Micelle-templated synthesis of Pt hollow nanospheres for catalytic hydrogen evolution

摘要

As an alternative to galvanic replacement reactions and hard/template strategies, we report an efficient, mild and simple synthesis strategy for fabrication of colloidal platinum (Pt) hollow nanospheres. An aqueous asymmetric triblock copolymer poly(styrene-b-vinyl-2-pyridine-b-ethylene oxide) [PS(20.1k)-PVP(14.2k)-PEO(26.0)] micelle with core-shell-corona architecture has been found to be an efficient soft scaffold for the synthesis of Pt hollow nanospheres using K2PtCl6 as a metal precursor and NaBH4 as a reducing agent. In the core-shell-corona type micelles, the core serves as a template for void volume creation, the shell domain acts reaction site for inorganic precursors, and the corona stabilizes the composite particles. The polymer/Pt composite particles were solvent-extracted by refluxing with dimethyl formamide (DMF) at 160 degrees C to remove polymeric materials and obtain hollow particles. Investigation of precursor concentrations suggested that the wall-structures become irregular and uneven as the molar ratio of PVP/Pt(IV) increases from 1 : 12 to 1 : 25, whereas the use of polymers with large PS block length [PS(45k)-PVP(16k)-PEO(8.5)] results in the formation of spherical particles with slightly increased hollow void-space diameters. The polymeric micelles and Pt hollow nanospheres were thoroughly characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), infra-red (FT IR), thermal (TG/DTA) and nitrogen sorption analyses. The catalytic activity of the Pt hollow nanospheres was investigated for hydrogen liberation from ammonia-borane (AB) by hydrolysis reaction at room temperature. The catalytic activity of the Pt hollow nanospheres reveals that they can serve as a promising heterogeneous catalyst towards hydrogen generation system using AB as solid hydrogen storage materials.