Construction of graphene supported TiO2 nanosheet array/CdS/Ni2P composite with dual heterojunctions for boosting photocatalytic hydrogen evolution

Abstract

Graphene supported TiO₂ nanosheet array (GT) was successfully fabricated via a hydrothermal route and modified by CdS and noble-metal-free Ni₂P cocatalyst. It is found that interlaced TiO₂ nanosheets with a thickness only ca. 12.7 nm are vertically grown on graphene surface, which greatly reduce the agglomeration of nanosheets and provide abundant anchoring sites for surface modification. The synthesized GT/CdS/Ni₂P (GTCN) composite exhibits superior photocatalytic hydrogen evolution rate of 1.91 mmol h⁻¹ g⁻¹, which is ca. 11.7-fold higher than that of GT. Density functional theory calculation and experimental results reveal the formation of TiO₂/CdS S-scheme heterojunction and CdS/Ni₂P Schottky heterojunction in GTCN composite, and the constructed dual heterojunctions with intimate interfaces offer double transfer channels for photogenerated electrons, which effectively improved the photocatalytic reaction kinetics and facilitated the photogenerated carrier separation. This work provides insight into the design and construction of multicomponent catalysts with ideal photocatalytic performance for hydrogen evolution.