Carbon nanotubes for clean energy applications

The issue of the sustainability of energy supply has attracted worldwide concern given the rapid depletion of fossil energy sources amid increasingly worsening environmental pollution and the drive to develop alternative, environment-friendly, renewable energy sources and energy carriers to secure our energy supply and sustainable development. Hydrogen is considered to be among the best solutions available, although technical barriers, in particular effective hydrogen storage, need to be dealt with. Quasi-one-dimensional carbon nanotubes (CNTs) with rich nanosized pore structures are considered to be a potential hydrogen storage medium; however, controversy over and discrepancies in both the experimental and theoretical results do exist. Therefore, the latest research progress in and the current situation pertaining to hydrogen storage in CNTs are reviewed and discussed in detail. Moreover, CNTs can have wide applications as alternative energy storage media, utilizing fully their unique structural characteristics. We summarize and analyse the advantages as well as the research progress made in using CNTs as electrode materials in lithium-ion batteries and supercapacitors. Further, future applications of CNTs in the energy storage field are explored.