W18O49/C-TiO2直接Z型光催化剂的制备及光解水制氢性能

采用水热法制备W18 O49/C-TiO2直接Z型光催化剂.使用XRD,SEM,TEM,HRTEM,PL等测试手段对样品的结构、形貌、光生载流子的输运特性及能带结构进行表征.在模拟太阳光照射下,不添加任何牺牲剂,研究样品的光解水制氢性能及其量子效率.结果表明:W18 O49/C-TiO2直接Z型光催化剂的构建显著提高催化剂的光吸收性能,加速光生电荷的分离和传输,使更多的光生电子参与光催化还原反应,从而使样品具有高效的光催化活性.光解水制氢测试显示,W18 O49/C-TiO2直接Z型异质结在模拟太阳光照射下,在不添加任何牺牲剂的条件下,产氢速率达209μmol·h-1·g-1,并具有较强的光催化稳定性,在24 h的循环测试中,产氢量保持不变.     

Promotion of generation of hydrogen by splitting of water by CNT over Pt/TiO2 catalysts

The generation of hydrogen over CNT/Pt/TiO2 catalysts by the splitting of water under irradiation with UV light is studied. The maximum rate of evolution of hydrogen was 2300 micromolg(-1)h(-1) on 0.06 wt% Pt/TiO2 (sol-gel) and reached a stable value of approximately 2000 micromolg(-1)h(-1) when the Pt loading exceeded at a Pt loading of over 0.06 wt%. Single wall carbon nanotubes (SWCNTs) were applied to enhance the hydrogen generation activity. The evolution rate of hydrogen on 0.06 wt% Pt/0.02 wt% SWCNT-TiO2 (sol-gel) was 3836 micromolh(-1)g(-1). 0.1 M NaCI yielded more hydrogen than any other tested salt. The XRD spectra show that the crystal lattices of commercial TiO2 (ST-21) and self-made TiO2 (sol-gel method) are of the anatase form. However, the TEM images and other catalytic activity data show that the SWCNTs act as wires for the transmission of electrons.     

Ozonation and H2O2/UV treatment of clofibric acid in water: a kinetic investigation

The presence of pharmaceuticals or their active metabolites in surface and ground waters has been recently reported as mainly due to an incomplete removal of these pollutants in sewage treatment plants (STP). Advanced oxidation processes may represent a suitable tool to reduce environmental release of these species by enhancing the global efficiency of reduction of pharmaceuticals in the municipal sewage plant effluents. The present work aims at assessing the kinetics of abatement from aqueous solutions of clofibric acid (a metabolite of the blood lipid regulator clofibrate) which has been found in surface, ground and drinking waters. Ozonation and hydrogen peroxide photolysis are capable of fast removal of this species in aqueous solution, with an almost complete conversion of the organic chlorine content into chloride ions for the investigated reaction conditions. A validation of assessed kinetics at clofibric acid concentrations as low as those found in STP effluents is presented for both systems.     

纳米CuAl2O4/CuO的制备及其模拟太阳光催化产氢

采用共沉淀法制备了纳米结构的CuAl2O4/CuO,用草酸作牺牲剂,在150W的氙灯照射下,考查了不同焙烧温度、催化剂用量对光催化活性的影响。并用XRD、SEM、TG-DTA对样品分别进行了分析与表征,表明CuAl2O4为尖晶石型结构,平均粒径10nm左右。在相同条件下分别考察了固相法、共沉淀法与柠檬酸溶胶-凝胶法对催化剂活性的影响,实验结果表明溶胶-凝胶法产氢活性最好,产氢速率为41mL/h;共沉淀法次之,为34mL/h;固相法最差,为25mL/h。     

Photogalvanic generation of dihydrogen by water splitting using MoS 4 2− as catalyst

A 4% solar energy efficiency has been achieved for photogeneration of dihydrogen (H₂) using MoS ₄ ²⁻ as catalyst, when the anode compartment of a photogalvanic cell is illuminated. The generated photocurrent rises slowly with time and reaches a limiting value. Ten hours after the reaction starts, a secondary dark reaction sets in which produces H₂ and photocurrent even when the light is switched off. Possible mechanisms in both cases have been suggested.     

Thermal conductivity of heavy-oxygen water H2O18

The ratio of thermal conductivity coefficients of heavy-oxygen water H₂O¹⁸ with different percentages of enrichment to the thermal conductivity coefficient of ordinary water is measured in the range of 0–40°C. Differences in the thermal conductivities and the temperature coefficients of the thermal conductivity of heavy-hydrogen water D₂O and and heavy-oxygen water H₂O¹⁸ are indicated.     

