Sol–gel preparation, band structure, and photochemical activities of double perovskite <i>A</i> ₂NiWO₆ (<i>A</i> =Ca, Sr) nanorods

Xu, Lei,Qin, Chuanxiang,Wan, Yingpeng,Xie, Hongde,Huang, Yanlin,Qin, Lin,Seo, Hyo Jin Elsevier 2017 JOURNAL- TAIWAN INSTITUTE OF CHEMICAL ENGINEERS Vol.71 No.-

<P><B>Abstract</B></P> <P> <I>A</I> <SUB>2</SUB>NiWO<SUB>6</SUB> (<I>A</I> =Ca, Sr) double perovskite semiconductors were prepared via the sol–gel method. The crystal phases were confirmed via X-ray powder diffraction (XRD) measurements together with Rietveld refinements. The morphological and chemical properties of the samples were investigated by the scanning electron microscope (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and the specific surface area measurements. The optical absorptions and the band structures of the two double perovskites were discussed based on the on the experimental results and theoretical calculation. The d–d allowed transitions in Ni<SUP>2</SUP> <SUP>+</SUP>–O octahedra have great contributions to the narrow band-gap. The Ni<SUP>2+</SUP>-containing tungstate perovskites were potential photocatalysts, which are efficient for its photodegradation for methylene blue (MB) under the irradiation of visible light (λ<ce:italic/>> 420nm). The photocatalytic activities were attributed to the special structure properties and multivalent Ni and W ions in the perovskite lattices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>A</I> <SUB>2</SUB>NiWO<SUB>6</SUB> (<I>A</I> =Ca, Sr) nano-perovskite were prepared via the sol–gel method. </LI> <LI> The crystalline crystal structure was refined. </LI> <LI> The optical absorption and band structure were clarified. </LI> <LI> The photocatalysis activities were discussed on structural properties. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Narrow band gap and visible light-driven photocatalysis of V-doped Bi₆Mo₂O₁₅ nanoparticles

Xu, Jian,Qin, Chuanxiang,Huang, Yanlin,Wang, Yaorong,Qin, Lin,Seo, Hyo Jin Elsevier 2017 APPLIED SURFACE SCIENCE - Vol.396 No.-

<P><B>Abstract</B></P> <P>Pure and V<SUP>5+</SUP>-doped Bi<SUB>6</SUB>Mo<SUB>2</SUB>O<SUB>15</SUB> (3Bi<SUB>2</SUB>O<SUB>3</SUB>·2MoO<SUB>3</SUB>) photocatalysts were synthesized through electrospinning, followed by low-temperature heat treatment. The samples developed into nanoparticles with an average size of approximately 50nm. The crystalline phases were verified via X-ray powder diffraction measurements (XRD). The surface properties of the photocatalysts were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses. The UV–vis spectra showed that V doping in Bi<SUB>6</SUB>Mo<SUB>2</SUB>O<SUB>15</SUB> shifted the optical absorption from the UV region to the visible-light wavelength region. The energy of the band gap of Bi<SUB>6</SUB>Mo<SUB>2</SUB>O<SUB>15</SUB> was reduced by V doping in the lattices. The photocatalytic activities of the pure and V-doped Bi<SUB>6</SUB>Mo<SUB>2</SUB>O<SUB>15</SUB> were tested through photodegradation of rhodamine B (RhB) dye solutions under visible light irradiation. Results showed that 20 mol% V-doped Bi<SUB>6</SUB>Mo<SUB>2</SUB>O<SUB>15</SUB> achieved efficient photocatalytic ability. RhB could be degraded by V-doped Bi<SUB>6</SUB>Mo<SUB>2</SUB>O<SUB>15</SUB> in 2h. The photocatalytic activities and mechanisms were discussed according to the characteristics of the crystal structure and the results of EIS and XPS measurements.</P> <P><B>Highlights</B></P> <P> <UL> <LI> V<SUP>5+</SUP>-doped Bi<SUB>6</SUB>Mo<SUB>2</SUB>O<SUB>15</SUB> was synthesized by the electrospinning preparation. </LI> <LI> The band gap energy of Bi6Mo12O15 was greatly reduced by V-doping in the lattices. </LI> <LI> V-doped Bi<SUB>6</SUB>Mo<SUB>2</SUB>O<SUB>15</SUB> shows high activity in RhB degradation under visible light. </LI> <LI> Crystal structure of Bi<SUB>6</SUB>Mo<SUB>2</SUB>O<SUB>15</SUB> is favorable for high photocatalytic capacity. </LI> </UL> </P>

