CdSe quantum dot/white graphene hexagonal porous boron nitride sheet (h-PBNs) heterostructure photocatalyst for solar driven H2 production

Abstract

In the world of photocatalytic hydrogen (H₂) evolution two-dimensional (2D) nanomaterials have attracted widespread attention owing to their high surface area, abundant active sites, and excellent photogenerated charge separation properties. In the present work, CdSe QDs coupled with different weight percent of ultra-thin layered hexagonal porous boron nitride sheets (h-PBNs) functionalized with 3-mercaptopropionic acid (3-MPA) have been synthesized and studied for photocatalytic hydrogen (H₂) evolution reaction. The h-PBNs/CdSe heterostructure with 30 wt% optimized loading shows an excellent photocatalytic H₂ evolution of 25 128 μmol g⁻¹ h⁻¹ which is 18.6 times higher than that offered by solely functionalized h-PBNs. The remarkable photocatalytic H₂ evolution benefits are anticipated to be attained owing to factors like the high specific surface area of porous h-PBNs (409 m² g⁻¹), which allows a uniform deposition of CdSe QDs on the surface providing more adsorption sites, and the presence of the thiol group on 3-MPA which strongly tethers the CdSe QDs to the h-PBNs which effectively reduces the photogenerated charge recombination as confirmed by PL and EIS studies. The 30% h-PBNs/CdSe photoelectrode shows excellent photoelectrochemical (PEC) performance. The photocurrent density achieved by the 30% h-PBNs/CdSe heterostructure is 1.2 mA cm⁻² at 1.2 V vs. Ag/AgCl, which is 4.13-fold and 2.56-fold higher compared to that achieved by h-PBNs and CdSe QDs. This study reveals that the 30% h-PBNs/CdSe heterostructure forms the type II heterojunction which offers new insight into the development of a heterojunction system for effective photocatalytic H₂ evolution from water.