可见光激发高光催化活性的纳米TiO2光催化剂——丙酮溶剂水热合成、特性表征与光催化活性起因

通过XRD、TEM、TG-DTA和漫反射谱(DRS)等手段,分析了采用丙酮溶剂水热法合成的在可见光波段对甲基橙具有高光催化降解率的纳米TiO2粉体的材料特性与光催化活性的起因。结果表明,经不同温度热处理得到的样品均为锐钛矿晶型、粒径基本相同,但在表面剩余吸附物含量以及可见光波段的光吸收率等方面差异明显,且样品表面剩余吸附物含量、可见光波段的光吸收率与其可见光催化活性之间存在直接关联。分析认为,TiO2表面剩余吸附有机物导致的对可见光的强烈吸收是其可见光波段高光催化活性的重要起因。     

可见光响应负载型Er3+∶YAlO3/TiO2-SAC光催化剂的制备及其性能研究

为使TiO2能在可见光下发挥其于紫外激发的高光催化活性,且易于从处理废水中分离,采用溶胶-凝胶法将TiO2与掺杂稀土离子Er3+的上转换发光剂Er3+∶YAlO3结合再负载到球形活性炭(SAC)表面,制备可见光响应的负载型Er3+∶YAlO3/TiO2-SAC光催化剂并对其进行表征。以甲基橙为目标污染物,研究了制备的催化剂在可见光下催化活性,并探讨不同Er3+∶YAlO3/TiO2的负载方式、负载量等制备条件对光催化剂活性的影响。结果表明,结合方式为Er3+∶YAlO3/TiO2烧结后与SAC在乙醇介质中混合并进行30min磁力搅拌、以Er3+∶YAlO3/TiO2与SAC质量比为1∶4时制备的光催化剂活性最高,甲基橙的脱色率在240min可达97%以上。     

多级离子注入法制备太阳选择性吸收膜

尝试采用离子注入法制备太阳选择性吸收膜层.利用多级离子注入后纵向浓度分布呈梯度分布的原理,对纯铝表面溅射Ti膜后进行了3种方案的多级N离子注入.测试了样品的吸收率和发射率,对各方案制备的样品进行了性能比较,并用x射线衍射仪分析了物相组成,用俄歇扫描系统分析了纵向元素的分布,用弯折法测试了膜层结合力.结果发现,膜层吸收率均在0.94以上,但发射率普遍偏大.太阳选择吸收性最好的样品吸收率a为0.95、发射率e为0.21,膜层中含有TiN0.76、TiN0.6O0.4、TiO、Al2、Ti、Al3、Ti等物相,氮元素在纵向由最表面到铝基体梯度递减,膜层与基底结合力良好.     

CdS量子点敏化TiO_2纳米颗粒多孔薄膜太阳能电池性能研究

以CdS量子点敏化TiO2纳米颗粒多孔薄膜为光阳极,与多硫电解液和Pt对电极组装太阳能电池,研究了光阳极厚度和敏化周期对光伏性能的影响。结果表明,TiO2纳米颗粒多孔薄膜的最佳厚度为14μm,最佳CdS量子点敏化周期为20,由此得到的太阳能电池的短路电流密度J sc、光电转换效率η和量子效率分别为4.51 mA/cm2、0.76%和69%。在光阳极中采用TiO2纳米颗粒/TiO2纳米线多孔薄膜双层工作电极,TiO2纳米线散射层增加了对入射光的利用率,使电池在可见光波段的量子效率增加,从而使电池的短路电流密度J sc和光电转换效率分别比原来提高了11.6%和10.5%。     

热处理对TiO2/膨润土纳米复合物结构及其光催化活性的影响

采用酸性溶胶法合成TiO2/膨润土纳米复合物,考察了热处理温度对其物理特性与光催化活性的影响.研究发现,制备的复合物具有较好的热稳定性,经973K热处理后,其结构仍基本保持不变.但随着煅烧温度的升高,层间隙逐渐减少.不同煅烧温度对复合物的催化活性影响较大,773 K热处理样品的光催化活性＞973K＞573K.煅烧温度对复合物的吸附性能与催化活性影响规律的差异表明了在吸附作用加强光催化性能的同时,复合物中的高分散的TiO2的形态等其他因素也发挥着重要作用.     