Degradation of 1,4-dioxane in water using TiO2 based photocatalytic and H2O2/UV processes

1,4-dioxane is a synthetic compound found in industrial effluent and subsequently contaminates water bodies due to its high solubility and high volatility. It is of concern due to its toxic and hazardous nature and has been listed as a class 2B carcinogen. This study involved optimisation of the photocatalytic and H(2)O(2)/UVC processes for 1,4-dioxane removal. Different photocatalysts and loadings were investigated for the degradation of low concentrations of 1,4-dioxane in water including a commercial P25, a synthesised magnetic photocatalyst and an immobilised sol-gel system. A commercial catalyst (Degussa P25) was the most efficient. A lifetime study of the sol-gel reactor showed that the coating was stable over the time period studied. The optimum H(2)O(2) concentration in the H(2)O(2)/UVC process was found to be 30ppm. The addition of H(2)O(2) to the photocatalytic process for 1,4-dioxane removal caused a decrease in rate for the commercial P25 photocatalyst and an increase in rate for the lab-made magnetic photocatalyst.     

Synthesis of Pt doped Bi2O3/RuO2 photocatalysts for hydrogen production from water splitting using visible light

This study was focused on the preparation of modified bismuth oxide photocatalysts, including Ru and Pt doped Bi2O3, using sonochemically assisted method to enhance their photocatalytic activity. The crystalline phase composition and surface structure of Bi2O3 photocatalysts were examined using SEM, XRD, UV-visible spectroscopy, and XPS. Optical characterizations have indicated that the Bi2O3 presents the photoabsorption properties shifting from UV light region into visible light which is approaching towards the edge of 470 nm. According to the experimental results, visible-light-driven photocatalysis for water splitting with the addition of 0.3 M Na2SO3 and 0.03 M H2C2O4 as sacrificing agents demonstrates that Pt/Bi2O3-RuO2 catalyst could increase the amount of hydrogen evolution, which is around 11.6 and 14.5 micromol g(-1) h(-1), respectively. Plausible formation mechanisms of modified bismuth oxide and reaction mechanisms of photocatalytic water splitting have been proposed.     

Photoexcitation of TiO2 photoanode in water splitting

TiO₂ is one of the most promising photoanodes for solar-hydrogen conversion by water splitting. However, the solar-hydrogen efficiency of TiO₂ remains limited because of a low photocurrent generation. A clear understanding of photoexcitations within photoanodes can predict the quantity of photocurrent and consequently determine the solar-hydrogen efficiency. In this work, hydrothermally synthesized rutile TiO₂ nanorods were investigated for their photoelectrochemical (PEC) performance. A photogenerated hole concentration of TiO₂ photoanode was derived as 8.40 × 10¹⁴ cm⁻³ under one sun illumination. In addition, Fermi level pinning associated with high density of surface states was also observed under PEC operation. Base on these results, a series of band diagrams of TiO₂ photoanode were established to describe the photogeneration of holes and current at various bias potential. The main limitation of photocurrent generation is the distribution of surface-trapped states, which determines the hole concentration at the surface and consequently determines the open-circuit potential and the photocurrent density.     

Liquid mutual diffusivities of the H2O/D2O system

The liquid-phase mutual diffusivities of the water (H₂O) and deuterium oxide (D₂O) system at 298.2 K were measured using an instrument based on the Taylor dispersion technique. The instrument has been designed to match, as closely as possible, the mathematical model of ideal Taylor dispersion, minimizing all the departures from the ideal model. The diffusivities were measured over the entire concentration range and the results follow a linear dependence on molar fraction given by 10⁹ D ₁₂ = , where D ₁₂ is in m²·s^–1. Comparison with highly accurate data obtained by a Rayleigh interferometer seems to indicate that the accuracy of the present instrument is 1%. The hard-sphere model was applied to the estimation of the mutual diffusivities of this system and good agreement was found with experiment, deviations being ±3.5%.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Resonant absorption of energy accompanying phase transitions in NaKC4H4O6·4H2O

Resonant absorption of external electric field energy was detected experimentally in the presence of phase transitions in Rochelle salt. An external alternating electric field leads to the appearance of an anomalous increase in the signal intensity at frequencies typical of those of the pulsed electric signal induced by a phase transition in the material. Pis’ma Zh. Tekh. Fiz. 24, 46–49 (August 26, 1998)     

High-precision laser spectroscopy D/H and 18O/16O measurements of microliter natural water samples

Newly available gas analyzers based on off-axis integrated cavity output spectroscopy (OA-ICOS) lasers have been advocated as an alternative to conventional isotope-ratio mass spectrometers (IRMS) for the stable isotopic analysis of water samples. In the case of H2O, OA-ICOS is attractive because it has comparatively low capital and maintenance costs, the instrument is small and field laboratory portable, and provides simultaneous D/H and 16O/18O ratio measurements directly on H2O molecules with no conversion of H2O to H2, CO, or H2/CO2-water equilibration required. Here we present a detailed assessment of the performance of a liquid-water isotope analyzer, including instrument precision, estimates of sample memory and sample mass effects, and instrumental drift. We provide a recommended analysis procedure to achieve optimum results using OA-ICOS. Our results show that, by using a systematic sample analysis and data normalization procedure routine, measurement accuracies of +/-0.8 per thousand for deltaD and +/-0.1 per thousand delta18O are achievable on nanoliter water samples. This is equivalent or better than current IRMS-based methods and at a comparable sample throughput rate.     

