太阳能光催化制氢反应体系及其材料研究进展

光催化制氢是利用太阳能获取氢能的重要途径,是当前研究热点。长期以来,人们致力于各种新型可见光光催化制氢材料的研究并取得较大进展。反应体系的设计和选择是实现高效光催化制氢和能否走向工业化的核心问题之一,因此,近年来研究者开始对光催化制氢反应体系加大研究。光催化制氢主要有非均相光催化制氢(HPC)和光电催化制氢(PEC),不同的体系具有各自的优缺点和应用范围。重点介绍光催化制氢半反应、光催化完全分解水和光电催化分解水3种主要反应体系,分析各种反应体系的特点,阐述各个体系涉及的光催化材料的发展进程,并展望太阳能光催化制氢研究前景,其中,新型高效的PEC-PV(光伏)耦合光化学转化系统有望为光解水制氢实现工业化提供一种重要的发展途径。     

几种光还原水催化体系产氢量子收率的研究(Ⅱ)

在光解水制氢研究中,光产氢量子收率是一个重要参数。太阳能的光化学储存效率主要取决于光敏催化体系的光波长吸收范围和效率以及所得预期产物的量子收率,即光反应生成产物的分子数与体系吸收的光子数的比值。 近几年来文献对以Ru(bpy)_3~(2+)等金属络合物为光敏剂的光产氢催化体系的量子收率报道较多,而对一些用有机染料为光敏剂的体系报道较少。某些有机染料光敏剂,具     

双刚性杂化分子的溶液自组装研究

为了了解以非共价键结合的双刚性杂化分子在不同溶剂体系下的溶液自组装,本文利用氨丙基七异丁基多面体低聚硅氧烷(Si_8O_(12)NC_(31)H_(71),简称BPOSS-NH_2)与亲水性硅酸钨(H_4SiW_(12)O_(40),简称HSiW)发生氨基质子化反应,形成双亲性杂化分子。通过核磁光谱、红外光谱、元素分析确定了杂化分子的成分。通过透射电子显微镜、扫描电子显微镜对溶液中自组装的纳米结构进行了表征。研究发现,质子化得到的杂化分子在丙酮-水体系中能够组装成层状的规则二维纳米片。当溶剂体系改为四氢呋喃-水时,杂化分子能够组装得到三维囊泡。在丙酮-水体系中,在组装过程中随着水的加入,杂化分子中的BPOSS-NH_2的溶解度变小,导致该双亲性杂化分子缺乏分子运动性,所以最终组装体为层状规则二维纳米片。在四氢呋喃-水体系中,尽管组装过程中有水的加入,由于BPOSS-NH_2在四氢呋喃中的溶解度较高,所以杂化分子中的BPOSS-NH_2具有一定的分子运动性,因而在自组装初期形成的双层结构具有一定的柔性,可以形成二维曲面,最终得到空心囊泡结构。     

臭氧提高纳米TiO_2光催化活性的ESR分析

以5,5-二甲基-1-吡咯啉-N-氧化物(DMPO)为自由基捕获剂,分别以去离子水和二甲基亚砜(DMSO)为溶剂,利用电子自旋共振(ESR)方法对UV、O_3、TiO_2/O_3、TiO_2/UV/O_2、UV/O_3和TiO_2/UV/O_3这6种体系中形成的羟基自由基(·OH)和超氧阴离子自由基(·O_2~-)进行了检测,同时考察了反应时间、催化剂投量以及体系溶解氧对TiO_2/UV/O_3体系形成·OH和·O_2~-的影响.结果显示,在纳米TiO_2光催化体系中加入臭氧,能显著增加反应体系中·OH和·O_2~-自由基的生成量,6种体系中DMPO-·OH和DMPO-·O_2~-加合物的ESR波谱峰信号强度分别为:TiO_2/UV/O_3>TiO_2/UV/O_2>UV/O_3>UV>TiO_2/ O_3>O_3和TiO_2/UV/O_3≈TiO_2/UV/O_2>TiO_2/O_3>UV>UV/O_3>O_3,在TiO_2/UV/O_3体系中成功监测到·O_3~-自由基的存在.     

