Abstract
The heterogeneous electrocatalytic ethanol oxidation reaction (EOR) in the gas phase has been studied in the temperature range of 120 °C to 180 °C under proton exchange membrane fuel cell (PEM-FC) conditions. Direct ethanol fuel cells (DEFC) offer the possibility to gain electrical energy from a renewable fuel with a pre-existing distribution infrastructure. However the high theoretical energy efficiency that is one of the major advantages of fuel cells cannot be achieved to date with ethanol. Reasons for this are the formation of incomplete oxidation products and inert adsorbates that hinder the electrocatalytic oxidation of ethanol. A better understanding of the reaction mechanism and the influence of reaction conditions is crucial for the optimization of DEFC technology. Several studies have been done on the EOR in aqueous solution, but none so far in the gas phase.For this purpose a test cell with a three electrode assembly has been built. It can operate at temperatures up to 180 °C and is connected to a mass spectrometer for online differential electrochemical mass spectrometry (DEMS) measurements to detect volatile oxidation products in the fuel cell exhaust. Thus the amount of the complete oxidation product carbon dioxide formed during electrooxidation of ethanol can be obtained and allows drawing conclusions on the efficiency of the reaction under varying conditions. In addition a qualitative detection of the side products of the EOR is possible. The effect of temperature on the EOR has been studied on Pt black catalyst in the temperature range of 120 °C to 160 °C. Another focus is the effect of the ethanol concentration on carbon supported Pt/C and PtRh/C catalysts at 150 °C and how the addition of Rh influences the performance and product selectivity of the EOR.