Oxide Nanofibers as Catalysts Toward Energy Conversion and Environmental Protection

Ultrathin oxide nanofibers are widely used in an array of catalytic applications toward energy conversion and environmental protection. Remarkable progress has been made with regard to the development of engineering oxide nanofibers into unique structures to suit or enable various functions. We aim to provide a comprehensive overview of oxide nanofibers, including the structure engineering, derivates, assemblies and their applications. We begin with a brief introduction to the production of nanofibers with diversified compositions, structures and properties, followed by discussions of the wet-chemistry derivates. Afterward, we discuss the applications of catalytic oxide nanofibers, including electrocata-lysis, photocatalysis and thermal-catalysis. Then we highlight the most significant role of oxide nanofibers as catalyst support for the immobilization of metal nanoparticles. Moreover, we showcase the advanced assemblies based on oxide nanofibers, including their use as multi-functional membranes and foams. In the end, we offer perspectives on the challenges, opportunities and new directions for future development.     

Synthesis and Characterization of a One- dimensional Molybdenum Oxide （H2enMe）[Mo3O10]

A hybrid organic-inorganic material (H2enMe)[Mo3O10] (C3H12Mo3N2O10, Mr = 523.97) has been synthesized under hydrothermal conditions and its crystal structure was determined by X-ray diffraction. It crystallizes in the orthorhombic system, space group Pnma with a = 12.430(2), b = 7.6089(12), c = 11.9553(19) , V = 1130.7(3) 3, Dc = 3.078 g/cm3, Z = 4, μ(MoKa) = 3.328 mm1, F(000) = 1000, the final R = 0.0256 and wR = 0.0716 for 1314 observed reflections with I > 2σ(I). A total of 11780 reflections were measured and 1325 were unique (Rint = 0.0244). It consists of infinite one-dimensional edge-sharing MoO6 octahedral chains with [Mo3O10]2 moieties. The protonated diaminopropane cations are located between the chains and linked to the oxygen atoms of the inorganic skeletal backbones by hydrogen bonds. It is indicated that the as-synthesized compound displays photochromic property in the solid state.     

CO oxidation of bare and TiO2-coated NiO-Ni(OH)2 nanoparticles

CO oxidation reactivity of bare and TiO₂-coated nanoparticles consisting of both NiO and Ni(OH)₂ surfaces was studied. For the deposition of TiO₂, atomic layer deposition was used, and formation of three-dimensional domains of TiO₂ on NiO-Ni(OH)₂ could be identified. Based on the data of X-ray Photoelectron Spectroscopy, we suggest that upon TiO₂ deposition only Ni(OH)₂ was remained on the surface, whereas NiO surface disappeared. Both CO adsorption and CO oxidation took place on NiO-Ni(OH)₂ surfaces under our experimental conditions. CO adsorption was almost completely suppressed after TiO₂ deposition, whereas CO oxidation activity was maintained to large extent. It is proposed that bare NiO cannot be active for CO oxidation, and can only uptake CO under our experimental condition, whereas hydroxylated surface of NiO can be active for CO oxidation.     

Study of surface-bulk mass transport and phase transformation in nano-TiO2 using hyperfine interaction technique

Phase transition from anatase to rutile for the 70 nm TiO₂ crystallite has been investigated by the time differential perturbed angular correlation (TDPAC) technique. The study involved the annealing of the TiO₂ nanocrystals, adsorbed with the nuclear probe (¹⁸¹Hf/¹⁸¹Ta) at trace level, at different temperatures for different durations. The TDPAC measurement was also supported by XRD measurement where the width of the peaks increases with the increase in annealing temperature indicating a crystal growth. The samples annealed up to 823 K for 4 h showed no phase transition, except for the growth of the crystallites. However, it showed phase transition at the same temperature (823 K), when annealed for longer duration, indicating the slower kinetics of the phase transition process. Further the sample, when annealed at 1123 K for 4 h, showed phase transition. It has also been observed that the ¹⁸¹Hf tracer, adsorbed on 70 nm anatase TiO₂, diffuses from surface to bulk during the phase transition process and the extent of diffusion in anatase differs from that in rutile phase. However, surface to bulk mass-transfer is found to play a significant role in the phase transition process.     

Influence of buffer layer thickness on the structure and optical properties of ZnO thin films

A series of ZnO thin films were deposited on ZnO buffer layers by DC reactive magnetron sputtering. The buffer layer thickness determination of microstructure and optical properties of ZnO films was investigated by X-ray diffraction (XRD), photoluminescence (PL), optical transmittance and absorption measurements. XRD results revealed that the stress of ZnO thin films varied with the buffer layer thickness. With the increase of buffer layer thickness, the band gap edge shifted toward longer wavelength. The near-band-edge (NBE) emission intensity of ZnO films deposited on ZnO buffer layer also varied with the increase of thickness due to the spatial confinement increasing the Coulomb interaction between electrons and holes. The PL measurement showed that the optimum thickness of the ZnO buffer layer was around 12 nm.     

二氧化钛-硫化镉/氧化石墨烯复合材料光催化降解废水中有机物的研究

本论文采用溶剂热法制备出TiO₂-CdS/rGO三元复合光催化材料,并对其降解亚甲基蓝、罗丹明B的光催化活性进行研究,发现TiO₂-CdS/rGO对于亚甲基蓝、罗丹明B的光催化降解活性优于TiO₂-CdS,催化效率明显提高,降解时间大大缩短;在可见光照射下,以TiO₂-CdS/rGO为光催化剂,光反应时间40 min,亚甲基蓝、罗丹明B的降解率可达100%。本文还研究了催化材料的稳定性、催化剂用量对光催化降解效果的影响。     

ICP—AES法测定高纯二氧化锆中痕量杂质

介绍了高纯二氧化锆中痕量杂质元素Ｆｅ，Ｎａ，Ｓｉ，Ｔｉ的ＩＣＰ－ＡＥＳ测定方法。样品以浓Ｈ２ＳＯ４及（ＮＨ４）２ＳＯ４溶解，采用空白背景校正法消除基体Ｚｒ的光谱干扰，以基体匹配法补偿基体效应。各元素平均回收率为９５％－１０６％，相对标准偏差为１．３％－３．０％。     

Single-crystal ZnO flocky sphere formed by three-dimensional oriented attachment of nanoparticles

The nanostructure of a single-crystal ZnO flocky sphere was synthesized by using a simple chemical route in the Zn²⁺–triethanolamine system. Formation of such quasi-single-crystal nanostructures was achieved through oriented attachment of a large number of ZnO nanoparticles in three dimensions. It is suggested that the adsorption of triethanolamine molecules on the surface of ZnO particles plays an important role in their oriented attachment, leading to the formation of flocky spheres with single-crystal structure.     

Improving the resolution and the uniformity of AFM tip induced oxide patterns with pulsed voltages

Oxide line patterns were fabricated on the surface of titanium (Ti) film using atomic force microscopy (AFM) tip induced local oxidation technique. The growth behavior of the oxide under static voltages was studied. It was found the lateral growth of the oxide experienced two stages and the growth rate at the initial stage was very high. Pulsed voltages were employed and their effects on the controlling of the oxidation dynamics were examined. The results indicated that the high lateral and vertical growth rates of oxide at the initial stage could be suppressed with pulsed voltages. A minimum line width of 8 nm and highly uniform patterns were obtained with optimized voltage pulses. These results indicated that applying pulsed voltage is an effective method for improving both the resolution and the uniformity of the fabricated structures with scanning probe microscopy (SPM) tip induced local oxidation technique.