A practical method for the production of hollow carbon onion particles

Abstract: Carbon onions with diameters ranging from 5 to 50nm and carbon-coated nickel nanoparticles with diameters ranging from 10 to 60nm have been synthesized on a large scale over Ni/Al catalyst by chemical vapor deposition. The approximate ratio of Ni-filled to empty onions as observed by TEM is 1:3.5. In order to eliminate the nickel nanoparticle and obtain pure hollow carbon onions, HNO3 acid was used to dissolve the nickel from the carbon-coated nickel nanoparticles. The carbon onion particles thus obtained have hollow cores and are mainly composed of well-crystallized graphite, as characterized by high-resolution TEM and Raman spectroscopy. In addition, we proposed a simple purification mechanism for Ni-filled carbon onions based on TEM observations. [Copyright &y& Elsevier]