Ethanol oxidation reaction (EOR) investigation on Pt/C, Rh/C, and Pt-based bi- and tri-metallic electrocatalysts: A {DEMS} and in situ {FTIR} study

By Delpeuch, Antoine Bach; Maillard, Fr
Published in Applied Catalysis B: Environmental NULL 2016

Abstract

Abstract The ethanol oxidation reaction (EOR) was studied on Pt/C, Rh/C, Pt-Rh/C, Pt-SnO2/C and Pt-Rh-SnO2/C using on-line differential electrochemical mass spectrometry (DEMS) in a flow-cell system and in situ Fourier transform infrared spectroscopy (in situ FTIR). The electrocatalysts were synthesized by a modified polyol method and physically characterized by inductively-coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The electrocatalytic activity of the materials was tested for the {EOR} and the electrooxidation of a monolayer of adsorbed {CO} (COad being an intermediate of the EOR). Both in situ {FTIR} and {DEMS} investigations revealed that {COad} electrooxidation occurs at lower potentials on Pt-SnO2/C and Pt-Rh-SnO2/C than on Pt/C, Rh/C and Pt-Rh/C. A good correspondence was found between the (intensity vs. potential) variations of the m/z = 22 mass-to-charge signal and of the {IR} band at 2343 cm?1, both strictly assigned to CO2. The addition of Rh to Pt enhances the tolerance to adsorbed {CO} molecules during the {EOR} (CO2 molecules were detected at more negative potentials in {FTIR} on Rh-containing electrocatalysts), and the simultaneous presence of Pt, Rh and SnO2 in the catalysts resulted in enhanced {EOR} selectivity towards CO2. The {CO2} current efficiency (CCE) calculations indicate quantitatively that the tri-metallic Pt-Rh-SnO2/C electrocatalyst yields more complete ethanol electrooxidation into CO2. Finally, {FTIR} experiments enabled to detect high-potential (E 0.95 V vs. RHE) {CO2} formation, which likely originates from the oxidation of either CHx- or ethoxy-adsorbates that only oxidize at high potential.

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