Nanocrystalline zinc indium vanadate: a novel photocatalyst for hydrogen generation

Hydrogen is a future fuel and hence production of cheap hydrogen is an important area of research. Recently, the photocatalysts were used to generate hydrogen from water and hydrogen sulfide splitting under solar light. Hence, we designed Zinc Indium Vanadate, a novel visible light active photocatalyst and used for the generation of hydrogen by using solar light. We have demonstrated the synthesis of ZnIn2V2O9 (ZIV) catalyst by sonochemical route using NH4VO3, In (NO3)3 and Zn(CH3COO)2 as a precursors and PVP as a capping agent. The obtained product was further characterized by XRD, UV-DRS and FESEM. The XRD pattern reveals the existence of monoclinic crystal structure and broader peaks indicating the nanocrystalline nature of the material. The particle size was observed in the range of 50-70 nm. The optical study showed the absorption edge cut off at 520 nm with estimated band gap about 2.3 eV. Considering the band gap in visible range, ZnIn2V2O9 was used as a photocatalyst for photodecomposition of H2S under visible light irradiation to produce hydrogen. We observed excellent photocatalytic activity for the hydrogen generation by using this photocatalyst.     

A metal-free polymeric photocatalyst for hydrogen production from water under visible light

The production of hydrogen from water using a catalyst and solar energy is an ideal future energy source, independent of fossil reserves. For an economical use of water and solar energy, catalysts that are sufficiently efficient, stable, inexpensive and capable of harvesting light are required. Here, we show that an abundant material, polymeric carbon nitride, can produce hydrogen from water under visible-light irradiation in the presence of a sacrificial donor. Contrary to other conducting polymer semiconductors, carbon nitride is chemically and thermally stable and does not rely on complicated device manufacturing. The results represent an important first step towards photosynthesis in general where artificial conjugated polymer semiconductors can be used as energy transducers.     

A CdS-modified TiO(2) nanocrystalline photoanode for efficient hydrogen generation by visible light

Cadmium sulfide (CdS) was in situ synthesized onto mesoporous TiO(2) films and used as a sensitizer to fabricate a photoelectrode for hydrogen generation in visible light. The incorporation of CdS extends the optical absorption threshold of a TiO(2) electrode to visible light, enhancing the visible-light-induced photocurrent. A maximum photoconversion efficiency of 3.67% was achieved for this CdS-sensitized TiO(2) electrode under visible light illumination of 100?mW?cm(-2). The hydrogen generation rate obtained at conditions of maximum efficiency is 95.5?μmol?cm(-2)?h(-1). To the best of our knowledge, the hydrogen generation rate is the highest among those reported for a photoelectrochemical cell under the illumination of visible light.     

Visible light-driven superoxide generation by conjugated polymers for organic synthesis

Nano Research - Benefiting from their unique delocalized electronic structure, conjugated polymer-based semiconductors are widely applied in the fields of organic electronics, sensors, and...     

Amorphous coating of metal by solid-state reaction

Journal of Materials Science Letters -     

Ferroelectric hollow particles obtained by solid-state reaction

Hollow particles of barium titanate were obtained by a two-step process combining colloidal chemistry and solid-state reaction. BaCO(3) crystals (size ≈1?μm) suspended in a peroxy-Ti(IV) aqueous solution were coated with an amorphous TiO(2) shell using a precipitation process. Calcination of the BaCO(3)@TiO(2) core-shell particles at 700?°C resulted in the formation of BaTiO(3) hollow particles (shell thickness of ≈70?nm) which retain the morphology of the BaCO(3) crystals. Formation of the cavity occurs because out-diffusion of the core phase is much faster than in-diffusion of the shell material. X-ray diffraction (XRD) and Raman spectroscopy indicate that the hollow particles possess a tetragonal ferroelectric structure with axial ratio c/a = 1.005. Piezoresponse force microscopy has shown strong piezoactivity and 180° ferroelectric domains. The process described provides a general route to fabricate hollow ferroelectric structures of several compounds.     

