Design and synthesis of micron-sized spherical aggregates composed of hollow Fe2O3 nanospheres for use in lithium-ion batteries

A novel structure denoted a "hollow nanosphere aggregate" is synthesized by introducing nanoscale Kirkendall diffusion to the spray pyrolysis process. The hollow Fe2O3 nanosphere aggregates with spherical shape and micron size are synthesized as the first target material. A solid iron oxide-carbon composite powder that is prepared by a one-pot spray pyrolysis process is transformed into the hollow Fe2O3 nanosphere aggregates by sequential post-pyrolysis treatments under reducing and oxidizing atmospheres. The nanoscale Kirkendall diffusion plays a key role in the formation of the hollow Fe2O3 nanosphere aggregates with spherical shape and micron size. The unique structure of the hollow Fe2O3 nanosphere aggregates results in their superior electrochemical properties as an anode material for lithium ion batteries by improving the structural stability during cycling. The hollow metal oxide nanosphere aggregates with various compositions for wide applications including energy storage can be prepared by the simple fabrication method introduced in this study.

General formation of tin nanoparticles encapsulated in hollow carbon spheres for enhanced lithium storage capability

A new simple process for synthesis of heterogeneous yolk-shell microspheres is introduced. The core/shell-structured microspheres are prepared by a one-pot spray pyrolysis process. The removal of one kind of metal oxide by a dry process produces heterogeneous yolk-shell microspheres. The yolk-shell Sn@C microspheres show superior electrochemical properties as anode materials for lithium-ion batteries.

Design and Synthesis of Bubble-Nanorod-Structured Fe2O3-Carbon Nanofibers as Advanced Anode Material for Li-Ion Batteries

A structure denoted as a "bubble-nanorod composite" is synthesized by introducing the Kirkendall effect into the electrospinning method. Bubble-nanorod-structured Fe2O3-C composite nanofibers, which are composed of nanosized hollow Fe2O3 spheres uniformly dispersed in an amorphous carbon matrix, are synthesized as the target material. Post-treatment of the electrospun precursor nanofibers at 500 °C under 10% H2/Ar mixture gas atmosphere produces amorphous FeOx-carbon composite nanofibers. Post-treatment of the FeOx-carbon composite nanofibers at 300 °C under air atmosphere produces the bubble-nanorod-structured Fe2O3-C composite nanofibers. The solid Fe nanocrystals formed by the reduction of FeOx are converted into hollow Fe2O3 nanospheres during the further heating process by the well-known Kirkendall diffusion process. The discharge capacities of the bubble-nanorod-structured Fe2O3-C composite nanofibers and hollow bare Fe2O3 nanofibers for the 300th cycles at a current density of 1.0 A g(-1) are 812 and 285 mA h g(-1), respectively, and their capacity retentions measured from the second cycle are 84 and 24%, respectively. The hollow nanospheres accommodate the volume change that occurs during cycling. The unique structure of the bubble-nanorod-structured Fe2O3-C composite nanofibers results in their superior electrochemical properties by improving the structural stability during long-term cycling.

Kilogram-scale synthesis of Pd-loaded quintuple-shelled Co3O4 microreactors and their application to ultrasensitive and ultraselective detection of methylbenzenes

We report the kilogram-scale, simple, and cost-effective synthesis of Pd-loaded quintuple-shelled Co3O4 microreactors by spray drying of aqueous droplets containing cobalt nitrate, palladium nitrate, citric acid, and ethylene glycol and subsequent heat treatment. Highly viscous gel spheres containing Co and Pd salts were successfully converted into multi thin-shelled Co3O4 reactors uniformly loaded with Pd catalysts by the sequential combustion of carbon and decomposition of the metal salts from the outer to the inner regions during one-step heat treatment. The responses (resistance ratio) of the Pd-loaded quintuple-shelled Co3O4 microreactors to 5 ppm toluene and p-xylene were 30.8 and 64.2, respectively, and the selectivity values to toluene and p-xylene against ethanol interference (response ratio) were 14.5 and 30.1, respectively. The unprecedented high response and selectivity were attributed to the effective dissociation of less reactive methylbenzenes into more active smaller species assisted both by catalytic Co3O4 and Pd during the prolonged retention within the microreactors. Kilogram-scale preparation of noble metal-loaded multishelled microreactors and their unique gas-sensing characteristics based on a novel microreactor concept can pave a new way to design of high-performance gas sensors for practical applications.

