Polyoxometalate-mediated green synthesis of a 2D silver nanonet/graphene nanohybrid as a synergistic catalyst for the oxygen reduction reaction

A polyoxometalate (POM)-mediated green, facile and large-scale synthesis of 2D (2-dimensional) Ag NN/GNS nanohybrids (where NN stands for the nanonet and GNSs for graphene nanosheets) is reported. The synthesis is convenient, rapid and environmentally friendly. The POMs serve as reducing, encapsulating and bridging molecules, and avoid introducing any organic toxic molecules. The nanohybrids have been thoroughly characterized using SEM, EDX TEM, XRD, XPS and Raman spectroscopy. Most importantly, the nanohybrids were demonstrated to act as low cost catalysts for the oxygen reduction reaction in fuel cells with similar performance to Pt catalysts. We attribute it to the high catalytic activity of the Ag NN and the excellent electron transfer properties of GNSs and also their synergistic effect, being reinforced by the presence of molybdenum species on the Ag NN/GNS surface.