Exploring Si-centered phthalocyanine as a single atom catalyst for N2O reduction: a DFT study

Abstract

To remove the greenhouse gas N₂O from the environment, recently, researchers have taken great interest in single-atom catalysts (SACs). In this study, we investigated various reaction pathways and barrier energies for the N₂O reduction process onto Si-coordinated phthalocyanine (Si@PthC) employing density functional theory. The outcomes validate that Si decoration in PthC is energetically stable while the corresponding electronic properties show that the Si atom acts as the reactive site for catalytic activity. The N₂O molecule exhibits spontaneous dissociation over the catalyst surface from the O-end with −4.01 eV dissociation energy. Meanwhile, N₂O dissociation via the N-end involves chemisorption onto the Si@PthC surface with an adsorption energy (E_ad) of −1.16 eV, and the dissociation needs an energy barrier of 0.51 eV. The bond distances and negative adsorption energies (−1.11 and −2.40 eV) evince that CO and O₂ species chemisorbed onto the Si@PthC surface. However, these energies are smaller than the N₂O dissociation energy, which demonstrates that the presence of CO and O₂ molecules cannot interrupt the N₂O reduction process. Additionally, the CO + O* → CO₂ reaction was executed for catalyst recovery, and the reaction proceeds very quickly on the Si@PthC catalyst, with a very small energy barrier (0.37 eV), indicating the excellent catalytic reactivity of the studied catalyst. These results propose that the designed catalyst can be valuable in the progress of novel noble metal-free catalysts for the elimination of harmful N₂O from the environment.