Preparation, structural characterization and activity for ethanol oxidation of carbon supported ternary Pt–Sn–Rh catalysts

Carbon supported ternary Pt–Sn–Rh (1:1:0.3 and 1:1:1) alloy catalysts were synthesized by reduction of the metal precursors with formic acid and characterized by EDX, XRD and TEM analyses. Their activity for ethanol oxidation was compared with that of binary Pt–Sn/C and Pt–Rh/C prepared with the same method. XRD analysis indicated that both the lattice parameter and the crystallite size of the Pt–Sn–Rh alloy catalysts are higher than those of Pt–Rh/C and lower than those of Pt–Sn/C. The intermediate value of the particle size of the ternary alloy catalysts was confirmed by TEM images. Linear sweep voltammetry measurements indicated that, for potentials higher than 0.45 V versus RHE, the ternary Pt–Sn–Rh alloy catalysts possess the higher activity for ethanol electro-oxidation, while for potentials lower than 0.45 V versus RHE the electrochemical activity of the ternary catalysts was lower than that of the binary Pt–Sn catalyst. The enhanced activity for ethanol electro-oxidation on the ternary Pt–Sn–Rh catalysts was ascribed to the formation of a ternary alloy and to the lower particle size.