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–YOx/C (Y/Pt=0.11–0.75) catalysts involving amorphous yttrium oxide were formed as major products. When the YOx component in the catalysts was removed by using HNO3 treatment, Pt99.1–99.6Y0.4–0.9/C alloy catalysts with low Y contents remained. Higher ORR activity was shown by Pt–YOx/C and PtY/C catalysts than by Pt–Y(OH)3/C, Pt–YOx/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 Pt99.5Y0.5/C catalyst, MA=245 A gPt−1 and SA=711 μA cmPt−2, were equal to or higher than those of the commercially used Pt86Co14/C catalyst, MA=245 A gPt−1 and SA=512 μA cmPt−2. The major reasons for the high ORR activity of these Pt–YOx/C and PtY catalysts are discussed. These Pt99.1–99.6Y0.4–0.9/C alloy catalysts prepared by using acid treatment are new and promising catalysts for use in proton exchange membrane fuel cells (PEMFCs).

These results show that Asn levels are strongly correlated with plasma ASNase activity even at low enzyme activities (<50 U/l) and that this sensitive ASNase assay can be used to estimate plasma Asn depletion levels.

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