Fine-tuning of ultrathin carbon shells coated on metal nanoparticles: carbon etching and defect healing effects.

Carbon-incorporated metal nanoparticles are heat-treated in various gas atmospheres to create carbon shells with different porosity. A highly porous carbon shell is formed due to the carbon etching effect by H 2 , and the defect healing effect by CO is discovered through additional CO gas treatment of the H 2 /N 2 gas-treated sample.