One-pot synthesis of graphene/carbon nanospheres/graphene sandwich supported Pt3Ni nanoparticles with enhanced electrocatalytic activity in methanol oxidation.

A facile method was demonstrated for the preparation of Pt 3 Ni alloy nanoparticles supported on a sandwich-like graphene sheets/carbon nanospheres/graphene sheets substrate (Pt 3 Ni–C/rGO) through a one-pot solvothermal process in N,N-dimethylformide without the addition of reducing agents and surfactants. Transmission electron microscopic measurements showed that carbon nanospheres were homogeneously dispersed in the matrix of exfoliated graphene sheets, and Pt 3 Ni nanoparticles were distributed on the graphene surfaces without apparent agglomeration, where the average core size was estimated to be 12.6 ± 2.4 nm. X-ray photoelectron spectroscopic studies demonstrated that electron transfer likely occurred from the Pt 3 Ni alloy nanoparticles to the graphene sheets. Electrochemical measurements showed that the mass activity of the Pt 3 Ni–C/rGO catalysts in methanol oxidation was 1.7-times higher than that of Pt 3 Ni nanoparticles supported on reduced graphene oxide alone (Pt 3 Ni/rGO), and 1.3-times higher than that of commercial Pt/C (20 wt%). Additionally, CO tolerance and durability were also remarkably enhanced. These superior electrocatalytic activities were attributed to the following major factors: (i) the insertion of carbon nanospheres into the graphene matrix prevented restacking/refolding of the graphene sheets, leading to an increasing number of accessible active sites as well as transport channels for mass and charges; and (ii) the synergetic effect between Pt 3 Ni nanoparticles and rGO weakened the bonding interactions with reactant species, as manifested by the enhanced kinetics of methanol oxidation and CO oxidative desorption. [ABSTRACT FROM AUTHOR]