XRD,TEM and thermal analysis of yttrium doped boehmite nanofibres and nanosheets

Yttrium doped boehmite nanofibres with varying yttrium content have been prepared at low temperatures using a hydrothermal treatment in the presence of poly(ethylene oxide) surfactant (PEO). The resultant nanofibres were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM images showed the resulting nanostructures are predominantly nanofibres when Y-doping is less than 5%; in contrast Y-rich phases were formed when doping was around 10%. The doped boehmite and the subsequent nanofibres/nanotubes were analyzed by thermogravimetric and controlled rate thermal analysis methods. The boehmite nanofibres produced in this research thermally transform at higher temperatures than boehmite crystals and boehmite platelets. Boehmite nanofibres decompose at higher temperatures than non-hydrothermally treated boehmite.     

Synthesis, characterization, and surface properties of iron-doped boehmite nanofibers

Iron-doped boehmite nanofibers with varying iron contents have been prepared at low temperatures using hydrothermal treatment in the presence of poly(ethylene oxide) surfactant. The resulting nanofibers were characterized by transmission electron microscopy (TEM), X-ray diffraction, energy-dispersive X-ray analysis, and N2 adsorption. TEM images showed that the resulting nanostructures are predominantly nanofibers when the doped iron content is less than 5% (mol/mol); in contrast, nanosheets were formed when iron doping was above 4%. Nanotubes instead of nanofibers and iron-rich particles were observed in samples with 20% added iron. A detailed characterization and discussion on the iron-doped nanofibers is presented.     

Synthesis and surface characterization of yttrium doped boehmite nanofibers

Yttrium doped boehmite nanofibers with varying yttrium content have been synthesized at low temperatures using a soft-chemistry route in the presence of polyglycol ether surfactant. The effect of yttrium content, hydrothermal temperature on the growth of boehmite nanostructures was systematically studied. Nanofibers were formed in all samples with varying doped Y% treated at 100 °C; large Y(OH)₃ crystals were also formed at high yttrium doping. Treated at an elevated temperatures resulted in a remarkable changes in size and morphology for samples with the same doped Y content. The resultant nanofibers were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy-dispersive X-ray analysis (EDX), N₂ adsorption and thermogravimetric analysis. The detailed characterization and discussion on the Y doped nanostructures are presented.     

Fe-doped and ZnO-pillared titanates as visible-light-driven photocatalysts

Fe-doped cesium titanate was obtained by a solid state reaction with a mixture of Cs(2)CO(3), TiO(2), and Fe(2)O(3). ZnO-pillared doped titanate nanocomposite was successfully fabricated by exfoliating doped titanate and restacking its nanosheets with ZnO nanoparticles. The resulting nanocomposite was characterized by powder X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, N(2) adsorption-desorption measurement, thermogravimetric analysis and UV-vis spectroscopy. It was revealed that the present nanocomposite exhibits greatly increased specific surface area with mesoporous texture and that there exists an electronic coupling between the host sheets and the guest nanoparticles in the pillared system. The results of degradation of methylene blue under visible light radiation suggest that doping iron ions improves the material spectral response region and that hybridizing with ZnO nanopillars can suppress the recombination of photogenerated electron-hole pairs.     

An internal doping method for the preparation of transparent hybrid xerogels containing nano-sized iron particles

Sol-gel copolymerization of iron tricarbonyl-2-(triisopropoxysilyl)-1,3-butadiene with 1,6-bistriethoxysilylhexane and 1,4-bistriethoxysilylbenzene followed by drying produced bridged polysilsesquioxane xerogels. These porous, transparent hybrid materials containing the iron metal precursor were irradiated (UV) and heated under vacuum resulting in the deposition of nano-sized iron particles doped in the xerogels. EDAX and electron diffraction techniques were used to characterize the iron phases. The TEM images of these doped xerogels provided additional information regarding the domain size of the iron phase.Using a combination of external doping of Cd²⁺ and S^2– ions and internal doping of Fe°, mixed Fe/CdS phases were prepared within the porous bridged polysilsesquioxane xerogels. The resulting doped xerogels were found to have retained their porous morphology.     

