Bossmann Stefan H, Jockusch Steffen, Schwarz Peter, Baumeister Bodo, Göb Sabine, Schnabel Claudia, Payawan Leon, Pokhrel Megh Raj, Wörner Michael, Braun André M, Turro Nicholas J
Lehrstuhl für Umweltmesstechnik am Engler-Bunte-Institut, Universität Karlsruhe, 76128 Karlsruhe, Germany.
Photochem Photobiol Sci. 2003 May;2(5):477-86. doi: 10.1039/b212377k.
A considerably arduous test of a novel class of composite materials consisting of [Ru(bpy)3]2+ and TiO2 codoped zeolites Y is presented here. The [Ru(bpy)3]2+ and TiO2 codoped zeolites Y served as photocatalysts in the oxidation of the model compounds 2,4-dimethylaniline (2,4-xylidine) by H2O2 in an acidic aqueous medium. Zeolite-embedded TiO2 (nano)particles play an important role in the degradation mechanism. The first step in this complex mechanism is the photoelectron transfer from photoexcited [Ru(bpy)3]2+, located inside the supercage of zeolite Y, to a neighboring TiO2 nanoparticle. During this electron transfer process, electron injection into the conduction band of TiO2 is achieved. The second decisive step is the reaction of this electron with H2O2, which was previously chemisorbed at the surface-region of the TiO2 nanoparticles. In this reaction, a TiO2 bound hydroxyl radical (TiO2-HO.) is created. This highly reactive intermediate initiates then the oxidation of 2,4-xylidine, which enters the zeolites framework in its protonated form (Hxyl+). The formation of 2,4-dimethylphenol as first detectable reaction product indicated that this oxidation proceeds via an electron transfer mechanism. Furthermore, [Ru(bpy)3]3+, which was created in the initiating photoelectron transfer reaction between [Ru(bpy)3]2+ and TiO2, also takes place in the oxidation of Hxyl+. [Ru(bpy)3]2+ is recycled in that reaction, which also belongs to the group of electron transfer reactions. In addition to the primary steps of this particular Advanced Oxidation Process (AOP), the dependence of the efficiency of the 2,4-xylidine degradation as a function of the [Ru(bpy)3]2+ and TiO2 loadings of the zeolite Y framework is also reported here. The quenching of [Ru(bpy)3]2+* by H2O2 as well as the photocatalytic activity of the [Ru(bpy)3]2+ and TiO2 codoped zeolite Y catalysts both follow a distinct percolation behavior in dependence of their TiO2 content.
本文介绍了一种对由[Ru(bpy)₃]²⁺和TiO₂共掺杂的Y型沸石组成的新型复合材料的相当艰巨的测试。[Ru(bpy)₃]²⁺和TiO₂共掺杂的Y型沸石在酸性水介质中通过H₂O₂氧化模型化合物2,4 - 二甲基苯胺（2,4 - 二甲苯胺）时用作光催化剂。嵌入沸石的TiO₂（纳米）颗粒在降解机制中起重要作用。这个复杂机制的第一步是光电子从位于Y型沸石超笼内的光激发态[Ru(bpy)₃]²⁺*转移到相邻的TiO₂纳米颗粒。在这个电子转移过程中，实现了电子注入到TiO₂的导带中。第二个决定性步骤是这个电子与先前化学吸附在TiO₂纳米颗粒表面区域的H₂O₂反应。在这个反应中，生成了与TiO₂结合的羟基自由基（TiO₂ - HO·）。这个高活性中间体随后引发2,4 - 二甲苯胺的氧化，2,4 - 二甲苯胺以其质子化形式（Hxyl⁺）进入沸石骨架。作为第一个可检测到的反应产物的2,4 - 二甲基苯酚的形成表明这种氧化是通过电子转移机制进行的。此外，在[Ru(bpy)₃]²⁺*与TiO₂之间的起始光电子转移反应中生成的[Ru(bpy)₃]³⁺也参与了Hxyl⁺的氧化。[Ru(bpy)₃]²⁺在该反应中被循环利用，该反应也属于电子转移反应组。除了这个特定的高级氧化过程（AOP）的主要步骤外，本文还报道了2,4 - 二甲苯胺降解效率随Y型沸石骨架中[Ru(bpy)₃]²⁺和TiO₂负载量的变化关系。[Ru(bpy)₃]²⁺*被H₂O₂猝灭以及[Ru(bpy)₃]²⁺和TiO₂共掺杂的Y型沸石催化剂的光催化活性都随其TiO₂含量呈现出明显的渗流行为。
