Surface engineering of CdS quantum dots modified SiO2@C3N4 nanospheres for effective photocatalytic hydrogen evolution

A new composite photocatalyst of SiO2@C3N4–CdS QDs was designed and synthesized, delivering enhanced hydrogen evolution performance. Under visible light irradiation, the hydrogen evolution rate of the photocatalyst is 225.1 μmol/g/h, which is about 80 times that of pure g-C3N4 and 2.1 times that of CdS. In this system, the g-C3N4 thin film was uniformly and compactly coated on the surface of the nanosphere with SiO2 as supporting template, which shortened the distance from the electron to the surface and accelerated the charge carrier transfer. Furthermore, the heterojunction formed by g-C3N4 and CdS QDs has a more suitable energy band structure and recover the scattered light near field of SiO2 nanospheres, which significantly enhances the light-trapping ability and the separation efficiency between electrons and holes. Consequently, the synergistic effect of SiO2, g-C3N4 and CdS QDs visibly improves the hydrogen evolution performance of photocatalyst.