Junhua Hu

Three-dimensional Porous Networks of Ultra-long Electrospun SnO2 Nanotubes with High Photocatalytic Performance

Recent progress in nanoscience and nanotechnology creates new opportunities in the design of novel SnO2 nanomaterials for photocatalysis and photoelectrochemical. Herein, we firstly highlight a facile method to prepare three-dimensional porous networks of ultra-long SnO2 nanotubes through the single capillary electrospinning technique. Compared with the traditional SnO2 nanofibers, the as-obtained three-dimensional porous networks show enhancement of photocurrent and photocatalytic activity, which could be ascribed to its improved light-harvesting efficiency and high separation efficiency of photogenerated electron–hole pairs. Besides, the synthesis route delivered three-dimensional sheets on the basis of interwoven nanofibrous networks, which can be readily recycled for the desirable circular application of a potent photocatalyst system.

OPTICAL AND ELECTRONIC PROPERTIES OF M2Si (M = Mg, Ca, Sr) GROWN BY REACTIVE DEPOSITION TECHNIQUE

Single phase M2Si (M = Mg, Ca, Sr) silicides were grown using Si substrates, by thermal treatment of the substrates in the vapors of the metallic sources, M, and the electronic structures and optical property of the silicides were investigated. The electronic band structures of the silicides were calculated using the first-principles total-energy calculation program in pseudopotential schemes with plane-wave basis functions. The calculated optical reflectance spectra were also deduced from the theoretical band structures, and roughly agreed with the experimental results except for the low reflectance intensity around 2 eV. This suggests that the energy band gap of the silicides roughly agree with the calculated values of 0.15, 0.31 and 0.35 eV for Mg2Si, Ca2Si and Sr2Si, respectively, within the underestimation of the band gap by the density functional calculation. The optical property of the silicides is also discussed in relation to the morphological structures of the silicides.

Pinecone biomass-derived hard carbon anodes for high-performance sodium-ion batteries

Hard-carbon is considered as one of the most promising anode materials for sodium-ion batteries (SIBs). Now it is imperative to develop a proper preparation method to obtain hard carbon anode particles with high initial coulombic efficiency and good cycling performance. In this paper, we have successfully prepared high performance hard carbon anodes, by selecting abundant and low-cost pinecones as biomass precursor and optimizing the preparation parameters of pinecone-derived hard carbon (PHC). The microstructure of PHC is studied by X-ray diffraction (XRD), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM) as well as nitrogen adsorption–desorption isotherm methods. The performance of PHC is highly dependent on the carbonization temperature. Increasing carbonization temperature of pinecone precursor can reduce surface area and thus improve the initial coulombic efficiency. Varying carbonization temperature can also adjust the slope and plateau capacity of PHC, and then regulate the energy density and power characteristics of PHC in battery operation. PHC1400 still delivers a capacity of 334 mA h g−1 after 120 cycles, with a high initial coulombic efficiency of 85.4%. Our results suggest that PHC is a promising anode material for practical large-scale SIB application.

In situ coupling of Ti2O with rutile TiO2 as a core–shell structure and its photocatalysis performance

The fabrication of high-performance, low-cost photocatalysis materials, which absorb in the visible-light region, is of significance for their practical applications. A Ti2O@TiO2 (rutile) core–shell structure was fabricated through dehydrogenation and oxidation from TiH2. Thermal analysis indicates that a bimodal oxidation behavior accounts for the formation of a bi-phasic composite. The response of the composite under UV and visible light was measured by PL (photoluminescence) spectra and a photo-degradation test. A pronounced improvement in photo-degradation performance is attributed to the synergistic function of exciton separation of the core–shell structure and the visible light response of the Ti2O cores.

Synthesis and structural control of silicon and silicide nanowires/microrods using metal chloride sources

Si and silicide nanowires/microrods were synthesized using metal-chloride-based sources by the CVD technique. In the case of Si nanowire synthesis, the morphological structures of the products depended on the distance from the source material. The distance dependence of the morphological and structural properties of the nanostructures was investigated to systemically clarify the shape modification phenomena in Si nanowire synthesis. The modification of the cross-sectional shape of the Si nanowires/microrods was successfully demonstrated. The triangular nanowire has a sawtooth faceting structure on its sidewall. In addition, the synthesis of Mn-silicide phases over the entire range of the Mn–Si system was examined. The effect of adding an impurity to the source materials on the structural modifications of the resulting nanowires/microrods was also investigated. It is expected that the morphological and structural control of the nanowires/microrods will be improved by a simple thermal treatment using a metal chloride as the source material.