Pyrogenic iron(III)-doped TiO2 nanopowders synthesized in RF thermal plasma: phase formation, defect structure, band gap, and magnetic properties

Iron(III)-doped TiO(2) nanopowders, with controlled iron to titanium atomic ratios (R(Fe/Ti)) ranging from nominal 0 to 20%, were synthesized using oxidative pyrolysis of liquid-feed metallorganic precursors in a radiation-frequency (RF) thermal plasma. The valence of iron doped in the TiO(2), phase formation, defect structures, band gaps, and magnetic properties of the resultant nanopowders were systematically investigated using M?ssbauer spectroscopy, XRD, Raman spectroscopy, TEM/HRTEM, UV-vis spectroscopy, and measurements of magnetic properties. The iron doped in TiO(2) was trivalent (3+) in a high-spin state as determined by the isomer shift and quadrupole splitting from the M?ssbauer spectra. No other phases except anatase and rutile TiO(2) were identified in the resultant nanopowders. Interestingly, thermodynamically metastable anatase predominated in the undoped TiO(2) nanopowders, which can be explained from a kinetic point of view based on classical homogeneous nucleation theory. With iron doping, the formation of rutile was strongly promoted because rutile is more tolerant than anatase to the defects such as oxygen vacancies resulting from the substitution of Fe(3+) for Ti(4+) in TiO(2). The concentration of oxygen vacancies reached a maximum at R(Fe/Ti) = 2% above which excessive oxygen vacancies tended to concentrate. As a result of this concentration, an extended defect like crystallographic shear (CS) structure was established. With iron doping, red shift of the absorption edges occurred in addition to the d-d electron transition of iron in the visible light region. The as-prepared iron-doped TiO(2) nanopowders were paramagnetic in nature at room temperature.     

Synthesis and characterization of Fe doped mesoporous Al<Subscript>2</Subscript>O<Subscript>3</Subscript> by sol–gel method and its use in trichloroethylene combustion

Two mesoporous alumina samples were synthesized using the sol–gel method, and these samples were tested as catalysts in trichloroethylene combustion reaction. One alumina sample was doped with Fe to study the influence of a small amount of this agent on the characteristics and properties of alumina as a catalyst. Both catalysts (pure alumina and alumina doped with Fe) were thoroughly characterized by different techniques, such as DTA/TGA, FT-IR, XRD, SEM and TEM, and the porous characterization was conducted using a N₂ physisorption technique. The doping agent presented a particular influence on the morphology and textural porosity in the alumina catalyst and therefore, it exhibited different catalytic behavior than the pure alumina catalyst. For both catalysts, the crystalline phase of γ-alumina was reported using XRD technique, and the crystallite size ranged from 7.8 to 12.8 nm. Using TEM images, the alumina catalyst doped with Fe revealed to contain a mixture of three types of iron oxide (maghemite, magnetite and hematite), mainly as roughly spherical nanoparticles. For both alumina catalysts, trichloroethylene catalytic combustion was conducted on a packed bed reactor in air at a temperature range of 50 to 600 °C. The alumina catalyst doped with Fe showed a higher catalytic activity than pure alumina, mainly due to the presence of micropores and grain morphology of flat faces.     

以陶瓷球为载体的铁掺杂氧化锌纳米棒光催化降解甲醛气体(英文)

采用简单的湿化学法在陶瓷球上制备了纯氧化锌和铁掺杂的氧化锌纳米棒。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和紫外可见分光光度计(UV-Vis)对样品的结构、形貌和光学性能进行了表征和分析。研究了纯氧化锌及铁掺杂的氧化锌在紫外光照射下对甲醛气体的降解效率。结果表明与纯氧化锌相比,铁掺杂的催化剂表现出更优越的光催化活性。当Fe的掺杂量为4%时,催化剂对甲醛的降解效率最高。催化剂具有良好的稳定性,可以重复利用,循环使用10次之后,催化效率仍可达到85%。     

Tuning the Surface Structure of Nitrogen‐Doped TiO2 Nanofibres—An Effective Method to Enhance Photocatalytic Activities of Visible‐Light‐Driven Green Synthesis and Degradation

Nitrogen‐doped TiO₂ nanofibres of anatase and TiO₂(B) phases were synthesised by a reaction between titanate nanofibres of a layered structure and gaseous NH₃ at 400–700 °C, following a different mechanism than that for the direct nitrogen doping from TiO₂. The surface of the N‐doped TiO₂ nanofibres can be tuned by facial calcination in air to remove the surface‐bonded N species, whereas the core remains N doped. N‐Doped TiO₂ nanofibres, only after calcination in air, became effective photocatalysts for the decomposition of sulforhodamine B under visible‐light irradiation. The surface‐oxidised surface layer was proven to be very effective for organic molecule adsorption, and the activation of oxygen molecules, whereas the remaining N‐doped interior of the fibres strongly absorbed visible light, resulting in the generation of electrons and holes. The N‐doped nanofibres were also used as supports of gold nanoparticle (Au NP) photocatalysts for visible‐light‐driven hydroamination of phenylacetylene with aniline. Phenylacetylene was activated on the N‐doped surface of the nanofibres and aniline on the Au NPs. The Au NPs adsorbed on N‐doped TiO₂(B) nanofibres exhibited much better conversion (80 % of phenylacetylene) than when adsorbed on undoped fibres (46 %) at 40 °C and 95 % of the product is the desired imine. The surface N species can prevent the adsorption of O₂ that is unfavourable for the hydroamination reaction, and thus, improve the photocatalytic activity. Removal of the surface N species resulted in a sharp decrease of the photocatalytic activity. These photocatalysts are feasible for practical applications, because they can be easily dispersed into solution and separated from a liquid by filtration, sedimentation or centrifugation due to their fibril morphology.     