电沉积制备铜铟镓硒(CIGS)太阳能电池吸收层的研究现状

概述了近几年水溶液体系中直流和脉冲电沉积法制备铜铟镓硒(cIGs)薄膜太阳能电池吸收层的研究情况,介绍了几种非水溶剂电沉积CIGS体系,展望了电沉积法制备CIGS薄膜的未来发展。     

P2O5液相催化环己酮肟重排制己内酰胺

研究了以环己酮肟、五氧化二磷(P_2O_5)、二甲基甲酰胺(DMF)组成的反应体系进行Beckmann重排制备己内酰胺工艺,考察了不同溶剂、催化剂用量、温度、浓度及水分含量对重排反应的影响。结果表明,由DMF、P_2O_5、少量水组成的反应体系,当P_2O_5与环己酮肟质量比为(1.0：4.5)～(1.0：5.6),温度为160～170℃,停留时间为0.75～1.00 h时,实现环己酮肟Beckmann重排制己内酰胺,转化率达99.5％以上,选择性达94.5％     

合肥研究院光催化制氢材料研究取得进展

正近日,中国科学院合肥物质科学研究院应用技术研究所先进材料中心研究团队,在金属/半导体复合光催化制氢材料研究方面取得了新进展。光催化可实现太阳能到化学能的转化(如光催化分解水制氢),是获取新能源的理想途径之一,开发宽光谱响应、高载流子分离效率的光催化材料,是实现太阳能高效光化学转化的前提和基础。研究人员制备了具有不同AuCu原子     

对-二氰基乙烯基-N,N-二甲基,十六烷基苯胺在混合溶剂中的光谱行为与簇集作用

本文合成了对-二氰基乙烯基-N,N-甲基、十六烷基苯胺(DCMCA),研究了它在正己烷-丙酮混合溶剂中的光谱行为,测定了DCMCA-丙酮生成的1:1络合平衡常数为0.5249;对照对-二氰基乙烯基-N,N-二甲基苯胺(DCDMA),研究了DCMCA在二甲基亚砜-水(DMSO-H_2O)体系中的簇集作用及簇集体内光物理及光化学过程。     

不同形貌氧化亚铜的制备及表征

采用水和有机溶剂相结合的双溶剂热法来合成一系列不同形貌下的氧化亚铜(Cu_2O)晶体;双溶剂主要是以水-乙醇(C_2H_6O,EtOH)体系和水-乙二醇(C_2H_6O_2,EG)体系为主。与传统合成方法相比,双溶剂热法是一种比较温和的技术,不需要制作模板或添加任何有污染的表面活性剂。以Cu(CH_3COO)_2为原料,柠檬酸钠(Na_3C_6H_5O_7)为形貌导向剂,控制氢氧化钠(NaOH)加入的浓度大小、调节原料之间的物质的量比、加料方式、还原剂葡萄糖(C_6H_(12)O_6)浓度等条件,利用双溶剂热法制备氧化亚铜(Cu_2O)微晶。探讨在以上条件的作用下,对制备Cu_2O不同形貌与粒径等方面有何影响。制备工艺过程中哪种方案最为简单、经济、环保。然后,将合成的Cu_2O产物采用X-射线衍射仪(XRD),扫描电子显微镜(SEM)等方法对其进行表征。最终,制得的Cu_2O可作为光催化剂有望在可见光作用下,催化降解染料污水。     

片状与颗粒状CoMn2O4电极材料的制备及电化学性能

分别以纯水、50%(体积分数,下同)纯水与50%乙醇混合溶液、乙醇为溶剂制备了CoMn_2O_4纳米电极材料,研究了溶剂对CoMn_2O_4材料形貌、微观结构及电化学性能的影响。结果表明:采用纯水为溶剂制备的CoMn_2O_4材料具有片状结构,在电流密度为1 A/g时,比电容为446 F/g,在电流密度为5 A/g条件下,1 000次充放电循环后电容保持率为77%;50%纯水加50%乙醇为溶剂制备的CoMn_2O_4材料具有颗粒与片状混合结构,在电流密度为1 A/g时,比电容为684 F/g,在电流密度为5 A/g条件下,1 000次充放电循环后电容保持率为81%;采用乙醇为溶剂制备CoMn_2O_4材料具有颗粒状多孔结构,在电流密度1 A/g条件下,比电容为850 F/g,在电流密度为5 A/g条件下,1 000次充放电循环后电容保持率达86%,乙醇为溶剂制备的颗粒状多孔的CoMn_2O_4材料表现出更为优异的超电容性能。     

Ionic solvation—I. Free energies of transfer of copper(II) ion from water to alcohols and to their mixtures with water

The emf of the cell: Cu|Cu²⁺ in water||Cu²⁺ in water + alcohol|Cu for different alcohols (methanol, ethanol, 1-propanol, 2-propanol, t-butanol, ethylene glycol, propylene glycol and glycerol) and their mixtures with water have been measured at 25°C. These data were used for calculation of Gibbs free energies of transfer of copper(II) ion from water to nonaqueous alcohols and to their mixtures with water, with the help of negligible liquid junction potential assumption. Determined free energies of transfer are positive for all solvents studied, which may be simply interpreted assuming that copper(II)ion interacts more strongly with water molecules than with alcohol molecules, without reference to any special structural properties of these solvents.     

