A one-pot green method to synthesize ultrafine AuPd nanoparticles (NPs) monodispersed on graphene nanosheets (GNs) is reported. Due to the reducing capability, moderate number of deposition sites and large surface area, GNs are used as a three-functional agent such as reductant, stabilizer and support in this synthesis. The morphology, structure and composition of thus-prepared AuPdNPs/GNs were characterized by transmission electron microscopy (TEM), high resolution TEM, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. As it is a surfactant-free formation process, the as-prepared AuPdNPs/GNs are very clean and can exhibit a high activity towards the reduction of 4-nitrophenol. Moreover, the optical properties and catalytic activities of the AuPdNPs/GNs composite are tunable via controlling the Au versus Pd atomic ratio during their synthesis. The catalytic activity of bimetallic AuPdNPs/GNs composites is highly enhanced over the monometallic AuNPs/GNs and PdNPs/GNs composites. This straightforward method is of significance for deposition of bimetallic NPs with high catalytic performance on graphene-based materials.

A facile and green method is described for the fabrication of PtPd alloy nanoparticles on graphene nanosheets (PtPdNPs/GNs). The keys of the synthesis strategy were to employ a low-cost and green solvent, ethanol, as the reductant, and a two-dimensional carbon material, GNs, as the supporting material. The morphology, structure and composition of the as-prepared PtPdNPs/GNs were characterized by transmission electron microscopy (TEM), high resolution TEM, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. It was found that by changing the preparation procedures and varying the molar ratio of the starting precursors, NPs with different shapes such as spherical NPs (Pt₁Pd₁NPs), nanoflowers (Pd@PtNFs) and nanodentrites (Pt₃Pd₁NPs) could be produced on GNs. Based on these observations, a plausible growth mechanism of PtPdNPs/GNs was discussed. In addition, the electrocatalytic properties of PtPdNPs/GNs for direct ethanol oxidation in alkaline media were systematically investigated. Due to the synergetic effects of Pt and Pd, and the enhanced electron transfer properties enhanced of GNs, PtPdNPs/GNs exhibited higher electrocatalytic ability and better tolerance to reaction intermediate poisoning in the electrooxidation of ethanol compared with Pt nanoflowers supported on GNs (PtNFs/GNs), PdNPs/GNs and PtPdNPs supported on carbon black (PtPdNPs/C). The presented method is a general, facile and green approach for the synthesis of GN-supported bimetallic PtM electrocatalysts, which is significant for the development of high performance electrocatalysts.

In this paper, Au nanoparticles (AuNPs) have been homogeneously deposited on citrate-functionalized graphene nanosheets (Cit-GNs) by a simple one-pot reducing method. The morphology and composition of the thus-prepared AuNPs/Cit-GNs were characterized by transmission electron microscopy (TEM), high resolution TEM, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The results showed that the AuNPs with a uniform size are well dispersed on the surface of the Cit-GNs. Significantly, the as-prepared AuNPs/Cit-GNs possess intrinsic peroxidase-like activity, which can catalyze the oxidation of the peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) by hydrogen peroxide (H₂O₂) to develop a blue color in aqueous solution. The catalysis was in accordance with Michaelis–Menten kinetics and the AuNPs/Cit-GNs showed a strong affinity for both H₂O₂ and TMB. Moreover, by comparing with Cit-AuNPs, AuNPs/GNs and AuNPs/PVP-GNs, the AuNPs/Cit-GNs composite exhibits a higher catalytic ability with a lower Michaelis constant (K_m) value, suggesting that the GNs with a large surface area and the citrate ions with more carboxyl groups around the AuNPs can greatly enhance the peroxidase-like activity of AuNPs/Cit-GNs. Taking the advantages of the high catalytic activity, the good stability and the low cost, the novel AuNPs/Cit-GNs represent a promising candidate as an enzyme mimic and may find a wide range of new applications in biochemistry and biotechnology.