Impact of water adsorbates on the acetaldehyde oxidation reaction on Pt- and Rh-based multimetallic electrocatalysts

By Antoine Bach Delpeuch and Carsten Cremers and Marian Chatenet
Published in Electrochimica Acta NULL 2016

Abstract

The influence of water adsorbates on the acetaldehyde oxidation reaction (AOR) was studied on 20 wt.% Pt/C, Rh/C, Pt-Rh/C and Pt-Rh-SnO2/C electrocatalysts by means of differential electrochemical mass spectrometry (DEMS) in an electrochemical flow cell. A polyol method was employed to synthesize the home-made electrocatalysts, the physical proprieties of which were analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The investigation by cyclic voltammetry of the \AOR\ was performed after potentiostatic formation of hydrogen- (Had) and oxygen-like (OHad, Oad) adsorbates on the electrocatalysts surface at Ead = 0.05 and 1 V vs. \RHE\ respectively. For comparison, another pre-treatment was achieved at Ead = 0.3 V vs. RHE, in the double layer region, where neither H+ nor OH? adsorption prevails. Comparing the \CVs\ demonstrates that Had formation slows down the \AOR\ initiation on Pt/C. The study on Rh/C reveals that water adsorbates are displaced by acetaldehyde species during their adsorption, owing to their stronger polarity. Acetaldehyde adsorption occurs quantitatively at potential as low as E = 0.05 V vs. \RHE\ on Pt-based electrocatalysts. The reaction pathway leading to the formation of \CO2\ is promoted during the \AOR\ on Rh-based electrocatalysts (Rh/C, Pt-Rh/C and Pt-Rh-SnO2/C). The lowest \AOR\ onset potential was recorded on Pt-Rh/C. The present results on the \AOR\ are discussed in the light of a previous similar study on the EOR.

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