Efficient solar-to-hydrogen conversion based on synergetic effects between Pd clusters and CdS nanoparticles supported on a sulfur-functionalized graphene

Abstract

A new hybrid, GSw-Pd-CdS, consisting of CdS nanoparticles and Pd clusters supported on S-functionalized graphene, GSw, has been obtained for photocatalytic water reduction. GSw has been prepared by mild treatment of graphene, G, with cold CS2 plasma allowing the G sp2 moieties to be preserved. GSw-Pd-CdS was prepared under mild conditions by the sequential adsorption on GSw of small-size Pd particles followed by the slow precipitation of CdS. The support of Pd clusters on GSw is controlled by the interaction with S-functions. The support of the CdS nanoparticles occurred by the physical adsorption on GSw. The GSw-Pd-CdS hybrid shows high photocatalytic activity in water reduction providing a constant average H2 production of 3.79 mmol g–1 h–1 during 20 h. This value outperforms 31.1 times that of CdS. The excellent behavior of the hybrid is based on suitable optical properties of Pd clusters and on the preservation of the graphene π-conjugated moieties act as active reduction sites. The analysis of both the structure and the optical properties of GSw-Pd-CdS and its components allowed to propose a reliable mechanism to the photocatalytic reduction in which the Pd clusters and the GSw cocatalysts act as hole receptor and electron receptor from CdS, respectively.