A Thermoanaerobacter ethanolicus secondary alcohol dehydrogenase mutant derivative highly active and stereoselective on phenylacetone and benzylacetone

The secondary alcohol dehydrogenase from Thermoanaerobacter ethanolicus 39E (TeSADH) is highly thermostable and solvent-stable, and it is active on a broad range of substrates. These properties make TeSADH an excellent template to engineer an industrial catalyst for chiral chemical synthesis. (S)-1-Phenyl-2-propanol was our target product because it is a precursor to major pharmaceuticals containing secondary alcohol groups. TeSADH has no detectable activity on this alcohol, but it is highly active on 2-butanol. The structural model we used to plan our mutagenesis strategy was based on the substrate's orientation in a horse liver alcohol dehydrogenase*p-bromobenzyl alcohol*NAD(+) ternary complex (PDB entry 1HLD). The W110A TeSADH mutant now uses (S)-1-phenyl-2-propanol, (S)-4-phenyl-2-butanol and the corresponding ketones as substrates. W110A TeSADH's kinetic parameters on these substrates are in the same range as those of TeSADH on 2-butanol, making W110A TeSADH an excellent catalyst. In particular, W110A TeSADH is twice as efficient on benzylacetone as TeSADH is on 2-butanol, and it produces (S)-4-phenyl-2-butanol from benzylacetone with an enantiomeric excess above 99%. W110A TeSADH is optimally active at 87.5 degrees C and remains highly thermostable. W110A TeSADH is active on aryl derivatives of phenylacetone and benzylacetone, making this enzyme a potentially useful catalyst for the chiral synthesis of aryl derivatives of alcohols. As a control in our engineering approach, we used the TbSADH*(S)-2-butanol binary complex (PDB entry 1BXZ) as the template to model a mutation that would make TeSADH active on (S)-1-phenyl-2-propanol. Mutant Y267G TeSADH did not have the substrate specificity predicted in this modeling study. Our results suggest that (S)-2-butanol's orientation in the TbSADH*(S)-2-butanol binary complex does not reflect its orientation in the ternary enzyme-substrate-cofactor complex.     

Preparation of ZnO nanorod by solvothermal reaction of zinc acetate in various alcohols

Solvothermal reaction of zinc acetate in various alcohols resulted in the formation of zinc oxide (ZnO) nanorods. The effects of reaction conditions on the product morphology as well as crystallization mechanism were investigated by using X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) techniques. It was found that average diameter and length of the nanorods increased with an increase in reaction temperature or the initial concentration of zinc acetate. On the contrary, the aspect ratio of the product depended upon type of alcohol used as the reaction medium. The aspect ratio of ZnO nanorods increased from 1.7 to 5.6 when the alcohol was changed from 1-butanol to 1-decanol. An investigation of the reaction mechanism suggested that the formation of ZnO nanorods was initiated from the esterification reaction between zinc acetate precursor and alcohol to form ZnO seeds.     

Thermodynamic properties of hydrobromic acid in 5 wt% 1-butanol-water,and 5 wt% 2-methyl-1-propanol-water-mixture from emf measurements

From the electromotive force measurements of the cell Pt (or Pd), H₂(g)|HBr(m), 5 wt% alcohol-water mixture|AgBrAg for different m in the temperature range from 288.15 to 308.15 K, the standard potential of AgAgBr electrode has been determined in the mixture where alcohol was 1-butanol and 2-methyl-1-propanol. The standard thermodynamic quantities for cell reaction and for HBr formation, the activity coefficients of HBr, and the standard thermodynamic quantities for the transfer of HBr from water to mixed solvents have been evaluated. The transfer functions were compared with those for water mixtures of other isomeric butanols as well as for the mixture with small proportions of other alcohols.     

