PtCu/C and Pt(Cu)/C catalysts: Synthesis, characterization and catalytic activity towards ethanol electrooxidation

Binary catalysts containing Pt and Cu have been synthesized by two different methods. The first method consists of mixing Pt4+ and Cu2+ cations in presence of NaBH4 to form PtCu/C alloy catalyst. In the second method, Cu/C nanoparticles were first synthetized then treated with Pt+4 in presence of NaBH4 in an attempt to form core shells Cu covered by Pt, Pt(Cu)/C. The synthesized catalysts PtCu/C and Pt(Cu)/C were characterized by Inductively Plasma Emission Spectroscopy (ICP), Transmission Electron Microscopy (TEM), Thermogravimetric Analysis (TGA), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and Electrochemistry. XRD studies indicate that Pt–Cu alloy has formed in both cases even using the second synthetic method that is supposed to yield Cu covered by Pt core shells. The latter was attributed to the dissolution of Cu/C nanoparticles during their treatment with Pt4+. This was confirmed by XRD and TEM where significant decrease in the grain size from∼37.2 nm obtained for Cu/C to∼3 nm for Pt(Cu)/C was observed. While ICP analysis revealed similar Pt and Cu contents in each catalyst, XPS showed that PtCu/C is Pt rich at the surface and Pt(Cu)/C is Cu rich at the surface of the nanoparticles. In turn, this surface segregation influences the catalytic activity of the catalysts towards ethanol oxidation. It is found that both catalysts show superior catalytic activity towards ethanol electrooxidation compared to pure Pt/C. However, PtCu/C displayed a better activity with respect to Pt(Cu)/C in terms of oxidation current and onset potential.