Methane (CH4) was purchased from Sumitomo Seika Chemicals Co.,Ltd. with Pure grade (>99.0%) and SEG grade (>99.99%), and Taiyo Nippon Sanso Corp. with G1 grade (>99.999%). High purity γ-alumina nanoparticles (γ-ANPs, SBa-200; γ-Al2O3, particle size: ~9 nm, specific surface area: 203 m 2 g -1 ) were donated from Sasol Limited. High purity θ-alumina nanoparticles (θ-ANPs, TM-100; θ-Al2O3, particle size: ~10 nm, specific surface area: 120 m 2 g -1 ) were from Taimei Chemicals Co.,Ltd. All chemicals were used as received unless otherwise noted. Synthesis of NPC and NPG using θ-ANPs (TM-100) and γ-ANPs (TM-300) as the templates were reported previously, and the modified procedure was used to prepare the carbon materials for this work. γ-ANPs (SBa-200, Sasol Limited.) with a BET surface area of 200 m 2 g -1 was used as the nanosized template for the synthesis of singlewalled 3D nanographene by chemical vapor deposition of CH4 (CH4-CVD). ca. 2 g of SBa-200 was mixed with well-sieved quartz sand (ca. 7-8 g, Wako Pure Chemical Industries). The mixture was placed either in a horizontal or vertical quartz chamber, then heated to 1173 K (900 ºC) at a rate of 10-15 K min -1 under a steady-flow of Ar (90-225 mL min -1 ). The temperature was maintained for 10-30 min, and a mixture of CH4 (20-31 vol%) and Ar (80-69 vol%) was then introduced to the chamber for 120-130 min at 1173 K for γ-alumina nanoparticles-catalyzed CH4-CVD. The temperature was maintained for 10-30 min under a steady flow of Ar. The chamber was then cooled down to room temperature, and the quartz sand was separated by sieving to obtain the carbon/alumina composite.