Facet-dependent performance of anatase TiO2 for photocatalytic oxidation of gaseous ammonia

Abstract Photocatalytic oxidation of gaseous ammonia (NH3) at room temperature is an efficient method for the elimination of NH3 emitted from indoor and outdoor sources, such as decorative materials, intensive livestock farming, chemical processes, etc. Herein, we prepared the anatase TiO2 with clean dominant {001}, {101} and {010} facets, and tested their photocatalytic activity for NH3 oxidation. The test results show that the photocatalytic activity order for NH3 oxidation is revealed as {001} > {101} > {010}. The catalysts were characterized by XRD, FE-SEM, XPS, UV–vis, in situ DRIFTS and TPD methods. It is indicated that TiO2 with dominant {001} facets has the highest separation efficiency of the photogenerated charges among three catalysts. Since the photogenerated holes is responsible for initiating the first step of NH3 oxidation, the TiO2 with dominant {001} facets demonstrated the exceptional activity. In addition, the photocatalytic oxidation of NH3 possibly follow the photo-iSCR mechanism. The photogenerated electrons activate O2 and then participate in the formation of reactive intermediate NOx followed by the photo-NH3-iSCR to final products. The present study will improve our understanding about the performance of anatase TiO2 for photocatalytic oxidation of NH3.