the energy threshold for N2 adsorption and successive protonation. Distinctive micro/nano-architectures exhibit high NRR electrocatalytic activities that might motivate researchers to explore and concentrate on the development of heterostructures for ambient electrocatalytic NH3 generation.

Heteroatom-doped hollow carbon spheres made from polyaniline as an electrode material for supercapacitors.

In this work, novel heteroatom-doped hollow carbon spheres (HHCSs) were prepared via the carbonization of polyaniline hollow spheres (PHSs), which were synthesized by one-pot polymerization. It was found that the carbonized PHSs at 700 °C exhibit high specific capacitance of 241 F g-1 at a current density of 0.5 A g-1 and excellent rate capability. The excellent electrochemical performance can be attributed to the heteroatom-doping and hollow carbon nanostructure of the HHCSs electrodes. Heteroatom groups in the HHCSs not only improve the wettability of the carbon surface, but also enhance the capacitance by addition of a pseudocapacitive redox process. Their unique structure provides a large specific surface area along with reduced diffusion lengths for both mass and charge transport.

Coupling of Bifunctional CoMn-Layered Double Hydroxide@Graphitic C3 N4 Nanohybrids towards Efficient Photoelectrochemical Overall Water Splitting.

The development of durable, low-cost, and efficient photo-/electrolysis for the oxygen and hydrogen evolution reactions (OER and HER) is important to fulfill increasing energy requirements. Herein, highly efficient and active photo-/electrochemical catalysts, that is, CoMn-LDH@g-C3 N4 hybrids, have been synthesized successfully through a facile in situ co-precipitation method at room temperature. The CoMn-LDH@g-C3 N4 composite exhibits an obvious OER electrocatalytic performance with a current density of 40 mA cm-2 at an overpotential of 350 mV for water oxidation, which is 2.5 times higher than pure CoMn-LDH nanosheets. For HER, CoMn-LDH@g-C3 N4 (η50 =-448 mV) requires a potential close to Pt/C (η50 =-416 mV) to reach a current density of 50 mA cm2 . Furthermore, under visible-light irradiation, the photocurrent density of the CoMn-LDH@g-C3 N4 composite is 0.227 mA cm-2 , which is 2.1 and 3.8 time higher than pristine CoMn-LDH (0.108 mA cm-2 ) and g-C3 N4 (0.061 mA cm-2 ), respectively. The CoMn-LDH@g-C3 N4 composite delivers a current density of 10 mA cm-2 at 1.56 V and 100 mA cm-2 at 1.82 V for the overall water-splitting reaction. Therefore, this work establishes the first example of pure CoMn-LDH and CoMn-LDH@g-C3 N4 hybrids as electrochemical and photoelectrochemical water-splitting systems for both OER and HER, which may open a pathway to develop and explore other LDH and g-C3 N4 nanosheets as efficient catalysts for renewable energy applications.

Methanobactin-mediated synthesis of bimetallic Au-Pd/Al2O3 toward an efficient catalyst for glucose oxidation.

A green bioreductive approach with methanobactin was adopted to fabricate bimetallic Au-Pd/Al2O3 catalysts for solvent-free oxidation of glucose to gluconic acid with H2O2 at atmospheric pressure. The catalyst was characterised by diffuse reflectance UV-vis spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction techniques to understand synergistic interactions between Au and Pd. Effects of Au to Pd molar ratio on the catalytic activity of Au-Pd/Al2O3 were investigated. The Au-Pd/Al2O3 catalyst with Au/Pd molar ratio of 0.8:0.2 exhibited excellent catalytic performance. With the catalyst, the oxidation activities of glucose to gluconic acid 2856 mmol min-1 g-1 and selectivity 99.6% were attained at 323 K with H2O2. The results indicated the activity and selectivity was affected by the ratio of Au/Pd on the Al2O3. The formation of Au0.8Pd0.2/Al2O3 was favourable for the catalytic reaction.

Ultrasonic-assisted ultra-rapid synthesis of monodisperse meso-SiO2@Fe3O4 microspheres with enhanced mesoporous structure.

A core-shell-type of meso-SiO2@Fe3O4 microsphere was synthesized via an ultrasonic-assisted surfactant-templating process using solvothermal synthesized Fe3O4 as core, tetraethoxysilane (TEOS) as silica source, and cetyltrimethyl ammonium bromide (CTAB) as templates. The samples were characterized by FT-IR, XRD, TEM, N2 adsorption-desorption technology, and vibrating sample magnetometer (VSM). The results show that as-prepared meso-SiO2@Fe3O4(E) and meso-SiO2@Fe3O4(C) microspheres, treated by acetone extraction and high temperature calcination, respectively, still maintain uniform core-shell structure with desirable mesoporous silica shell. Therein, the meso-SiO2@Fe3O4(E) microspheres possess a distinct pore size distribution in 1.8-3.0 nm with large specific surface area (468.6 m(2)/g) and pore volume (0.35 cm(3)/g). Noteworthily, the coating period of this ultrasonic-assisted method (40 min) is much shorter than that of the conventional method (12-24 h). The morphology of microspheres and the mesoporous structure of silica shell are significantly influenced by initial concentration of CTAB (CCTAB), ultrasonic irradiation power (P) and ultrasonic irradiation time (t). The acceleration roles of ultrasonic irradiation take effect during the whole coating process of mesoporous silica shell, including hydrolysis-condensation process of TEOS, co-assembly of hydrolyzed precursors and CTAB, and deposition of silica oligomers. In addition, the use of ultrasonic irradiation is favorable for improving the homogeneity of silica shell and the monodispersity of meso-SiO2@Fe3O4 microspheres.