A new silver niobate photocatalyst AgNb₁₃O₃₃: Synthesis, structure and photochemical properties

Liu, Xuanxuan,Qin, Chuanxiang,Huang, Yanlin,Qin, Lin,Seo, Hyo Jin Elsevier 2017 JOURNAL- TAIWAN INSTITUTE OF CHEMICAL ENGINEERS Vol.78 No.-

<P><B>Abstract</B></P> <P>Ag-containing niobate AgNb<SUB>13</SUB>O<SUB>33</SUB> has been prepared by the sol–gel polymerized complex method. The structure was investigated via a good XRD Rietveld refinement in a typical perovskite-like framework. The morphological properties of the AgNb<SUB>13</SUB>O<SUB>33</SUB> nanoparticles were tested via transmission electron microscopy (TEM), scanning electron microscope (SEM), and energy dispersive spectra (EDS) measurements. AgNb<SUB>13</SUB>O<SUB>33</SUB> is a typical direct allowed semiconductor with band energy of 2.81 eV, which is much narrower than 3.4 eV of Nb<SUB>2</SUB>O<SUB>5</SUB>. This silver niobate can harvest both UV and near UV light, which is benefited from the (O-2p/Ag-4d) hybridization in the valence band. The photocatalytic abilities of AgNb<SUB>13</SUB>O<SUB>33</SUB> nanoparticles were reported. The sample presents more efficient photocatalytic effects on photo-degradation of methylene blue (MB) dye solutions than that of Nb<SUB>2</SUB>O<SUB>5</SUB>. The photocatalytic mechanism was discussed on band energy levels, trapping experiments, photoluminescence and the decay lifetime.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new silver-containing niobate nanoparticle AgNb<SUB>13</SUB>O<SUB>33</SUB> was prepared. </LI> <LI> Typical perovskite-like structure was verified by Rietveld refinements. </LI> <LI> AgNb<SUB>7</SUB>O<SUB>18</SUB> shows an efficient absorption with a narrow gap 2.81 eV. </LI> <LI> AgNb<SUB>7</SUB>O<SUB>18</SUB> has an efficient photocatalytic activity on MB photo-degradation. </LI> <LI> AgNb<SUB>13</SUB>O<SUB>33</SUB> has more advanced photocatalytic activities than Nb<SUB>2</SUB>O<SUB>5</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A silver niobate photocatalyst AgNb₇O₁₈ with perovskite-like structure

Liu, XuanXuan,Qin, Chuanxiang,Cao, Lei,Feng, Yongyi,Huang, Yanlin,Qin, Lin,Seo, Hyo Jin Elsevier 2017 Journal of Alloys and Compounds Vol.724 No.-