Synergetic compositional and morphological effects for improved Na⁺ storage properties of Ni₃Co₆S₈-reduced graphene oxide composite powders

The electrochemical properties of binary transition metal sulfide-reduced graphene oxide (RGO) composite powders, relevant for their performance as anode materials in sodium ion batteries, were firstly studied. (Ni,Co)O-RGO composite powders prepared by spray pyrolysis are transformed into Ni3Co6S8-RGO composite powders by a simple sulfidation process. Plate-shape nanocrystals of nickel-cobalt sulfide (Ni3Co6S8) are uniformly distributed over the crumpled RGO structure. The discharge capacities of the Ni3Co6S8-RGO composite powders for 2(nd) and 100(th) cycles at a current density of 0.5 A g(-1) are 504 and 498 mA h g(-1), respectively. However, the discharge capacities of the bare Ni3Co6S8 powders for 2(nd) and 100(th) cycles are 522 and 125 mA h g(-1), respectively. The NiO-Co3O4 and (Ni,Co)O-RGO composite powders prepared by spray pyrolysis also show low discharge capacities of 122 and 119 mA h g(-1), respectively, after 100 cycles. The high structural stability of the Ni3Co6S8-RGO composite powders during repeated sodium ion intercalation/deintercalation processes results in excellent cycling and rate performances for Na(+) storage.

A highly efficient recombinant laccase from the yeast Yarrowia lipolytica and its application in the hydrolysis of biomass

A modified thermal asymmetric interlaced polymerase chain reaction was performed to obtain the first yeast laccase gene (YlLac) from the isolated yeast Yarrowia lipolytica. The 1557-bp full-length cDNA of YlLac encoded a mature laccase protein containing 519 amino acids preceded by a signal peptide of 19 amino acids, and the YlLac gene was expressed in the yeast Pichia pastoris. YlLac is a monomeric glycoprotein with a molecular mass of ~55 kDa as determined by polyacrylamide-gel electrophoresis. It showed a higher catalytic efficiency towards 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (kcat/Km = 17.5 s(-1) μM(-1)) and 2,6-dimethoxyphenol (kcat/Km = 16.1 s(-1) μM(-1)) than other reported laccases. The standard redox potential of the T1 site of the enzyme was found to be 772 mV. The highest catalytic efficiency of the yeast recombinant laccase, YlLac, makes it a good candidate for industrial applications: it removes phenolic compounds in acid-pretreated woody biomass (Populus balsamifera) and enhanced saccharification.

Sodium ion storage properties of WS₂-decorated three-dimensional reduced graphene oxide microspheres

Layered WS2 nanosheet-decorated three-dimensional reduced graphene oxide (3D-RGO) microspheres are prepared as anode materials for sodium ion batteries. WO3 nanocluster-decorated 3D RGO microspheres are transformed into multi-layered WS2-3D RGO microspheres by a simple sulfidation process. The WS2-3D RGO microspheres show Na(+) storage properties superior to those of the WO3-3D RGO microspheres.

Simultaneous pretreatment and saccharification: green technology for enhanced sugar yields from biomass using a fungal consortium

Two different biomasses were subjected to simultaneous pretreatment and saccharification (SPS) using a cocktail of hydrolytic and oxidizing enzymes. Application of a novel laccase as a detoxifying agent caused the removal of 49.8% and 32.6% of phenolic contents from the soaked rice straw and willow, respectively. Hydrolysis of soaked substrates using a newly developed fungal consortium resulted in saccharification yield of up to 74.2% and 63.6% for rice straw and willow, respectively. A high saccharification yield was obtained with soaked rice straw and willow without using any hazardous chemicals. The efficiency of each step related to SPS was confirmed by atomic force microscopy. The suitability of the developed SPS process was further confirmed by converting the hydrolysate from the process into bioethanol with 72.4% sugar conversion efficiency. To the best of our knowledge, this is the first report on the development of a less tedious, single-pot, and eco-friendly SPS methodology.

Formation of core-shell-structured Zn2SnO4-carbon microspheres with superior electrochemical properties by one-pot spray pyrolysis

Core-shell structured Zn2SnO4-carbon microspheres with different carbon contents are prepared by one-pot spray pyrolysis without any further heating process. A Zn2SnO4-carbon composite microsphere is prepared from one droplet containing Zn and Sn salts and polyvinylpyrrolidone (PVP). Melted PVP moves to the outside of the composite microsphere during the drying stage of the droplet. In addition, melting of the phase separated metal salts forms the dense core. Carbonization of the phase separated PVP forms the textured and porous thick carbon shell. The discharge capacities of the core-shell structured Zn2SnO4-carbon microspheres for the 2(nd) and 120(th) cycles at a current density of 1 A g(-1) are 864 and 770 mA h g(-1), respectively. However, the discharge capacities of the bare Zn2SnO4 microspheres prepared by the same process without PVP for the 2(nd) and 120(th) cycles are 1106 and 81 mA h g(-1), respectively. The stable and reversible discharge capacities of the Zn2SnO4-carbon composite microspheres prepared from the spray solution with 15 g PVP decrease from 894 to 528 mA h g(-1) as current density increases from 0.5 to 5 A g(-1).

