三元杂化TiO2-SiO2-POMs催化剂的合成及其在可见光降解罗丹明B中的应用

采用分步溶胶-凝胶法制备的三元杂化催化剂TiO₂-SiO₂-杂多酸(POMs)在可见光降解工业染料罗丹明B中表现出了高效反应活性. 利用时间分辨微波传导(TRMC)和漫反射光谱(DRS)研究了催化剂在可见光区的光催化性能, 实验结果表明: 在三元杂化催化剂内, 二氧化钛和二氧化硅的键合加强了催化剂在可见光区的响应和吸收, 二氧化钛和杂多酸的结合提高了反应活性位(空穴-电子对)的稳定性. 三元杂化催化剂TiO₂-SiO₂-POMs中组分之间的协同效应促进了可见光光催化性能的提高.     

锌掺杂BiOBr合成及可见光下对CO2光催化还原机理

溴氧化铋（BiOBr）半导体已被应用于光催化CO₂还原,但其活性仍然极低。通过简单的水热法合成了Zn-BiOBr光催化剂,并在可见光照射下研究其对CO₂催化效果。结果表明,合成的Zn-BiOBr样品在可见光照射下具有比原BiOBr更高的光催化还原CO₂转化活性,其对CO₂光催化还原速率最高可达到8.49 μmol·h^-1,是原BiOBr的13倍。同时,我们亦对光催化活性增强机理进行了研究,发现在可见光照射下,Zn-BiOBr半导体被激发,产生光致电子空穴对,光诱导电子有效还原CO₂,生成CO。锌的掺杂为BiOBr提供了更合适的带边位置和能带缺陷,降低了光生电子与空穴对的复合速率,大大提高了光催化还原CO₂的能力。     

微/纳复合型可见光光电材料Ag-石墨烯-TiO2的制备及应用

基于静电纺丝技术构筑了稳定均一的Ag-石墨烯-TiO₂纳米复合纤维;并利用SEM、TEM、XRD、EDS和Raman等表征了材料的微观结构与组分;随后,我们研究了该复合纤维在可见光下的光电转换性能。结果表明：掺杂既可降低TiO₂材料的禁带宽度,也能减缓光生电子与空穴的复合淬灭;Ag纳米晶的局域等离激元可增强纤维对可见光的吸收,石墨烯能促进光生电子与空穴的有效分离;可见光条件下,相比较于单一的TiO₂纳米纤维,复合纤维的光电流密度提高4倍,达到0.81 μA·cm^-2。     

TiO2光催化剂的形貌与晶面调控

二氧化钛（TiO₂）具有化学稳定性高、无毒、价格低廉、来源广泛及光电性能优异等优点,被广泛应用于太阳能电池和光催化等领域,尤其是在污染物的光催化降解方面,可很好地解决当前的环境污染问题。但一方面受带隙宽度限制,使其对太阳光的利用率不足5%,不能充分利用太阳光中的可见光;另一方面由于光生电子-空穴容易结合,催化效率低,从而使TiO₂的实际应用受到限制。因此必须采取合适的措施,一方面要增强TiO₂对可见光的吸收,提高对太阳光的利用率;另一方面要抑制光生电子-空穴的复合,提高光催化效率。目前越来越多的科学家通过控制TiO₂的形貌、晶型、特殊晶面暴露等手段来提高TiO₂光生电子-空穴的传输速率和光电转换效率。本文主要综述了近年来在TiO₂光催化剂的特殊形貌和特殊晶面暴露等方面的研究进展,对未来的研究和发展方向作了展望。     

微/纳复合型可见光光电材料Ag-石墨烯-TiO2的制备及应用

基于静电纺丝技术构筑了稳定均一的Ag-石墨烯-TiO₂纳米复合纤维;并利用SEM、TEM、XRD、EDS和Raman等表征了材料的微观结构与组分;随后,我们研究了该复合纤维在可见光下的光电转换性能。结果表明：掺杂既可降低TiO₂材料的禁带宽度,也能减缓光生电子与空穴的复合淬灭;Ag纳米晶的局域等离激元可增强纤维对可见光的吸收,石墨烯能促进光生电子与空穴的有效分离;可见光条件下,相比较于单一的TiO₂纳米纤维,复合纤维的光电流密度提高4倍,达到0.81μA·cm^-2。     

