Improved catalytic activity of cobalt core-platinum shell nanoparticles supported on surface functionalized graphene for methanol electro-oxidation

Poly (diallyldimethylammonium chloride) (PDDA) functionalized graphene supported bimetallic catalysts of shell platinum on core cobalt (Co@Pt/PDDA-G) are synthesized using a two-step procedure involving the microwave synthesis method and replacement method. TEM indicate that a uniform dispersion of Co@Pt nanoparticles on PDDA functionalized graphene have the average particle size of 1.9 nm. The composite is applied to electrocatalysis for methanol oxidation. And the electrochemical surface areas of the as-prepared Co@Pt/PDDA-G, Pt supported on PDDA-graphene (Pt/PDDA-G), Co@Pt supported on graphene (Co@Pt/G) are evaluated by cyclic voltammetry, which are calculated to be 105.6 m(2) g(Pt)(-1), 92.8 m(2) g(Pt)(-1), and 83.4 m(2) g(Pt)(-1), with respect to 37.8 m(2) g(Pt)(-1) of commercial Pt/C (TKK) catalyst. The current being examined by chronoamperometry reach a constant at 23 mA mg(-1) for Co@Pt/PDDA-G catalyst, which is roughly 3.3-fold higher than that of commercial Pt/C catalyst. The electrochemical tests show that the activity and stability of Co@Pt supported on PDDA-G is highly better than the widely used Pt supported on PDDA-graphene sheets, also better than that of Co@Pt on unfunctional graphene with the same Pt content on the electrode. This improved activity could be attributed to not only the PDDA playing a crucial role in the dispersion and stabilization of Co@Pt on graphene, but also the high use ratio of Pt for its shell structure and the electronic effect of the underlying metal and Pt surface layer. (C) 2015 Elsevier Ltd. All rights reserved.