Abstract

Flexible and hierarchical nanostructured Pd/SiO₂-TiO₂ nanofibrous catalytic membranes were fabricated via combining electrospinning technique and a two-step hydrothermal method. The size and distribution of TiO₂ nanorods immobilised on SiO₂ nanofibrous membranes can be regulated via adjusting the dosage of TiCl₃ solution in the first step hydrothermal process. When using an optimal TiCl₃ solution dosage of 0.2 mL, a hierarchical structured Pd/SiO₂-TiO₂-0.2 nanofibrous catalytic membrane with uniformly dense TiO₂ nanorods loaded on SiO₂ nanofibers is obtained, and still shows good tensile strength and flexibility. The catalytic activity of Pd/SiO₂-TiO₂-0.2 increases 5 times as compared to Pd/SiO₂-TiO₂-0 in the reduction of p-nitrophenol (PNP) to p-aminophenol (PAP). The modification with TiO₂ nanorods can provide more surface areas for loading the Pd nanoparticles, thereby increased active sites. The three-dimensional open-cell network stacked and assembled by thousands of SiO₂ nanofibers and TiO₂ nanorods enhances the contact between the reactants and Pd nanoparticles. Both aspects contribute the superior catalytic activity of Pd/SiO₂-TiO₂-0.2. Furthermore, a continuous and complete conversion of PNP to PAP can be stably operated over 240 min in a gravity-driven catalytic membrane reactor constructed by Pd/SiO₂-TiO₂-0.2.

摘要

结合电纺丝技术和两步水热法制备了柔性，分级的纳米结构Pd / SiO ₂ -TiO ₂纳米纤维催化膜。在第一步水热过程中，可以通过调节TiCl ₃溶液的用量来调节固定在SiO ₂纳米纤维膜上的TiO ₂纳米棒的尺寸和分布。当使用0.2 mL的最佳TiCl ₃溶液剂量时，分层结构化的Pd / SiO ₂ -TiO ₂ -0.2纳米纤维催化膜具有均匀致密的TiO ₂纳米棒负载在SiO _2上获得了纳米纤维，并且仍然显示出良好的拉伸强度和柔韧性。与Pd / SiO ₂ -TiO ₂ -0相比，Pd / SiO ₂ -TiO ₂ -0.2在对硝基苯酚（PNP）还原为对氨基苯酚（PAP）方面的催化活性提高了5倍。TiO ₂纳米棒的修饰可以提供更多的表面积来装载Pd纳米颗粒，从而增加活性位。数以千计的SiO ₂纳米纤维和TiO ₂纳米棒堆叠和组装的三维开孔网络增强了反应物与Pd纳米颗粒之间的接触。这两方面都有助于Pd / SiO的优异催化活性₂ -TiO ₂ -0.2。此外，在由Pd / SiO ₂ -TiO ₂ -0.2构成的重力驱动催化膜反应器中，PNP连续和完全转化为PAP可以在240分钟内稳定运行。