Photocatalytic water reduction under visible light on a novel ZnIn2S4 catalyst synthesized by hydrothermal method

A novel ZnIn2S4 catalyst synthesized by hydrothermal method shows high and stable photocatalytic activity for water reduction under visible light illumination.

HYDROGEN-RELATED DONOR IN SILICON-CRYSTALS GROWN IN A HYDROGEN ATMOSPHERE

Neutron transmutation doped (NTD) silicon crystals grown in a hydrogen atmosphere have been investigated by infrared absorption spectroscopy at a low temperature (10 K). An effective-mass-like donor state HD0/+ has been found at 110.8 me V below the conduction band bottom after rapid thermal annealing (RTA). The HD0/+ formation mechanism after NTD and RTA is briefly discussed, and tentatively attributed to H atoms present in the vicinity of some residual irradiation defects, like a complex of a H atom and a H-saturated vacancy.

Enhancement of field emission of the ZnO film by the reduced work function and the increased conductivity via hydrogen plasma treatment

The ZnO films deposited by magnetron sputtering were treated by H/O plasma. It is found that the field emission (FE) characteristics of the ZnO film are considerably improved after H-plasma treatment and slightly deteriorated after O-plasma treatment. The improvement of FE characteristics is attributed to the reduced work function and the increased conductivity of the ZnO H films. Conductive atomic force microscopy was employed to investigate the effect of the plasma treatment on the nanoscale conductivity of ZnO, these findings correlate well with the FE data and facilitate a clearer description of electron emission from the ZnO H films.

The role of hydrogen in semi-insulating INP

Complexes of vacancy at indium site with one to four hydrogen atoms and isolated hydrogen or hydrogen dimer and other infrared absorption lines, tentatively be assigned to hydrogen related defects were investigated by FTIR. Hydrogen cam passivate imperfections, thereby eliminating detrimental electronic states from the energy bandgap. Incorporated hydrogen can introduce extended defects and generate electrically-active defects. Hydrogen also can acts as an actuator for creating of antistructure defects. Isolated hydrogen related defects(e.. H-2*) may play an important role in the conversion of the annealed wafers from semiconducting to the semi-insulating behavior. H-2* may be a deep donor, whose energy level is very near the iron deep acceptor level in the energy gap.

Ultrahigh compression of water using intense heavy ion beams: laboratory planetary physics

Intense heavy ion beams offer a unique tool for generating samples of high energy density matter with extreme conditions of density and pressure that are believed to exist in the interiors of giant planets. An international accelerator facility named FAIR (Facility for Antiprotons and Ion Research) is being constructed at Darmstadt, which will be completed around the year 2015. It is expected that this accelerator facility will deliver a bunched uranium beam with an intensity of 5x10(11) ions per spill with a bunch length of 50-100 ns. An experiment named LAPLAS (Laboratory Planetary Sciences) has been proposed to achieve a low-entropy compression of a sample material like hydrogen or water (which are believed to be abundant in giant planets) that is imploded in a multi-layered target by the ion beam. Detailed numerical simulations have shown that using parameters of the heavy ion beam that will be available at FAIR, one can generate physical conditions that have been predicted to exist in the interior of giant planets. In the present paper, we report simulations of compression of water that show that one can generate a plasma phase as well as a superionic phase of water in the LAPLAS experiments.

Water reduction and oxidation on Pt-Ru/Y2Ta2O5N2 catalyst under visible light irradiation

Y2Ta2O5N2 is presented as a novel photocatalyst with high activity for water splitting under visible-light irradiation in the presence of appropriate sacrificial reagents; the activity for reduction to H-2 is increased by the incorporation of Pt or Ru as a co-catalyst, with a significant increase in production efficiency when both Pt and Ru are present.

High-performance dye-sensitized solar cells based on solvent-free electrolytes produced from eutectic melts

Low-cost excitonic solar cells based on organic optoelectronic materials are receiving an ever-increasing amount of attention as potential alternatives to traditional inorganic photovoltaic devices. In this rapidly developing field, the dye-sensitized solar cell(1) (DSC) has achieved so far the highest validated efficiency of 11.1% (ref. 2) and remarkable stability(3).

Design of Narrow-Gap TiO2: A Passivated Codoping Approach for Enhanced Photoelectrochemical Activity

To improve the photoelectrochemical activity of TiO2 for hydrogen production through water splitting, the band edges of TiO2 should be tailored to match with visible light absorption and the hydrogen or oxygen production levels. By analyzing the band structure of TiO2 and the chemical potentials of the dopants, we propose that the band edges of TiO2 can be modified by passivated codopants such as (Mo+C) to shift the valence band edge up significantly, while leaving the conduction band edge almost unchanged, thus satisfying the stringent requirements. The design principle for the band-edge modification should be applicable to other wide-band-gap semiconductors.

