Study of the products distribution during a direct ethanol PEM fuel cell operation

Abstract

In the present work the effect of both cell discharge current and operating temperature on (a) the ethanol conversion, (b) the reaction products distribution and (c) the reaction yield towards each released product, during a Direct Ethanol PEM fuel cell is examined. More precisely, the results of the continuous and on-line product analysis are presented and thoroughly discussed. The MEA of the fuel cell is comprised of a PtRu/C anode, a Nafion®-115 membrane and a Pt/C cathode. It is found that the increase of the cell current and the operating temperature lead to an increase of the ethanol conversion. The main products detected during the fuel cell operation are acetaldehyde (CH3CHO), acetic acid (CH3COOH) and small amounts of carbon dioxide (CO2). The selectivity of acetaldehyde ranges from 45% to 70%, the selectivity of acetic acid ranges from 25% to 45% and the selectivity of CO2 ranges from 5% to 15%. Moreover, as it concerns the reaction yield towards each product, it is found that the increase of the temperature results in an increase of the yield. Furthermore, from the Arrhenius plots based on the products formation rate, it is found that the acetaldehyde is favored over PtRu/C compared to the other products. Finally, based on the apparent activation energy of the COi formation rate, it is concluded, that the C-C bond breakage of the ethanol molecule is difficult to occur over the examined anode catalyst.