Hierarchical electroless Pt deposition at Au decorated reduced graphene oxide via a galvanic exchanged process: an electrocatalytic nanocomposite with enhanced mass activity for methanol and ethanol oxidation

Abstract

We present a facile and simple method to synthesize a thin layer of platinum on gold as Au@Pt core–shell nanoparticles on the surface of reduced graphene oxide (rGO) via Cu under potential deposition (UPD) followed by a galvanic Pt replacement reaction. The difference in the reduction potential is the driving force for the reaction where Pt⁴⁺ ions were reduced and deposited simultaneously on the surface of Au by replacing the Cu surface. The as-synthesized catalyst was characterized by scanning electron microscopy (SEM), energy dispersive X-ray mapping analysis (EDAX), high resolution transmission electron microscopy (HRTEM), high angle annular dark-field scanning/transmission electron microscopy (STEM-HAADF), X-ray diffraction (XRD), Raman spectroscopy and electrochemical studies. It exhibits an excellent electrocatalytic activity towards methanol and ethanol oxidation in alkaline medium due to its enhanced mass and specific activities. The galvanic replacement method plays an important role in the architecture of a thin layer of Pt on the Au surface. On the other hand, the rGO surface acts as a solid support in uniform arrangement of Au nanoparticles and promotes the catalytic activity of Pt. Furthermore the electrocatalytic activity and the stability of the as-synthesized catalyst decorated electrode were compared with those of commercial catalysts such as Pt₄₀/C and Pt₂₀/C decorated electrodes. Importantly, it is proved that the stability of the as-synthesized catalyst is quite higher even after 1000 s compared to that of commercial catalysts in alcohol oxidation. Thus, the core–shell bimetallic graphene supported catalyst, rGO–Au@Pt NPs, acts as a promising electrocatalyst for alcohol oxidation.