Direct evidence of multichannel-improved charge-carrier mechanism for enhanced photocatalytic H2 evolution

In the field of photocatalysis, the high-charge recombination rate has been the big challenge to photocatalytic conversion efficiency. Here we demonstrate the direct evidence of multichannel-improved charge-carrier mechanism to facilitate electron-hole transfer for raising photocatalytic H2 evolution activity. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and UV-Vis diffuse reflectance spectroscopy (DRS), were used to characterize the as-fabricated samples. The result shows that the present design of Au/Pt nanoparticles (NPs) decorated one-dimensional Z-scheme TiO2/WO3 heterostructure composite nanofibers have been fabricated, which even exhibited excellent light absorption in the visible region and greatly enhanced photocatalytic activities on H2 generation comparing with pure TiO2, TiO2/WO3 and Pt/WO3/TiO2 nanofibers. This greatpromotion is mainly on account of the photosynthetic heterojunction system, which include the surface plasmon resonance (SPR) of Au nanoparticles, low overpotential of Pt nanoparticles, and more importantly, the one-dimensional multichannel-improved charge-carrier photosynthetic heterojunction system with Pt as an electron collector and WO3 as a hole collector. Transferring photoinduced electrons and holes at the same time, leading to effective charge separation was directly proved by ultraviolet photoelectron spectroscopy, electrochemical impedance spectroscopy, photocurrent analysis and incident photon-to-electron conversion spectrum.

RGO-functionalized polymer nanofibrous membrane with exceptional surface activity and ultra-low airflow resistance for PM2.5 filtration

A polar polymer nanofibrous membrane (NFM) made by electrospinning is capable of capturing particulate matter (PM) on the junctions of cross-linked nanofibers through dipole–dipole intermolecular forces. However, the realization of fast and high-efficiency PM2.5 filtration under a high gas-velocity condition is still a big challenge for the pure polymer NFM. Herein, we introduce reduced graphene oxide (rGO) nanosheets (NSs) into the electrospun polyacrylonitrile (PAN) NFM to enhance both the surface activity and the gas permeability of the composite NFM during air filtration. By combining the experimental results with the theoretical calculations, we demonstrate that the rGO NSs dispersed on/in the PAN NFM remarkably increase the PM2.5 capture sites on the uncross-linked nanofibers based on both hydrogen bonding and dipole–dipole interaction forces. Furthermore, the tensile strength of the rGO-functionalized PAN NFM (0.48–1.25 MPa) is much higher than that of the pure PAN NFM (0.19 MPa) due to the excellent mechanical properties of the rGO NSs. The enhanced tensile strength of the composite NFM effectively boosts the gas permeability during air filtration. In this way, the optimal NFM containing 2.5 wt% rGO NSs exhibited >99.9% PM2.5 removal efficiency, ∼0.094 Pa−1 quality factor, and only ∼70 Pa pressure drop for resisting the airflow with a high gas velocity of ∼20 L min−1.

CORRIGENDUM: "OPTICAL AND ELECTRONIC PROPERTIES OF M2Si (M = Mg, Ca AND Sr) GROWN BY REACTIVE DEPOSITION TECHNIQUE"

[International Journal of Modern Physics B, Vol. 24 No. 19 (2010) 3693–3699]JUNHUA HUGraduate School of Science and Technology, Shizuoka University,3-5-1 Johoku, Naka-ku, Hamamatsu, 432-8011, Japanf5645032@ipc.shizuoka.ac.jpAKIHIKO KATOFDK Corporation, 2281 Washizu, Kosai, 431-0495, Japankato@fdk.co.jpTAIZOH SADOHDepartment of Electronics, Kyushu University,Fukuoka 819-0395, JapanYOSHUHITO MAEDADepartment of Energy Science and Technology, KyotoUniversity,Kyoto606-8501, JapanKONSTANTIN N. GALKIN, TARAS V. TURCHIN and NIKOLAY G. GALKINInstitute for Automation and Control Processes ofFar Eastern Branch of Russian Academy of Science,5 Radio St., 690041 Vladivostok, RussiaHIROKAZU TATSUOKA