复合光催化剂CdS-Pt/TiO_2低温制备及可见光制氢性能

用不同方法制备了CdS-Pt/TiO2复合光催化剂。催化剂通过X射线衍射、比表面和紫外-可见漫反射吸收进行了表征。以可见光光解水制氢为探针反应,考察了CdS-Pt/TiO2复合光催化剂的可见光活性。结果表明制备方法极大地影响CdS-Pt/TiO2复合光催化剂的活性。低结晶度的CdS与Pt/TiO2复合形成的CdS-Pt/TiO2复合光催化剂具有最高的可见光活性,其光解水的量子效率为6.95%。     

Visible light-activated cadmium-doped ZnO nanostructured photocatalyst for the treatment of methylene blue dye

An attempt was made to prepare Cd-doped ZnO photocatalyst for visible light assisted degradation of a textile dye (methylene blue, MB) in aqueous solutions by a traditional sol–gel process. The as-prepared nanoparticles were characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy, and photoluminescence spectra techniques. The results showed that the Cd-doped ZnO possess the single-phase hexagonal wurtzite structure. The photocatalytic activity of the nanoparticles under visible light was investigated by measuring the photodegradation of MB in aqueous dispersion. The effects of key operation parameters such as initial dye concentration, catalyst loading as well as initial pH value on the decolorization extents were investigated. The results indicate that the decolorization of the organic molecule followed a pseudo-first-order kinetics according to the Langmuir–Hinshelwood model. Under the optimum operation conditions, approximately 85.0% dye removal was achieved within 3.5 h.     

Formation of NbC and TaC by solid-state reaction

The formation of NbC and TaC by solid-state reaction of Nb₂O₅ and Ta₂O₅ with carbon, respectively, was studied at 1000 to 1285° C by X-ray diffraction. Factors affecting the formation of the carbides, such as the nature of the reaction vessel, the molar ratio of carbon/oxide, the form of reactant carbon, etc., were examined. By covering the graphite crucible and increasing the molar ratio of carbon to oxide, complete formation of NbC and TaC could be achieved in about 60 min at low temperatures (1170 and 1225° C, respectively). The beneficial effect of covering the crucible is ascribed to the retention of CO which facilitates the reaction at low temperatures. The formation kinetics of NbC and TaC obey a first-order equation, with activation energies of 90 and 93 kcal mol^–1, respectively. Possible mechanisms for the solid-state reactions are discussed.     

Dimethylammonium iodide stabilized bismuth halide perovskite photocatalyst for hydrogen evolution

Metal halide perovskites have emerged as novel and promising photocatalysts for hydrogen generation.Currently,their stability in water is a vital and urgent research question.In this paper a novel approach to stabilize a bismuth halide perovskite[(CH₃)₂NH₂]₃[Bil₆](DA₃Bil₆)in water using dimethylammonium iodide(DAI)without the assistance of acids or coatings is reported.The DA3Bil6 powder exhibits good stability in DAI solutions for at least two weeks.The concentration of DAI is found as a critical parameter,where the I^-ions play the key role in the stabilization.The stability of DA3Bil6 in water is realized via a surface dissolution-recrystallization process.Stabilized DA3Bil6 demonstrates constant photocatalytic properties for visible light-induced photo-oxidation of I^-ions and with PtCI4 as a co-catalyst(Pt-DA₃Bil₆),photocatalytic H2 evolution with a rate of 5.7μmol·h^-1from HI in DAI solution,obtaining an apparent quantum efficiency of 0.83%at 535 nm.This study provides new insights on the stabilization of metal halide perovskites for photocatalysis in aqueous solution.     

A silicon/zinc 2,9,16,23-tetraaminophthalocyanine coaxial core-shell nanowire array as an efficient solar hydrogen generation photocatalyst

In this work, we have demonstrated that a silicon nanowire (SiNW) array can be an efficient visible light photocatalyst for hydrogen generation after being modified by the 2,9,16,23-tetraaminophthalocyanine of zinc (ZnTAPc). A photoelectrochemical (PEC) cell employing a ZnTAPc modified SiNW array as photoanode was found to be able to effectively produce hydrogen at a rate of 13 μmol (cm(2) h)(-1) under 100 mw cm(-2) irradiation from a xenon lamp. It is believed that the loading of ZnTAPc can enhance the efficiency of hydrogen generation and the stability of the SiNW array. This demonstrates that the ZnTAPc modified SiNW is a promising material for solar hydrogen generation.     