有机污染物的半导体光催化降解研究进展

以半导体催化剂TiO2为例，讨论了光催化降解有机污染物的机理，介绍了其晶型、粒径大小和制备方法等对催化活性的影响。同时讨论了光强、污染物溶液的pH值、温度、O2，O3及H2O2等因素对反应速度的影响。总结了半导体光催化降解在消除重要的水污染物(有色燃料、氯代物和芳香类化合物、农药、表面活性剂)方面的应用。     

TiO_2光催化氧化对染料降解脱色行为的研究

在以紫外光为光源的TiO2悬浮光催化反应体系中,以RB、AG和MG三种染料作为模型污染物,对染料光催化氧化的脱色行为进行了研究。研究结果表明:①染料在TiO2表面上的吸附是进行光催化反应的前提条件之一,而染料在TiO2表面吸附能力的大小直接影响着光催化反应效率的高低;②OHg的主要来源是由TiO2表面光生空穴进行离子反应提供的;溶解O2主要是抑制TiO2表面光生电子—空穴的复合;染料主要是通过TiO2表面光生空穴直接氧化分解的或由光生空穴产生的OHg氧化分解的。     

TiO2-xNx光催化剂的制备及其活性研究

在sol-gel法制备TiO2的过程中引入氨水进行水解,制备了具有可见光活性的TiO2-xNx催化剂,采用UV-Vis、BET、XPS等手段进行表征,以苯甲酸为模型污染物,氙灯为模拟太阳光源,评估了催化可见光催化活性.结果表明,随着焙烧温度的升高,TiO2-xNx的吸光特性增加,当温度超过350%后TiO2-xNx中的氮会在高温下被氧化掉,其吸光特性又降低;此时TiO2-xNx的吸收阈值为422nm,对应的禁带宽度为2.9eV;孔径分布在2.5～8.2nm之间,BET比表面积为139.3m2/g;经计算其x=0.0282,即TiO2-xNx可表示为Ti1.9718N0.0282;在入射波长分别为500nm和600nm时,TiO2-xNx对苯甲酸的去除率分别为6.5%和4.6%,相应的矿化率为3.2%和2.5%.     

TiO2相结纳米棒制备及其光催化深度脱除烟气汞的实验研究

采用溶剂热法制备了不同形貌和不同晶相掺杂的TiO2相结纳米棒,研究不同物质的量比下TiO2的形貌及相结对光催化氧化脱汞性能的影响.结果 表明:TB、ET、HAc与LiAc物质的量比为1∶20∶20∶5时,TiO2纳米棒的性能最佳,光响应范围可扩展到可见光;在可见光下光催化脱汞效率达到44.7％,且光催化剂的稳定性良好.     

上转光剂掺杂新型纳米TiO2催化剂的制备及利用可见光降解结晶紫染料的研究

合成了一种新型含有稀土金属Er的上转光剂,此上转光剂在488nm可见光的激发下,产生了5个波长均小于387nm的上转换紫外发射峰。采用超声波分散的方法制备出了上转光剂掺杂纳米TiO2可见光光催化剂。以结晶紫为研究对象,研究了光催化剂在可见光(三基色灯下发出)照射下的催化降解性能,并与未掺杂的纳米TiO2粉末的催化性能进行了对比。实验结果表明作为掺杂成分的上转光剂可有效地将可见光转化为紫外光并被纳米TiO2粉末吸收利用,其中380nm转光效率为0.78%。紫外光谱和离子色谱表明,在可见光照射8.0h后降解率达95%以上,高于未掺杂纳米TiO2的48%,结晶紫降解后生成的Cl-和NO3-作为一种无机离子进入溶液中。所有结果表明,掺入上转光剂的TiO2光催化剂是一种有效利用可见光的催化剂,为未来利用太阳光处理工业废水开辟了道路。     

Evaluation of in-situ formed La2O3–TiO2–La2O2CO3 nanocomposite photocatalyst for H2 production

The photocatalytic evolution of H₂ over La₂O₃ decorated TiO₂ catalyst was examined under solar light. It was observed that during the course of the reaction, the transformation of La₂O₃/TiO₂ into La₂O₃–TiO₂–La₂O₂CO₃ occurred and these species effectively suppressed electron-hole pair recombination by forming electron trapping centres on the surface, resulting in an increased visible light absorption and improved H₂ yield. The 2 wt%La₂O₃/TiO₂ nanocomposite demonstrated better H₂ yield (～8.76 mmol (g_cat)^?1) than the bare TiO₂ (～1.1 mmol (g_cat)^?1). The catalyst was stable even after several consecutive recycles with no substantial loss of hydrogen production rate. The H₂ rates were correlated with the physicochemical characteristics of the catalysts examined by BET–SA, H₂-TPR, XRD, UV-DRS, Raman spectroscopy, FTIR, HRTEM, EPR and PL spectroscopy.     

