Layered Perovskite Pb2Bi4Ti5O18 for Excellent Visible Light-Driven Photocatalytic NO Removal

A grand challenge in photocatalysis is to seek chemically stable photcatalysts with minimized recombination of photoinduced charges in order to maximize the efficiency of the subsequent redox reactions. Because of the structural noncentrosymmetry, TiO2-based and lead-containing perovskite-type photocatalysts exhibit excellence in both stability and ferroelectricity to facilitate charge separation state. To extend their visible light activity, we use molten salts synthesis methodology to prepare Pb2Bi4Ti5O18 perovskites with various nanoscale morphologies and evaluated their visible light-driven photocatalytic activity for NO removal. The results show that perovskite Pb2Bi4Ti5O18 samples exhibit excellent stability as well as display over 50% NO removal efficiency under visible light in contrast to no more than 15% for commercial P25. A set of radical scavengers were used to probe the reaction mechanism. A bond valence method was used to calculate the direction and magnitude of the dipole moments of the asymmetric unit in the structure. We revealed that the photocatalytic Pb2Bi4Ti5O18 possesses distorted units in which the dipole-induced internal fields promote the charge separation, leading to the enhanced photocatalytic activity. Because this novel photocatalytic NO removal is a solid gas reaction in which the lead content is secured in solid phase, this work finds a suitable application for Pb-containing perovskite photocatalysts with great industrial interests and add a new fundamental coordination for better photocatalysts-by-designing.