水溶液中纳米二氧化钛光催化降解甲基橙的影响因素

用沸腾回流直接水解法制备了粒径为25～35 nm纯锐钛矿型纳米二氧化钛(TiO2).用X射线衍射和透射电镜表征材料的结构与形貌.用该催化剂催化降解甲基橙,研究了催化剂用量、甲基橙的起始浓度、溶液pH值、光强度、溶液中添加金属离子的影响.结果表明:在较强紫外光照射下,当甲基橙的起始浓度为0.02 g/L,TiO2用量为1.0g/L,光催化效率最高.酸性条件有利于光催化降解甲基橙.掺加Fe3 或Zn2 的光催化效率显著增加.掺加Mn2 或Ca2对光催化活性没有影响.在紫外光区域(366 nm),样品对催化降解水溶液中甲基橙的活性较高.     

液相合成纳米氧化锌及其光催化性能探讨

以硝酸锌和氢氧化钠为原料,分别以水和醇作为溶剂,采用液相直接沉淀法合成纳米氧化锌。在以水为反应溶剂条件下,研究了反应时间、反应温度、反应物浓度和反应物配比对纳米氧化锌中位径和形貌的影响,得到制备较小中位径及合适长径比纳米氧化锌的最优反应条件,即:反应时间为3 h、反应温度为70 ℃、锌离子浓度为0.5 mol/L、锌离子与氢氧根浓度比为1:2。在上述最优反应条件下,研究了不同醇溶剂对纳米氧化锌中位径、形貌及其光催化性能的影响。研究发现,随着溶剂碳链长度的增长,纳米氧化锌中位径呈现上下波动,无明显变化规律,形貌由球状向柱状发展,光催化性能总体不断减弱。     

沉积Ag的TiO_2纳米管的制备及其光催化性能的研究

采用电化学阳极氧化法制备了管长约为1.48μm,管径约为87 nm的Ti O2纳米管,然后采用光还原沉积法在不同浓度的AgNO3溶液中制备了沉积单质Ag的Ti O2纳米管.利用SEM,XRD和XPS对Ag-Ti O2纳米管进行了表征,并以罗丹明B溶液为目标降解物评价了其光催化活性.结果表明:Ag微粒是以稳定的单质形式存在,Ag-Ti O2纳米管的光催化活性随着AgNO3溶液浓度的增大而呈增大的趋势,当AgNO3浓度达到0.08 mol/L时其活性达到最大值,而后随着浓度的增大活性反而下降.     

超声波制备TiO2光催化降解气相苯的研究

文章以钛酸四丁酯为原料,采用超声波分散450℃焙烧物得到了纳米TiO2光催化剂,以苯为模拟气体,在静态反应装置中考察了该催化剂对气相苯的光催化降解性能。结果表明,采用超声波制备的TiO2光催化剂能显著提高对苯的光催化降解性能,超声波制备的TiO2上苯转化率是搅拌制备的TiO2的1.7倍。BET结果显示超声波制备的光催化剂比表面比搅拌制备的光催化剂高;XRD表征结果表明TiO2呈锐钛型;紫外-可见漫反射结果显示超声波制备的TiO2在可见区吸收增强。     

外界条件对纳米TiO2光催化性能的影响

为找到纳米TiO2的最佳催化条件,以钛酸丁酯为原料,采用溶胶-凝胶法制备纳米级的掺杂Fe3+的TiO2粉末.通过XRD确定其相组成,利用紫外可见分光光度计测定光催化活性,研究外界条件包括光强度、溶液的pH值及环境温度对光催化反应的影响.结果表明:光强度在一定范围内越大光催化活性越高;pH值在4时光催化活性最大;环境温度对光催化反应无太大影响.在较高的光强度、pH=4的条件下光催化活性最好.     

提高纳米二氧化钛可见光光催化活性研究的进展

综述了近年来提高纳米TiO2可见光光催化活性的研究,主要包括:对纳米TiO2进行表面复合与衍生、金属离子掺杂、半导体偶合、非金属元素掺杂改性和染料敏化等技术,并分析了各种不同掺杂改性机理.最后,展望了提高纳米TiO2可见光光催化活性研究进展的前景.     