<P><B>Abstract</B></P> <P>Silver-containing niobate AgNb<SUB>7</SUB>O<SUB>18</SUB> nanoparticles were prepared via sol-gel polymerized complex synthesis. The sample was given a good XRD Rietveld refinement in a typical perovskite-like structure. The detailed surface properties of AgNb<SUB>7</SUB>O<SUB>18</SUB> nanoparticles were tested by SEM, EDS, TEM, nitrogen adsorption-desorption isotherms and XPS measurements. AgNb<SUB>7</SUB>O<SUB>18</SUB> is characterized via a direct transition and the band energy is 2.76 eV. The hybridization between O 2p and Ag 3d states in valence band contributes to the narrowed band gap. The first principles electronic structure elucidation supports the narrow band gap of AgNb<SUB>7</SUB>O<SUB>18</SUB>. The sample shows an efficient degradation of methylene blue dye (MB) solutions. The trapping tests were performed to elucidate the real active species in the photocatalytic reactions. The results indicate that the superoxide radical is the main active species in the photocatalytic system, and the photocatalyst also shows a good stability and durability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new semiconductor nanoparticle AgNb<SUB>7</SUB>O<SUB>18</SUB> was prepared. </LI> <LI> The silver niobate has a typical perovskite-like structure. </LI> <LI> AgNb<SUB>7</SUB>O<SUB>18</SUB> shows an efficient absorption with a narrow gap 2.76 eV. </LI> <LI> AgNb<SUB>7</SUB>O<SUB>18</SUB> has an efficient photocatalytic activity on MB photo-degradation. </LI> <LI> The photocatalysis mechanism and stabilities were discussed. </LI> </UL> </P>

Synthesis and photochemical properties of ferrotitanate In₄FeTi₃O_13.5 with layer structure

Liu, Xuanxuan,Huang, Yanlin,Qin, Chuanxiang,Seo, Hyo Jin Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.427 No.1

<P><B>Abstract</B></P> <P>In<SUB>4</SUB>FeTi<SUB>3</SUB>O<SUB>13.5</SUB> (InTi<SUB>0.75</SUB>Fe<SUB>0.25</SUB>O<SUB>3.375</SUB>) semiconductor was prepared via sol-gel citrate-complexation synthesis. This ferrotitanate derives from a solid-solution with InFeO<SUB>3</SUB>:In<SUB>2</SUB>Ti<SUB>2</SUB>O<SUB>7</SUB> =2:3. Phase formation and crystal structure of the sample were confirmed via XRD Rietveld refinement. Structural analyses indicated that there were two dimensional layers in the structure. The mutual repulsion in the layers induces great displacements of oxygen ions. The optical properties of In<SUB>4</SUB>FeTi<SUB>3</SUB>O<SUB>13.5</SUB> nanoparticles were investigated. The direct allowed band gap (2.56eV) shows a characteristic charge-transfer (CT) transitions of (O2p+Fe3d)→(Ti/Fe)3d in visible-light region. The band structure and energy positions were discussed. In<SUB>4</SUB>FeTi<SUB>3</SUB>O<SUB>13.5</SUB> nanoparticles are demonstrated to be efficient for the photodegradation of Rhodamine B (RhB) under visible light irradiation (λ>420nm). The photocatalytic activities were attributed to the special layer structure and the catalytic mediators of multivalent Ti<SUP>4+/3+</SUP> and Fe<SUP>3+/2+</SUP> confirmed by XPS measurements.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new ferrotitanate semiconductor In<SUB>4</SUB>FeTi<SUB>3</SUB>O<SUB>13.5</SUB> nanoparticles were prepared. </LI> <LI> Rietveld refinement was given in monoclinic layered structure. </LI> <LI> Special 2D layered structure reduced the visible light optical absorption. </LI> <LI> The direct allowed band transitions were reported. </LI> <LI> Multivalent Fe<SUP>3+/2+</SUP> ions were confirmed by calculations and experiments. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Formation of Poly(vinyl alcohol)/SWNTs Fibers with Hierarchical Structure under High-Speed Shear Flow

Xia Wang,Changcun Wu,Jun Sun,Chuanxiang Qin,Jianjun Wang,Qiqi Zhuo,Lixing Dai 한국섬유공학회 2020 Fibers and polymers Vol.21 No.5

This study introduces a facile method to prepare syndiotactic poly(vinyl alcohol) (s-PVA) fibers containing singlewalledcarbon nanotubes (SWNTs) from the corresponding composite dispersions with tea polyphenols (TP) as dispersantunder high-speed shear flow. The formation of the composite fibrous precipitates at high shear rate is largely facilitated by theSWNTs in the dispersions and slight flow resistance. Interestingly, the obtained s-PVA/SWNTs composite precipitatespossess a three-level hierarchical structure, that is, a single fiber is assembled by fibrils which are composed of microfibrils ofs-PVA-coated SWNTs. And the s-PVA fibrous precipitates containing high amounts of SWNTs could be obtained by shearingthe dispersion with relatively low SWNTs loadings, as a result, the composite fiber containing 20.7 wt% SWNTs wasprepared from the dispersion with 10.0 wt% SWNTs. In addition, with the increase of SWNTs loadings, the amount of theprecipitates increases, but crystallinity of the precipitates decreases instead.

