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High mass loading Ni-decorated Co9S8 with enhanced electrochemical performance for flexible quasi-solid-state asymmetric supercapacitors
No full textAt present, it is a significant challenge to design electrode materials with both desirable electrochemical performance and high mass loading for supercapacitors by using a simple, efficient and safe method. With the introduction of Ni2+ ions, the hollow Ni-decorated Co9S8 nanospheres meeting the above requirements have been successfully synthesized by one-step electrodeposition method under a two-electrode system. As electrodes for supercapacitors, such Ni-decorated Co9S8 electrodes deliver an ultrahigh areal and volumetric specific capacitance of 5.64 F cm(-2) and 171.85 F cm(-3) at a current density of 1 mA cm(-2), superior rate capability (88.9% retention at a current density of 20 mA cm(-2)) and remarkable cycling stability with a capacitance retention of 89% after 8500 cycles. Also, the as-fabricated flexible quasi-solid-state asymmetric supercapacitors based on Nidecorated Co9S8 nanospheres and active carbon electrodes present high energy density. The practicability and operability of the device were successfully demonstrated by lighting up the LEDs with five different colors
Dynamics studies of O+ + H-2 -> OH+ + H reaction
No full textIn the present work, the long-range interaction potential part of potential energy surface (PES) of OH2+ system is revised and the new resulting PES apparently is more reasonable than the old one in the long-range part. Based on the new PES, the dynamics calculations of O+ + H-2 -> OH+ + H reaction are carried out at a state-to-state level of theory by using time-dependent quantum wave packet method with second order split operator in a collision energy range from 0.01 to 1.0 eV. The dynamic properties such as reaction probability, ro-vibrational resolved statereaction probability, integral cross section, differential cross section, and state specific rate constant are calculated and compared with available theoretical and experimental results. The results of ro-vibrational resolved state reaction probability reflect some dynamic properties such as resonances which is attributed to the deep well located on the reaction path. The vibrational resolved state reaction probability indicates that the excitation efficiency of the OH+ product is relatively low. The results of integral cross sections indicate that the present results are in better agreement with the experimental values than with previous theoretical calculations, especially in the low collision energy region. However, the state specific rate constant results underestimate the experimental values. The comparison betweenour calculations and the experimental results indicates that the contribution of the rotational excitation of H2 molecule should be included in the calculations. However, only the initial state v = 0, j = 0 is calculated in the present work. We suppose that the deviation of the present results from the experimental data is due to the fact that the rotational excitation of reactant isnot included in the present calculation. The differential cross section signals indicate that the complex-forming reaction mechanism isdominated in the case of low collision energy, but it transforms into abstract reaction mechanism as the collision energy further increases
Catalytic selective hydrogenation and rearrangement of 5-hydroxymethylfurfural to 3-hydroxymethyl-cyclopentone over a bimetallic nickel-copper catalyst in water
No full textThe selective hydrogenation and rearrangement of 5-hydroxymethylfurfural (5-HMF) to 3-hydroxymethyl-cyclopentone (HCPN) were studied over a MOF-derived bimetallic nickel-copper catalyst in water. The combination of nickel and copper dramatically improved the efficiency in both the selective hydrogenation of the carbonyl group of 5-HMF and the hydrogenative ring-rearrangement of the C5 ring, affording 70.3% yield for HCPN and 99.8% yield for the rearrangement products. Moreover, it was indicated that water acted as a solvent, reactant, and proton donor by dissociation at an elevated temperature, which supplied slightly acidic conditions and promoted the rearrangement reaction
Selective Hydrodeoxygenation of Guaiacol to Phenolics by Ni/Anatase TiO2 Catalyst Formed by Cross-Surface Migration of Ni and TiO2
No full textThe catalytic properties of physical mixtures of Ni particles (100-200 nm) with nanoparticles of anatase TiO2 (TiO2-A), ZrO2, Al2O3, rutile TiO 2 (TiO2-R), and CeO2 were investigated for the hydrodeoxygenation (HDO) of guaiacol. High selectivities to phenolics were obtained only for Ni mixed with anatase TiO2 (Ni and TiO2-A), while saturated hydro- carbons were the main products for the mixtures with other supports. By thermal treatment in hydrogen gas only at 300 degrees C or higher and subsequently separating the large Ni particles from the TiO2-A particles with a magnet, it was further discovered that there was migration of TiO 2 from TiO2-A onto the large Ni particles, resulting in an amorphous TiO2 overlayer on the Ni particles as evidenced by high-resolution TEM, and vice versa, migration of Ni onto TiO2-A. The TiO2 