以陶瓷球为载体的铁掺杂氧化锌纳米棒光催化降解甲醛气体

采用简单的湿化学法在陶瓷球上制备了纯氧化锌和铁掺杂的氧化锌纳米棒。利用X射线衍射仪（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）和紫外可见分光光度计（UV-Vis）对样品的结构、形貌和光学性能进行了结构表征和分析。研究了纯氧化锌及铁掺杂的氧化锌在紫外光照射下对甲醛气体的降解效率。结果表明与纯氧化锌相比,铁掺杂的催化剂表现出更优越的光催化活性。当Fe的掺杂量为4%时,催化剂对甲醛的降解效率最高。催化剂具有良好的稳定性,可以重复利用,循环使用10次之后,催化效率仍可达到85%。     

Synthesis and Microstructural Properties of Fe-TiO2 Nanocrystalline Particles Obtained by a Modified Sol-Gel Method

A series of iron/titanium oxide nanocrystalline particles with Fe/Ti molar ratios up to 0.15 were synthesized by a modified sol-gel technique using Ti(IV)-isopropoxide and anhydrous Fe(II)-acetate. The precursors were mixed and subsequently hydrolyzed with water molecules generated in situ by an esterification reaction between acetic acid and ethanol. As-synthesized samples were amorphous for XRD, independently of the relative amount of doped iron. The undoped samples and samples with the molar ratio Fe/Ti = 0.01, treated at up to 500°C, contained anatase as the dominant phase and rutile as the minor phase. The samples with the Fe/Ti molar ratio of 0.15, treated at the same temperature, contained anatase (major phase), rutile (minor phase) and a very small amount of an unidentified phase. The crystallite size of the dominant phase in the samples was estimated from the XRD line broadening using the Scherrer formula. Thermogravimetric analysis showed that weight loss was accelerated and completed at lower temperatures as the relative concentration of iron in the Fe-TiO₂ samples increased. The strong exothermic peak in the DTA curve between 300 and 450°C in the undoped TiO₂ sample shifted to the lower temperatures and became much more asymmetrical with increased iron doping. This DTA peak corresponded to the amorphous-to-anatase-transition and it included several steps such as (i) the thermal degradation of strongly bound organic molecules, (ii) the condensation of unhydrolyzed –OR groups, (iii) the sintering and growth of particles and (iv) the rearrangement of newly formed chemical bonds. The center of the most intense Raman band of the E _g mode at 143.8 cm^–1 in the undoped TiO₂ sample continually shifted to higher wave numbers and the full-width at half maximum increased with iron doping. Transmission electron microscopy revealed decrease of the mean particle size from 16.3 nm in undoped sample to 9.7 nm in the highest iron doped sample. The particle size distribution becomes narrower with iron doping. The narrowest particle size distribution was found in sample with the Fe/Ti molar ratio of 0.05, calcined at 500°C. Scanning electron microscopy of undoped samples calcined at 580°C showed irregular aggregates having a relatively flat surface. On the contrary, the samples doped with 15 mol% of iron and treated at the same temperature exhibited a non-uniform sponge-like surface with distributed micrometer holes.     

碳量子点在八面双锥和纳米片TiO2上的光催化

依次用溶剂热法和水热法制备得到暴露(101)晶面的八面双锥体二氧化钛OBP-TiO2和不同碳负载量的N-CDs/OBP-TiO2复合催化剂,以及暴露(001)晶面的纳米片二氧化钛TNS和不同碳负载量的N-CDs/TNS复合催化剂。利用TEM、XRD、XPS等表征手段对这2类复合催化剂的形貌结构、化学成分等作了鉴定。系统研究了碳量子点负载量对可见光降解RhB的光催化性能影响。实验发现,由于N-CDs的加入,均能较大提高2类复合催化剂的光催化性能。(101)高裸露晶面N-CDs/OBP-TiO2比(001)高裸露晶面N-CDs/TNS的光催化活性高。     

