Latest ArticlesTwo-dimensional mesoporous materials combing ultrathin nanosheet morphology with well-defined mesoporous structures, are now emerging and becoming increasingly important for their promising applications in energy storage, electronic devices, electrocatalysts and so on. Here, we synthesized a kind of polypyrrole-based two-dimensional mesoporous materials with uniform pore size, ultrathin thickness and high surface area. Serving for electrochemical NH3 sensor, they exhibited a fast response and high sensitivity. Therefore, our study would promote much interest in design of new materials for gas sensor applications.
Surface chemical properties of supports have an important influence on active sites and their catalytic behavior. Here, we fabricated a series of cobalt-based catalysts supported by carbon layer-coated ordered mesoporous silica (OMS) composites for higher alcohol synthesis (HAS). The carbon layers were derived from different sources and uniformly coated on the porous surface of OMS. Combined with the characterization results of carbonized catalysts, it is demonstrated that the carbon layer-coated supports significantly enhanced the metal dispersion and increased the ratio of Co2+ to Co0 sites, which further increased the CO conversion and alcohols selectivity. Moreover, it is found that the catalytic activity changed in line with the amount of defects and surface oxygenic groups of carbon layers, which resulted from the different carbon sources. The highest space time yield of C2+OH was 27.5 mmol gcat-1 h-1) obtained by the catalyst coated with glucose-derived carbon layer. But the carbon source is not the key factor influencing the distribution of Co-Co2+ dual sites and shows little effect on selectivity in HAS. These results may guide for further design of carbon supported catalysts.
Developing low-cost and high performance catalysts to replace precious metal based catalysts for oxygen reduction reaction (ORR) is one of the most feasible ways to promote the commercial application of fuel cells. In this work, flower-like CoS and octahedral CoS2 are synthesized by a facile one-pot hydrothermal method without any adjunction of surfactants or follow-up thermolysis, their catalytic performance towards ORR in alkaline electrolyte are comparatively investigated. The results reveal that CoS2 outperforms CoS owing to the higher electron density around S-S bond of S22- in the crystal structure, which promotes the adsorption of oxygen on catalyst surface and facilitates the breakage of O-O bond in oxygen, leading to direct 4-electron transfer ORR. When CoS2 particles are dispersed on the surface of rGO with large surface area, their ORR performance could be further improved.
ZnO-CeO2/SBA-15 catalysts were prepared by two kinds of solid-state grinding method and used for the production of 1, 3-butadiene (1, 3-BD) from ethanol. A mixture of SBA-15 (with or without organic template) and metal precursors were ground in solid-state. The obtained catalysts were characterized by TG, N2 adsorption-desorption, TEM, XRD, Py-FTIR and NH3-TPD techniques. Superior dispersion of metal oxides and more exposed acid sites were achieved on the catalyst 10Zn1Ce5-AS with the presence of organic template in SBA-15 during the solid-state grinding process. The catalytic performance was evaluated in a fixed-bed reactor and a 1, 3-butadiene selectivity of as high as 45% is achieved. This is attributed to the coupling effect of Zn and Ce species in the mesopores of SBA-15, in which Zn promotes ethanol dehydrogenation and Ce enhances aldol-condensation, respectively. Additionally, solvent-free method inspires new catalyst synthesis strategy for the production of 1, 3-butadiene from ethanol.
The toxic organic dye contaminants in wastewater are extremely harmful to the ecosystem. Surface enhanced Raman scattering (SERS) is a technique with high sensitivity and chemical specificity which fulfills the requirements for monitoring dye contaminants in wastewater. However, as one of the common dye contaminants, methyl orange (MO) has very weak affinity to metallic surfaces and is difficult to be detected by SERS at low concentrations. Therefore, a new type of SERS substrate with Ag nanoparticle monolayer functionalized by mono-6-deoxy-6-thio-β-cyclodextrin (β-CD-SH) was prepared to efficiently capture and detect MO in wastewater with a limit of detection of 5×10-7 mol/L. The hydrophobic cavity of β-CD is responsible for the efficient trap and enrichment of MO on the Ag NPs surface, achieving a strong SERS signal of MO at low concentrations and at different pH values. This study provides new insight into designing a well-performed adsorbent for the capture and detection of organic contaminants.
