Pt and Au are not miscible within a whole range of concentrations. To obtain PtAu alloys, severe thermal treatments are required that to provide aggregation phenomena. However, it is possible to synthesize bimetallic PtAu nanoparticles provided the proper synthesis route is employed. When they are prepared from water-in-oil microemulsions or with the impregnation technique, it is possible to obtain nanosized bimetallic PtAu particles. In contrast, other colloidal routes have been seen to be adequate for the synthesis of other bimetallic Pt-based particles, affording segregated samples with Pt- or Au-enriched zones. When alloyed, bimetallic PtAu nanoparticles display unique physicochemical properties that are different from those of monometallic and nonalloyed solids. Thus, the performance of alloyed PtAu samples as electrocatalysts for the oxygen reduction reaction is superior to that of the PtAu-segregated samples. In fact, the ability of carbon-supported bimetallic PtAu samples in the oxygen reduction reactions equals or even surpasses that of archetypal Pt/C electrocatalysts.

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