In this paper, we demonstrate that, a one-pot synthesis of a reduced graphene oxide (RGO)-supported freely assembled binary alloy catalyst (PtAu/RGO) under alkaline conditions. The synthesized PtAu/RGO catalyst has been characterized by powder X-ray diffraction (pXRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). It was found that graphene oxide (GO) was successfully reduced to RGO and that the PtAu nanoparticles exhibited alloy structure about 3.60 ± 0.20 nm in diameter and uniformly distributed on RGO surface. Further, the electrocatalytic activity of the catalyst was examined toward formic acid (FA) oxidation, which exhibited better catalytic activity toward FA

The electrocatalytic activity of PtAu/RGO (Pt mass loading: 20%) was examined with the solution of 0.1 M H₂SO₄ + 0.5 M HCOOH. The catalytic activity of PtAu/RGO was compared with the Pt/RGO (Pt mass loading: 20%) and commercial Pt/CB (Pt mass loading: 20%). Figure 1 shows that the linear sweep voltammograms of (a) Pt/RGO, (b) PtAu/RGO and (c) Pt/CB in 0.5 M HCOOH containing 0.1 M H₂SO₄ aqueous solution. It could be observed from the Fig. 5, two oxidation peaks can be clearly observed, the peak I is related to the direct oxidation of HCOOH to CO₂, whereas the peak II is correspond to the oxidation of the CO_ads generated from the dissociative adsorption step. The peak I current densities are in the order of PtAu/RGO > Pt/RGO > commercial Pt/CB, which indicates that the RGO can effectively enhance the activity of PtAu and Pt catalysts, which may be due to the strong interaction between PtAu or Pt NPs and RGO surface. In contrast, the peak II current densities are in the order of PtAu/RGO < Pt/RGO < commercial Pt/CB, indicating that the presence of RGO in PtAu/RGO hold back the formation of poisoning intermediate CO_adsduring the FA oxidation. Based on the present and previously reported results, it can be considered that the uniform distribution of NPs and electronic interaction between PtAu NPs and RGO could enhance the catalytic activity.

To sum up, freely assembled PtAu/RGO nanocomposites were synthesized under alkaline conditions. On the basis of pXRD, TEM, STEM, XPS, the GO was converted to RGO and PtAu NPs were highly dispersed and uniformly distributed through out the surface. The PtAu/RGO catalyst exhibited higher catalytic activity for FA oxidation compared to the other catalysts Pt/RGO and commercial Pt/CB. This work provides a simple and fast approach to synthesize a novel RGO based catalyst with high electrocatalytic activity.  

Figure 1. Linear sweep voltammograms of (a) Pt/RGO, (b) PtAu/RGO and (c) Pt/CB in 0.5 M HCOOH containing Ar-saturated 0.1 M H₂SO₄ aqueous solution at 2000 rpm.