Sulfamethazine (SMZ) is an important sulfonamide antibiotic. Although the concentration in the environment is small, it is harmful. The drug residues can be transferred, transformed or accumulated, affecting the growth of animals and plants. In this study, the integrated fixed-film activated sludge membrane bioreactor (IFAS-MBR) were constructed to investigate the performance and degradation mechanism of SMZ. The addition of SMZ had a significant impact on the removal of the chemical oxygen demand (COD) and ammonia nitrogen (NH4+-N). The optimal operating conditions were hydraulic retention time (HRT) at 10 h and solid retention time (SRT) at 80 d, respectively. On this basis, the effects of different SMZ concentrations on nutrient removal, degradation, and sludge characteristics were compared. The removal efficiency of SMZ increased with the increase of SMZ concentration. The maximum removal rate was as high as 87%. The SMZ dosage also had an obvious effect on sludge characteristics. As the SMZ concentration increased, the extracellular polymer substances (EPS) concentration and the membrane resistance both decreased, which were beneficial for the reduction of membrane fouling. Finally, seven kinds of SMZ biodegradation intermediates were identified, and the possible degradation pathways were speculated. The microbial community results showed that the microbial diversity and richness in the reactor decreased after adding SMZ to the influent. The relative abundance of Bacteroidetes, Actinobacteria, Saccharibacteria and Nitrospirae increased at the phylum level. Sphingobacteria and Betaproteobacteria became dominant species at the class level. The relative abundance of norankp-Saccharibacteria and Nitrospirae increased significantly, and norank-p-Saccharibacteria may be the dominant bacteria for SMZ degradation.
Constructing a Z-scheme is a significant approach to improve the separation of photogenerated carriers for effective organic pollutant degradation. Herein, a BiVO4/ZnIn2S4 (BZ) Z-scheme composite was successfully synthesized, and applied to photodegrade methyl orange (MO) irradiated by a LED lamp. Anchoring the BiVO4 on the ZnIn2S4 nanoparticles promoted the separation of photogenerated electronholes and broadened the light response range. The detailed characterizations, including surface morphology, elements valence state, and photocurrent performance, demonstrated that the enhanced separation of photogenerated carriers was the pivotal reason for the enhanced photocatalysis reaction. Benefiting from the excellent photocatalytic characteristics, the 5% mass ratio of BZ composite presented the highest MO degradation rate of 0.00997 min-1, which was 1.9 and 10.3 times greater than the virgin ZnIn2S4 and BiVO4, respectively. Furthermore, the BZ hybrid materials indicated a well photo-stability in the four recycling tests.
X-ray imaging functionalization of biodegradable polyesters is a great demand and challenge in biomedical applications. In this work, a strategy of in-chain functionalization through the combination of ring opening copolymerization and oxime "Click" postfunctionalization was developed towards X-ray opaque polylactide copolymers. A functionalized cyclic carbonate was first synthesized and used as comonomer of polylactide copolymers, which were subjected to postfunctionalization of oxime "Click" reaction towards iodinated polylactide copolymers. The chemical structure and physical properties of the target products were traced and confirmed. In vitro cytotoxicity evaluation with 3T3-Swiss albino by Alamar blue demonstrated a low cytotoxicity. The X-ray radiopacity was analyzed by Micro-CT and quantified by Hounsfield Units value, which could be tailorable by the feedstock. It is a promising X-ray visible implantable biomaterial in biomedical applications.
(C6H14N2)[NH4(ClO4)3] is a newly developed porous hybrid inorganic-organic framework material with easy access and excellent detonation performances, however, its thermal properties is still unclear and severely hampered further applications. In this study, thermal behaviors and non-isothermal decomposition reaction kinetics of (C6H14N2)[NH4(ClO4)3] were investigated systematically by the combination of differential scanning calorimetry (DSC) and simultaneous thermal analysis methods. In-situ FTIR spectroscopy technology was applied for investigation of the structure changes of (C6H14N2)[NH4(ClO4)3] and some selected referents for better understanding of interactions between different components during the heating process. Experiment results indicated that the novel molecular perovskite structure renders (C6H14N2)[NH4(ClO4)3] better thermal stability than most of currently used energetic materials. Under high temperatures, the stability of the cage skeleton constructed by NH4+ and ClO4- ionsdetermined the decomposition process rather than organic moiety confined in the skeleton. The simple synthetic method, good detonation performances and excellent thermal properties make (C6H14N2)[NH4(ClO4)3] an ideal candidate for the preparation of advanced explosives and propellants.
In this paper, we introduced a novel method to prepare the few-layer nitrogen-doped graphene (FNG) from expandable graphite with melamine. The super-capacitive properties of FNG were thoroughly characterized by a three-electrode system, and the results showed the FNG electrode achieved a specific capacitance as high as 83.8 mF/cm2 together with excellent cycling stability. This method could be a novel approach to combine the pseudo-capacitors and electric double layer capacitors.
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