Nicl2 6h2o

Nickel oxide nanoparticles/reduced graphene oxide (NiO NPs/rGO) was synthesized using a microwave-assisted method. First, 10 mg of rGO (Angstron Materials, Dayton, OH, USA) and 50 mL of diethylene glycol (DEG, Junsei, Tokyo, Japan, 99%) were mixed in a 50 mL glass vial with ultrasonication for 3 h. Subsequently, 1 mL of 50 mM nickel (II) chloride hexahydrate (NiCl₂∙6H₂O, Junsei, 97%) and 1 mL of 0.5 M sodium hydroxide (NaOH, Junsei, 97%) were added into the solution, followed by sonication for 1 h. The solution was transferred to a 250 mL round flask and heated in a microwave oven with 700 W for 2 min. After cooling to room temperature, the solution was transferred to a 50 mL conical tube and centrifuged at 8000 rpm for 50 min. Then, the supernatant liquid was decanted, and the residual catalyst was washed with acetone (Daejung, Siheung, Korea, 99.9%) several times. Finally, the samples were dried in a vacuum oven at 60 °C overnight. As a control sample, nickel oxide nanoparticles/graphene oxide (NiO NPs/GO) were also synthesized by the same process.

For the Ni adsorption on the graphite, 50 g of pristine graphite (MCMB, Osaka gas), 6 g of nickel chloride hexahydrate (NiCl₂· 6H₂O, >97.0%, JUNSEI), and 0.2 g of sodium hydroxide (anhydrous NaOH, >98.0%, bead form, SAMCHUN) were dissolved in methanol (>99.5%, SAMCHUN)/deionized water (5:5, v/v), followed by the addition of 1 ml of hydrazine monohydrate (N₂H₄·H₂O, 98.0%, Sigma-Aldrich). The solution was heated at 78 °C for 30 min in air atmosphere by reflux technique. The Ni adsorbed graphite was obtained through the centrifugation. In order to trigger the catalytic hydrogenation, the prepared samples were annealing in the furnace at 1000 °C for 3 h under H₂ (99.999%, KOSEM) atmosphere (1000 sccm). In succession, for the formation of both the graphitic carbon shell and a-Si nanolayer on the graphite, C₂H₂ gas (10.0%, N₂ balance, KOSEM) was flowed at 900 °C for 10 min (1000 sccm) and then SiH₄ gas (99.9999%, KOSEM) was introduced into the furnace at 500 °C for 30 min (50 sccm). In case of SEAG with Ni silicide, the process of C₂H₂ flow was omitted.