Carbon supported Pt-Au catalysts with different bimetallic compositions were prepared by water in oil (w/o) microemulsion. Carbon Vulcan XC-72 was added during the synthesis of particles in order to obtain their good dispersion and a mean particle size distribution of 5.02 +/- 0.56 nm. Structural characterization was performed using XRD at wide angles (WAXS), which showed that Pt-Au particles exhibited alloy properties. Electrochemical characterization allowed to estimate the surface composition of Pt-Au alloys, which was close to that of the bulk material Pt(20)Au(80). This catalyst composition displayed the best catalytic activity in steady-state conditions in comparison with Pt(50)Au(50) or Pt and Au alone. Moreover, a Pt-Au/C catalyst with a metal loading of 40 wt % was immobilized onto a carbon porous tube as anode. A membrane-less biofuel cell was tested using laccase/ABTS biocathode in phosphate buffer (pH 5).