The saving of energy when cooling milk and heating water on farms

The heat generated in the condenser of a refrigerated farm tank can be used for heating the water, needed for cleaning the milking equipment, to 60°C.Some experimental results (rise in water temperature, consumption of electricity), are discussed for one of the systems, in which a so-called boiler-condenser is used for the heating of water. If, in addition, a precooler is used, the total consumption of electricity for cooling and heating can be reduced by about 50%.It is expected in the Netherlands that in future 50% of milk will be produced on farms with 60 or more cows. At most of them the use of precoolers and heat pumps will be economically justified.     

Photodegradation of 17beta-estradiol in water by UV-vis/Fe(III)/H2O2 system

Photodegradation of 17beta-estradiol (E2) in aqueous solutions by UV-vis/Fe(III)/H(2)O(2) system, namely Photo-Fenton system, was preliminarily investigated under a 250 W metal halide lamp (lambda > or = 313 nm). The influences of initial pH value, initial concentration of H(2)O(2) and E2 on photodegradation efficiency of E2 were discussed and the amount of CO(2) produced by the photodegradation reaction was measured. The results indicates that E2 could be decomposed efficiently in UV-vis/Fe(III)/H(2)O(2) system. Under the condition of 10.0 micromol L(-1) Fe(III), 1000 micromol L(-1) H(2)O(2) and pH 3.0, the degradation efficiency of 18.4 micromol L(-1) E2 reach 75.2% after the irradiation of 160 min. Over the range of pH 3.0-6.0, the higher acidity, the higher the degradation efficiency of E2 and initial reaction rate are. The degradation efficiency of E2 increases with increasing of initial concentration of H(2)O(2) and with decreasing of initial concentration of E2. The E2 mineralization efficiency increases with reaction time but the mineralization efficiency was lower. When the initial concentration of Fe(III) and H(2)O(2) were 10.0 and 1000 micromol L(-1), respectively, the mineralization efficiency of 18.4 micromol L(-1) E2 solution with pH 3.0 was only 21.6% after 160 min irradiation. It is suggested that the mineralization occurred probably only at aromatic ring.     

Phase-junction Ag/TiO2 nanocomposite as photocathode for H2 generation

Developing anatase/rutile phase-junction in TiO2 to construct Z-scheme system is quite effective to improve its photoelectrochemical activity.In this work,the anatase/rutile phase-junction Ag/TiO2 nanocomposites are developed as photocathodes for hydrogen production.The optimized Ag/TiO2 nanocomposite achieves a high current density of 1.28 mA cm-2,an incident photon-to-current con-version efficiency(IPCE)of 10.8％,an applied bias photon-to-current efficiency(ABPE)of 0.32 at 390 nm and a charge carriers'lifetime up to 2000s.Such enhancement on photoelectrochemical activity can be attributed to:(i)the generated Z-scheme system in the anatase/rutile phase-junction Ag/TiO2 photocath-ode enhances the separation,diffusion and transformation of electron/hole pairs inside the structure,(ii)Ag nanodots modification in the anatase/rutile phases leading to the tuned band gap with enhanced light absorption and(iii)the formed Schottky barrier after Ag nanodots surface modification provides enough electron traps to avoid the recombination of photogenerated electrons and holes.Our results here sug-gest that developing phase-junction nanocomposite as photocathode will provide a new vision for their enhanced photoelectrochemical generation of hydrogen.     

Hydrogen substitutes for the in situ generation of H2O2: an application in the Fenton reaction

This study investigates the ability of formic acid, hydrazine and hydroxylamine to act as H₂ substitutes in conducting phenol degradation by Fenton reaction using in situ generated hydrogen peroxide. The processes were performed with semi-heterogeneous (Pd/Al₂O₃ + soluble Fe²⁺) and fully heterogeneous (FePd/Al₂O₃) catalytic systems under ambient conditions. In contrast to bulk H₂O₂ production conditions, hydrazine is able to produce H₂O₂in situ followed by phenol degradation using Pd/Al₂O₃ + Fe²⁺ at pH 3 without the need for halide ions. However, a degree of mineralization exceeding 37% could not be achieved. The significant production of in situ H₂O₂ at the inherent acidic pH of hydroxylammonium sulfate in the presence of Pd/Al₂O₃ + Fe²⁺ was also found to differ from the bulk production of H₂O₂, in which no H₂O₂ was detected. A remarkable degree of mineralization (ca. 65%) as well as fast phenol degradation during the reaction started at pH 7 over FePd/Al₂O₃ may be an advantage of using hydroxylamine. On the other hand, using formic acid, H₂O₂ was produced at a moderate rate, thereby achieving higher efficiency in the mineralization of phenol. Most importantly, the catalysts were more stable in the presence of formic acid than hydrazine or hydroxylamine.