Nanocomposite Catalyst Derived from Ultrafine Platinum Nanoparticles and Carbon Nanotubes for Hydrogen Generation
Clay Huff, Qui Quach, Julia M. Long, Tarek M. Abdel‐Fattah
Abstract
Beta-cyclodextrin was used as structure directing agent for the formation of a novel small, uniform platinum nanoparticles. The resultant platinum nanoparticles were supported over multi-walled carbon nanotubes (PtMWCNTs) and used as catalyst for hydrogen generation. The resultant composite was characterized via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The TEM displayed the diameter of MWCNT ranged from 20 to 35 nm, and the average size of Pt nanoparticles was 2.8 nm. Testing of catalytic activity showed that the highest rate achieved was 21.2 ml min −1 g cat −1 at 303 K with pH 7 and 835 μ moles of NaBH 4 . In the pH adjusted trials, the greatest rate achieved was 16.9 ml min −1 g cat −1 outperforming both pH 7 and pH 6 despite the known increase in hydrolysis rate at lower pH. The activation energy of the reaction as catalyzed by the PtMWCNTs was calculated to be 46.2 kJ mol −1 , which is competitive when compared to other heterogeneous catalysts reported to date. The lower activation energy results from the small Pt nanoparticles (∼3 nm) that create more active sites to adsorb the borohydride ion and facilitate the generation of hydride ions via electron transfer. The generated hydride ions immediately combine with the protons generated from the weakened H−O−H bond to produce hydrogen gas. The MWCNTs composite displayed its durability and stability though its reusable test that generated 15.2 ml of hydrogen.