Amorphous Co3O4 modified CdS nanorods with enhanced visible-light photocatalytic H-2-production activity

In this work, amorphous Co3O4 modified CdS nanorods were synthesized by a two-step solvothermal/hydrothermal method, and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy, UV-visible spectroscopy, nitrogen absorption and X-ray photoelectron spectroscopy. The photocatalytic performance of the as-synthesized Co3O4-CdS nanorods was evaluated through H-2 generation from an aqueous solution containing sulfide and sulfite under visible light (lambda >= 420 nm). The results showed that the photocatalytic activity of CdS nanorods for H-2 evolution could be significantly enhanced by loading the amorphous Co3O4. The optimal Co3O4 loading was found to be approximately 3.0 mol%. The as-prepared CdS nanorods with 3 mol% Co3O4 exhibited the highest photocatalytic activity for H-2 evolution under visible light irradiation, 236 mu mol g(-1) h(-1), which is 33-fold higher than that of the pristine CdS nanorods. Furthermore, the co-loading of 1 wt% Pt can lead to another three times enhancement in the photocatalytic H-2-production activity. The mechanism for the enhanced H-2-production performance of Co3O4-CdS nanorods was discussed. The excellent performance of Co3O4-CdS nanorods is mainly ascribed to the loading of amorphous Co3O4 onto the surface of CdS nanorods, which could promote the separation of electron-hole pairs and enhance the stability of CdS nanorods due to the formation of p-n heterojunctions between the Co3O4 and CdS nanorods, thus leading to an enhanced activity for H-2 generation. This work demonstrated that the loading of amorphous Co3O4 is a facile strategy to enhance the photocatalytic activity of CdS nanorods, which may provide some potential opportunities for designing other composite photocatalysts for water splitting.