In situ synthesis of an advanced Z-scheme Bi/BiOI/black TiO2 heterojunction photocatalysts for efficient visible-light-driven NO purification

Abstract Limited light absorption and severe charge recombination have been widely acknowledged as the two main obstacles restricting the application of P25 in NO photocatalytic conversion. In this work, an advanced heterojunction photocatalyst of Bi/BiOI/black TiO2 was synthesized via an in-situ solid-state chemical reduction method. The black TiO2 extended the light absorption to the full spectral region. It constructed a direct Z-scheme heterojunction with BiOI nanosheets, not only promoting the charge separation, but also preserving the strong oxidation ability of photogenerated holes in black TiO2 and strong reducing ability of photogenerated electrons in BiOI. Thus, more •O2− and •OH radical could form when Bi/BiOI/black TiO2 was subjected to visible light irradiation. Besides, the introduced Bi metal nanoparticles could also enhance the light utilization and served as a cocatalyst to accept the electrons. Therefore, enhanced NO photocatalytic oxidation activity was obtained, with the optimal sample Bi/BiOI/black TiO2 exhibiting a high NO conversion efficiency of ~70% and NOx removal of ~45%. This work may provide a refreshing perspective for the design of heterojunction photocatalysts for efficient NO photocatalytic purification and other photocatalytic applications.