Influence of the temperature for the ethanol oxidation reaction (EOR) on Pt/C, Pt-Rh/C and Pt-Rh-SnO2/C

The electrocatalytic activity of Pt/C, Pt-Rh/C and Pt-RhSnO2/C electrocatalysts toward the ethanol oxidation reaction (EOR) was investigated in a three-electrode assembly at 25 degrees C, 40 degrees C and 70 degrees C in acidic medium. The 10 wt.% electrocatalysts were prepared with a modified polyol method and physically characterized by both X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The CO-stripping study revealed that COad oxidation initiates at lower potential on Pt-Rh/C and Pt-Rh-SnO2/C than on Pt/C and shifts negatively when the temperature increases. The positive effect of the temperature is maintained for the EOR: the three electrocatalysts exhibit a higher activity and a negative shift of the EOR wave at higher temperature. Pt-Rh-SnO2/C demonstrates the lowest EOR onset potential of the three electrocatalysts. The steady-state Tafel slopes and apparent activation energies Ea were determined in 0.5 M H2SO4 + 0.1 M EtOH between E = 0.4 and 0.7 V vs. RHE in the temperature range 25-70 degrees C. The results show rather comparable rate determining steps (rds) for the ethanol electrooxidation on Pt/C and Pt-Rh/C in the ranges of potential and temperature studied. The EOR on Pt-Rh-SnO2/C seems less influenced by the potential than on Pt/C and Pt-Rh/C electrocatalysts, but is more temperature sensitive.