Efficient electrocatalytic oxygen evolution at ultra-high current densities over 3D Fe,N doped Ni(OH)2 nanosheets

Developing highly efficient nickel or iron based hydroxide electrocatalysts is primary essential but challenging for oxygen evolution reaction (OER) at ultra-high current densities. Herein, we developed a facile method to prepare nitrogen and iron doped nickel(II) hydroxide nanosheets on self-supported conductive nickel foam (denoted as Fe,N-Ni(OH)₂/NF) through ammonia hydrothermal and impregnation methods. Owing to the optimization of the electronic structure by nitrogen doping and the strong synergistic effect between Fe and Ni(OH)₂, the three-dimensional (3D) Fe,N-Ni(OH)₂/NF nanosheets delivered superior electrocatalytic OER performances in basic solution with low potentials of 1.57 V and 1.59 V under 500 mA/cm² and 1000 mA/cm² respectively and robust operation for 10 h with ignored activity decay, comparing well with the potentials of previously reported NiFe based electrocatalysts as well as the benchmark commercial Ir/C/NF. In-situ Raman spectroscopy revealed that the main active species were NiOOH during the OER process. The present results are expected to provide new insights into the study of OER process towards ultra-high current densities.     

超细钴掺杂二氧化钛的制备、表征及气相光催化性能

以四氯化钛为原料、硝酸钴为掺杂剂,制备了粒径10 nm～30 nm的钴掺杂超细二氧化钛并进行了XRD、TEM和FT-IR表征及气相光催化性能的评价。钴掺杂造成了锐钛矿向金红石相的转变温度明显降低,掺杂量从0增加到4%时,相变温度下降了90 ℃左右。制备过程中的pH值对相变也有影响,pH值很小时相变在较低的温度下就能发生。当pH<3,500 ℃焙烧的样品中就基本是金红石型TiO2;红外光谱分析证明掺杂样品比纯样品有更强的吸水性;以苯作为反应物在一个固定床光反应器中考察了钴掺杂二氧化钛的光催化活性。结果表明,钴掺杂对催化剂的光催化性能有影响。反应初期掺杂样品与纯二氧化钛样品相比活性相差不大,但随着反应的进行活性差别逐渐增大。在实验条件下160 min后纯样品基本失活,掺杂样品的活性仍大于50%。     

铁、氮共掺杂二氧化钛薄膜的亲水性能

采用溶胶-凝胶法制备了铁掺杂TiO2(Fe-TiO2)薄膜, 将Fe-TiO2薄膜放置氨气气氛中高温处理, 形成铁、氮共掺杂TiO2(Fe/N-TiO2)薄膜. 通过XRD、XPS、SEM、UV-Vis法进行吸收光谱分析及薄膜表面亲水接触角分析, 研究了铁、氮掺杂浓度, 热处理温度, 膜厚等因素对薄膜亲水性能的影响. 结果表明, Fe/N-TiO2(0.5%Fe, 摩尔百分数)显示出更佳的亲水性能, 在可见光下优势尤为明显. 铁掺杂主要作用是降低电子和空穴的复合几率, 氮掺杂可以增强TiO2薄膜在可见光区的吸收, 两种效应相互结合, 共同提高了薄膜在可见光下的亲水性能.     

Nickel Doping in Atomically Thin Tin Disulfide Nanosheets Enables Highly Efficient CO2 Reduction

Engineering electronic properties by elemental doping is a direct strategy to design efficient catalysts towards CO₂ electroreduction. Atomically thin SnS₂ nanosheets were modified by Ni doping for efficient electroreduction of CO₂. The introduction of Ni into SnS₂ nanosheets significantly enhanced the current density and Faradaic efficiency for carbonaceous product relative to pristine SnS₂ nanosheets. When the Ni content was 5 atm %, the Ni‐doped SnS₂ nanosheets achieved a remarkable Faradaic efficiency of 93 % for carbonaceous product with a current density of 19.6 mA cm^?2 at ?0.9 V vs. RHE. A mechanistic study revealed that the Ni doping gave rise to a defect level and lowered the work function of SnS₂ nanosheets, resulting in the promoted CO₂ activation and thus improved performance in CO₂ electroreduction.     

