Preparation of Ultra-Thin-Film Anchored Metal Oxide Catalysts Via Laser Excitation and Their Photocatalytic Activities

在273K下，利用光活化的VOCl3与脱水的Vycor玻璃和二氧化硅表面的羟基发生简单的反应，实现了VOCl3在多孔Vycor玻璃和二氧化硅上的锚定。用紫外可见光谱和红外光谱监测了分子筛表面锚定的VOCl3和反应的表面羟基的数目。锚定的样品被抽真空，用H2O水解，最后在O2中焙烧。结果表明，光化学锚定的钒物种转移到四面体配位的超薄膜锚定氧化钒中，超薄膜锚定氧化钒催化剂对各种光催化反应的反应活性远远高于传统浸渍法制备的氧化钒催化剂。在反式-2-丁烯存在下，紫外光照射下的超薄膜固定氧化钒发生了光催化异构化反应，生成顺式-2-丁烯和1-丁烯。首次发现，在有NO存在的情况下，在275K的紫外光照射下，超薄膜锚定氧化钒可将NO直接分解为N_2和O_2。在NO和CH_4混合物的存在下，紫外光照射超薄膜锚定氧化钒可导致CH_4氧化偶联反应，生成C_2H_6、C_2H_4和CH_3OH。本研究项目不仅为激光激发法制备超薄膜锚定氧化钒的优势提供了有用的信息，而且也展示了光化学方法制备的超薄锚定氧化钒在常温下对各种反应具有很高的光催化活性。

Anchoring of VOC1_3 onto porous Vycor glass and silica was performed using a facile reaction of photoactivated VOC1_3 with surface OH groups of the dehydrated Vycor glass and silica at 273 K. Photoactivation of adsorbed VOC1_3 molecules was carried out by a N_2 laser excitation of VOC1_3 (Photo-CVD). The number of anchored VOC1_3 and reacted surface OH groups was monitored by UV and IR spectroscopy. Anchored samples were evacuated, hydrolyzed with H_2O, and finally calcined in O_2. It was found that photochemically anchored vanadium species were transferred to tetrahedrally coordinated ultra-thin-film anchored vanadium oxide.Ultra-thin-film anchored vanadium oxide catalysts exhibited much higher reactivities for the various photocatalytic reactions than those of the vanadium oxides prepared by conventional impregnation method. UV irradiation of ultra-thin-film anchored vanadium oxide in the presence of trans-2-butene led to the photocatalytic isomerization, the formation of cis-2-butene and 1-butene. It was first found that UV irradiation of ultra-thin-film anchored vanadium oxide at 275 K in the presence of NO led to the direct decomposition of NO into N_2 and O_2. It was also found that UV irradiation of ultra-thin-film anchored vanadium oxide in the presence of a mixture of NO and CH_4 led to the oxidative coupling reaction of CH_4, resulting in the formation of C_2H_6, C_2H_4, and CH_3OH.Thus, the present research project not only provided useful information on the advantage of the laser-excitation processes to prepare the ultra-thin-film anchored vanadium oxide but also showed the high photocatalytic activities of the photo-chemically prepared ultra-thin anchored vanadium oxide forvarious reactions at normal temperature.