Improved photochemical properties of Aurivillius Bi₅Ti₃FeO₁₅ with partial substitution of Ti⁴⁺ with Fe³⁺

Liu, Xuanxuan,Xu, Lei,Huang, Yanlin,Qin, Chuanxiang,Qin, Lin,Seo, Hyo Jin Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.15

<P><B>Abstract</B></P> <P>This work improved the optical absorption and photocatalytic ability of four-layered Aurivillius Bi<SUB>5</SUB>Ti<SUB>3</SUB>FeO<SUB>15</SUB> through microstructural modification via partial substitution of Ti<SUP>4+</SUP> with Fe<SUP>3+</SUP>. Bi<SUB>5</SUB>Ti<SUB>3−x</SUB>Fe<SUB>1+x</SUB>O<SUB>15</SUB> (x = 0–0.6) photocatalysts were prepared through sol-gel citrate-complexation synthesis. The sample crystallized into plate-like nanoparticles with [001] facets. Phase formation and crystal structure were confirmed via X-ray powder diffraction (XRD) Rietveld refinements. Bi<SUB>5</SUB>Ti<SUB>3−x</SUB>Fe<SUB>1+x</SUB>O<SUB>15</SUB> (x = 0–0.6) maintained its structural characteristic, i.e., a perovskite unit of (Bi<SUB>3</SUB>Ti<SUB>3−x</SUB>Fe<SUB>1+x</SUB>O<SUB>13</SUB>)<SUP>2–</SUP> sandwiched by two (Bi<SUB>2</SUB>O<SUB>2</SUB>)<SUP>2+</SUP> layers along <I>c</I> axis. The samples were investigated via scanning electron microscope (SEM), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDX), and specific surface area analyses. The band gap showed characteristic transitions from the valence band (VB) of (O2p+Fe<I>t</I> <SUB>2g</SUB>+Bi6s) to the conduction band (CB) of (Ti-3d+Fe-<I>e</I> <SUB>g</SUB>). With increasing substitution of Ti<SUP>4+</SUP> with Fe<SUP>3+</SUP>, the sample greatly red shifted its absorption edges. The d–d transitions in FeO<SUB>6</SUB> greatly contribute to the narrow band-gap. Aurivillius is a potential photocatalyst and demonstrated photodegradation of Rhodamine B (RhB) under visible light irradiation (λ > 420nm). Such photocatalytic activities were attributed to the special structural layer and the catalytic mediators of multivalent Ti<SUP>4+/3+</SUP> and Fe<SUP>3+/2+</SUP> ions in the perovskite slabs as confirmed by XPS measurements. Results suggested that substitution of Ti<SUP>4+</SUP> with Fe<SUP>3+</SUP> in an Aurivillius phase was an efficient method to modify the bandwidth and structure of Aurivillius phase. This phenomenon can be used as a strategy to improve the photochemical properties of Ti/Fe-containing Aurivillius phases.</P>

Hydrothermal synthesis and optical properties of CsV₃O₈ microplates

Mi, Longqing,Huang, Yanlin,Qin, Chuanxiang,Qin, Lin,Seo, Hyo Jin Elsevier 2018 Journal of luminescence Vol.194 No.-