铁基载氧体煤化学链制氢的强化反应

为促进铁基载氧体的深度还原提高氢气产量,通过优化反应过程形成强化煤化学链制氢(强化煤CLHG)工艺。采用浸渍法制备铁基载氧体;以梅花井烟煤为原料,在固定床上研究煤与铁基载氧体的质量比对强化煤CLHG的影响;对比了三反应器煤CLHG和强化煤CLHG的制氢过程,对不同阶段的铁基载氧体进行XRD表征;对比二反应器、三反应器以及强化煤CLHG在6次循环实验中的碳转化率和氢气产量。结果表明:当煤与载氧体质量比为1:15时,氢气产量最高达1.74 L/g;强化煤CLHG中的铁基载氧体更多地被还原为FeO或Fe,还原程度加深,同时还原阶段的残炭在蒸汽氧化阶段进一步反应,使得氢气产量比三反应器煤CLHG的高18.4%;在6次循环实验中,强化煤CLHG的碳转化率与三反应器煤CLHG的相差不大,远高于二反应器煤CLHG的;强化煤CLHG的氢气产量始终高于二反应器煤CLHG和三反应器煤CLHG的;强化煤CLHG的单次最高氢气产量为1.76 L/g,循环累计氢气产量为9.54 L。强化煤CLHG缩短制氢时间,制氢能力更优异。     

New materials technologies for hydrogen generation

Abstract

A thermochemical cycle is described that demonstrates the use of biomass or lignite-derived synthesis gas to reduce New Zealand ironsand, which is subsequently steam-oxidised to generate pure hydrogen. The redox reactions for this cycle have been thermodynamically modelled, giving an indication of the temperature ranges required to achieve water splitting and the potential sensitivity of the process to partial pressures of CO₂. A fixed bed reactor showed reproducible oxide reduction behaviour over 10 redox cycles but only achieved limited conversion to 64% residual Fe₃O₄ (18%Fe). Fluidised bed reactor studies carried over a comparable timeframe using CO/N₂ mixtures demonstrated a high degree of reduction to 76%Fe.     

Fe3+偶联吨染料敏化TiO2可见光催化制氢活性

通过Fe3+分别把3种吨染料(xanthene)曙红Y(Eosin Y)、藻红B(Erythrosin B)、虎红(Rose-bengal)固定在TiO2表面制备xanthene-Fe3+-TiO2敏化催化剂.在可见光(λ≥420nm)下,以三乙醇胺为电子给体,3种xanthene-Fe3+-TiO2放氢活性明显高于Fe3+偶联前xanthene-TiO2.UV-vis吸收表征表明3种xanthene-Fe3+-TiO2在可见光的吸收比xanthene-TiO2更强.吸附实验和FTIR表征显示Fe3+均增加3种吨染料在TiO2的吸附量和吸附强度.因而,Fe3+偶联的光催化剂活性大大提高.讨论了吨染料结构对敏化TiO2催化荆活性的影响.     

纳米光催化剂Sm2InNbO7的制备及其可见光产氢活性

采用溶胶-凝胶法制备了纳米光催化剂Sm2InNbO7,通过XRD、FE-SEM、BET以及UV-Vis DRS测试对该材料的结构、粒径、比表面积和光吸收性能进行了表征。结果表明,Sm2InNbO7的晶粒尺寸和比表面积与柠檬酸(CA)加入量和煅烧温度有关。着重考察了不同条件下制备的Sm2InNbO7系列催化剂的光催化分解水产氢活性。实验结果表明,当CA与金属阳离子(Nb5++Sm3++In3+)的物质的量的比为2、煅烧温度为1073K时,获得的Sm2InNbO7纳米粉体具有最高的光催化产氢活性,测得的8h内平均产氢速率为8.32μmol/h,为固相法制备的Sm2InNbO7粉体的产氢速率的2.2倍。     