Numerical study of the O2/CO2, O2/CO2/N2, and O2/N2-syngas MILD combustion: Effects of oxidant temperature,O2 mole fraction,and fuel blends

Moderate or Intense Low-oxygen Dilution (MILD) combustion of a syngas fuel under air-fuel, oxygen-enhanced, and oxy-fuel condition are numerically studied with using counterflow diffusion flame. Fuel composition, temperature of oxidant (T_ox), and oxygen mole fraction (X_O2) are selected as the main parameters. Fake species (FCO₂) with the same CO₂ physical properties is used for separation the physical and chemical effects of replacing CO₂ with N₂. According to the results, under the high preheating temperatures, the chemical effect of changing the oxidant composition from N₂ to CO₂ is the main reason of the changes in flame structure, ignition delay time (IDT) and heat release rate (HRR) while physical differences play a more prominent role in the low preheating temperature MILD combustion. In all X_O2, the physical and chemical effects of replacing CO₂ with N₂ have almost the same role on the maximum flame temperature. The results of IDT expressed that chemical discrepancies of CO₂ and N₂ play a key role on IDT enhancement by increasing CO₂ in the oxidant composition. The sensitivity analysis of CH₂O for variations of T_ox and X_O2 shows that reactions R54, R56, R58, and R101 are the main responsible of lower HRR and higher IDT by moving from air-syngas to oxy-fuel MILD combustion.     

Photocatalytic H2 production over RuO2@ZnS and RuO2@CuS nanostructures

Photocatalytic hydrogen production is a promising approach of sustainable economy, because a use of sunlight and water to produce a fuel will solve a problem of fossil fuels depletion. Metal sulfides are well known photocatalysts in water splitting process, but in absence of sacrificial electron donor they undergo a photocorrosion. In this paper we studied a possible strategy to protect the sulfide photocatalysts and to improve its photostability by a deposition of small amount of ruthenium oxide at surface of sulfides. Nanocrystalline zinc sulfide and copper sulfide were prepared in a hydrothermal way and have been functionalized by RuO₂. As prepared photocatalysts showed good activity towards hydrogen formation. Modification of sulfides with ruthenium oxide had a few positive effects: it expanded a light absorption range by photocatalysts, enhanced the photocatalytic activity towards H₂ formation, improved a photostability in comparison with neat ZnS and CuS as well as protected from the electronic and structural changes within semiconductors due to irradiation.     

保护气氛烧结炉

介绍了HIC封装管壳中玻璃绝缘子网带烧结炉的特殊机械结构、氮氢保护气氛系统和电气保护措施。确立了网带炉低速爬行力学模型及炉内合理的气氛流向。     

Photocatalytic reduction of CO2 using TiO2 powders in supercritical fluid CO2

The photocatalytic reduction of CO₂ was investigated using TiO₂ powders in supercritical fluid CO₂. These were irradiated in a stainless steel vessel at 9.0 MPa and 35°C. After reducing the CO₂ pressure to the ordinary state, pure water was added to the vessel while avoiding air contamination. No gaseous reduction products were observed. Formic acid was obtained only in aqueous solution. The optimal irradiation time for the production of formic acid was 5 h. Addition of acidic solutions rather than pure water was preferable for formic acid formation. Formic acid seems to be produced through the protonation of reaction intermediates on TiO₂ powders in solutions. The CO₂-reduction system described here may be of practical value for efficient CO₂-conversion and fixation, storage of solar energy, and production of raw materials for the photochemical industry.     

New gas chromatographic packing ZIF-67@NH2–SiO2 for separation of hydrogen isotope H2/D2

ZIF-67@NH₂–SiO₂ composites were prepared by loading the metal-organic frameworks ZIF-67 on amino modified SiO₂ gel particles (NH₂–SiO₂, 80–100 mesh) through layer-by-layer self-assembly method. Systematic investigation on the effects of ZIF-67 loading amounts on NH₂–SiO₂ packed stainless steel chromatographic column (specification 1.0 m×2.0 mm I.D.), the flow rate of He as carrier gas and the injection amount of mixed gas (H₂/D₂) on the hydrogen isotope H₂/D₂ separation performance at liquid nitrogen temperature, unraveled the optimal conditions for H₂/D₂ isotope separation. The results showed that the optimal stationary phase materials under the optimized conditions can effectively separate H₂ and D₂ with separation resolution R = 1.52 and the separation time t = 10.15 min. The superior performance of the ZIF-67 is tentatively thought to be due to kinetic quantum sieving (pore size 3.3 Å) effect and chemical affinity sieving effect of Co ion in ZIF-67.