Mechanism of Transition Metal-Assisted Healing of Defective Graphene

In graphene synthesis, the emergence of atomic vacancy defects is inevitable. These defects compromise the lattice's capacity to conduct heat, resulting in a diminished thermal transport efficiency for graphene-based devices. The introduction of adatoms to these vacancies termed the healing of defected graphene, has been identified as a method to enhance thermal conductivity. However, the details of the healing process remain unclear. This study delves into the mechanism underlying the healing of mono-vacancy (MV) defected graphene using Pt atoms, employing neural network potential (NNP)-assisted molecular dynamics (MD) simulations. In contrast to the marginal increase in thermal conductivity observed with pure Pt atoms, healing with C-Pt fragments significantly elevates the lattice thermal conductivity of defected graphene as the healing progresses. Upon full healing, the thermal conductivity of defected graphene healed by C-Pt fragments reaches 5.2 times that of the pre-healing state. During the healing process with C-Pt fragments, the fragments dissociate, allowing Pt atoms to move freely on the surface while carbon atoms remain stationary at the vacancies. Subsequently, Pt atoms gather to form a metal cluster, influencing the distribution of phonon density of states and causing a change in lattice thermal conductivity. The study also explores alternative transition metals such as Ni and Pd, with the resulting lattice thermal conductivities for C-Ni, C-Pd, and C-Pt fragment-healed graphene recorded as 382.1 W/m K, 976.9 W/m K, and 1159.7 W/m K, respectively. This variation is attributed to differences in mass and adsorption energy. The findings of this research present the effectiveness of utilizing transition metals as a promising strategy for rectifying defective graphene and controlling lattice thermal conductivity, particularly for applications in thermal management.<br/><br/>This work was supported by the National Research Foundation of Korea funded by the Ministry of Science and ICT under Grant (2022M1A3C2074536, Future Space Education Center) and Grant (2021R1A2C2004207).