TiO2 and Co Nanoparticle-Decorated Carbon Polyhedra as Efficient Sulfur Host for High-Performance Lithium-Sulfur Batteries.

Metal organic frameworks (MOFs)-derived porous carbon is proposed as a promising candidate to develop novel, tailorable structures as polysulfides immobilizers for lithium-sulfur batteries because of their high-efficiency electron conductive networks, open ion channels, and abundant central ions that can store a large amount of sulfur and trap the easily soluble polysulfides. However, most central ions in MOFs-derived carbon framework are encapsulated in the carbon matrix so that their exposures as active sites to adsorb polysulfides are limited. To resolve this issue, highly dispersed TiO2 nanoparticles are anchored into the cobalt-containing carbon polyhedras that are converted from ZIF-67. Such a type of TiO2 and Co nanoparticles-decorated carbon polyhedras (CCo/TiO2 ) provide more exposed active sites and much stronger chemical trapping for polysulfides, hence improving the sulfur utilization and enhancing reaction kinetics of sulfur-containing cathode simultaneously. The sulfur-containing carbon polyhedras decorated with TiO2 nanoparticles (S@CCo/TiO2 ) show a significantly improved cycling stability and rate capability, and deliver a discharge capacity of 32.9% higher than that of TiO2 -free S@CCo cathode at 837.5 mA g-1 after 200 cycles.

Application of the soluble salt-assisted route to scalable synthesis of ZnO nanopowder with repeated photocatalytic activity.

In this paper, the soluble salt-assisted route has been extended to the low-cost and scalable preparation of ZnO nanostructures via the simple oxidation of Zn-Na2SO4 mixture followed by washing with water. The as-prepared ZnO nanopowders are of nanoscaled size, hexagonal phase, and pure, without being stained by Na2SO4. Their optical band gap is 3.22 eV, exhibiting a red-shift of 0.15 eV in comparison with pure ZnO bulk, and their optical absorbance is strong in the region of 200-400 nm, suggesting their full utilization of most of the UV light in sunlight. The product shows evident photocatalytic activity in degradation of RhB under solar light irradiation, and then its solar light degradation efficiency is close to that under UV irradiation, indicating that there is a possibility of practical application. More importantly, the obtained ZnO nanoparticles, because of the quick precipitation by themselves in solution with no stirring, could be easily recycled without any accessorial means such as high-speed centrifuge. The low-cost and scalable preparation, high photocatalytic activity, and convenient recycling of this ZnO nanomaterial gives it potential in purifying waste water. Hence the interesting results in this study indicate the wide range of the soluble salt-assisted route for the industrial preparation of many other advanced nanomaterials.

Chemical functionalization of magnetic carbon-encapsulated nanoparticles based on acid oxidation.

Carbon-encapsulated nickel nanoparticles were used as the representative magnetic carbon-encapsulated nanoparticles for chemical functionalization. After oxidation with the mixed acid of H2SO4/HNO3 under a moderate ultrasonic bath, carboxylic acid groups (-COOH) were effectively generated on the fullerene-like carbon shells, which in turn were utilized to covalently link octadecylamine through an amide reaction. The whole chemical process is well characterized by many methods such as Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetry-differential scanning calorimetry, transmission electron microscopy, and so on, and the self-consistent experimental results were obtained. The results suggested that the magnetic nanoparticles could be well protected, while their magnetic properties could be utilized to guide the transfer of the grafted functional species on the particle surface. This provides many possibilities for potential applications in chemical and biochemical fields.

High-temperature anodized WO3 nanoplatelet films for photosensitive devices.

Anodization at elevated temperatures in nitric acid has been used for the production of highly porous and thick tungsten trioxide nanostructured films for photosensitive device applications. The anodization process resulted in platelet crystals with thicknesses of 20-60 nm and lengths of 100-1000 nm. Maximum thicknesses of approximately 2.4 microm were obtained after 4 h of anodization at 20 V. X-ray diffraction analysis revealed that the as-prepared anodized samples contain predominantly hydrated tungstite phases depending on voltage, while films annealed at 400 degrees C for 4 h are predominantly orthorhombic WO3 phase. Photocurrent measurements revealed that the current density of the 2.4 microm nanostructured anodized film was 6 times larger than the nonanodized films. Dye-sensitized solar cells developed using these films produced 0.33 V and 0.65 mA/cm2 in open- and short-circuit conditions.