Black Phosphorus Sensitized TiO2 Mesocrystal Photocatalyst for Hydrogen Evolution with Visible and Near-Infrared Light Irradiation

Wide absorption from the ultraviolet (UV) to near-infrared (NIR) region and enhanced charge separation are two main requirements for promising semiconductor photocatalysts. Here, we studied visible–NIR-driven photocatalytic hydrogen evolution over black phosphorus nanosheets/TiO2 mesocrystals loaded with a Pt heterostructure (BP NS/Pt (3 wt %)/TMC ). BP NS/Pt (3 wt %)/TMC can harvest photons from UV to NIR and simultaneously has enhanced charge separation to increase the generation of electrons for photocatalytic reduction of water. BP NS/Pt (3 wt %)/TMC exhibited photocatalytic H2 evolution rates of 1.9 and 0.41 μmol h–1 under visible (λ > 420 nm (420–1800 nm)) and NIR (λ > 780 nm (780–1800 nm)) irradiation, respectively, in comparison with 0.3 and 0.10 μmol h–1 for BP NS/Pt (3 wt %)/P25. Moreover, a comparative study was made to examine the effect of thickness of BP NS on the photocatalytic H2 evolution. Femtosecond time-resolved diffuse reflectance spectroscopy (fs-TRDRS) was integrated together with photoelectrochemical measurement to shed light on the importance of charge transfer and separation, confirming that decreasing the thickness of BP NS enhances electron injection from BP NS to TMC to increase the photocatalytic activity.