Synergy of semiconductor components of non-covalent functionalized (PdS doped)-G CdS NPs composite provide efficient photocatalytic water reduction under visible light

Abstract

A new composite based on a few-layered pristine graphene, G, was prepared under mild conditions by adsorption of a functionalized pyrimidine derivative, Tren, followed by sequential precipitation of PdS and CdS NPs. The composite G-Tren-PdS-CdS showed high photocatalytic activity in water reduction providing a constant average H2 production of 2.3 mmol·g−1·h−1 during 24 h, which exceded 18.9 times that of the bare CdS. Structural analyses of the fresh and used phocatalyst revealed high robustness of the material. A systhematic study of the structure and optical properties of the materials revealed the pyrimidine-G moiety, G-Tren, behaves as a semiconductor with a band gap which can be finelly tuned through the control of the amount of adsorbed pyrimidine. The study also allowed to propose a reliable mechanism for the photocatalytic process. The excellent performance of the photocatalyst, in which CdS acts as electron provider for the hydrogen reduction and PdS and G-Tren moieties as cocatalysts, is attributed mainly to the complementary of the ranges of visible light absorption of the components, G-Tren, CdS and PdS, and to the possible role played by the arene basic centers provided by the unaltered π-conjugated structure of G, as reduction active sites.