The Structure and Catalytic Properties of MoVTeNbO Catalysts Modified by Adding Cr,Fe, Ce and W

Cr, Fe, Ce and W doped MoVTeNbO M2 phase catalysts were synthesized and used in the selective oxidation of propylene to acrylic acid (AA). Results show that the introduction of Cr, Fe, Ce and W substantially affects the physicochemical properties and catalytic performance of MoVTeNbO-based catalysts. Un-doped catalyst consists of M2 phase and TeO₂, while Cr, Fe, Ce and W-doped catalysts are mainly composed of M2 and MoO₃. It is indicated that doping of Cr, Fe, Ce and W can restrain the formation of TeO₂, but favour the formation of MoO₃. Un-doped, Cr and W-doped catalysts display irregular-shaped particles morphology, while Fe and Ce-doped catalysts display nanosheets morphology. In addition, the valence of superficial elements of catalysts changed greatly with the doping elements. For catalytic performance, in addition to Cr, the propylene conversion of the catalyst decreases obviously with doping of other elements, probably due to the drastically reduced specific surface area with doping of Fe, Ce and W. The existence of Cr and Ce can increase the selectivity to AA at all test temperatures (360–440 ℃), while Fe and W-doped catalysts only show higher selectivity than the un-doped one at high temperature of 420 and 440 ℃. It is illustrated that the catalysts with redox ability at relatively low temperature is more favorable for the selectivity to AA. Among them, Cr-doped catalyst shows the highest selectivity (85.3%) and yield (63.5%) of AA at test temperature of 380 ℃, which are 15.3 and 7.5% higher than that of un-doped catalyst, respectively.

Graphic Abstract

The M2 phase MoVTeNbO catalysts doped with Cr, Fe, Ce and W have been synthesized. It is demonstrated that the addition of Cr improves the stability of Te⁴⁺, and Cr-doped M2 phase shows excellent catalytic performance in the selective oxidation of propylene to acrylic acid.

     

Thermogravimetric Analysis of Vanadium Phosphorus Oxide Catalysts Doped with Cobalt and Iron

The transformation of VOHPO4·0.5H2O (VPO) precursor doped with cobalt or iron for n-butane oxidation to maleic anhydride was investigated by thermogravimetric analysis under air and nitrogen, with and without n-butane in the flow. While almost no effect was observed in nitrogen or air, a strong influence of the doping was observed when n-butane was added to the nitrogen or air. This resulted in a delay of the decomposition of the precursor and a further reoxidation of the VPO catalyst, particularly for doping with cobalt at low percentage (1%). This shows that doping can change the oxidation state of vanadium phosphorus oxide catalysts, which can explain differences in their catalytic performances and the favourable effect of doping by cobalt. This revised version was published online in July 2006 with corrections to the Cover Date.     

Blue phase liquid crystals affected by graphene oxide modified with aminoazobenzol group

Liquid-crystalline blue phases (BPs) are stable only for very narrow temperature range between the isotropic and the chiral nematic phase that severely hinders their applicability. Herein, the aminoazobenzol group was chemically grafted onto epoxy group of graphene oxide (GO) via addition reaction. Successful grafting of aminoazobenzol group was confirmed using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), UV–vis absorption spectra and thermogravimetric analysis (TGA). The resultant aminoazobenzol group–modified GO sheets, which is reduced (RGO-Az), were easily redispersable in common organic solvents or liquid crystals (LCs). By doping different contents of RGO-Az, nanosheets could stabilise BP and increase the BP range. When doped with 0.5 wt% RGO-Az, the mixtures show the wider range with 5.9°C than the range with 3.6°C of BPLCs without RGO-Az. Meanwhile, the phase sequence and the range of the aforementioned phases are reproducible upon heating and cooling, which shows that the BPs doped with RGO-Az nanosheets are thermodynamically stable.     

Co~(2+)/Dy~(3+)掺杂纳米立方Fe_3O_4的热还原制备及磁靶向滞留性能

采用热还原沉淀法制备了一系列Co~(2+)/Dy~(3+)掺杂的纳米立方MxFe3-xO4磁性颗粒.利用X射线衍射仪、透射电子显微镜和振动样品磁强计研究了不同含量掺杂离子对MxFe3-xO4晶体结构、形貌及磁性的影响.研究发现,掺杂未改变母体的对称性,但母体形貌逐渐从立方体向球体过渡;Co~(2+)和Dy~(3+)的掺杂对于铁氧体磁学性质的影响明显不同,当Co~(2+)实际掺杂量为0.44和Dy~(3+)实际掺杂量为0.05时,MxFe3-xO4立方磁性粒子的饱和磁化强度(Ms)达到最大值,分别为76.65和70.21 A·m2·kg-1.与超顺磁性Fe_3O_4球体相比,高磁性掺杂Fe_3O_4立方体在体外模拟磁流体磁靶向定位实验中显示出较高的滞留率.