Kirkwoodsche Korrelationsfaktoren von binären Systemen mit Alkoholen und Diäthyläther

Kirkwood Correlation Factors of Binary Systems with Alcohols and Diethylether The KIRKWOOD theory allows the calculation of a correlation factor for describing the association of polar substances. For the systems n-hexane + diethylether cyclohexane + 1-propanol cyclohexane + 1-butanol benzene + methanol benzene + ethanol benzene + 1-propanol benzene + 1-butanol benzene + 1-hexanol benzene + 1-octanol the experimental values of dielectric constant and the calculated correlation factors are presented. From the concentration dependence of the correlation factors, calculated by use of the KIRKWOOD -FRÖHLICH -equation for mixtures, the existence of widely ramified associations of methanol and the formation of clusters of ethanol, propanol-(1), butanol-(1), hexanol-(1) and octanol-(1) is deduced. In the systems benzene + alcohol in most of the cases some specific interactions between the two components are supposed to exist.     

Investigation of liquid–liquid equilibrium of the ternary system(water +1,6-diaminohexane + 2-methyl-1-propanol or 3-methyl-1-butanol) at different temperatures

In this study, the LLE data of ternary system (water+1,6-diaminohexane+2-methyl-1-propanol) and (water+1,6-diaminohexane+3-methyl-1-butanol) were measured at 293.15, 303.15 and 313.15 K under atmospheric pressure. Reliability of the experimental tie-line data was checked by empirical Hand, Othmer-Tobias and Bachman equations. Distribution coefficient (D) and selectivity (S) were calculated in order to investigate capability of the studied organic solvents for 1,6-diaminohexane extraction. The high values of separation factors demonstrated that 2-methyl-1-propanol and 3-methyl-1-butanol were applicable for this purpose. The experimental data were correlated by nonrandom two-liquid (NRTL) and universal quasi-chemical (UNIQUAC) models. The percent-root-mean-square deviation (RMSD) values for NRTL and UNIQUAC models were less than 0.15, which indicated that the experimental data have been sufficiently correlated.     

Ternary phase diagrams for gasoline-water-alcohol mixtures

The ternary phase diagrams for gasoline-water-alcohol (where the alcohol is methanol, ethanol, 1-propanol, 1-butanol or a ‘SASOL alcohol substitute’) mixtures have been determined over the whole composition range at temperatures between 2 °C and 40 °C. The result shows that the miscibility of water in these blends is strongly dependent on the type of alcohol present. Furthermore the tie-line results show the composition of the separated water-rich phase are also strongly dependent on the type of alcohol. It is believed that these results have a bearing on the carburettor corrosion problems experienced when using gasoline-SASOL alcohol substitute blends.     

Prevaporation of water/alcohol mixtures through the PVA membranes containing cyclodextrin oligomer

Prevaporation through the PVA membrame containing β-cyclodextrin oligomer (PVA/CD membrane) was performed for the mixtures of water/ethanol, water/1-propanol, and water/2-propanol. At higher alcohol concentrations, the water selectivities were greatly increased by CD for all the mixtures, in the order of 2-propanol/water>1-propanol/water>ethanol/water. The water permeation rate was decreased by CD, and the alcohol permeation rate was decreased much more for each mixture. At lower alcohol concentrations, the water selectivity for 1-propanol/water was slightly increased by CD, and that for 2-propanol/water was scarcely affeted, whereas that for ethanol/water was greatly increased. The water permeation rate was increased by CD for each mixture, and the relative increases in the water rates for propanols/water were smaller than that for ethanol/water. The permeation rate of 1-propanol as well as that of ethanol was decreased by CD, but the rate of 2-propanol was was increased. These effects of CD can be explained in terms of the inclusion strength. © 1994 John Wiley & Sons, Inc.     

Conversion of used frying oil to diesel fuel by transesterification: Preliminary tests

Used frying oil was transesterified by reaction with excess alcohol under both acidic and basic conditions. The alcohols used were: methanol, ethanol, 1-propanol, 2-propanol, 1-butanol and 2-ethoxyethanol. Yields of the fuels determined by gas chromatography and their viscosities are reported. The best result was obtained using methanol with catalysis by potassium hydroxide. The methyl ethyl and 1-butyl esters all ran very well in short-term engine tests with a laboratory high-speed diesel engine.     

Mechanism of photoelectrocatalytic dehydrogenation of 2-propanol on a polycrystalline ZnO photoelectrode

The mechanism of photoelectrocatalytic dehydrogenation of 2-propanol on a ZnO photoelectrode is re-examined. The effect of gaseous atmosphere is studied. The change of pH due to the reaction is followed under different experimental conditions. The larger part of the dissolution of ZnO occurs in the dark itself due to the solubility of ZnO. The photodissolution is comparatively small. 2-Propanol inhibits the photocorrosion slightly. H₂O₂ is detected in the electrolyte irrespective of the presence of 2-propanol. An electron transfer process followed by a free radical mechanism for the formation of H₂O₂ is proposed and discussed.