[In situ diffuse reflectance FTIR spectroscopy study of CO adsorption on Ni2P/mesoporous molecule sieve catalysts].

Abstract The supported nickel phosphate precursors were prepared by incipient wetness impregnation using nickel nitrate as nickel source, diammonium hydrogen phosphate as phosphorus source, and MCM-41, MCM-48, SBA-15 and SBA-16 as supports, respectively. Then, the supported Ni2 P catalysts were prepared by temperature-programmed reduction in flowing Hz from their nickel phosphate precursors. The in situ diffuse reflectance FTIR spectroscopy (DRIFTS) analysis with the probe molecule CO was carried out to characterize the surface properties. The results indicated that there were significant differences in the spectral features of the samples. The upsilon(CO) absorbances observed for adsorbed CO on mesoporous molecule sieve was attributed to weak physical adsorption. There are four different kinds of upsilon(CO) absorbances observed for adsorbed CO on Ni2 P/MCM-41 catalyst with the following assignments: (1) the formation of Ni(CO)4 at 2055 cm(-1). (2) CO terminally bonded to cus Ni(delta+) (0

Preparation of Ni-based metal monolithic catalysts and a study of their performance in methane reforming with CO2.

A series of Ni/SBA-15/Al(2)O(3)/FeCrAl metal monolithic catalysts with Ni loadings varying between 3 % and 16 % were prepared, and their structure was characterized by various techniques. The catalytic activity of the catalyst for methane reforming with CO(2) leading to synthesis gas was evaluated using a fixed-bed reactor. The results indicate good catalytic activity of the Ni/SBA-15/Al(2)O(3)/FeCrAl samples under the reaction conditions. The catalyst with a Ni loading of 8.0 % displays excellent activity and stability at 800 degrees C over 1400 h time on stream. After reaction, the hexagonal mesoporous structure of SBA-15 is still present and the pore walls of SBA-15 prevent the aggregation of nickel. Interactions between NiO, SBA-15, and the Al(2)O(3)/FeCrAl support modify the redox properties of the Ni/SBA-15/Al(2)O(3)/FeCrAl catalysts.

Preparation of Pd-based metal monolithic catalysts and a study of their performance in the catalytic combustion of methane.

A series of Pd/SBA-15/Al2O3/FeCrAl and Pd/5 wt% Ce(1-x)Zr(x)O2/SBA-15/Al2O3/FeCrAl (x = 0-1) metal monolithic catalysts were prepared and characterized by various techniques. The catalytic activity and the stability of the catalysts for methane combustion were evaluated. All the catalysts retain the SBA-15 mesoporous structure, with PdO being confined in its channels. The results show that the addition of Ce(1-x)Zr(x)O2 as promoters can improve the activity and stability of the catalysts. The stabilities of the metal monolithic catalysts are much better than those of Pd/ SBA-15 particle catalysts. The catalyst with ZrO2 as promoter exhibits the best activity and stability (T90= 395 degrees C), and the conversion of methane remains constant during the 700 h test.

Preparation and characterization of tungsten carbide confined in the channels of SBA-15 mesoporous silica.

A series of WO3/SBA-15 materials with different Si/W ratios have been prepared by impregnating the host material SBA-15 with aqueous ammonium paratungstate solutions. After temperature-programmed carburization (TPC) in flowing CH4/H2 (20/80 v/v mixture), the materials are converted to the corresponding W2C/SBA-15 species. Both the oxide and carbide materials are characterized using X-ray diffraction, nitrogen adsorption-desorption, 29Si NMR spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and TEM measurements. The XRD results show that after impregnation with different amounts of tungsten and subsequent carburization, the materials retain the mesopore structure of SBA-15. The nitrogen adsorption-desorption results indicate that a thin layer of W2C covers the internal walls of SBA-15. Quantitative 29Si single-pulse excitation MAS experiments and FTIR spectroscopy show that the incorporation of W2C in the channels of SBA-15 is correlated with the formation of Si-O-W bonds. Some Si-O-W bonds are transformed into Si-O-H bonds after carburization. The TEM results show that the thickness of the W2C thin layer is 1.7-1.9 nm in W2C/SBA-15. A model involving a discrete W2C thin layer in the channels of SBA-15 is proposed on the basis of the NMR data. The calculated thickness of the discrete W2C thin layer is consistent with value given by HRTEM.

Study of the inclusion processes of styrene and alpha-methyl-styrene in beta-cyclodextrin.

The inclusion complexes of styrene and alpha-methyl-styrene with beta-cyclodextrin (beta-CD) were investigated by using [1H] NMR titration in solution and X-ray diffraction (XRD) analysis, thermo-gravimetric analysis (TGA), elemental analysis (EA) in the solid state. The inclusion process has been studied by using PM3 quantum-mechanical semi-empirical method. The calculated results are in agreed with the experimental data. All results show that alpha-methyl-styrene has stronger interaction with beta-cyclodextrin than styrene does, so the complex of beta-CD-alpha-methyl-styrene is more stable.

CeO2-promoted W-Mn/SiO2 catalysts for conversion of methane to C3-C4 hydrocarbons at elevated pressure.

A CeO2-doped Na-Mn-W/SiO2 catalyst for oxidative conversion of methane has been studied in a micro-stainless-steel reactor under elevated pressure; a CH4 conversion of 47.2% with a C3-C4 selectivity of 47.3% (C2:C3:C4 = 1:1:3.3) was obtained at 983 K with 1.0 x 10(5) ml g-1 h-1 GHSV, CH4/O2 = 2.5 and P = 0.6 MPa.