Effect of structure of carbon-supported PtRu electrocatalysts on the electrochemical oxidation of methanol

Carbon-supported binary PtRu electrocatalysts were prepared by coimpregnati on using ethanolic solutions of Pt(NH3)(2)(NO2)(2) as the Pt source, variou s Ru sources [RuCl3, Ru-3(CO)(12) and RuNO(NO3)(x)], and carbon black by th ermal decomposition under reducing conditions, and their structure, morphol ogy, and electrocatalytic properties were investigated, X-ray diffraction a nalysis and high resolution scanning electron microscopy indicated that the use of Cl-free Ru sources, i.e., Ru-3(CO)(12) Or RuNO(NO3)(x), afforded hi ghly dispersed and uniform PtRu nanoparticles. Surface area measurements co nducted by electro-oxidation of preadsorbed carbon monoxide indicated that the use of Ru-3(CO)(12) as the Ru source yielded high surface area catalyst s. In terms of the surface-area specific current density (current density n ormalized by the specific surface area of PtRu metal obtained from preadsor bed CO electro-oxidation measurements), the electrocatalytic activity of Pt (NH3)(2)(NO2)(2)-Ru-3(CO)(12) and Pt(NH3)(2)(NO2)(2)-RuNO(NO3)(x) were equa l. PtRu/C electrocatalysts prepared from ethanolic solutions of Pt(NH3)(2)( NO2)(2)-Ru-3(CO)(12) resulted in high mass-specific activity toward methano l oxidation, with mass-specific current density as high as 159 mA mg(-1) Pt at 500 mV. The efficiency of PtRu/C electrodes is discussed based on the s ignificance of the use of Cl-free Ru sources. (C) 2000 The Electrochemical Society. S0013-4651(00)06-019-5 All rights reserved.