Adsorption and Decomposition Mechanisms of Vapor Growth Carbon Fiber on SiO2 in Non-Catalytic Conditions: A First-Principles Study

In this study, the authors employed first-principles calculations to investigate the adsorption and decomposition processes involved in non-catalytic growth of vapor-growth carbon fiber (VGCF) using a non-catalytic growth method. The adsorption and decomposition mechanisms of methane and its decomposition products on the substrate were investigated with the adsorption energy, transition state analysis, and projected density of states (PDOS). The results indicated that the surface adsorption difficulty for CH4 and its decomposition products followed the following order: H > CH4 ≈ CH3 > CH2 > CH > C. The adsorption energy analysis indicates that the adsorption of CH4, CH3, and H is classified as physical adsorption, whereas the adsorption of CH2, CH, and C is classified as chemical adsorption. Adsorption of all particles is exothermic and adsorption can occur. The transition state calculations indicate that the decomposition of CH4 is the rate-determining step in the decomposition reaction. PDOS analysis not only verified the results of adsorption energy analysis but also investigated the effect of adsorption particles. This work is helpful for advancing the application of non-catalytic growth processes to the synthesis of VGCF and enhancing the understanding of the mechanisms governing non-catalytic VGCF formation.