CdSe纳米颗粒敏化TiO_2纳米管阵列的光催化降解及光电催化制氢

采用胶体化学法制备不同尺寸的硒化镉纳米颗粒(CdSe-NP)胶体,并利用原位吸附法将CdSe-NP与由阳极氧化法得到的TiO2纳米管阵列(TN)复合,在可见光下降解甲基橙溶液和外加偏压制氢,分别考察CdSe-NP敏化的TiO2纳米管阵列(CdSe-NP/TN)的光催化性能和光电催化性能。对比TN,CdSe-NP/TN表现出明显增强的光催化活性及更优异的光电催化性能,而过大的CdSe-NP尺寸则不利于复合材料的催化活性。表征结果表明,CdSe-NP/TN优异的性能是由于敏化CdSe-NP后吸收边红移以及光生电子和空穴复合率降低。     

Fabrication of plasmonic Au/TiO2 nanotube arrays with enhanced photoelectrocatalytic activities

Uniformly dispersed Au nanoparticles (NPs) deposited on the surface of highly ordered TiO₂ nanotube arrays (Au/TiO₂ NTs) were synthesized through a two-step process including anodization method and microwave-assisted chemical reduction route. The investigation indicated that Au NPs grew uniformly on the walls of TiO₂ NTs. Au/TiO₂ NTs exhibited excellent visible light absorption due to the LSPR effect of Au NPs. Au/TiO₂ NTs exhibited much higher photocurrent density and the photoconversion efficiency of Au decorated TiO₂ NTs was about 2.05 times greater than that of bare TiO₂ NTs. Besides, the PL intensity of Au/TiO₂ NTs was much lower than that of TiO₂ NTs, revealing a decrease in charge carrier recombination. The prepared Au/TiO₂ NTs exhibited superior photoelectrocatalytic activity and stability in the degradation of MB under simulated solar light irradiation. The synergy effect between nanotubular structures of TiO₂ and uniformly dispersed Au nanoparticles, as well as the small bias potential and strong interaction between Au and TiO₂, facilitated the Au plasmon-induced charge separation and transfer, which lead to highly efficient and stable photoelectrocatalytic activity.     

Nanoflower-like CdS and SnS2 loaded TiO2 nanotube arrays for photocatalytic wastewater treatment and hydrogen production

In this work, nanoflower-like CdS/SnS₂/TiO₂ NTs ternary heterojunction photocatalysts were synthesized by a hydrothermal method, the relationship between the morphology, microscopic morphology, crystallinity, elemental presence state and hydrogen production performance of the ternary photocatalysts were investigated by SEM, TEM, XRD and XPS, respectively. The photocatalytic performance, electrochemical property and hydrogen production capacity of CdS/SnS₂/TiO₂ NTs were compared with pure TiO₂ NTs, CdS/TiO₂ NTs and SnS₂/TiO₂ NTs. After 2 h of photocatalytic reaction, the removal efficiency of MB wastewater reached 100%, and the photocatalytic efficiencies toward RhB and Cr(VI) removal reached 86.08% and 80.93% after 3 h, respectively. The electron spin resonance (ESR) technique certified the active radical groups that played a role in the catalytic process and further investigated the possible photocatalytic mechanism. Hydrogen production per unit time achieved 97.14 μmol h^?1 cm^?2, this work provides the new technique to achieve solar energy conversion for hydrogen generation.     

Hydrothermal preparation of Sn3O4/TiO2 nanotube arrays as effective photocatalysts for boosting photocatalytic dye degradation and hydrogen production

The efficient TiO₂ NTs/Sn₃O₄ photocatalysts were synthesized by the hydrothermal deposition of Sn₃O₄ on TiO₂ nanotube arrays (TiO₂ NTs), and the morphology, microstructure and photocatalytic property were adjusted by changing the alkali kind. The TiO₂ NTs/Sn₃O₄ prepared with NaOH exhibited the outstanding photoelectric conversion and photocatalytic environment remediation/H₂ evolution. The methylene blue (MB) dye and Cr(VI) could be removed by the as-prepared photocatalysts under visible light irradiation, and ?O₂^?/?OH radicals were the main active species for MB photodegradation. Furthermore, the high photocatalytic H₂ evolution rate was as high as 6.49 μmol cm^?2 h^?1. The outstanding photocatalytic activity and stability of TiO₂ NTs/Sn₃O₄ photocatalysts would exhibit attractive prospect in the wastewater remediation and electric energy/hydrogen generation.     