Formation of pseudobrookite through gaseous chlorides and by solid-state reaction

Pseudobrookite (Fe₂TiO₅) was prepared from Fe₂O₃–TiO₂ mixtures at 850 and 950 °C in air, argon and chlorine atmospheres. In the latter case, an experimental arrangement in which Fe₂O₃ and TiO₂ were placed in separated compartments under the same chlorine atmosphere was also used. Pseudobrookite was identified by X-ray powder diffraction and microstructurally characterized by scanning electron microscopy. The very different pseudobrookite morphologies in each atmosphere allow us to propose that the formation mechanism involves Ti⁴⁺ diffusion in the Fe₂O₃ surface in air and argon atmospheres and vapour transport through FeCl₃(g) and TiCI₄(g) in the chlorine atmosphere.     

Materials for hydrogen generation via water electrolysis

A review is presented of materials that could be utilized as electrolytes (and their associated electrodes and interconnect materials) in solid-state electrolysis cells to convert water (or steam) into hydrogen and oxygen. Electrolytes that function as oxygen ion conductors or proton conductors are considered for various operating temperatures from approximately 80 °C to 1000 °C. The fundamental electrochemical reactions are reviewed with some discussion of special sources of steam and DC electricity (advanced nuclear) to drive the reactions at the higher temperatures.     

Materials that emit light by chemical reaction

Many chemical reactions are associated with the emission of electromagnetic radiation in the form of heat and/or light. This paper reviews the categories of materials that produce visible light when they react, either spontaneously upon contact with air or upon ignition, as well as the processes by which such materials are synthesized. Emphasis is placed on compositions and processes that relate most closely with those found in nature.     

室温固相反应合成碱式碳酸锌

以七水硫酸锌(ZnSO4.7H2O)和碳酸氢铵(NH4HCO3)为原料,以聚乙二醇-400(PEG-400)为模板,通过室温固相反应制备了碳酸锌(ZnCO3)和碱式碳酸锌(ZnCO3.3Zn(OH)2.H2O,basic zinc carbon-ate,BZC)。通过XRD测试及其半定量成分分析,研究了PEG-400剂量和NH4HCO3与ZnSO4.7H2O摩尔比x值对合成产物物相的影响。总结了PEG-400模板辅助合成ZnCO3和BZC的反应机制。结果表明,PEG-400包覆ZnSO4.7H2O颗粒形成模板,模板层的厚度影响固相反应的微观机制———薄层单向扩散与厚层互扩散,局部微环境的酸碱性决定着产物物相,酸性抑制ZnCO3水解,碱性促进ZnCO3水解生成BZC。由据此设计的较高x值(x=3.0)、较低PEG-400剂量(70μL)的合成工艺,制备了单相BZC粉体。     

A visible light response TiO2 photocatalyst realized by cationic S-doping and its application for phenol degradation

S-doped TiO2 photocatalyst with high visible light activity was prepared by acid catalyzed hydrolysis method using thiourea (TU) as sulfur source. The catalyst was characterized by DRS, XPS, XRD, FTIR, SEM and N2 adsorption. It was found that cation S6+ was homogeneously incorporated into the bulk phase of TiO2 and substitutes for some of the lattice titanium (Ti4+). Doped S can form a new band above the valence band and narrow the band-gap of the photocatalyst, giving rise to a second absorption edge in the visible light region. The activity of the catalyst was examined by photodegradation of phenol in aqueous solution under both artificial visible light and solar light irradiation. The activity of catalyst was found to be dependent on the doping amount of S and the maximum activity was observed when the catalyst was obtained by calcinated at 600 degrees C with the mass ratio of TU/TiO2=1. Too much of new-generated band-gap structures due to higher S-doping could act as recombination centers for electron-hole pairs. Catalyst with optimum S-doping exhibited the highest activity under both artificial light and solar irradiation for phenol degradation. In addition, doped S also beneficial for the better dispersion, large S(BET) and phase transformation retardation of TiO2.