水处理纳米材料的制备、性能及应用研究

工业的高速发展使地球上有限的水资源受到日益严重的污染，去除水中的有毒、有害化学物质已成为环保领域的一项重要工作。纳米材料与技术的开发应用为实现高效、低成本的水处理开辟了新的途径。 本课题组开发的纳米-亚纳米功能新材料（生态宝）可用作养殖生态环境改良剂，它对“三氮”、硫化物、CODCr、BOD5、重金属等有害物质具有很好的去除能力。生态宝用于养殖幼参，有显著的促生长、增加成活率的作用。生态宝用于养殖对虾，对虾体内重金属含量有明显降低。 以粉末状P25型纳米TiO2为光催化剂，系统的研究了它对染料AB80的光催化降解。在紫外光照射下，光催化反应75min，染料AB80溶液完全脱色，光催化反应135min，染料溶液完全矿化；AB80的光催化脱色反应遵从准一级反应动力学；催化剂的最佳剂量为1.0g/L。AB80在TiO2颗粒表面的吸附符合Langmuir方程式，随着pH值的增加吸附量迅速减少；pH值在反应中起着重要的作用，碱性溶液中的反应速度比酸性溶液的大，pH=10.0初始反应速度最大；电子捕获剂（H2O2）的加入能够显著的提高反应速率，H2O2浓度为5mmol/L时，反应速度变为原来的2.78倍。 以硅藻土为载体，采用溶胶-凝胶法制备了负载型的纳米TiO2，SEM分析结果表明，TiO2的包覆量对负载光催化剂的形貌有很大影响，TiO2包覆量较低(14.5%)的复合物无团聚现象发生。XRD分析结果表明，所制备的TiO2为锐钛矿和金红石混晶型，平均粒径11nm。FT-IR分析结果表明，TiO2和硅藻土之间没有生成化学键。以染料AB80和B-2BF为模型污染物，利用制备的光催化剂复合物进行了吸附-光催化试验，结果表明，TiO2包覆量为14.5%的复合物具有较高的吸附-光催化活性，对模型污染物的降解效果好于德国Degussa公司的商品纳米P25-TiO2。溶液pH对TiO2/硅藻土复合物光催化活性影响很大，弱酸性条件有利于反应的进行。TiO2/硅藻土对实际印染废水有较好的降解效果，试验条件下，废水光催化反应3.5h，色度去除率为100%。研究了液固多相光催化反应的催化剂失活原因及再生手段，提出TiO2/硅藻土复合物再生的方法为酸洗和高温烧结。对于模拟印染废水来说，光催化剂重复使用对光催化活性几乎没有影响，重复使用15次后，催化活性仅降低了12%。而对实际印染废水来说，重复使用对光催化活性有影响，光催化剂复合物重复使用7次后，催化活性降低了41%。TiO2/硅藻土复合光催化剂成本低，简便易行，光催化效果好，有望在环境污染物治理中得到广泛的应用。 采用CuCl水解法制得了硅藻土负载的纳米Cu2O，并利用XRD、SEM等手段对其进行表征。研究了负载的纳米Cu2O对B-2BF和AB80染料废水的光催化降解，发现纳米Cu2O经过负载后，团聚减少，分散性好，对染料废水的光催化降解效率成倍增长。纳米Cu2O包覆量为31.3%的光催化剂复合物光催化活性最好，其光催化效率是纯的Cu2O的6倍。负载的纳米Cu2O可以有效的利用太阳光进行光催化反应，而且太阳光下纳米Cu2O的光催化活性比纳米TiO2的强。太阳能是取之不尽、用之不竭的清洁能源，利用太阳能来处理染料废水成本低、无污染，是一种非常有发展前景的环境治理新技术。pH 5-pH 7是负载纳米Cu2O光催化降解B-2BF的最佳反应范围。负载的纳米Cu2O光催化剂有较好的稳定性，重复使用8次以后，其脱色率仍能达到75%以上。

Hydrogen passivation of multi-crystalline silicon solar cells

The effects of hydrogen passivation on multi-crystalline silicon (mc-Si) solar cells are reported in this paper. Hydrogen plasma was generated by means of ac glow discharge in a hydrogen atmosphere. Hydrogen passivation was carried out with three different groups of mc-Si solar cells after finishing contacts. The experimental results demonstrated that the photovoltaic performances of the solar cell samples have been improved after hydrogen plasma treatment, with a relative increase in conversion efficiency up to 10.6%. A calculation modelling has been performed to interpret the experimental results using the model for analysis of microelectronic and photonic structures developed at Pennsylvania State University.

The enhancement of TiO2 photocatalytic activity by hydrogen thermal treatment

In this study, conventional TiO2 powder was heated in hydrogen (H-2) gas at a high temperature as pretreatment. The photoactivity of the treated TiO2 samples was evaluated in the photodegradation of sulfosalicylic acid (SSA) in aqueous suspension. The experimental results demonstrated that the photodegradation rates of SSA were significantly enhanced by using the H-2-treated TiO2 catalysts and an optimum temperature for the H-2 treatment was found to be of 500-600 degreesC. The in situ electron paramagnetic resonance (EPR) signal intensity of oxygen vacancies (OV) and trivalent titanium (Ti3+) associated with the photocatalytic activity was studied. The results proved the presence of OV and Ti3+ in the lattice of the H2-treated TiO2 and indicated that both were contributed to the enhancement of photocatalytic activity. Moreover, the experimental results presented that the EPR signal intensity of OV and Ti3+ in the H-2-treated TiO2 samples after 10 months storage was still significant higher than that in the untreated TiO2 catalyst. The experiment also demonstrated that the significant enhancement occurred in the photodegradation of phenol using the H-2-treated TiO2. (C) 2002 Elsevier Science Ltd. All rights reserved.

Transition films from amporphous to microcrystalline silicon and solar cells

A series of hydrogenated silicon films near the threshold of crystallinity was prepared by very high frequency plasmaenhanced chemical vapor deposition (VHF-PECVD)from a mixture of SiH4 diluted in H-2. The effect of hydrogen dilution ratios R = [H-2]/[SiH4] on the microstructure of the films was investigated. The photoelectronic properties and stability of the films were studied as a function of crystalline fraction. The results show that the diphasic films gain both the fine photoelectric properties like a-Si: H and high stability like mu w-Si:H. By using the diphasic silicon films as the intrinsic layer, p-i-n junction solar cells were prepared. Current-voltage (J-V) characteristics and stability of the solar cells were measured under an AM1.5 solar simulator. We observed a light-induced increase of 5.2% in the open-circuit voltage (V-oc) and a light-induced degradation of similar to 2.9% inefficiency.