鞭毛辅助CdS/TiO_2纳米复合薄膜的制备以及显著增强的光电催化活性

采用鞭毛作为生物模板剂制备Cd S/TiO_2复合纳米结构薄膜,采用SEM、XRD、IR、紫外-可见漫反射和电化学工作站等对其结构和光电化学性质进行表征。结果表明,鞭毛的引入不但减小了CdS颗粒尺寸和增大了比表面积,而且改善了复合材料的带隙结构。该薄膜可见光光电催化活性比未加入鞭毛的空白样品高1.4倍。提供了一个利用生物模板剂控制半导体纳米结构单元生长与组装及改善光电性能的简单方法。     

Preparation of Ag nanoparticles loaded TiO2 nanoplate arrays on activated carbon fibers with enhanced photocatalytic activity

Ag loaded TiO₂ nanoplate array which grew on activated carbon fiber (ACF) was prepared in the present work. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–Vis diffuse reflectance spectra (DRS). The photocatalytic degradation of methylene blue (MB) was used to investigate the activity of the synthesized samples. Under both UV and visible light irradiation, the Ag loaded samples showed enhanced photocatalytic activity. Besides, the effect of the deposition dosage of Ag nanoparticles on the photocatalytic activity was also investigated. Under UV light irradiation, the Ag nanoparticles acted as electron traps, which enhanced electron–hole separation efficiency of TiO₂. Under visible light irradiation, the Ag nanoparticles showed surface plasmon resonance, which induced the visible light responsive photocatalytic activity for the obtained samples.     

Electrochemically multi-anodized TiO2 nanotube arrays for enhancing hydrogen generation by photoelectrocatalytic water splitting

An enhanced hydrogen production by photoelectrocatalytic water splitting was obtained using extremely highly ordered nanotubular TiO₂ arrays in this work. Highly ordered TiO₂ nanotube arrays with a regular top porous morphology were grown by a facile and green three-step electrochemical anodization. The well ordered hexagonal concaves were uniformly distributed on titanium substrate by the first anodization, served as a template for further growth of TiO₂ nanotubes. As a result, the TiO₂ nanotube arrays constructed through the third anodization showed appreciably more regular architecture than that of the sample by conventional single anodization under the same conditions. The enhanced photoelectrochemical activity was demonstrated through the hydrogen generation by photoelectrocatalytic water splitting, with an exact H₂ evolution rate up to 420 μmol h⁻¹ cm⁻² (10 mL h⁻¹ cm⁻²) in 2 M Na₂CO₃ + 0.5 M ethylene glycol. The photocurrent density of the third-step anodic TiO₂ nanotubes is about 24 mA cm⁻² in 0.5 M KOH, which is 2.2 times higher than that of the normal TiO₂ nanotubes (∼11 mA cm⁻²) by a single electrochemical anodization.     

Preparation of CdS/TiO2 nanotube arrays and the enhanced photocatalytic property

In this paper, a series of CdS/TiO₂ NTs have been synthesized by SILAR method. The as-prepared CdS/TiO₂ NTs have been analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectrometer (EDS), and ultraviolet–visible (UV–vis). And their photocatalytic activities have been investigated on the degradation of methylene blue under simulated solar light irradiation. XRD results indicate that TiO₂ NTs were anatase phase, CdS nanoparticles were hexagonal phase. FESEM results indicate that low deposition concentration can keep the nanotubular structures. UV–vis results indicate that CdS can be used to improve the absorbing capability of TiO₂ NTs for visible light, and the content of CdS affects the band gap. Photocatalytic results indicate that CdS nanoparticles are conducive to improve the photocatalytic efficiency of TiO₂ NTs, and the highest degradation rate can reach 93.8%. And the photocatalytic mechanism of CdS/TiO₂ NTs to methylene blue is also described.     

