Synthesis of Carbon-Supported Pt–YO_x and PtY Nanoparticles with High Catalytic Activity for the Oxygen Reduction Reaction Using a Microwave-based Polyol Method

Carbon-supported PtY alloy nanoparticles were prepared as oxygen reduction reaction (ORR) catalysts by reducing a mixture of cis-[Pt(NH₃)₂(NO₂)₂] or Pt(C₅H₇O₂)₂ and Y(CH₃COO)₃⋅4 H₂O in ethylene glycol (EG) with microwave (MW) heating. Microstructure and composition analyses of products by using TEM, TEM–energy-dispersive X-ray spectroscopy (EDS), XRD, X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma atomic emission spectroscopy (ICP-AES) data showed that Pt–YO_x/C (Y/Pt=0.11–0.75) catalysts involving amorphous yttrium oxide were formed as major products. When the YO_x component in the catalysts was removed by using HNO₃ treatment, Pt_99.1–99.6Y_0.4–0.9/C alloy catalysts with low Y contents remained. Higher ORR activity was shown by Pt–YO_x/C and PtY/C catalysts than by Pt–Y(OH)₃/C, Pt–YO_x/C, or PtY/C catalysts prepared by using other conventional chemical reduction methods and thermal treatment methods under a H₂/Ar or Ar atmosphere. The mass activity (MA) and surface specific activity (SA) of the best Pt_99.5Y_0.5/C catalyst, MA=245 A g_Pt ⁻¹ and SA=711 μA cm_Pt ⁻², were equal to or higher than those of the commercially used Pt₈₆Co₁₄/C catalyst, MA=245 A g_Pt ⁻¹ and SA=512 μA cm_Pt ⁻². The major reasons for the high ORR activity of these Pt–YO_x/C and PtY catalysts are discussed. These Pt_99.1–99.6Y_0.4–0.9/C alloy catalysts prepared by using acid treatment are new and promising catalysts for use in proton exchange membrane fuel cells (PEMFCs).