Monodisperse Bimetallic AgPt Nanocrystals/Graphene Oxide Nanocomposites:Facile Preparation And Catalytic Application

ABSTRACT:A one-pot strategy to synthesize AgPt nanocrystals (NCs) monodispersed on graphene oxide (GO) is reported. Here an aqueous dispersion of GO is able to self-reduce silver ions via redox reduction, and to further guide their growth to nanocrystals. Using homogeneous nucleation technique, silver nanoparticles nucleated, and then grown in one reaction vessel in presence of GO and PVP (as reducing and stabilizing agent respectively) at a specific temperature and synthesis time. With silver nanoparticles decorated on its surface, the Graphene-AgNCs nanocomposite is then used as a sacrificial template for platinum immobilized onto the preformed Ag nanocubes through galvanic exchange. Monodispersity was achieved by carefully separating the nucleation, growth and introduction of platinum salt in time by using a correct combination of reducing and stabilizing agents as well as suitable reaction conditions. The changes in morphology, structure and composition during these syntheses were carefully followed. We found that AgCl byproduct was present as a foreign surface on the particles structures and was responsible for the retention of the cubic morphology after galvanic replacement reaction.The as-prepared AgPt/GO hybrid was found to efficiently catalytize the degradation of rhodamine B (RhB) in presence of NaBH4. As a way of improving the economic efficiency of the degradation process, significant reduced amount of both reductant and catalyst was used and perfectly out-performed traditional bimetallic AgPtNCs as well as supported monometallic counterparts. Structural characterization revealed that the catalytic performance is linked to the tri-layer core shell nanocubes structure of the nanocrystal and also to the contribution of the support material. These structural changes are correlated with observed monometallic and non supported bimetallic activities for the same reaction, providing new insight into the structure-activity relationships of bimetallic nanocatalysts. This synthetic method should be extendable to other multimetallic compositions and shapes, and can be improved by using AgNCs particles with a narrower size distribution. Our work not only aims to provide an exciting addition to the expanding library on green chemistry but also paves the way for the future design of multicomponent hybrid material.