Synthesis of Magnetite–Semiconductor–Metal Trimer Nanoparticles through Functional Modular Assembly: A Magnetically Separable Photocatalyst with Photothermic Enhancement for Water Reduction

Hybrid nanoparticles have intrinsic advantages to achieve better activity in photocatalysis compared to single-component materials, as it can synergistically combine functional components, which promote light absorption, charge transportation, surface reaction, and catalyst regeneration. Through functional modular assembly, a rational and stepwise approach has been developed to construct Fe3O4–CdS–Au trimer nanoparticles and its derivatives as magnetically separable catalysts for photothermo-catalytic hydrogen evolution from water. In a typical step-by-step synthetic process, Fe3O4–Ag dimers, Fe3O4–Ag2S dimers, Fe3O4–CdS dimers, and Fe3O4–CdS–Au trimers were synthesized by seeding growth, sulfuration, ion exchange, and in situ reduction consequently. Following the same reaction route, a series of derivative trimer nanoparticles with alternative semiconductor and metal were obtained for water-reduction reaction. The experimental results show that the semiconductor acts as an active component for photocatalysis, the metal nanoparticle acts as a cocatalyst for enhancement of charge separation, and the Fe3O4 component helps in the convenient separation of catalysts in magnetic field and improves photocatalytic activity under near-infrared illumination due to photothermic effect.