Mechanism of Metal Catalyzed Healing of Large Structural Defects in Graphene

Structural defects are almost unavoidable
in graphene synthesis
and they may significantly deteriorate the performance of graphene
in applications. Although defects of small sizes may be easily healed
by the rearrangement of a few C atoms near the defect site, the healing
of large ones is rather complicated and the healing mechanism remains
unclear. In this work, we reveal a catalytic healing of large structural
defects in graphene based on both classical molecular dynamics simulations
and density functional theory calculations. The kinetic healing processes
of large vacancy holes in graphene with and without a nickel catalyst
are explored. Our results show that the presence of a single Ni atom
can (1) catalyze the dissociation of carbon feedstock, (2) heal nonhexagonal
C rings formed during the addition of C atoms, and (3) prevent the
formation of hanging C chains and arching C patches, and ultimately
lead to the successful healing of large structural defects in graphene.