The objective of this study was to evaluate the suitability of mixed oxides of silica (SiO2) and ruthenia (RuO2) for use as electrocatalyst supports in polymer electrolyte fuel cells (PEFCs). The RuO2:SiO2 oxides were synthesized in three different molar ratios (0.1:0.9,0.3:0.7 and 0.5:0.5). Of these formulations, RuO2-SiO2 (0.5:0.5) displayed high BET surface area (similar to 290 m(2) g(-1)), high electronic conductivity (>5 S cm(-1)), and outstanding electrochemical stability (change in double layer capacitance of <10% compared to 360% for Vulcan XC72 carbon upon rigorous accelerated potential cycling tests that mimic automotive drive cycles). The RuO2-SiO2 (0.5:0.5) support material was subsequently catalyzed by deposition of 24 wt% of platinum nanoparticles. The resultant electrocatalyst yielded a mass activity of 50 mA mg(Pt)(-1) and an area specific activity of 156.3 mu A cm(-2) at 0.9 V vs. RUE when tested in a fuel cell operating at 80 degrees C and 75% relative humidity. (C) 2013 Elsevier B.V. All rights reserved.