Optimal engineering of CdS/PbS co-sensitized TiO2 nanotube arrays for enhanced photoelectrochemical performance

TiO₂ nanotube arrays (NTAs) are decorated with CdS/PbS nano-sensitizers by successive ionic layer adsorption and reaction (SILAR) method. The uniform growth of the CdS and PbS nanoparticles on the surface and inner side of TiO₂ Nanotube Arrays (NTAs) has been confirmed by Transmission Electron microscopy measurements. The impact of the CdS and PbS semiconductor quantum dots (SQDs) on the photoelectrochemical performance (PEC) of TiO₂ NTAs was systematically investigated, and the optimal decoration of the CdS and PbS SQDs on the TiO₂ NTAs was obtained. CdS/PbS co-sensitized TiO₂ NTA photoanode films show excellent response to visible light (with absorption extended to 825 nm) and enhanced PEC performance. The best performing device showed an enhanced photocurrent density under the 0.62V vs SCE up to 8.2 mA/cm², and high photoconversion efficiency up to 5.35%, which is 16.7 times higher than the pure TiO₂ NTAs. The enhanced PEC performance of TiO₂ NTAs is attributed to the co-sensitization, heterojunction formation and electron “pool” effect imparted on the NTAs by the coupling of CdS and PbS SQDs.     

氧化钛纳米管阵列制备及应用

氧化钛纳米管阵列因其独特的高度有序的阵列结构而具有良好的力学、化学稳定性以及抗腐蚀性能,在光解水制氢、太阳能电池、光催化、环境净化、气敏传感器等领域具有潜在的应用价值,引起了人们的广泛关注。对近年来TiO2纳米管在制备技术、形成机理、离子掺杂及其应用研究方面取得的成果做了综合评述,在此基础上探讨了TiO2纳米管制备及改性方面存在的问题,并对今后的发展方向予以展望。     

Cu2O/TiO2 heterostructure nanotube arrays prepared by an electrodeposition method exhibiting enhanced photocatalytic activity for CO2 reduction to methanol

Cu₂O/TiO₂ composite nanotube arrays demonstrating enhanced photocatalytic performance were synthesized using an electrodeposition method to impregnate the p-type Cu₂O into the n-type titanium dioxide nanotube arrays (TNTs). The morphological results confirmed that the TNTs are wrapped by the Cu₂O nanoparticles and the UV–Vis absorption spectra showed that the Cu₂O/TNTs display a better ability for visible light absorption compared to the pure TNTs. CO₂ photocatalytic reduction experiments carried out by using Cu₂O/TNT nanocomposites proved that Cu₂O/TNTs exhibit high photocatalytic activity in conversion of CO₂ to methanol, while pure TNT arrays were almost inactive. Furthermore, Cu₂O/TNTs also exhibited augmented activity in degradation of target organic pollutant like acid orange (AO) under visible light irradiation. The ultra enhanced photocatalytic activity noticed by using Cu₂O/TNTs in CO₂ reduction and degradation of organic pollutant could be attributed to the formation of Cu₂O/TiO₂ heterostructures with higher charge separation efficiency.     