过硫酸盐激活协同可见光催化降解四环素的机理和降解路径

为了提升微污染水体中抗生素的降解效率,利用过硫酸钠(PDS)激活协同手性介孔TiO₂可见光催化(PDS/vis-TiO₂)对四环素(TC)进行降解。详细对比研究了以手性TiO₂作为催化剂的PDS激活(PDS/TiO₂)、可见光催化(vis-TiO₂)和PDS/vis-TiO₂三种体系中,降解污染物的活性物种和污染物降解路径等的差异。结果表明,不对称的螺旋堆积结构在手性介孔TiO₂中引入了丰富的Ti³⁺,不仅提升了其可见光响应,同时能够激活PDS生成自由基。PDS/vis-TiO₂体系中光生空穴h⁺和·OH等多种自由基可以同时参与TC的降解,5 h内其对TC去除率可达到95%以上,远超PDS/TiO₂体系(TC去除率为48.9%)和vis-TiO₂体系(TC去除率为71.1%)。PDS加入到光催化体系中,会受到光生电子的激活而产生自由基,从而消耗光生电子,提升光生空穴和电子的分离率,达到协同增强污染物的降解能力。另外PDS激活后产生自由基也会大大增加体系对TC的降解性能。密度泛函理论计算和中间产物分析结果表明,TC在PDS/vis-TiO₂体系中的降解路径包含了光生空穴h⁺攻击TC的降解路径,同时也包括自由基攻击TC的降解路径。     

过硫酸盐激活协同可见光催化降解四环素的机理和降解路径

为了提升微污染水体中抗生素的降解效率,利用过硫酸钠（PDS）激活协同手性介孔TiO₂可见光催化（PDS/vis-TiO₂）对四环素（TC）进行降解。详细对比研究了以手性TiO₂作为催化剂的PDS激活（PDS/TiO₂）、可见光催化（vis-TiO₂）和PDS/vis-TiO₂三种体系中,降解污染物的活性物种和污染物降解路径等的差异。结果表明,不对称的螺旋堆积结构在手性介孔TiO₂中引入了丰富的Ti³⁺,不仅提升了其可见光响应,同时能够激活PDS生成自由基。PDS/vis-TiO₂体系中光生空穴h⁺和·OH等多种自由基可以同时参与TC的降解,5 h内其对TC去除率可达到95%以上,远超PDS/TiO₂体系（TC去除率为48.9%）和vis-TiO₂体系（TC去除率为71.1%）。PDS加入到光催化体系中,会受到光生电子的激活而产生自由基,从而消耗光生电子,提升光生空穴和电子的分离率,达到协同增强污染物的降解能力。另外PDS激活后产生自由基也会大大增加体系对TC的降解性能。密度泛函理论计算和中间产物分析结果表明,TC在PDS/vis-TiO₂体系中的降解路径包含了光生空穴h+攻击TC的降解路径,同时也包括自由基攻击TC的降解路径。     

水热法制备Pr掺杂Bi2WO6三维花状微球的光催化性能

通过水热法制备稀土Pr掺杂Bi₂WO₆三维花状微球,利用XRD、SEM、N₂吸附-脱附、紫外-可见吸收光谱和光致发光光谱对所制备的光催化材料进行表征。通过降解亚甲基蓝评价样品的光催化活性。结果表明,1.0% Pr-Bi₂WO₆样品的可见光催化活性最佳,降解率达到95%。Pr掺杂提高了催化剂的可见光吸收性能并且能够束缚光生电子使得电子空穴对有效分离从而获得强氧化物质。对其光催化降解做出了合理的解释。     

