Synergistic effect of coordinating interface and promoter for enhancing ammonia synthesis activity of Ru@N-C catalyst.

Triruthenium dodecacarbonyl (Ru3(CO)12) was applied to prepare the Ru-based ammonia synthesis catalysts. The catalyst obtained from this precursor exhibited higher activity than the other Ru salts owing to its unique atomic reorganization under mild temperatures. Herein, Ru3(CO)12 as a guest metal source incorporated into the pore of ZIF-8 formed the Ru@N-C catalysts. The results indicated that the Ru nanoparticle (1.7 nm) was dispersed in the confined N coordination environment, which can increase the electron density of the Ru nanoparticles to promote N[triple bond, length as m-dash]N bond cleavage. The promoters donate the basic sites for transferring the electrons to Ru nanoparticles, further enhancing ammonia synthesis activity. Ammonia synthesis investigations revealed that the obtained Ru@N-C catalysts exhibited obvious catalytic activity compared with the Ru/AC catalyst. After introducing the Ba promoter, the 2Ba-Ru@N-C(450) catalyst exhibited the highest ammonia synthesis activity among the catalysts. At 360 °C and 1 MPa, the activity of the 2Ba-Ru@N-C(450) is 16 817.3 µmol h-1 gRu-1, which is 1.1, 1.6, and 2 times higher than those of 2Cs-Ru@N-C(450) (14 925.4 µmol h-1 gRu-1), 2K-Ru@N-C(450) (10 736.7 µmol h-1 gRu-1), and Ru@N-C(450) (8604.2 µmol h-1 gRu-1), respectively. A series of characterizations were carried out to explore the 2Ba-Ru@N-C(450) catalysts, such as H2-TPR, XPS, and NH3-TPD. These results suggest that the Ba promoter played the role of an electronic and structural promoter; moreover, it can promote the NH3 desorption from the Ru nanoparticles.

In situ synthesis of Ag/Ag2O-cellulose/chitosan nanocomposites via adjusting KOH concentration for improved photocatalytic and antibacterial applications.

This work proposed a facile way to construct cellulose/chitosan-loaded Ag/Ag2O nanocomposite films (ACC) from alkali/urea solution by increasing the content of alkali KOH in the solvent. The saturated alkali and hydroxyl groups of the cellulose and chitosan chains were accelerated to convert AgNO3 to Ag0. Ag2O served as nuclei to lower the energy barrier. The formation of Ag/Ag2O nanoparticles (NPs) endowed the cellulose bio-reduced Ag composites with multifunction and stronger photocatalytic activity. Ag/Ag2O NPs with the diameter of 139-360 nm were uniformly dispersed in the composite films, resulting in superior mechanical properties (64.6 MPa) and thermal stability. Almost 92 % of methyl orange was degraded under UV-irradiation within 40 min by ACC. After 3 runs of degradation, the photocatalytic abilities of ACC remained. Moreover, the films exhibited good antibacterial activities. The width of inhibition zones around ACC reached 9.2-12 mm and 8.6-10.4 mm for S. aureus and E. coli. The strategy provided a new avenue to construct multifunctional cellulose/chitosan materials for various applications, such as wastewater treatment, and electrocatalysis.

A Study on the Static Magnetic and Electromagnetic Properties of Silica-Coated Carbonyl Iron Powder after Heat Treatment for Improving Thermal Stability.

In order to study the thermal stability of coated carbonyl iron powder (CIP) and its influence on magnetic properties, carbonyl iron powder was coated with a silica layer and then annealed in an air atmosphere at elevated temperatures. Transmission electron microscopy (TEM) analysis and Fourier transform infrared spectroscopy confirmed the existence of a silicon dioxide layer with a thickness of approximately 80~100 nm. Compared with uncoated CIP, the silicon-coated CIP still maintained a higher absorption performance after annealing, and the calculated impedance matching value Z only slightly decreased. It is worth noting that when the annealing temperature reached 300 °C, coercivity (Hc) increased, and the real and imaginary parts of the permeability decreased, which means that the silicon dioxide layer began to lose its effectiveness. On the contrary, the significant decrease in microwave absorption ability and impedance matching value Z of uncoated CIP after annealing were mainly because the newly formed oxide on the interface became the active polarization center, leading to an abnormal increase in permittivity. In terms of the incremental mass ratio after annealing, 2% was a tipping point for permeability reduction.

