Black N/H-TiO2 Nanoplates with a Flower-Like Hierarchical Architecture for Photocatalytic Hydrogen Evolution.

A facile two-step strategy was used to prepare black of hydrogenated/nitrogen-doped TiO2 nanoplates (NHTA) with a flower-like hierarchical architecture. In situ nitriding and self-assembly was realized by hydrothermal synthesis using tripolycyanamide as a N source and as a structure-directing agent. After thorough characterization, it was found that the hydrogenation treatment did not damage the flower-like architecture but distorted the anatase crystal structure and significantly changed the band structure of NHTA owing to the increased concentration of oxygen vacancies, hydroxyl groups, and Ti3+ cations. Under AM 1.5 illumination, the photocatalytic H2 evolution rate on the black NHTA was approximately 1500 μmol g-1  h-1 , which was much better than the N-doped TiO2 nanoplates (≈690 μmol g-1  h-1 ). This improvement in the hydrogen evolution rate was attributed to a reduced bandgap, enhanced separation of the photogenerated charge carriers, and an increase in the surface-active sites.