Amorphous Co3O4 modified CdS nanorods with enhanced visible-light photocatalytic H2-production activity

Abstract

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 H₂ generation from an aqueous solution containing sulfide and sulfite under visible light (λ ≥ 420 nm). The results showed that the photocatalytic activity of CdS nanorods for H₂ 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 H₂ evolution under visible light irradiation, 236 μmol 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 H₂-production activity. The mechanism for the enhanced H₂-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 H₂ 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.