overlayer rendered the Ni particles completely inactive as a hydrogenation/hydrodeoxygenation catalyst. Conversely, the small amounts of Ni (<1.5 wt %) migrated onto TiO2-A formed highly dispersed Ni, undetectable by high-resolution TEM (<2 nm), that were remarkably highly active for HDO of guaiacol, producing selectively phenolics. Such highly selective HDO catalysts could also be formed by incipient wetness impregnation of Ni in loadings above 2 wt % onto the TiO2-A, but it was essential to pretreat the sample in H-2 at 300 degrees C or higher. Pretreatment in H-2 at 200 degrees C generated catalysts that produced saturated ring products. The activity of the impregnated catalysts, as measured by guaiacol conversion, increased linearly with Ni loading below 0.5 wt %. The activity continued to increase with Ni loading but more slowly up to 2 wt %, beyond which there was little further change. The results suggested that two types of Ni species existed on the TiO2-A surface. One type consisted of a cluster of Ni atoms that were dominant on larger Ni particles that were active in aromatic ring hydrogenation and hydrodeoxygenation. They were readily covered by reducible TiO2-A at 300 degrees C or higher due to the traditional strong metal support interaction (SMSI) effect and became inactive. Another type was clusters of a very small number of Ni atoms, perhaps one atom, that were present as highly dispersed Ni clusters interacting strongly with the defect sites of TiO2-A. The strong interaction of this type of Ni with the TiO2 defect deterred TiO, migration allowing surface exposed Ni atoms to catalyze the HDO of guaiacol with very high selectivities that were not characteristic of typical Ni particles
Organic polymorphs with fluorescence switching: direct evidence for mechanical and thermal modulation of excited state transitions
No full textHerein, we provide a direct observation of the modulation of the excited state transition under mechanical and thermal stimuli in the solid state by two organic polymorphs based on a tetraphenylethene derivative (APMOB). It enriches the insight in the research of stimuli responsive luminescent materials
Ligand-Mediated Reactivity in CO Oxidation of Niobium-Nickel Monoxide Carbonyl Complexes: The Crucial Roles of the Multiple Adsorption of CO Molecules
No full textThe heteronuclear metal oxide complexes are of great significance in heterogeneous catalytic oxidation of CO. However, previous studies are mainly focused on the composition of metal oxide, charge state, the support and the active oxygen species, with little attention paid to adsorbed CO ligands. Herein, the ligand-mediated reactivity in CO oxidation of niobium-nickel monoxide carbonyl complexes has been successfully identified. The NbNiO(CO)(n)(-) (n = 5-6) anions are determined to be O-bridged complexes. In contrast, the NbNiO(CO)(n)(-) (n = 7-8) anions are characterized to be eta(2)-CO2-tagged complexes. The crucial roles of the multiply adsorbed CO molecules that can facilitate not only the competitive binding with bridging oxygen atom to the transition metal centers but also the electron accumulation of transition metal atoms have been discovered. The fascinating results are of substantial importance to understand the mechanisms of CO oxidation over heteronuclear metal oxide under CO-rich feed condition
Candle soot: onion-like carbon, an advanced anode material for a potassium-ion hybrid capacitor
No full textAlthough potassium-ion storage technology has started to receive significant attention, its development is still in its infancy; thus, exploration of suitable electrode materials is critical at this stage. Herein, onion-like carbon (OLC) was obtained from the combustion soot as the candle burnt and used as a promising anode material for potassium-ion storage. This OLC delivered high reversible capacity and exhibited good rate performance and cycling stability. Taking advantage of these features, a potassium-ion hybrid capacitor (PIHC) with OLC as the battery-type anode and activated carbon as the capacitor-type cathode was constructed. The constructed device displayed the high energy density of 142W h kg(-1), the ultrahigh power output of 21 kW kg(-1), and a long cycling life (83% capacity retention after 6000 cycles). Thus, this device may simultaneously cater to the requirements of high power and high energy densities in a wide range of applications
Biochemical characterization of three new alpha-olefin-producing P450 fatty acid decarboxylases with a halophilic property
No full textBackground: The CYP152 family member OleT(JE) from Jeotgalicoccus sp. ATCC 8456 has been well-known to catalyze the unusual one-step decarboxylation of free fatty acids towards the formation of terminal alkenes. Efforts to tune up its decarboxylation activity for better production of biological alkenes have been extensively explored via approaches such as site-directed mutagenesis and electron source engineering, but with limited success. To gain more insights into the decarboxylation mechanism and reaction bifurcation (decarboxylation versus hydroxylation), we turned to an alternative approach to explore the natural CYP152 resources for a better variety of enzyme candidates.
