Saturday, September 13, 2014

portable power supply in the species future



nanowerk |  Aligned carbon nanotube/graphene sandwiches for high-rate lithium-sulfur batteries 

(Nanowerk Spotlight) Sp2-bonded carbon nanomaterials – such as carbon nanotubes (CNTs) and graphene – have attracted enormous research interest over the past decades. Due to their superior intrinsic physical properties, such as mechanical strength, electrical and thermal conductivity, these nanocarbons find numerous applications in areas such as catalysis, energy storage or nanocomposites. In addition to these intrinsic physical properties, what makes these materials so attractive are their tunable chemical characters, such as functional groups, doping, and surface modification.

However, the demonstration of their intrinsic physical properties and performances in as-fabricated materials and practical devices has been suffering from the self-aggregation and re-stacking of nanocarbon materials due to strong van der Waals interactions. This prevents the full utilization of the active sites for catalytic reactions.

Researchers consider the rational combination of CNTs and graphene into three-dimensional (3D) hybrids an effective route to amplify the inherent physical properties at the macroscale. From post-treatment methods to in situ growth, various strategies have been explored to fabricate such CNTs/graphene hybrids. Most of these approaches, though, still require barrier layers, which hinders the full demonstration of the excellent properties of these hybrid materials.

By in situ nitrogen doping and structural hybridization of carbon nanotubes and graphene, a team from Tsinghua University, led by professors Qiang Zhang and Fei Wei, have now successfully fabricated nitrogen-doped aligned carbon nanotube/graphene (N-ACNT/G) sandwiches. In this work, aligned CNTs and graphene layers were anchored to each other, constructing a sandwich-like hierarchical architecture with efficient 3D electron transfer pathways and ion diffusion channels.