Silicon-coordinated nitrogen-doped graphene as a promising metal-free catalyst for N 2 O reduction by CO: a theoretical study.

Metal-free catalysts for the transformation of N 2 O and CO into green products under mild conditions have long been expected. The present work proposes using silicon-coordinated nitrogen-doped graphene (SiN 4 G) as a catalyst for N 2 O reduction and CO oxidation based on periodic DFT calculations. The reaction proceeds via two steps, which are N 2 O reduction at the Si reaction center, producing Si-O*, which subsequently oxidizes CO to CO 2 . The N 2 O reduction occurs with an activation energy barrier of 0.34 eV, while the CO oxidation step requires an energy of 0.66 eV. The overall reaction is highly exothermic, with a reaction energy of -3.41 eV, mostly due to the N 2 generation step. Compared to other metal-free catalysts, SiN 4 G shows the higher selectivity because it not only strongly prefers to adsorb N 2 O over CO, but the produced N 2 and CO 2 are easily desorbed, which prevents the poisoning of the active catalytic sites. These results demonstrate that SiN 4 G is a promising metal-free catalyst for N 2 O reduction and CO oxidation under mild conditions, as the reaction is both thermodynamically and kinetically favorable.