(A) study on the hydrogen generation and storage properties of ammonia borane using nano-materials

Abstract

Hydrogen is one of most promising energy materials, which contains large chemical energy per mass than any fuels and produces only water as a by-product. However, the most challenging issue is how to store and deliver hydrogen with safe, efficient, and light way. While many different technologies have been considered as hydrogen storage system, chemical hydrides are much focused on advanced hydrogen storage materials. In this dissertation, the two different approaches of ammonia borane hydrogen storage have been considered by using nano-materials with high specific surface area. The hydrolysis of ammonia borane can be easily control their hydrogen release rate by introducing the catalysts. However, the widely known catalysts are composed of Pt, which is very expensive. Therefore, the need for researching cheaper materials with high catalytic performance has been floating. The nanoparticles on the supporting materials could be the solution to enhance catalytic property by increasing their surface area. First, we synthesized the transition metal nanoparticles on carbon nitride nanotubes where the nitrogen atom can be act as a nucleation site for the transition metal particle formation, enabling the very fine and uniform distribution of sub-nanosized nanoparticles on carbon nitride nanotubes. Moreover, bi-metallic nanoparticles on carbon nitride nanotubes can be also produced via above criteria, having excellent catalytic property for hydrogen generation of aqueous ammonia borane solution up to 27.6 kg/hour/kg-catalyst. This phenomenon is very interesting. While typical solid solution of two different elements shows the mean property, our Ni-Pt bi-metallic nanoparticles show much higher property than Ni or Pt alone. We also investigated the mechanism of having such a high property on hydrolysis of ammonia borane via Ni-Pt bi-metallic nanoparticles on carbon nitride nanotubes. The calculation could show the steric accessibility on the Ni-Pt alloy, where Pt atoms c...