Crumpled Graphene-Storage Media for Hydrogen and Metal Nanoclusters

Abstract

Understanding the structural behavior of graphene flake, which is the structural unit of bulk crumpled graphene, is of high importance, especially when it is in contact with the other types of atoms. In the present work, crumpled graphene is considered as storage media for two types of nanoclusters—nickel and hydrogen. Crumpled graphene consists of crumpled graphene flakes bonded by weak van der Waals forces and can be considered an excellent container for different atoms. Molecular dynamics simulation is used to study the behavior of the graphene flake filled with the nickel nanocluster or hydrogen molecules. The simulation results reveal that graphene flake can be considered a perfect container for metal nanocluster since graphene can easily cover it. Hydrogen molecules can be stored on graphene flake at 77 K, however, the amount of hydrogen is low. Thus, additional treatment is required to increase the amount of stored hydrogen. Remarkably, the size dependence of the structural behavior of the graphene flake filled with both nickel and hydrogen atoms is found. The size of the filling cluster should be chosen in comparison with the specific surface area of graphene flake.

Methodologyfor Molecular Dynamics Simulation of Plastic Deformation of a Nickel/Graphene Composite

“…The starting configuration, which is not yet a composite, but just the precursor—a system of graphene flakes with Ni nanoparticles inside each flake—is shown in Figure 1 , stage A . Note that in previous studies [ 39 , 40 , 41 ] it was shown that to obtain a Ni/graphene composite with high strength, it is necessary to take into account the difference in the diameter of Ni nanoparticle and the diameter of the rolled graphene flake. If the diameter of the nickel nanoparticle is large, then the graphene flake completely covers the nanoparticle, which makes the formation of strong bonds between the graphene flakes difficult, and therefore, complicates the composite fabrication.…”

“…The dimensions along x , y , and z directions are 100 Å, 101 Å, and 85 Å, respectively. A more detailed description of the formation of the starting configuration of the Ni/graphene composite is presented in [ 40 , 41 , 42 , 43 ].…”

“…The second step of deformation—high-temperature compression–is applied at 1000 K to obtain the final composite state (see Figure 1 , stage D ). This temperature is enough to facilitate the formation of new valent bonds between graphene flakes, but not enough to melt Ni nanoparticles [ 40 , 41 ]. The compression rate in the loading process is 5 ps .…”

“…After high-temperature compression, the structure is relaxed to minimize the internal elastic stresses that appear during the preparation of the Ni/graphene composite. It should be noted that in early works [ 40 , 41 , 42 , 43 ], the relaxation of the structure after the production of the composite is not carried out, which led to the appearance of excess stress, which affects the final mechanical properties of the composite.…”

Effect of Nanoparticle Size on the Mechanical Strength of Ni–Graphene Composites

“…The size of nickel nanoparticles was chosen because a rigid graphene flake interacting with given size nanoclusters destroys their crystal structure, which does not happen with larger nanoparticles. The dynamics of the interaction of a graphene flake with nickel nanoclusters of different sizes was described in detail in our early work [ 52 ]. Taking into account the peculiarity of the interaction of crumpled graphene with nickel nanoparticles, it is possible to achieve a denser structure of the metal/graphene composite with a smaller pore volume fraction.…”