Graphitic carbon is the key: A Pt catalyst that is supported on carbon nanocages with a graphitic structure is found to exhibit not only a high catalytic activity, but also a superior thermal stability and electrochemical durability in harsh operating conditions when compared with a counterpart that is supported on conventional carbon black (see graphic).

No abstract

Carbon nanocages (CNCs) with a hollow core and a thin wall of a few graphitic layers have a wide range of applications. However, the preparation of such a material remains a great challenge. In this study, we report the preparation of thin-walled CNCs through the pyrolysis of a mixture composed of pyridine and liquid iron pentacarbonyl, subsequent heat treatment in the presence of NH 4 Cl at a low temperature, and finally washing and filtering in water. The finding that pyridine is completely mutually soluble with liquid iron pentacarbonyl in any proportion stands out to be a crucial advantage for reducing the thickness of the graphitic wall formed on a metal core. To obtain hollow CNCs, heattreatment proves to be simple and effective in removing the metal core and, more importantly, maintaining the thin graphitic wall when compared with conventional boiling in a strong oxidant, such as HNO 3 . The thin-walled hollow CNCs are demonstrated to be suitable nanocontainers for encapsulating iodine, as iodine can easily get into and out of the CNCs when it is heated at a relatively low temperature. Considering the large internal space and thin graphitic wall, the hollow CNCs could be widely used in many fields, such as biology, medicine and chemistry.

Empty cages: Iron/graphite core–shell nanoparticles are produced by pyrolysis of a mixture of acetylene and iron carbonyl. Then, the core–shell nanoparticles are heat treated in the range of 300–500 °C in the presence of NH4Cl. After filtration in water, the trapped iron particles are completely removed and hollow carbon nanocages with a good graphitic structure are obtained (see graphic).