Synthesis and investigation of TiO2 nanotube arrays prepared by anodization and their photocatalytic activity

TiO₂ nanotube arrays were successfully prepared by anodic oxidation method in the electrolyte of ethylene glycol and deionized water mixed in 9:1 volumetric ration including 0.5 wt.% NH₄F. The microstructure and phase compositions of samples annealing from 0 °C to 800 °C were characterized by field-emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). FESEM showed that the obtained nanotubes with diameter 80–100 nm and length 4.89 μm were highly ordered and perpendicular to Ti substrate. The tubular structure collapsed at 680 °C. The photocatalytic activity of samples annealing at different temperature were calculated by the degradation of a model dye, methyl orange (MO), under UV light illumination. The results indicated the phase composition and the morphology of TiO₂ nanotubes both played an important role in the degradation of MO. In addition, the effects of initial solution pH and dye concentration on degradation of MO had also been investigated. As a result, the optimum values of calcination temperature, initial solution pH and dye concentration were found to be 550 °C, 3, 10 mg/l, respectively. The best photodegradation of MO was 76% under illumination for 3 h.     

Synthesis and growth mechanism of multilayer TiO2 nanotube arrays

High-aspect-ratio TiO(2) nanotube arrays formed by anodic oxidation have drawn extensive attention due to their easy fabrication and various excellent optical, electrical and biomedical properties. In contrast to conventional single-layer TiO(2) nanotubes prepared via constant-voltage anodization, we synthesize multilayer TiO(2) nanotube arrays with high surface area by using alternating-voltage anodization steps. This work presents synthesis and growth mechanisms of single-layer smooth TiO(2) nanotubes, bamboo-type nanotubes and double-layer nanotubes, by tuning various parameters such as voltage, time, and water content in the electrolyte. It is found that ion diffusion inside the nanotubes dominates growth of these three structures. A stable pH and ion-diffusion profile allows the steady growth of smooth TiO(2) tubes in NH(4)F-containing ethylene glycol (EG). The addition of a low-voltage anodization step reduces the pH and ion-diffusion gradient in the nanotubes and induces formation of bamboo-type nanotubes and double-layer nanotubes when a second high-voltage anodization is conducted. Ion diffusion through a nanotube takes time; thus formation of lower-layer TO(2) nanotubes costs more time if longer nanotubes are grown in the upper layer, since ions diffuse through these longer nanotubes. This ion-diffusion controlled growth mechanism is further confirmed by tailoring the water content (0-20 vol%) in the electrolyte and the voltage gaps to control the time needed for initiation of lower-layer TiO(2) nanotube arrays. The fundamental understanding of the growth characteristics of double-layer TiO(2) nanotubes presented in this paper offers us more flexibility in engineering morphology, tuning dimensions and phase compositions of multilayer TiO(2) nanotubes. In addition, we synthesize double-layer TiO(2) nanotube arrays composed of one layer of anatase phase and another layer of amorphous phase.     

TiO2纳米管阵列电催化降解甲基橙

采用阳极氧化法制备了TiO2纳米管阵列电极,通过考察其对模拟染料废水甲基橙(MO)的光催化降解效率来优化制备条件。研究了TiO2纳米管阵列电极电催化降解MO的活性及其影响因素,并考察了MO降解反应动力学。结果表明,MO溶液pH、电解槽压、支持电解质浓度等是TiO2纳米管阵列电极催化效率的重要影响因素。TiO2纳米管阵列电催化降解MO的反应遵守一级反应动力学规律,与TiO2纳米管阵列光催化降解MO的行为一致,且表观反应速率常数不随MO溶液浓度不同而发生改变。     

Pt/TiO2上的污染物降解耦合光解水制氢研究

以三乙胺和乙醚为目标污染物,研究了Pt/TiO₂上光催化分解水产氢和污染物同时降解的光催化反应。研究了作为电子给体的污染物浓度对光解水制氢反应的影响,污染物本身的降解规律符合Langmuir-Hinshelwood准一级动力学方程。使用拉曼光谱仪和紫外-可见光分光光度计对降解产物浓度进行了表征,讨论了可能的降解反应机理。     

