▎ 摘　　要

Core-shell few layer-graphene-coated metal nanoparticles (GCMNP) were synthesized by methane catalytic chemical vapor deposition (CVD). The GCMNPs of cobalt and iron dispersed on an alumina support catalyze themselves the decomposition of methane, which is the source of carbon. Different synthesis operating conditions were investigated to achieve a good control of the coverage of GCMNPs and to understand the mechanism of GCMNP (particularly with respect to their size) and carbon coverage formation. Moreover, the reactor outlet gas was continuously monitored on-line during the catalyst activity. Several techniques were utilized to characterize the catalyst and the reaction products and to correlate their properties with the reactor operating conditions. The reaction yield was monitored to produce small body-centered-cubic-Co/Fe nanoparticles (4.1 nm mean diameter) with a very narrow size distribution, selectively covered by two graphene layers. (C) 2014 Elsevier B.V. All rights reserved.