ReaxFF molecular dynamics investigation on the oxidation mechanism of Fe surface in supercritical CO2 mixed with O2

In the present study, the oxidation reaction of Fe surface in supercritical CO2 (SCO2) mixed with O2 was studied at atomic scale by ReaxFF molecular dynamics simulation. The microscopic oxidation mechanism was explored, the charge evolution was observed and the effects of gas composition and temperature on the oxidation were determined. The results indicate that in the initial stage of the reaction, both of O2 and SCO2 molecules are adsorbed on the Fe surface, and O2 reacts with Fe atoms prior to SCO2. The initial consumption rates of O2 and SCO2 increase with the increase of their content in the system. The reaction degrees of O2 and SCO2 increase with temperature. The consumption of SCO2 is always greater than O2 at different temperatures. The thermal motion of atoms rises significantly with the increase of temperature, which is beneficial to the oxidation reaction.