Preparation and photocatalytic properties of RuO2/TiO2 composite nanotube arrays

RuO₂/TiO₂ composite nanotube arrays were prepared using an anodic oxidation method combined with dipping. The photocatalytic properties of RuO₂/TiO₂ nanotube arrays in methylene blue solution were investigated under visible light irradiation. The results showed that Ru existing in the form of RuO₂ was dispersed uniformly on the surface of TiO₂ nanotubes, and the RuO₂ did not change the crystal structure of TiO₂ nanotubes. The load of RuO₂ on TiO₂ had a little influence on the band-gap energy and the absorption band edge, but could increase the amount of Ti-OH functional groups on the surface of TiO₂ nanotubes. The RuO₂/TiO₂ nanotube arrays with the optimal photocatalytic activity were formed in the ruthenium chloride solution with a concentration of 0.0030 mol/L. The 2 h photocatalytic degradation rate of methylene blue increased from 38% for pure TiO₂ nanotubes to 69% for RuO₂/TiO₂ nanotube arrays. This work demonstrated that RuO₂/TiO₂ nanotube arrays showed an improved photocatalytic property over pure TiO₂ nanotubes due to the fact that RuO₂ could capture the photo-generated holes, which greatly decreased the recombination of the photo-generated electrons and holes, and hence lengthen the lifetime of photo-induced electrons and increased the amount of hydroxyl groups absorbed on the TiO₂ nanotubes surface.     

The growth and morphology of copper phthalocyanine on TiO2 nanotube arrays

Nanostructured copper phthalocyanine was deposited by thermal vacuum evaporation, spin-coating, immersion, and electrochemical reactions onto titania nanotubes prepared by the anodization of titanium foil so as to attain interdigited heterojunctions between them for improved interfacial contact. The effects of the titania's crystal structure on the deposition were analyzed. A sodium salt derivative of copper phthalocyanine was used to enhance its affinity to the titania. The deposited copper phthalocyanine could be grown and transformed into diverse morphologies such as polyhedrons, nanorods, and nanowires. The factors affecting the morphology of the deposited copper phthalocyanine were analyzed by SEM and crystal structure analysis.     

Construction of metallic nanocrystalline TaB2 coupled with TiO2 for enhanced photocatalytic degradation

The search for new low-cost co-catalysts that can replace precious metals is highly desirable and challenging. Transition metal diboride can be ideal candidates due to their excellent electrical conductivity and suitable work function. In this work, a novel TaB₂@TiO₂ heterostructure has been successfully constructed by a facile sol-gel method. The results show that TaB₂ has a suitable work function and B–O bonds are formed at the interface of the TaB₂@TiO₂ heterojunction, which makes it easier for the photogenerated electrons of TiO₂ to migrate to the surface of TaB₂ and promotes the effective separation of photogenerated carriers. In addition, the metallic nanocrystalline TaB₂ also significantly increases the specific surface area of the heterojunction. The above two points lead to more hydroxyl radicals and superoxide radicals production, thus substantially improving the photocatalytic degradation performance. Therefore, the 3 wt% TaB₂ (TT3) catalyst degraded rhodamine B (RhB, 20 mg/L) with an efficiency of 100% under 90 min irradiation, which is much higher than pristine TiO₂～92% and commercial TiO₂ (P25)～64%. Furthermore, its photocatalytic rate is about 1.73 times and 3.77 times of pristine TiO₂ and commercial TiO₂ (P25), respectively. This finding can provide new insights for the replacement of photocatalytic noble metal co-catalysts.     

TiO2/MOFs的制备及污染物降解现状

TiO2是较为成熟的半导体光催化材料,但因TiO2分散性差、量子利用率低、比表面积小、难回收等问题难以工业化.多孔金属有机框架(MOFs)的引入可增强TiO2/MOFs复合材料的光吸收性能,提高电子-空穴对分离效率和提高回收率.基于TiO2/MOFs制备时前驱体添加顺序不同,综述了TiO2/MOFs的3种制备方法(即Ship-in-a-bottle法、Bottle-around-ship法、One-pot法)及TiO2/MOFs光催化机理与性能影响因素,并探讨不同MOFs与TiO2结合的作用机理.最后,对TiO2/MOFs存在的问题提出建议.