Influence of H- and OH-adsorbates on the ethanol oxidation reaction – a DEMS study

Abstract

The ethanol oxidation reaction (EOR) was investigated by potentiodynamic techniques on Pt/C, Rh/C, Pt-Rh/C, Pt-SnO2/C and Pt-Rh-SnO2/C by differential electrochemical mass spectrometry (DEMS) in a flow cell system. Prior to the cyclic voltammetries, adsorption of H- and OH-species was carried out by chronoamperometry at Ead = 0.05 and 1 V vs. RHE, respectively, in order to examine their influence on the EOR on the different electrocatalysts. For the sake of comparison, another adsorption potential was chosen at Ead = 0.3 V vs. RHE, in the double layer region (i.e. in the absence of such adsorbates). For this study, 20 wt% electrocatalysts were synthesized using a modified polyol method and were physically characterized by inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD) and transmission electron microscopy (TEM). When comparing the first and second cycles of the cyclic voltammograms (CVs) on Pt/C and Pt-SnO2/C, the presence of Had on the electrocatalyst surface seems to hinder the initiation of the ethanol electrooxidation, whereas the reaction onset potential is shifted negatively with the presence of OH-adsorbates. In contrast to them, the EOR on Rh/C is enhanced when the electrocatalyst surface is covered with Had and is inhibited after adsorption at Ead = 0.3 and 1 V vs. RHE. Finally, on Pt-Rh/C and Pt-Rh-SnO2/C, neither the H- nor OH-adsorbates do impact the EOR initiation. The lowest EOR onset was recorded on Pt-SnO2/C and Pt-Rh-SnO2/C electrocatalysts. The CO2 currency efficiency (CCE) was also determined for each electrocatalyst and demonstrated higher values on Pt-Rh-SnO2/C.

Replicating the Defect Structures on Ultrathin Rh Nanowires with Pt to Achieve Superior Electrocatalytic Activity toward Ethanol Oxidation

“…Thus, the Rh @ Pt 5.3L NW/C catalysts presented the highest capacity for producing acetic acid but poor selectivity toward CO 2 . It has been demonstrated that the CO 2 current efficiency (a quantification of the current generated form the CO 2 pathway reported to the EOR overall current) is generally found to be only between 5 and 20% . The overall activity for EOR should integrate both the CO 2 and CH 3 CH 2 OH pathways into account.…”

The influence of mass-transport conditions on the ethanol oxidation reaction (EOR) mechanism of Pt/C electrocatalysts

“…The calibration of the m/z = 22 mass-to-charge signal was carried out according to the protocol detailed in ref. 23…”

Supporting PtRh alloy nanoparticle catalysts by electrodeposition on carbon paper for the ethanol electrooxidation in acidic medium

“…In spite of the performance increase observed in DEFCs currently operating at temperatures between 80-120 °C, the selectivity towards CO2 of most of these materials still remains low [39]. The most promising are the PtRh/C-based catalysts, which show an increase in the current density for the ethanol oxidation and an enhancement in the CO2 yield under mild operating conditions (T ≤ 90 °C) [40][41][42][43][44][45][46][47].…”