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

Highlights: • Z-scheme Bi/BiOI/black TiO₂ were first prepared via a gas–solid reduction approach. • The NO conversion and NO_x removal of Bi/BiOI/black TiO₂-x were much promoted. • Bi/BiOI/black TiO₂-x preserved the strong redox capacity of black TiO₂ and BiOI. • Bi NPs served as co-catalysts for improved light harvesting and electron sinks. 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 NO_x 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.