Yolk–shell structured Gd2O3:Eu3+ phosphor prepared by spray pyrolysis: the effect of preparation conditions on microstructure and luminescence properties

Yolk–shell Gd₂O₃:Eu³⁺ phosphor powders with high photoluminescence intensity were prepared by spray pyrolysis. The formation mechanism of yolk–shell Gd₂O₃:Eu³⁺ was systematically investigated by observing the microstructures of particles produced under various preparation conditions.

Two-step spray-drying synthesis of dense and highly luminescent YAG:Ce3+ phosphor powders with spherical shape

Two-step spray drying using a commercially available spray dryer was carried out to prepare YAG:Ce³⁺ phosphor particles. The two-step spray-drying process was a potential method for producing YAG:Ce³⁺ phosphor particles with spherical shape, narrow size distribution, and good luminescence properties.

Synthesis of hollow cobalt oxide nanopowders by a salt-assisted spray pyrolysis process applying nanoscale Kirkendall diffusion and their electrochemical properties

A new concept for preparing hollow metal oxide nanopowders by salt-assisted spray pyrolysis applying nanoscale Kirkendall diffusion is introduced.

Superior lithium-ion storage properties of si-based composite powders with unique Si@carbon@void@graphene configuration

Composite powders of the configuration Si@carbon@void@graphene were prepared by a one-step spray pyrolysis process, by adding polyvinylpyrrolidone (PVP) to a precursor solution containing graphene oxide (GO) sheets and silicon nanoparticles (NPs). Morphological analysis indicates that the individual Si NPs are coated with amorphous carbon and encapsulated in a micrometer-sized graphene ball structure that offers a large amount of buffer space. The addition of PVP improves the stability of the colloidal spray solution containing the GO sheets and the Si NPs. Consequently, the prepared Si@C@void@graphene composite powders have a relatively more uniform morphology than the Si@void@graphene composite powders prepared from the spray solution without PVP. The first charge and discharge capacities of the Si@C@void@graphene electrode measured at 0.1 A g(-1) are as high as 3102 and 2215 mA h g(-1) , respectively. With an increase in the current rate from 0.5 to 11 A g(-1) , 46 % of the original capacity (i.e., 2134 mA h g(-1) ) is maintained. After 500 cycles at a high rate of 7 A g(-1) , the Si@C@void@graphene electrode shows 84 % capacity retention and 99.8 % of the average Coulombic efficiency. The superior cycling and rate capabilities of the prepared Si@C@void@graphene electrode could be attributed to the uniform carbon coating of the Si NPs and the graphene ball structure, which facilitates efficient diffusion of Li ions and prevents the penetration of electrolyte into graphene ball during cycling.

Controllable synthesis of yolk-shell-structured metal oxides with seven to ten components for finding materials with superior lithium storage properties

A new concept for discovering multicomponent nanostructured materials with good electrochemical properties is proposed. Yolk-shell-structured transition metal oxide powders with seven to ten components and simple crystal structures are prepared by continuous spray pyrolysis. The multicomponent yolk-shell powders with complex compositions show excellent Li(+) storage properties for lithium ion batteries.

Enhanced ethanol sensing characteristics of In2O3-decorated NiO hollow nanostructures via modulation of hole accumulation layers

In this work, we report a dramatic enhancement in ethanol sensing characteristics of NiO hollow nanostructures via decoration with In2O3 nanoclusters. The pure NiO and 1.64-4.41 atom % In-doped NiO and In2O3-decorated NiO hollow spheres were prepared by ultrasonic spray pyrolysis, and their gas sensing characteristics were investigated. The response (the ratio between the resistance in gas and air) of the In2O3-decorated NiO hollow spheres to 5 ppm ethanol (C2H5OH) was 9.76 at 350 °C, which represents a significant improvement over the In-doped NiO and pure NiO hollow spheres (3.37 and 2.18, respectively). Furthermore, the 90% recovery time was drastically reduced from 1880 to 23 s, and a selective detection of ethanol with negligible cross-response to other gases was achieved. The enhanced gas response and fast recovery kinetics were explained in relation to the thinning of the near-surface hole accumulation layer of p-type NiO underneath n-type In2O3, the change of charge carrier concentration, and the variation of oxygen adsorption.

Hierarchical MoSe₂ yolk-shell microspheres with superior Na-ion storage properties

Yolk-shell-structured MoSe₂ microspheres were prepared via a simple selenization process of MoO₃ microspheres. The yolk-shell-structured MoSe₂ and MoO₃ microspheres delivered initial discharge capacities of 527 and 465 mA h g(-1) in the voltage range of 0.001-3 V vs. Na/Na(+) at a current density of 0.2 A g(-1), respectively, and their discharge capacities after 50 cycles were 433 and 141 mA h g(-1), respectively. The yolk-shell-structured MoSe₂ microspheres also exhibited outstanding high rate capabilities. The hierarchical yolk-shell structure comprised of wrinkled nanosheets facilitated fast Na-ion and electron kinetics, and buffered the large volume changes encountered during cycling.