Removal of NO with silicene: a DFT investigation

Abstract

Removing or reducing NO is meaningful for environment protection. Herein, the investigation of the probability of NO reduction on silicene is presented utilizing DFT calculations. Two mechanisms for NO reduction on silicene are provided: a direct dissociation mechanism and a dimer mechanism. The direct dissociation mechanism is characterized as the direct breaking of the N–O bond. The calculated potential energy surfaces show that the total energy barrier in the favored direct dissociation pathway is 0.466 eV. On the other hand, the dimer mechanism is identified to undergo a (NO)₂ dimer formation on silicene, which then decomposes into N₂O + O_ad or N₂ + 2O_ad. The (NO)₂ dimer formation on silicene is found to be feasible both in thermodynamics and kinetics. The formation energy barriers for (NO)₂ dimer are lower than 0.231 eV. The calculation results indicate that the (NO)₂ dimers can be readily reduced into N₂O or N₂. The energy barriers in the favored decomposition pathways to produce N₂O are quite low (<0.032 eV). The energy barrier for the release of N₂ is calculated to be 0.156 eV. The further reduction of N₂O to N₂ on silicene is also investigated. The results indicate it is easy to reduce N₂O to N₂ with an energy barrier of only 0.445 eV. NO reduction on silicene hence prefers to generate N₂ via the dimer mechanism when compared to the direct dissociation. NO reduction on silicene with silicane as substrate is further proved to proceed via the same reduction mechanism as compared with the free-standing model. Hence, our results presented here suggest that silicene can be a potential material in NO removal, which will reduce NO into environmentally-friendly gases.