A new strategy to construct cellulose-chitosan films supporting Ag/Ag2O/ZnO heterostructures for high photocatalytic and antibacterial performance.

The industrial wastewater contaminants including dyes and bacteria have caused serious environmental pollutions. Herein, ternary Ag/Ag2O/ZnO heterostructure decorating cellulose-chitosan films were constructed via in situ synthesis. Cellulose and chitosan dissolved in alkali/urea solvent and regenerated in ethylene glycol to form cellulose/chitosan nanofiber network, which was an ideal supporter for ZnO and Ag nanoparticles and beneficial for recycle usage. The hydroxyl groups of cellulose and chitosan chains exposed and were utilized for the synthesis of Ag particles, as well as ZnO nanoparticles by biomineralization. The Ag/Ag2O/ZnO decorating cellulose/chitosan (AZ@CC) films exhibited excellent antibacterial activity against Staphylococcus aureus and Escherichia coli. The width of inhibition zones around AZ@CC films reached 10.0-19.6 mm and 12.4-15.0 mm for S. aureus and E. coli, respectively. Moreover, AZ@CC films exhibited good photocatalytic activity against methyl orange (MO), almost 97% degradation of methyl orange (MO) within 50 min was achieved with the assistance of AZ@CC film. Importantly, the nanocomposite films exhibited excellent tensile strength and thermal stability. This facile and eco-friendly approach provided a new route to utilize cellulose and chitosan advantages for constructing multifunctional materials.

One-step degradation of cellulose to 5-hydroxymethylfurfural in ionic liquid under mild conditions.

One-step conversion of cellulose to HMF (5-hydroxymethylfurfural) has been achieved by using metal chlorides (CrCl3, CuCl2, SnCl4, WCl6) in [BMIM]Cl. The effects of temperature, reaction time, amount of catalysts, and the purity of [BMIM]Cl on the performance have been studied and discussed in detail. More than 63% yield of HMF and 80% yield of TRS (total reducing sugar) were obtained in [BMIM]Cl with CrCl3 at 120 °C under atmospheric pressure. Filter paper and cotton were also used as a source for cellulose degradation to HMF, but only a moderate yield of HMF was obtained (40% for filter paper and 12% for cotton). The reutilization of this system was examined and the reaction mechanism was also discussed.

Oxidative degradation of chitosan to the low molecular water-soluble chitosan over peroxotungstate as chemical scissors.

Low molecular water-soluble chitosan was prepared by the depolymerization of chitosan in the presence of a series of catalysts with active W(O2) sites. Both the peroxo species [W2O3(O2)4]2- and {PO4[WO(O2)2]4}3- showed high efficiency in the degradation of chitosan, indicating that the degradation mechanism did not follow the radical mechanism. That means •OH is not the active species, which has been proven by the fluorescence spectra. H2O2 acted as an oxidant to regenerate the active W(O2) sites in the depolymerization of chitosan. The developed catalyst (TBA)3{PO4[WO(O2)2]4} is recoverable.

Conversion of cellulose to HMF in ionic liquid catalyzed by bifunctional ionic liquids.

A new kind of bifunctional ionic liquid catalysts was synthesized to degrade microcrystalline cellulose in [BMIM]Cl at atmospheric pressure. The effects of reaction temperature, amount of catalysts, reaction time, ionic liquid purity and cellulose concentration on conversion were investigated. At low temperature cellulose can be degraded with being heated in [BMIM]Cl by oil bath. Among the as-synthesized catalysts, Cr([PSMIM]HSO4)3 exhibited the best performance. The HMF yield of 53% and TRS yield of 94% can be achieved at 120 °C in [BMIM]Cl for 5 h over 0.05 g Cr([PSMIM]HSO4)3/2.0 g [BMIM]Cl with 95% cellulose conversion.