Fig. 3: CVD growth mechanisms of graphene on γ-Al2O3-AF.
a Comparisons of adsorption energy and lifetime of CH4 on Si- and O-terminated SiO2 (0001) surface (SiO2-Si and SiO2-O, respectively), and γ-Al2O3 (110) surface. b Fourier transform-infrared (FT-IR) spectra of pyridine adsorbed on AF and QF (top), and schematic for the structure of Lewis acid site on AF and its interaction with the absorbed hydrocarbon (bottom). L and L + B indicated Lewis and Lewis and Brønsted acid sites, respectively. c Comparisons of the energy barriers for CH4 stepwise decomposition on γ-Al2O3 (110) and without substrate supporting, where RL was the rate-limiting step. d Kinetic energy profile and atomic configurations for CH2 species participating in graphene CVD growth on γ-Al2O3 (110). TS1 and TS2 were transition states 1 and 2, respectively, and represented arrows indicated the processes of reactions I, II, and III. e C–H bond lengths and electron localization function (ELF) diagrams of CH2-Gr and CH-Gr at growing graphene edge with (left) and without (right) γ-Al2O3 substrate supporting. f The -COHP of C–H bonds in CH2-Gr with (red region) and without (blue region) γ-Al2O3 substrate supporting. The two C–H bonds in CH2-Gr were marked as C-H1-Gr and C-H2-Gr. g, h Schematics of graphene vapor-solid (VS) growth model on traditional catalytically inert nonmetallic substrates (g) and graphene vapor-surface-solid (VSS) growth model on γ-Al2O3-AF (h).
