Constructing TiO2 p-n homojunction for photoelectrochemical and photocatalytic hydrogen generation

Constructing junctions between semiconductors is an effective way to promote charge separation and thus to improve the photoelectrochemical and photocatalytic H2 generation, and specifically, p-n homojunction is considered as a very promising structure. Herein, we fabricate TiO2 p-n homojunction by in-situ decorating n-type oxygen-defected TiO2 QDs on p-type titanium-defected TiO2 surface. The composite structure and O-/Ti-vacancies are testified by TEM, XRD, XPS, EPR and UV–vis DRS characterizations. The “V-shaped” Mott-Schottky plot and anodic shift of onset potential in I-V curves verify the characteristics of p-n homojunction. PL and EIS analyses indicate p-n homojunction is much more efficient in charge separation and transfer than p-type, n-type and n-n type-II homojunction, subsequently leading to the significantly high photoactivity. Compared with p-TiO2, p-n homojunction TiO2 possesses 5-fold and 1.7-fold higher performances in photoelectrochemical and photocatalytic hydrogen generation, respectively. This work provides new opportunities to design and fabricate highly efficient TiO2 photocathodes for hydrogen generation.