Fabrication Of Electrospun Nanofibers Supported Noble Metal Composite Nanocatalysts And Their Catalytic Properties

In recent years, nanocatalysts play an increasingly important role in the production of chemicals and the sustainable chemical industry. With the continuous development of nanocatalysts, both high catalytic activity and good recyclability are required for the high performance nanocatalysis. Electrospun nanofibers can be used as excellent supports for nanocatalyst due to their large specific surface area, high porosity, high aspect ratio, good flexibility and easy preparation. Noble metal nanocatalysts show excellent catalytic activities whereas they are restricted by high cost, ease to aggregate and difficulty to recycle. In order to solve these problems, the noble metal nanoparticles can be supported on the surface of electrospun nanofibers to fabricate composite nanocatalysts.To prepare the noble-metal/electrospun-nanofibers composite nanocatalysts, two approaches are introduced that one is assisted self-assembly polymerization and electrostatic adsorption process, the other is in situ chemical reduction process. In this thesis, we have investigated the catalytic activity and recyclability of as-prepared composite nanocatalysts. The conclusions are as follows:1. We have fabricated Au nanoparticles supported on the surface of electrospun Co Fe2O4 nanofibers as a magnetically recoverable nanocatalyst by using a strategy involving electrospinning, calcination, polyaniline assisted self-assembly polymerization, and electrostatic adsorption process. The Au nanoparticles distributed uniformly on the surface of core-sheath Co Fe2O4/PANI nanofibers which acid doped PANI coated on the surface of Co Fe2O4 nanofibers and nearly no aggregation of Au nanoparticles happens. When employed as nanocatalyst for the reduction of 4-nitrophenol, the as-prepared Co Fe2O4/PANI/Au nanofibers displayed a high catalytic activity with the kinetic apparent rate constant of about 7.8 × 10-3 s-1. In addition, the nanocatalyst also showed a good recyclability under a magnetically recoverable process. The conversion rate of three cycles is 98.16%, 81.11% and 72.67%, respectively.2. We have developed a facile and effective method for synthesizing PAN/Pd-Pt alloy composite nanofiber membrane through an electrospinning technique and subsequent in situ chemical reduction process. The diameter of the nanofibers was in the range of 200-400 nm. Pd-Pt noble metal alloy nanoparticles with diameters from several to tens of nanometers were uniformly dispersed on the surface of the nanofibers. The composition of the Pd-Pt alloy nanoparticles could be easily regulated by adjusting the feeding molar ratio of Pd and Pt precursors. The as-prepared PAN/Pd-Pt(1:1) composite nanofiber membrane possessed high catalytic activity and excellent recycling property for the hydrogen generation from the hydrolysis of AB under ambient atmosphere at room temperature. The turnover frequency(TOF) was calculated to be about 51.9 mol H2 min-1(mol Pd-Pt alloy)-1. The PAN/Pd-Pt nanofiber membrane could be separated from the solution easily with just a tweezer. After washing with water and ethanol several times, the membrane was dried for the next cycle. The nanocatalysts did not exhibit an obvious loss of catalytic activity even after five times of recycling.