Well-coupled graphene and Pd-based bimetallic nanocrystals nanocomposites for electrocatalytic oxygen reduction reaction.

In this paper, a series of well-coupled graphene (G) and MPd3 (M = Fe, Cu, Ag, Au, Cr, Mo, W) nanocrystals nanocomposites (G-MPd3 NCPs) have been synthesized via a versatile electrostatic assembly and hydrogen reduction strategy, i.e., sequential assembly of coordination anions and cations on excess cationic polymer modified graphene oxide to form composite precursors and then thermal treating under H2/Ar gases atmosphere. In those NCPs, the MPd3 components are uniform and smaller than 10 nm, which are well anchored on G with "naked" or "clean" surfaces. By adjusting reaction temperature, the interplay of MPd3 nanocrystals and G can be well-controlled. Below 700 °C, no sintering phenomena are observed, indicating the unprecedented dispersion and stability effect of G for MPd3 nanocrystals. All the obtained NCPs can be directly used to catalyze oxygen reduction reaction in alkaline media. Compared with single component, monometallic, and some reported non-Pt catalysts, greatly enhanced electrocatalytic performances are observed in those NCPs due to strong synergistic or coupling of their constituents. Among them, G-FePd3 NCPs exhibit the highest catalytic activity, but their current density needs to be improved compared with G-CrPd3, G-MoPd3, and G-WPd3 ones. This work not only provides a general strategy for fabricating well-coupled G-MPd3 NCPs but also paves the way for future designing multicomponent NCPs with multiple interfaces to apply in alkaline fuel cells.