Morphology-controlled synthesis and photocatalytic properties of K_(1.9)Na_(0.1)Ta_2O_6·2H_2O

The controllable synthesis of tantalate K1.9Na0.1Ta2O6·2H2O has been successfully achieved by a two-step technique,namely,the molten salt and hydrothermal methods,at a low temperature. By simply varying the KOH concentration in the hydrothermal process,K1.9Na0.1Ta2O6·2H2O particles with spherical,cuboctahedral,and durian-like morphologies were synthesized. The photocatalytic activity of the obtained samples for the degradation of rhodamine B was studied under ultraviolet light,which indicates that the photocatalytic properties of the samples are highly dependent on their morphologies. The K1.9Na0.1Ta2O6·2H2O nanospheres,with rough surfaces and the highest specific surface area,exhibit the best performance. The present work provides a unique approach for the controlled synthesis of tantalate photocatalysts,which are difficult to achieve through other synthetic approaches.

Enhancing the hydration reactivity of hemi-hydrate phosphogypsum through a morphology-controlled preparation technology

The distribution of water channels in the crystal morphology of type-α hemi-hydrated gypsum(α-HH) was theoretically detected to investigate the effect of water channels on the hydration reactivity of hemi-hydrate phosphogypsum(HPG). Results showed that water channels were mainly distributed in the cylinders of α-HH crystal,whereas no water channel existed in the conical surfaces parallel to the z-axis. Increasing the number of water channels was critical to enhance the hydration activity of HPG compared with the hydration reactivity of industrial HPG and type-α high-strength gypsum. Controlling the technological parameters of crystallization by concentration of liquid-phase SO_4^(2-) made it possible to obtain HPG which had the stumpy crystals of α-HH and high hydration reactivity.

Morphology-Controlled Growth of A1N One-Dimensional Nanostructures

Aluminum nitride （AIN） nanowires, serrated nanoribbons, and nanoribbons were selectively obtained through a simple chloride assisted chemical vapor deposition process. The morphologies of the products could be controlled by adjusting the deposition position and the flux of the reactant gas. The morphologies and structures of the AIN products were investigated in detail. The formation mechanism of the as-prepared different morphologies of AIN one-dimensional （ID） nanostructures was discussed on the basis of the experimental results.

Morphology-controlled synthesis of SrTiO_3 micro-scale particles

A novel and simple strategy of morphology-controlled Sr Ti O3（ST） micro-scale particle synthesis by the flux method is reported. Systematic experiments are designed to realize the tunable morphologies of the particles when the flux salt,sintering process, and the precursors are changed. The ST plates can be synthesized by plate-like Bi4Ti3O12（BIT） precursors in Na Cl flux. However, the as-synthesized Bi4Ti3O12 grains transform into reticular particles and finally into rods at higher temperature in Na Cl and KCl compounds. Besides, cubic ST particles are also prepared using different precursors as a comparative experiment. This study provides a strategy for further investigations in designing the morphology-controlled particles and efficient anisotropic materials of perovskite structure such as ferroelectric and photocatalyst.

Fabrication of morphology-controlled TiO_2 photocatalyst nanoparticles and improvement of photocatalytic activities by modification of Fe compounds

Our previous studies suggested that redox reaction proceeded separately on specific exposed crystal faces of TiO2 nanoparticles. Site-selective deposition of metal or metal oxide on TiO2 specific exposed crystal faces successfully proceeded using the unique reactivity properties on the surface of TiO2 nanoparticles under photoexcitation. A remarkable improvement ofphotocatalytic activity of shape- controlled brookite and rutile TiO2 nanorods with modification of Fe^3＋ compounds was observed under visible light. Crystal face-selective metal compound modification on exposed crystal faces of TiO2 nanorods with brookite and futile phases was successfully prepared. Brookite and rutile TiO2 nanorods prepared by site-selective modification with metal compounds should be ideal visible-light responsive TiO2 photocatalysts because of the remarkable suppression of back electron transfer from TiO2 to oxidized metal com- pounds on the surface of the TiO2 nanorod with a brookite or rutile phase. In this paper, the development of exposed crystal face-controlled TiO2 nanorods with rutile and brookite phases was described. The obtained rutile and brookite TiO2 nanorod, showing remarkably high activity for degra- dation of organic compounds compared with the photocatalytic activities of anatase fine particles （ST-01）, is one of the most active commercially available photocatalysts for environmental cleanup in Japan. The technology of visiblelight responsive treatment for morphology-controlled rutile and brookite TiO2 nanorods by crystal face-selective modification of Fe^3＋ compounds was also discussed in this paper. The Fe^3＋ compound-modified rutile and brookite TiO2 nanorods show much higher activity than conventional visible-light responsive N-doped TiO2, which is commercially available in Japan.

Solution-phase synthesis of inorganic nanostructures by chemical transformation from reactive templates

The solution-phase synthesis by chemical transformation from reactive templates has proved to be very effective in morphology-controlled synthesis of inorganic nanostructures. This review paper summarizes the recent progress in solution-phase synthesis of one-dimensional and hollow inorganic nanostructures via reactive templates, focusing on the approaches developed in our lab. The formation mechanisms based on reactive templates are discussed in depth to show the general concepts for the preparation processes. An outlook on the future development in this area is also presented.

Uniform-dispersed ZnS quantum dots loading on graphene as a promising anode for potassium-ion batteries

The potassium-ion batteries(PIBs)have become the promising energy storage devices due to their relatively moderate cost and plenteous potassium resources.Whereas,the main drawback of PIBs is unsatisfacto ry electrochemical perfo rmance induced by the larger ionic radius of potassium ion.Herein,we report a well-designed,uniform-dispersed,and morphology-controllable zinc sulfide(ZnS)quantum dots loading on graphene as an anode in the PIBs.The directed uniform dispersion of the in-situ growing ZnS quantum dots(~2.8 nm in size)on graphene can mitigate the volume effect during the insertionextraction process and shorten the migration path of potassium ions.As a result,the battery exhibits superior cycling stability(350.4 mAh/g over 200 cycles at 0.1 A/g)and rate performance(98.8 mAh/g at2.0 A/g).We believe the design of active material with quantum dot-minimized size provides a novel route into PIBs and contributes to eliminating the major electrode failure issues of the system.