Undoped Layered Perovskite Oxynitride Li₂LaTa₂O₆N for Photocatalytic CO₂Reduction with Visible Light

Abstract

Oxynitrides are promising visible‐light‐responsive photocatalysts, but their structures are almost confined with three‐dimensional (3D) structures such as perovskites. A phase‐pure Li₂LaTa₂O₆N with a layered perovskite structure was successfully prepared by thermal ammonolysis of a lithium‐rich oxide precursor. Li₂LaTa₂O₆N exhibited high crystallinity and visible‐light absorption up to 500 nm. As opposed to well‐known 3D oxynitride perovskites, Li₂LaTa₂O₆N supported by a binuclear Ruᴵᴵ complex was capable of stably and selectively converting CO₂ into formate under visible light (λ>400 nm). Transient absorption spectroscopy indicated that, as compared to 3D oxynitrides, Li₂LaTa₂O₆N possesses a lower density of mid‐gap states that work as recombination centers of photogenerated electron/hole pairs, but a higher density of reactive electrons, which is responsible for the higher photocatalytic performance of this layered oxynitride.