Effect of oxygen concentration on ammonia combustion: A combined ReaxFF and DFT study.

In order to investigate the effect of oxygen concentration on ammonia combustion, the effect of oxygen concentration on ammonia combustion and its mechanism were systematically investigated by using the ReaxFF molecular dynamics simulations and density functional theory (DFT) calculations. The results show that different oxygen concentrations significantly affect the concentration of reactants, free radicals, intermediates and products in the ammonia combustion process. High oxygen concentration significantly increases the concentration of free radicals, which effectively promotes the ammonia reaction. However, more free radicals such as ·H and ·OH are produced in the early stage of the reactions, which react with ·NH 2 radicals. It promotes the production of the intermediates HNO and indirectly inhibits the production of the intermediates N 2 H 4 and N 2 H 2. It promotes the production of NO X. The results of the DFT calculations show that the relative Gibbs free energy barrier of the reaction of ·OH with NH 3 is low at 1.00 kcal/mol, so the increase in ·OH concentration greatly facilitates the reaction of NH 3. These results not only identify the intrinsic effect of oxygen concentration on ammonia combustion and its mechanisms, but also provide some theoretical guidance for the study of efficient and clean ammonia utilization. • NH 3 combustion with different O 2 numbers was studied by ReaxFF MD simulations. • The main chain reactions of NH 3 combustion were studied by DFT calculations. • The effect of O 2 concentration on NH 3 combustion was studied by DFT calculations. • High oxygen concentration promotes the NH 3 combustion. • High oxygen concentration promotes the production of NO X of NH 3 combustion. [ABSTRACT FROM AUTHOR]