Polytriptycene@CdS double shell hollow spheres with enhanced interfacial charge transfer for highly efficient photocatalytic hydrogen evolution

Abstract

A double-shell triptycene covalent polymer@CdS hollow sphere (TCP@CdS HS) composite has been successfully synthesized by in situ growing a TCP on the surface of CdS@SiO₂ spheres and then removal of the SiO₂ template via alkali etching. Characterization indicates that an amorphous TCP layer is coated on the thin CdS shell via an electrostatic self-assembly process, and the TCP layer thickness can be tuned by adjusting TCP loading. The photocatalytic hydrogen generation rate of the optimal TCP@CdS HS composite is up to 9480 μmol h⁻¹ g⁻¹ under visible-light irradiation, which is 57, 37 and 18 times higher than those of pristine CdS HS, SiO₂@CdS HS and SiO₂@CdS@SiO₂, respectively. Besides, the TCP@CdS HS composite possesses excellent stability, which is superior to that of SiO₂@CdS HS and SiO₂@CdS@SiO₂. An in-depth study of the electron transfer process and the photocatalytic mechanism was performed by in situ transient photovoltage experiments, which indicate that the TCP can facilitate the diffusion of hydrogen and stabilize the photoinduced electrons. This work provides an effective strategy to design novel hollow sphere heterostructures for solar energy conversion.