Core-Shell Nanostructures of Graphene-Wrapped CdS Nanoparticles and TiO₂ (CdS@G@TiO₂): The Role of Graphene in Enhanced Photocatalytic H₂ Generation

Aiming to achieve enhanced photocatalytic activity and stability toward the generation of H₂
from water, we have synthesized noble metal-free core-shell nanoparticles of graphene (G)-wrapped
CdS and TiO₂ (CdS@G@TiO₂) by a facile hydrothermal method. The interlayer thickness of G
between the CdS core and TiO₂ shell is optimized by varying the amount of graphene quantum dots
(GQD) during the synthesis procedure. The most optimized sample, i.e., CdS@50G@TiO₂ generated
1510 µmole g−1 h
−1 of H₂ (apparent quantum efficiency (AQE) = 5.78%) from water under simulated
solar light with air mass 1.5 global (AM 1.5G) condition which is ~2.7 times and ~2.2 time superior to
pure TiO₂ and pure CdS respectively, along with a stable generation of H₂ during 40 h of continuous
operation. The increased photocatalytic activity and stability of the CdS@50G@TiO₂ sample are
attributed to the enhanced visible light absorption and efficient charge separation and transfer
between the CdS and TiO₂ due to incorporation of graphene between the CdS core and TiO₂ shell,
which was also confirmed by UV-vis, photoelectrochemical and valence band XPS measurements