This work reports the electrochemical measurements of 20 wt.% RuxSey/C for oxygen reduction reaction (ORR) in presence of different concentration of HCOOH and its use as cathode catalyst in a microfluidic formic acid fuel cell (mu FAFC). The results were compared to those obtained with commercial Pt/C. Half-cell electrochemical measurements showed that the chalcogenide catalyst hs a high tolerance and selectivity towards ORR in electrolytes containing up to 0.1 M HCOOH. The deporlarization effect was higher on Pt/C than on RuxSey/C by a factor of ca. 23. Both catalysts were evaluated as cathode of a mu FAFC operating with different concentrations of HCOOH. When 0.5 M HCOOH was used, maximum current densities of 11.44 mA cm(-2) and 4.44 mA cm(-2) were obtained when the cathode was RuxSey/C and Pt/C, respectively. AT 0.5 M HCOOH, the peak power density of the mu FAFC was similar for both catalysts, ca. 1.9 mW cm(-2). At 5 M HCOOH the power density of the mu FAFC using RuxSey, was 9.3 times higher than the obtained with Pt/C. (C) 2010 Elsevier B.V. All rights reserved.