Oxygen functionalized carbon obtained from pyrolysis of heterocyclic compounds with their decomposition mechanism

Abstract

In this study, two heterocyclic compounds, 2,2-dimethyl-1,3-dioxane-4,6‑dione (DMDO) and 2,2,5-trimethyl-1,3-dioxane-4,6‑dione (5-DMDO), were thermally decomposed in an inert atmosphere of nitrogen to obtain oxygen functionalized carbon. The decomposition of these compounds was investigated by thermal gravimetric analysis (TGA) and gas chromatography-mass spectroscopy (GCMS) as well as hybrid-density functional theory (h-DFT). DMDO was found to have better thermal stability compared to 5-DMDO and thus gave a higher yield of carbon after decomposition at 1000 °C. This experimental observation was supported by the h-DFT analysis of the energy barriers of the two decomposition mechanisms proposed from the initial decomposition products detected above 100 °C with GCMS analysis and the thermodynamic spontaneity of the final product (solid carbon) at 800 to 1000 °C with TGA. X-ray photoelectron spectroscopy, scanning electron microscopy / energy dispersion spectroscopy and cyclic voltammetry were used to characterize the carbon and evidence was found to suggest that the electrochemical activity of the material towards the [Fe(CN)₆]⁴⁻/[Fe(CN)₆]^3- redox couple was dependent on the oxygen content of the carbon.