Dark-Light Tandem Catalytic Oxidation of Formaldehyde over SrBi₂Ta₂O₉ Nanosheets

Formaldehyde (HCHO), as one of the main indoor toxic pollutions, presents a great threat to human health. Hence, it is imperative to efficiently remove HCHO and create a good indoor living environment for people. Herein, a layered perovskite material SrBi₂Ta₂O₉ (SBT), was studied for the first time and exhibited superior photocatalytic efficiency and stability compared to commercial TiO₂ (P25). Furthermore, a unique dark-light tandem catalytic mechanism was constructed. In the dark reaction stage, HCHO (Lewis base) site was adsorbed on the terminal (Bi₂O₂)²⁺ layer (Lewis acid) site of SBT in the form of Lewis acid-base complexation and was gradually oxidized to CO₃^2- intermediate (HCHO → DOM (dioxymethylene) → HCOO^- → CO₃^2-). Then, in the light reaction stage, CO₃^2- was completely converted into CO₂ and H₂O (CO₃^2- → CO₂). Our study contributes to a thorough comprehension of the photocatalytic oxidation of HCHO and points out its potential for day-night continuous work applications in a natural environment.