水热法制备Pr掺杂Bi2WO6三维花状微球的光催化性能

通过水热法制备稀土Pr掺杂Bi₂WO₆三维花状微球,利用XRD、SEM、N₂吸附-脱附、紫外-可见吸收光谱和光致发光光谱对所制备的光催化材料进行表征。通过降解亚甲基蓝评价样品的光催化活性。结果表明,1.0% Pr-Bi₂WO₆样品的可见光催化活性最佳,降解率达到95%。Pr掺杂提高了催化剂的可见光吸收性能并且能够束缚光生电子使得电子空穴对有效分离从而获得强氧化物质。对其光催化降解做出了合理的解释。     

BiOI/Bi2WO6对甲基橙和苯酚的光催化降解及光催化机理

采用简单的沉积方法制备了不同碘化氧铋含量的BiOI/Bi₂WO₆光催化剂,通过X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HR-TEM)、紫外-可见漫反射光谱(UV-VisDRS)和BET比表面积测量对其进行了表征。在紫外和可见光的照射下,使用甲基橙和苯酚的光催化降解评价了BiOI/Bi₂WO₆催化剂的光催化性能。结果表明：与商业P₂₅和纯Bi₂WO₆相比,13.2%BiOI/Bi₂WO₆光催化剂具有更高的紫外和可见光催化性能。这明显增加的光催化活性主要归功于光生电子和空穴在Bi₂WO₆和BiOI界面上的有效转移,降低了电子-空穴对的复合。基于BiOI和Bi₂WO₆的能带结构,提出了光生载流子的一种转移过程。自由基清除剂的实验表明,OH,h⁺,O₂和H₂O₂,特别是h⁺,共同支配了甲基橙和苯酚的光催化降解过程。     

杂多蓝在可见光照射下对TiO2的光敏作用研究

利用磷钨酸、硅钨酸经光还原后制得的杂多蓝对Pt/TiO₂进行了光敏化. 所制备的催化剂在可见光区对光催化还原水产氢反应具有较高活性. 当以丙三醇为电子给体时, 该催化剂在可见光区(650～700 nm)制氢反应的表观量子效率最高可达3.4%.     

反应萃取法合成戊二醛中H3PMoxW12—xO40的催化作用

杂多酸Ｈ３ＰＭｏｘＷ１２－ｘＯ４０是通过其适宜的酸性,氧化性的双功能的配合催化,使Ｈ２Ｏ２氧化环戊烯为戊二醛,液－液相转移反应萃取氧化过程是杂多酸与相转移催化剂形成油溶性配合物,此配合物在相界面被Ｈ２Ｏ２氧化为过氧化杂多酸配合物,过氧化杂多酸配合物在有机相可能机理是Ｈ２Ｏ２氧化杂多酸为过氧化杂多酸。     

Tuning the concentration of surface/bulk oxygen vacancies in CeO2 nanorods to promote highly efficient photodegradation of organic dyes

To enhance the photodegradation ability of CeO₂ for organic dyes, an effective strategy is to introduce oxygen vacancies (V_o). In general, the introduced V_o are simultaneously present both on the surface and in the bulk of CeO₂. The surface oxygen vacancies (V_o-s) can decrease the band gap, thus enhancing light absorption to produce more photogenerated e⁻ for photodegradation. However, the bulk oxygen vacancies (V_o-b) will inhibit photocatalytic activity by increasing the recombination of photogenerated e⁻ and V_o-b. Therefore, regulating the concentrations of V_o-s to V_o-b is a breakthrough for achieving the best utilization of photogenerated e⁻ during photodegradation. We used an easy hydrothermal method to achieve tunable concentrations of V_o-s to V_o-b in CeO₂ nanorods. The optimized CeO₂ presents a 70.2% removal of rhodamine B after 120 min of ultraviolet−visible light irradiation, and a superior photodegradation performance of multiple organics. This tuning strategy for V_o also provides guidance for developing other advanced metal-oxide semiconductor photocatalysts for the photodegradation of organic dyes.     

