Transition metals play a pivotal role in catalyzing the growth of graphene through chemical vapor deposition (CVD). Their unique catalytic properties give them an edge over other materials. Extensive research has focused on metals such as nickel (Ni), copper (Cu), palladium (Pd), ruthenium (Ru), iridium (Ir), and platinum (Pt) for facilitating the growth of single-layer graphene. Among these, Ni and Cu are the most frequently employed substrates due to their proven ability to effectively control graphene's growth, making them ideal for scalable production. . Nickel (Ni) has been integral in the growth of graphene layers for over 50 years, with its applications observed in various industrial settings. Among transition metals, Ni(111) is particularly favorable for graphene growth due to its minimal lattice mismatch with graphene, only around (1%). This close alignment makes Ni(111) catalytically superior compared to other metals, allowing for more controlled and uniform growth of graphene layers. This property, combined with its industrial viability, has made nickel a key substrate in the chemical vapor deposition (CVD) process for graphene production. .The mechanism of graphene growth on Ni is a bulk diffusion process. Carbon atoms dissolve in the nickel substrate because of the metal carbon solubility. While cooling, these carbon atoms segregate from the bulk, precipitating onto the surface and forming graphene layers. The advantage of this method is that the properties of solubility of Ni enable control of graphene formation during cooling and yield high-quality graphene layers. Grain boundaries and defects on the substrate's surface increase nucleation sites, leading to more heterogeneous graphene growth . Testing different metallic substrates, copper rapidly proved to be an excellent substrate for CVD graphene growth . This is supported by the first works, for instance by Li et al., where they have demonstrated that low carbon solubility of copper at high temperatures decreases the precipitation on the surface and allows more uniform single-layer graphene to grow . Figure is a schematic illustration of the difference in graphene growth process originating between Ni and Cu: Graphene growth on Cu is attributed to the surface adsorption mechanism of carbon atoms on the copper surface. The stable electronic configuration of Cu makes its interaction with carbon atoms in the form of weak forces, which decreases the bulk diffusion of carbon atoms into the Cu substrate. That gives copper an advantage in growing single-layer graphene, as the process mostly proceeds on the surface. . In brief, it is now possible to summarize the growth mechanism of graphene on catalytic metal substrates. The decomposition of CH 4 in the CVD reactor is highly complex and can involve numerous chain reactions. In the absence of a catalyst, CH 4 can react in the gas phase either by pyrolysis or via chain reactions if the temperature is sufficiently high to assist thermal decomposition and when P CH4 is high. Reactions within the gas phase supply CH 3 , H 2 , H, and C 2 H x (x = 1-6). . In the case of Cu substrate, CH 4 is considered to be thermally and catalytically decomposed on the substrate because Cu is a well-known dehydrogenation catalyst. The catalytic decomposition of CH 4 involves its initial absorption and the final product in the form of one carbon atom and four hydrogen atoms on the surface of Cu substrate through three kinds of intermediates which are methyl (CH 3 ), methylene (CH 2 ) and methylidyne (CH). :