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

Carbon-supported binary PtRu electrocatalysts were prepared by coimpregnation using ethanolic solutions of Pt(NH3)(2)(NO2)(2) as the Pt source, various Ru sources [RuCl3, Ru-3(CO)(12) and RuNO(NO3)(x)], and carbon black by thermal decomposition under reducing conditions, and their structure, morphology, and electrocatalytic properties were investigated, X-ray diffraction analysis 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 highly dispersed and uniform PtRu nanoparticles. Surface area measurements conducted by electro-oxidation of preadsorbed carbon monoxide indicated that the use of Ru-3(CO)(12) as the Ru source yielded high surface area catalysts. In terms of the surface-area specific current density (current density normalized by the specific surface area of PtRu metal obtained from preadsorbed 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 equal. PtRu/C electrocatalysts prepared from ethanolic solutions of Pt(NH3)(2)(NO2)(2)-Ru-3(CO)(12) resulted in high mass-specific activity toward methanol 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 significance of the use of Cl-free Ru sources. (C) 2000 The Electrochemical Society. S0013-4651(00)06-019-5 All rights reserved.