Evaporation of graphite electrodes in H 2 gas by DC arc discharge was found to form not only multiwalled carbon nanotubes (MWNTs) but also graphene sheets in the cathode deposit. By irradiating the deposit surface using an infrared radiation heating system in air, the MWNTs could be easily purified. The morphology and structure of as-grown MWNTs, graphene sheets and purified MWNTs were investigated using scanning electron microscopy, high-resolution transmission electron microscopy and X-ray diffraction. X-ray diffraction patterns of MWNTs and graphene sheets were similar to each other.