Selectively Deposited Noble Metal Nanoparticles on Fe3O4/Graphene Composites: Stable, Recyclable, and Magnetically Separable Catalysts

A simple, efficient, and general approach was developed to selectively deposit noble metal (Pt, Pd, or PtPd) nanoparticles 35 nm in size on magnetite/graphene composites. The biomolecule L-lysine with two kinds of functional groups (NH2 and COOH) played the key role of connecter between noble metals and Fe3O4/graphene composites. These composites were characterized by TEM, XRD, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results indicated that the noble metals are mostly dispersed on the magnetite surfaces of the composites. The as-obtained composites are ideal recyclable catalysts for liquid-phase reactions owing to their stability and efficient magnetic separation. Among these catalysts, the PtPd-based composites exhibited the highest activity and resistance to poisoning during the catalytic reduction of 4-nitrophenol to 4-aminophenol by NaBH4. Such hybrid catalysts obtained by this simple, efficient method are expected to find use in industrial applications, where separation and recycling are critically required to reduce cost and waste production.