Novel synthesis of reed flower-like SmMnOx catalyst with enhanced low-temperature activity and SO2 resistance for NH3-SCR.

In this work, a novel co-precipitation coupled solvothermal procedure is proposed to prepare a SmMnOx catalyst (SmMnOx-CP + ST) with a reed flower-like structure for the selective catalytic reduction of NOx by NH3 (NH3-SCR). Over 90% NOx conversion and N2 selectivity was achieved at a low temperature range (25-200 °C), and 96% NOx conversion was achieved in the presence of 100 ppm SO2 at 75 °C. While the NH3-SCR of the SmMnOx catalysts prepared by co-precipitation (SmMnOx-CP) and solvothermal (SmMnOx-ST) methods performed much poorer than the SmMnOx-CP + ST catalyst. All catalysts were characterized by XRD, BET, SEM, XPS, H2-TPR, NH3-TPD, NOx-TPD, and FT-IR. The results revealed that the superior performance of the SmMnOx-CP + ST is due to the unique reed flower-like structure morphology, which endows the SmMnOx-CP + ST with the largest surface area, the strongest synergistic reaction of Sm and Mn, abundant surface oxygen species and surface active sites, and significantly enhances the redox ability. Furthermore, the amorphous reed flower-like structure showed strong short-range ordered interaction between the active components and weaken the formation of sulfates species. In addition, the highest content of Mn4+ and Mn3++Mn4+ greatly promotes the redox cycles of Sm2+↔Mn4+ and Sm2+↔Mn3+, and suppresses the production of sulfate species in the presence of SO2.

A facile route to synthesize n-SnO2/p-CuFe2O4 to rapidly degrade toxic methylene blue dye under natural sunlight.

In the present study, the n-SnO2/p-CuFe2O4 (p-CFO) complex was prepared by a two-step process. p-CFO synthesized by the molten salt method was coated with SnO2 synthesized by a facile in situ chemical precipitation method. The formation of n-SnO2/p-CFO was confirmed by powder X-ray diffraction (PXRD). Scanning electron microscopy (SEM) images showed that the sharp edges of uncoated pyramid-like p-CFO particles were covered by a thick layer of n-SnO2 on coated p-CFO particles. The complete absence of Cu and only 3 wt% Fe on the surface of the n-p complex observed in the elemental analysis using energy-dispersive X-ray spectroscopy (EDX) on the n-p complex confirmed the presence of a thick layer of SnO2 on the p-CFO surface. Diffuse reflectance spectroscopy (DRS) was employed to elucidate the bandgap engineering. The n-SnO2/p-CFO complex and p-CFO showed 87% and 58.7% methylene blue (MB) degradation in 120 min under sunlight, respectively. The efficiency of the n-p complex recovered after 5 cycles (73.5%) and was found to be higher than that of the uncoated p-CFO (58.7%). The magnetically separable property of the n-p complex was evaluated by using vibration sample magnetometry (VSM) measurements and it was confirmed that the prepared photocatalyst can be easily recovered using an external magnet. The study reveals that the prepared complex could be a potential candidate for efficient photodegradation of organic dyes under sunlight due to its efficient recovery and reusability owing to its magnetic properties.

Equivalence of difluorodichloromethane (CFC-12) hydrolysis catalyzed by solid acid(base) MoO3(MgO)/ZrO2.

In this paper, a solid acid(base) MoO3(MgO)/ZrO2 was prepared for the catalytic hydrolysis of difluorodichloromethane (CFC-12). The effects of the catalyst preparation method, calcination temperature, and hydrolysis temperature on the conversion rate of CFC-12 were studied. The catalysts were characterized by XRD, N2 isotherm adsorption desorption, NH3-TPD, and CO2-TPD. Meanwhile, the equivalence of the catalytic activity of MoO3(MgO)/ZrO2 for CFC-12 was studied. Research shows that the solid acid MoO3/ZrO2 and solid base MgO/ZrO2 catalyzed hydrolysis of CFC-12 is equivalent; the solid acid MoO3/ZrO2 is calcined at 600 °C for 3 h and the solid base MgO/ZrO2 is calcined at 600 °C for 6 h (co-precipitation) and 700 °C for 6 h (impregnated) at a catalytic hydrolysis temperature of 300-400 °C and CFC-12 concentration of 4%. The catalytic hydrolysis products obtained were CO, HCl, and HF, and the CFC-12 conversion rate almost reached 100%.