A New p‐Metal‐n Structure AgBr‐Ag‐BiOBr with Superior Visible‐Light‐Responsive Catalytic Performance

A novel visible‐light‐driven AgBr‐Ag‐BiOBr photocatalyst was synthesized by a facile hydrothermal method. Taking advantage of both p‐n heterojunctions and localized surface plasmon resonance, the p‐metal‐n structure exhibited a superior performance concerning degradation of methyl orange under visible‐light irradiation (λ>420 nm). A possible photodegradation mechanism in the presence of AgBr‐Ag‐BiOBr composites was proposed, and the radical species involved in the degradation reaction were investigated. HO₂^?/^?O₂^? played the same important role as ^?OH in the AgBr‐Ag‐BiOBr photocatalytic system, and both the electron and hole were fully used for degradation of organic pollutants. A dual role of metallic Ag in the photocatalysis was proposed, one being surface plasmon resonance and the other being an electron‐hole bridge. Due to the distinctive p‐metal‐n structure, the visible‐light absorption, the separation of photogenerated carriers and the photocatalysis efficiency were greatly enhanced.     

Polyoxometalate encapsulated in metal‐organic gel as an efficient catalyst for visible‐light‐driven dye degradation applications

Contamination of industrial sewage by organic dye pollutants is one of the most common challenges to the daily life. Decontamination can be achieved by adsorption and photodegradation of the pollutants. Herein, an effective visible light‐driven photocatalyst of polyoxometalate encapsulated in metal–organic gel was presented. The resulting composite was named PMA@ MOG‐Cr [PMA= H₃PMo₁₂O₄₀, MOG= metal‐organic gel]. Photodegradation of dye pollutants with PMA@ MOG‐Cr were tested. The introduction of Phosphomolybdic Acid significantly enhanced the light‐absorption properties of MOG‐Cr. The PMA@MOG‐Cr showed an excellent photodegradation efficiency of MB, RhB and MO as high as 99% and 97% in 60 min and 91% in 120 min of visible‐light irradiation with only 10 mg photocatalyst, which was the highest among the tested samples MOG‐Cr, PMA@ MOG‐Cr and Degussa P‐25. The mechanism of the photodegradation of dye pollutants with H₂O₂ over PMA@MOG‐Cr under the visible light was further illustrated. The introduction of PMA promotes effective separation of electron–hole pair by trapping and transferring photogenerated electron. Thus, the two components act in synergy to result in much improved adsorption of certain common organic dyes as well as enhanced oxidative degradation. This work provides a new approach to design MOG encapsulated Polyoxometalate for visible light‐induced photodegradation of organic contaminants for the environmental remediation.     

Visible‐Light‐Induced Photoredox Catalysis of Dye‐Sensitized Titanium Dioxide: Selective Aerobic Oxidation of Organic Sulfides

TiO₂ photoredox catalysis has recently attracted much interest for use in performing challenging organic transformations under mild reaction conditions. However, the reaction scheme is hampered by the fact that TiO₂ can only be excited by UV light of wavelengths λ shorter than 385 nm. One promising strategy to overcome this issue is to anchor an organic, preferably metal‐free dye onto the surface of TiO₂. Importantly, we observed that the introduction of a catalytic amount of the redox mediator TEMPO [(2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl] ensured the stability of the anchored dye, alizarin red S, thereby resulting in the selective oxidation of organic sulfides with O₂. This result affirms the essential role of the redox mediator in enabling the organic transformations by visible‐light photoredox catalysis.     