<P><B>Abstract</B></P> <P>Nano-sized V<SUB>2</SUB>O<SUB>5</SUB> has been widely investigated as photocatalysis due to good chemical stability and smaller band gap than TiO<SUB>2</SUB>. However, it suffers some disadvantages such as narrow optical absorption, easy recombination of photo-generated charges. In this work, CsV<SUB>3</SUB>O<SUB>8</SUB> was prepared by a facile hydrothermal synthesis without help of any additive inorganic chemicals. The samples developed into well-crystalized microplates with the length and width of about 1 and 3µm, respectively. Phase formation and structure were investigated by XRD structure refinement. CsV<SUB>3</SUB>O<SUB>8</SUB> has an unusual V–O framework consisting of VO<SUB>6</SUB> octahedra, which constructs V<SUB>2</SUB>O<SUB>5</SUB>-like layer-structure. The samples were characterized with SEM, TEM, EDS and optical absorption. CsV<SUB>3</SUB>O<SUB>8</SUB> has an indirect allowed electronic transition with band energy 2.18eV. Efficient photo-degradation of Rhodamine B (RhB) solutions in presence of CsV<SUB>3</SUB>O<SUB>8</SUB> was confirmed. The result suggests that vanadate semiconductor CsV<SUB>3</SUB>O<SUB>8</SUB> is a potential candidate for photocatalytic application under visible-light irradiation.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Synthesis and Gas Adsorption Properties of Carbide-Derived Carbons from Titanium Tin Carbide

Yuanyuan Zhu,Aiguo Zhou,Jin Jia,Junjun Wang,Jiang Liu,Baolin Xing,Chuanxiang Zhang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.4

Here we reported the synthesis of nanoporous carbide-derived carbons (CDCs) from a new precursor, titanium tin carbides (Ti2SnC), via chlorination at 400–1100℃. At low chlorination temperature (400–500℃), as-synthesized CDCs mainly consisted of amorphous carbon and chlorides. As the chlorination temperature increased up to 600℃, chlorides disappeared, and the main composition of CDCs was amorphous carbon. At high chlorination temperature, there was a trend of graphitization. The microstructure of CDCs was observed and characterized by scanning electron microscopy and transmission electron microscopy. Some graphite-like sheet structures in CDCs were found. Specific surface area (SSA) and pore volume of CDCs increased with chlorination temperature, except an abnormal decrease of the CDC chlorinated at 900℃. CDC chlorinated at 1100℃ had the largest SSA, 1580 m2 /g. In order to apply these materials as novel hydrogen/methane storage media in the area of energy efficient transport, gas adsorption properties of CDCs were measured. For CDC chlorinated at 1100℃, pore volume uptakes are 206 cm3 /g at 60 bar (25℃) for methane, and ~442 cm3 /g at 35 bar (-196℃) for hydrogen, respectively. It was suggested that CDCs from Ti2SnC are promising materials for hydrogen/ methane adsorptive storage.

Synthesis and Electrochemical Performance of Ti3C2Tx with Hydrothermal Process

Libo Wang,Heng Zhang,Bo Wang,Changjie Shen,Chuanxiang Zhang,Qianku Hu,Aiguo Zhou,Baozhong Liu 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.5

In this study, a simple hydrothermal method has been developedto prepare Ti3C2Tx from Ti3AlC2 as a high-performance electrodematerial for supercapacitors. This method is environmentallyfriendly and has a low level of danger. The morphology andstructure of the Ti3C2Tx can be controlled by hydrothermalreaction time, temperature and NH4F amounts. The preparedTi3C2Tx was characterized by X-ray diffraction, field emissionscanning electron microscopy, Raman spectroscopy, X-rayphotoelectron spectroscopy and Brunauer-Emmet-Teller. Theresults show that the prepared Ti3C2Tx is terminated by O, OH,and F groups. The electrochemical properties of the Ti3C2Txsample exhibit specific capacitance up to 141 Fcm−3 in 3 MKOH aqueous electrolyte, and even after 1000 cycles, nosignificant degradation of the volumetric capacitance wasobserved. These results indicate that the Ti3C2Tx materialprepared by this hydrothermal method can be used in highperformance supercapacitors.