Results: We biochemically characterized three new P450 fatty acid decarboxylases including OleT(JH), OleT(SQ) and OleT(SA), with respect to their substrate specificity, steady-state kinetics, and salt effects. These enzymes all act as an OleT(JE)-like fatty acid decarboxylase being able to decarboxylate a range of straight-chain saturated fatty acids (C-8-C-20) to various degrees. Site-directed mutagenesis analysis to the lower activity P450 enzyme OleT(SA) revealed a number of key amino acid residues within the substrate-binding pocket (T47F, I177L, V319A and L405I) that are important for delicate substrate positioning of different chain-length fatty acids and thus the decarboxylation versus hydroxylation chemoselectivity, in particular for the mid-chain fatty acids (C-8-C-12). In addition, the three new decarboxylases exhibited optimal catalytic activity and stability at a salt concentration of 0.5 M, and were thus classified as moderate halophilic enzymes.
Conclusion: The P450 fatty acid decarboxylases OleT(JE), OleT(JH), OleT(SQ) and OleT(SA) belong to a novel group of moderate halophilic P450 enzymes. OleT(JH) from Jeotgalicoccus halophilus shows the decarboxylation activity, kinetic parameters, as well as salt tolerance and stability that are comparable to OleT(JE). Site-directed mutagenesis of several key amino acid residues near substrate-binding pocket provides important guidance for further engineering of these P450 fatty acid decarboxylases that hold promising application potential for production of alpha-olefin biohydrocarbons
High Anti-Interfering Profiling of Endogenous Glycopeptides for Article Human Plasma by the Dual-Hydrophilic Metal-Organic Framework
No full textGlycopeptidome profiling provides large-scale information about the glycosylation level of endogenous peptides, reflecting the dynamic processes of disease occurrences and developments. However, endogenous glycopeptides are usually submerged in complex fluids containing a wide variety of interference molecules, such as high concentration proteins, nonglycopeptides, and salts, which confounds attempts to identify glycopeptidome. Here, a dual hydrophilic metal organic framework is developed to selectively capture endogenous glycopeptides in complex biological fluid. The hydrophilic matrix material provides specific selectivity toward glycopeptides, while the deliberate surface regulation using hydrophilic species enhances its interaction with glycopeptides. This hydrophilic probe presents an extremely high performance in anti-interfering enrichment of glycopeptides from mimic complex samples, even when the molar ratio of immunoglobulin G versus bovine serum albumin was up to about 1:5000. More excitingly, in the practical application of glycopeptidome analysis, a total of 380 endogenous N-glycopeptides with 180 unique N-glycopeptide sites were identified from human plasma. This strategy is expected to broaden the application of dual-hydrophilic MOF-based materials, especially in dealing with the challenges of extremely complex biological samples
Transcriptome profile of polycyclic aromatic hydrocarbon-degrading fungi isolated from Taxus rhizosphere
No full textThe present study aims to examine polycyclic aromatic hydrocarbon (PAH)-degrading fungal strains isolated from rhizosphere soil of Taxus mairei. Talaromyces verruculosus strain DJTU-SJ5 showed the higher PAH degradation than other strains. Improved degradation of five PAHs was attained using the two-member consortium. The industrial potential of DJTU-SJ5 has been highlighted. The transcriptome profiles of DJTU-SJ5 before and after PAH challenge were decoded by high-throughput RNA sequencing. A total of 33,084 unigenes were obtained by de novo assembly of 19.9 Gb clean sequencing reads; 10,532, 1,104 and 11,779 unigenes were expressed distinctly between control and phenanthrene (phen)-treated samples; control and pyrene (pyre)-treated samples, and phen and pyre respectively. These included numerous PAH degradation, defence and stress-related genes. The degradation pathway of PAHs in strain DJTU-SJ5 is proposed based on the metabolites and transcriptome analyses