Layered SiC sheets: A promising metal-free catalyst for NO reduction

Recently, the catalytic reduction is shown to be an effective method to remove the harmful NO. In terms of the high cost and limited supply of the traditional transition metal-based catalysts, the novel metal-free catalyst is highly desirable for NO reduction. Here, density functional theory (DFT) computations were performed to explore the potentials of layered SiC sheets as a metal-free catalyst for NO reduction. From our DFT results, it can be predicted that layered SiC sheets exhibit superior catalytic activity toward NO reduction. In particular, a dimer mechanism is shown to be more favorable than the direct dissociation one for NO reduction on this metal-free catalyst and a three-step mechanism is involved in this process: (1) the formation of a (NO)2 dimer on layered SiC sheet, followed by (2) its dissociation into N2O+Oad, and (3) the recovery of catalyst by subsequent NO. The trans-(NO)2 dimer might be a necessary intermediate, in which the calculated barrier for the rate-determining step along the energetically most favorable pathway is 0.722 eV. The high reactivity of layered SiC sheets may be attributed to the certain amount of charge transfer from the catalyst to (NO)2 dimer, which shortens the NN bonding and thus stabilizes these systems due to the extra electrons on the dimers. This excellent catalytic activity provides a useful guidance to design the next generation catalysts for NO reduction with lower cost and higher activity.