Ag@AgI等离子体负载TiO2酸蚀纳米带的制备及可见光光催化性能的研究

采用沉积-沉淀法将AgI分散到TiO2酸蚀纳米带上,然后通过光照进而分解出Ag颗粒,最终获得了Ag@AgI等离子体负载的TiO2酸蚀纳米带(AIST)。利用UV-Vis吸收光谱、XRD、SEM对产物进行表征,并研究了可见光下对甲基橙(MO)的光催化降解性能。结果表明,纳米带酸蚀后利于AgI的沉积,Ag的表面等离子体共振效应可以增强催化剂对于可见光的吸收,使可见光下AIST的光催化降解性能显著提高。     

Photocatalytic mineralization of chlorinated organic pollutants in water by polyoxometallates. Determination of intermediates and final degradation products

Homogeneous aqueous solutions of organochlorine pesticides and chlorophenols, namely, lindane, hexachlorobenzene and 2,4-dichlorophenol (2,4DCP), undergo effective photodegradation upon photolysis with UV and near visible light in the presence of a characteristic polyoxometallate catalyst PW₁₂O₄₀ ³⁻. These substrates remained, practically, intact (lindane, HCB) or underwent minor degradation under similar conditions in absence of catalyst. The main oxidant appears to be OH radicals formed by the reaction of the excited polyoxometallate with H₂O. The system compares with the widely published TiO₂. Chlorohydroquinone (ClHQ), hydroquinone (HQ), chlorobenzoquinone (ClBQ), benzoquinone (BQ), 3,5-dichlorocatechol (3,5DCC) and 4-chlorocatechol (4CC), among others, were identified as the main aromatic intermediates in the photodegradation of 2,4DCP. Acetic acid was detected as ring cleavage product. In all cases the final photodegradation leads to complete mineralization of substrates to CO₂ and HCl.     

Improvement of the Visible‐Light Photocatalytic Performance of TiO2 by Carbon Mesostructures

An improvement in the photodegradation performance for dyes due to interaction between carbon and titania in a self‐assembled mesoporous C? TiO₂ composite catalyst, even for the difficult degradation of azo dyes, is reported herein. The dye removal process involves adsorption of the dye from water by the mesoporous carbon–titania, followed by photodegradation on the separated dye‐loaded solid. Such adsorption–catalysis cycles can be carried out more than 80 times without discernible loss of photocatalytic activity or the anatase content of the composite. In each run, about 120 mg dye per g catalyst can be degraded. The mesoporous carbon–titania catalyst also exhibits a high capacity for converting methyl orange in aqueous solution under visible light. Characterization by XRD, TEM, and N₂ sorption techniques has revealed that the self‐assembled composite catalyst has an ordered mesostructure, uniform mesopores (4.3 nm), a large pore volume (0.30 cm³ g^?1), and a high surface area (348 m² g^?1). The pore walls are composed of amorphous carbon and anatase nanoparticles of size 4.2 nm, which are well dispersed and confined. X‐ray photoelectron spectroscopy (XPS), surface photovoltage spectroscopy (SPS), and UV/Vis absorption results indicate doping of carbon into the anatase lattice and a change in the bandgap of the semiconductor. The synergistic improvement in the composite catalyst can be attributed to the following features: (1) carbon doping of the anatase lattice modifies its bandgap and enhances its activity under visible light; (2) confinement within carbon pore walls prevents aggregation of tiny anatase nanoparticles, improving their activity and stability; (3) the mesopores provide a confined space for photocatalysis; and (4) the strong adsorption ability of porous carbon for organic substances ensures that large quantities can be processed and inhibits further diffusion of the adsorbed organic substances, thereby enhancing the mineralization on anatase.     

Coupling of Phenol with Ketones in the Presence of Heteropoly Acids with Different Structures and Compositions

The reactions of phenol coupling with ketones MeCOR (R = CH₃, C₂H₅, C₃H₇, and C₄H₉) are studied in the presence of heteropoly acids with different structures and compositions in toluene solutions ([PhOH]/[MeCOR] = (2–8)/1 mol/mol; 50–70°C) with thioglycolic acid added as a promoter. The reaction rate depends on ketone and heteropoly acid, and the yield of bisphenols is as high as 24–72%. The reaction orders are 0.68, 0.77, and 0.97 with respect to H₆P₂W₂₁O₇₁, H₃PW₁₂O₄₀, and H₄SiW₁₂O₄₀, respectively, and the activation energies are 25.1, 21.0, and 20.6 kcal/mol, respectively. Heteropoly acids of the Dawson structure exhibited the highest activity.