Density functional study on the CO oxidation reaction mechanism on MnN2-doped graphene

The CO oxidation mechanisms over three different MnN2-doped graphene (MnN2C2: MnN2C2-hex, MnN2C2-opp, MnN2C2-pen) structures were investigated through first-principles calculations. The vacancy in graphene can strongly stabilize Mn atoms and make them positively charged, which promotes O2 activation and weakens CO adsorption. Hence, CO oxidation activity is enhanced and the catalyst is prevented from being poisoned. CO oxidation reaction (COOR) on MnN2C2 along the Eley–Rideal (ER) mechanism and the Langmuir–Hinshelwood (LH) mechanism will leave one O atom on the Mn atom, which is difficult to react with isolated CO. COOR on MnN2C2-opp along the ER mechanism and termolecular Eley–Rideal (TER) mechanism need overcome low energy barriers in the rate limiting step (RLS), which are 0.544 and 0.342 eV, respectively. The oxidation of CO along TER mechanism on MnN2C2-opp is the best reaction pathway with smallest energy barrier. Therefore, the MnN2C2-opp is an efficient catalysis and this study has a guiding role in designing effective catalyst for CO oxidation.