Enhancing high-rate and elevated-temperature properties of Ni-Mg co-doped LiMn2O4 cathodes for Li-ion batteries.

The improvements of cyclability and rate capability of lithium ion batteries with spinel LiMn2O4 as cathode are imperative demands for the large-scale practical applications. Herein, a nickel (Ni) and magnesium (Mg) co-doping strategy was employed to synthesize LiNi0.03Mg0.05Mn1.92O4 cathode material via a facile solid-state combustion approach. The effects of the Ni-Mg co-doping on crystalline structure, micromorphology and electrochemical behaviors of the as-prepared LiNi0.03Mg0.05Mn1.92O4 are investigated by a series of physico-chemical characterizations and performance tests at high-rate and elevated-temperature. The resultant LiNi0.03Mg0.05Mn1.92O4 has the intrinsic spinel structure with no any impurities, and exhibits an elevated average valence of manganese in comparison to the pristine LiMn2O4. Owing to the Ni and Mg dual-doped merits, the LiNi0.03Mg0.05Mn1.92O4 sample demonstrates a robust spinel structure and high first discharge specific capacity of 112.3 mAh g-1, whilst undergoing a long cycling of 1000 cycles at 1 C. At a high current rate of 20 C, the capacity of 91.2 mAh g-1 with an excellent retention of 77% is obtained after 1000 cycles. Even at 10 C under 55 °C, an excellent capacity of 97.6 mAh g-1 is also delivered. These results offer a new opportunity for developing high-performance lithium ion batteries with respect to the Ni-Mg co-doping strategy.

Enhancing the durable performance of LiMn2O4 at high-rate and elevated temperature by nickel-magnesium dual doping.

Various nickel and magnesium dual-doped LiNixMg0.08Mn1.92-xO4 (x ≤ 0.15) were synthesized via a modified solid-state combustion method. All as-prepared samples show typical spinel phase with a well-defined polyhedron morphology. The Ni-Mg dual-doping obviously decreases the lattice parameter that gives rise to the lattice contraction. Owing to the synergistic merits of metal ions co-doping, the optimized LiNi0.03Mg0.08Mn1.89O4 delivers high initial capacity of 115.9 and 92.9 mAh·g-1, whilst retains 77.1 and 69.7 mAh·g-1 after 1000 cycles at 1 C and high current rate of 20 C, respectively. Even at 10 C and 55 °C, the LiNi0.03Mg0.08Mn1.89O4 also has a discharge capacity of 92.2 mAh·g-1 and endures 500 cycles long-term life. Such excellent results are contributed to the fast Li+ diffusion and robust structure stability. The anatomical analysis of the 1000 long-cycled LiNi0.03Mg0.08Mn1.89O4 electrode further demonstrates the stable spinel structure via the mitigation of Jahn-Teller effect. Hence, the Ni-Mg co-doping can be a potential strategy to improve the high-rate capability and long cycle properties of cathode materials.

Facile Synthesis of Heterostructured WS2/Bi2MoO6 as High-Performance Visible-Light-Driven Photocatalysts.

In this paper, novel WS2/Bi2MoO6 heterostructured photocatalysts were successfully fabricated via a facile solvothermal growth method using pre-exfoliated layered WS2 nanoslices as a substrate. The structure, morphology, and optical properties of the as-prepared WS2/Bi2MoO6 samples were characterized by XRD, XPS, SEM, TEM (HRTEM), and UV-vis diffuse reflectance spectra (DRS). Results confirmed the existence of an excellent nanojunction interface between layered WS2 nanoslices and Bi2MoO6 nanoflakes. Under visible light (>420 nm), the WS2/Bi2MoO6 composites exhibit significantly enhanced photocatalytic activity compared with pure Bi2MoO6 toward the decomposition of rhodamine B (RhB). Meanwhile, the active species trapping experiments indicated that holes (h+) were the main active species during the photocatalytic reaction. The enhanced photocatalytic performance can be ascribed to the effective light harvesting, fast photogenerated electron-hole pairs separation, and excellent charge carrier transport of the WS2/Bi2MoO6 heterostructures. Moreover, the prepared WS2/Bi2MoO6 composites also show good structural and activity stability in repeatability experiments.