Nanotubes, nanofibers and nanowires as supports for catalysts

Abstract

The use of nanotechnology towards improving clean energy solutions is very important. There is a growing awareness that nanotechnology will have a profound impact on energy generation, storage, and utilization by understanding the significant differences of energy states and transport in nanostructures compared to macrostructures. Nanotechnology-based solutions are being developed for a wide range of energy solutions such as solar cells, hydrogen generation and storage, batteries, and fuel cells. Energy shortages and environmental pollution are serious challenges that humanity is starting to face. The world demand for energy is expected to double from 14 terawatts (TW) in the year 2000 to 28 TW by the year 2050. Fuel cells are non-polluting and efficient energy conversion devices that are expected to play a dominant role in energy solutions of the future. However, fuel cells still face significant technological roadblocks that need to be overcome before they will become economically viable. One of the biggest challenges towards the commercialization of fuel cells is their low stability and the high cost of materials. Many scientists see research in advanced nanotechnology and nanomaterials as an opportunity to address our significant energy and environmental challenges (e.g., see the article by R. Smalley, a winner of the Nobel Prize, in the June issue of MRS Bulletin in 2005). Nanomaterials have attracted great interest in recent years because of their unusual catalytic, mechanical, electrical and optical properties, all of which are obtained by confining their dimensions. For example, gold in bulk form is not chemically active, but at the nanoscale, a gold particle 3 nm in size is highly chemically active. Gold nanoparticles used as catalysts are therefore considered promising in chemical reactions such as the oxidation of CO. Further, gold nanowires are 100 times stronger than bulk gold because nanowires have fewer defects. Nanowires will be discussed in more detail later in the chapter. Among the advanced nanomaterials, nanotubes and nanowires are a class of novel nanostructures that have attracted much attention as model systems for nanoscience and for various potential applications, including those related to composite materials, electrode materials, field emitters, nanoelectronics, and nanoscale sensors. © 2008 Springer-Verlag.