Mechanistic insights into the photocatalytic reduction of nitric oxide to nitrogen on oxygen-deficient quasi-two-dimensional bismuth-based perovskites

Abstract

The decomposition of nitric oxide (NO) into stoichiometric N₂ and O₂ under ambient conditions merely with light as the driving force remains a great challenge owing to the huge activation barrier for both the cleavage of NO bonds and the subsequent reconstruction of NN triple bonds. In this work, ultrathin SrBi₂Nb₂O₉ with the thickness of three atomic layers was fabricated, and oxygen vacancies (Vo) were spontaneously generated due to the drastically shrunk thickness. Such ultrathin SrBi₂Nb₂O₉ displayed the capability to photocatalytically decompose NO into N₂ and O₂ at the close-to-stoichiometric ratio, whereas the defect-free counterpart SrBi₂Nb₂O₉ hardly exhibited such activity. Theoretical calculations and in situ FT-IR studies revealed the critical roles of Vo in favoring the adsorption of two NO molecules on the neighboring Bi sites around Vo. In such adsorption mode, the subsequent partial overlapping of electron orbitals of two N atoms guaranteed preferential N–N coupling, based on which the decomposition of NO into N₂ and O₂via the intermediate of N₂O was achieved upon illumination.