用偏钛酸作原料制备纳米TiO2粉末以及颗粒相结构与光催化性能关系的研究

米用常温氨水水解TiOSO4过程中加入自制的表面活性剂制备了超细纳米TiO2粉末,用XRD,TEM和比表面仪对不同煅烧温度下的纳米TiO2粉末结构、粒径大小和比表面等进行了表征,研究了纳米TiO2粉末对甲基橙的光催化降解能力。研究表明煅烧温度在400℃～800℃时得到的纳米TiO2粉末呈锐钛矿结构,粒径约为5．5nm～9．6nm,比表面积高达189．45m^2/g;在850℃煅烧后所得的纳米TiO2粉末为锐钛矿与金红石型混晶结构;在l100℃时得到的纳米TiO2粉末为金红石型纳米TiO2粉末,同时微粒出现团聚且粒径变大。光催化实验表明：纳米TiO2粉末的光催化活性与煅烧温度密切相关,850℃煅烧1．5h所制得的混晶结构纳米TiO2粉末表现出较高的光催化活性。与国产商品纳米锐钛矿型TiO2相比,其降解甲基橙的速率约为国产商品纳米TiO2的1倍。     

Growth of Au nanocrystals on CdS nanorods

Nanorods of S²⁻ rich CdS were synthesized by a reaction of excess S versus Cd precursors in the presence of ethylene diamine. The photoluminescence (PL) emission from the S²⁻ rich CdS nanorods was broad with a peak at ∼710 nm, which was 40 nm longer in wavelength than the PL peak from Cd²⁺ rich CdS (∼670 nm) nanorods. The influence of surface electron or hole trap states on the luminescent pathway of CdS nanorods will be discussed to explain these shifts in wavelength. Nanocrystals of Au ∼2 nm in size were grown on S²⁻ rich surfaces of CdS nanorods. Significant luminescence quenching was observed from the Au nanocrystals on the CdS nanorods due to interfacial charge separation. Change separation by the Au nanocrystals on the CdS resulted in enhanced photocatalytic degradation of Procion red mix-5B (PRB) dye in an aqueous solution under UV light irradiation.     

表面修饰TiO2光催化薄膜的表征

利用射频磁控溅射技术，以Ar和O2气混合气体为溅射气体在载玻片上制备了锐钛相TiO2薄膜。为了提高Ti02薄膜的光催化活性，在TiO2薄膜表面进行了钽修饰。利用X射线衍射(XRD)，原子力显微镜(AFM)和UV-VIS-NIR分光光度计等技术对薄膜进行了表征。结果表明：对TiO2薄膜的表面进行适量的Ta元素修饰可以提高其光催化活性。     

Single-Atom Metal Sites Anchored Hydrogen-Bonded Organic Frameworks for Superior “Two-In-One” Photocatalytic Reaction

Photoredox catalysis is a green solution for organics transformation and CO₂ conversion into valuable fuels, meeting the challenges of sustainable energy and environmental concerns. However, the regulation of single-atomic active sites in organic framework not only influences the photoredox performance, but also limits the understanding of the relationship for photocatalytic selective organic conversion with CO₂ valorization into one reaction system. As a prototype, different single-atomic metal (M) sites (M²⁺ = Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) in hydrogen-bonded organic frameworks (M-HOF) backbone with bridging structure of metal-nitrogen are constructed by a typical “two-in-one” strategy for superior photocatalytic C N coupling reactions integrated with CO₂ valorization. Remarkably, Zn-HOF achieves 100% conversion of benzylamine oxidative coupling reactions, 91% selectivity of N-benzylidenebenzylamine and CO₂ conversion in one photoredox cycle. From X-ray absorption fine structure analysis and density functional theory calculations, the superior photocatalytic performance is attributed to synergic effect of atomically dispersed metal sites and HOF host, decreasing the reaction energy barriers, enhancing CO₂ adsorption and forming benzylcarbamic acid intermediate to promote the redox recycle. This work not only affords the rational design strategy of single-atom active sites in functional HOF, but also facilitates the fundamental insights upon the mechanism of versatile photoredox coupling reaction systems.