Oxidation of methane and ethylene over Al incorporated N-doped graphene: A comparative mechanistic DFT study.

It is generally recognized that developing effective methods for selective oxidation of hydrocarbons to generate more useful chemicals is a major challenge for the chemical industry. In the present study, density functional theory calculations are conducted to examine the catalytic partial oxidation of methane (CH) and ethylene (CH) by nitrous oxide (NO) over Al-incorporated porphyrin-like N-doped graphene (AlN-Gr). Adsorption energies for the most stable configurations of CH, CH, and NO molecules over the AlN-Gr catalyst are determined to be -0.25, -0.64, and -0.40 eV, respectively. According to our findings, NO can be efficiently split into N and O species with a negligible activation energy on the AlN-Gr surface. Meanwhile, CH and CH molecules compete for reaction with the activated oxygen atom (O) that stays on the surface. The energy barriers for partial methane oxidation through the CH + O → CH° + HO and CH° + HO → CHOH reaction steps are 0.16 eV and 0.27 eV, respectively. Furthermore, the produced CHOH may be overoxidized by O to give formaldehyde and water molecules by overcoming a relatively low activation barrier. The activation barriers for CH epoxidation are small and comparable to those for CH oxidation, implying that AlN-Gr is highly active for both reactions. The high energy barrier for the 1,2-hydrogen shift in the OCHCH intermediate, on the other hand, makes the production of acetaldehyde impossible under normal conditions. According to the population analysis, the AlN-Gr serves as a strong electron donor to aid in the charge transfer between the Al atom and the O moiety, which is necessary for the activation of CH and CH. The findings of the present study may pave the way for a better understanding of the catalytic oxidation the CH and CH, as well as for the development of highly efficient noble-metal free catalysts for these reactions.