Parametric study on direct ethanol fuel cell (DEFC) performance and fuel crossover

Abstract

A parametric study was carried out to investigate the effect of fuel concentration (0.5 M–3.0 M), operating temperature (ambient temperature to 85 °C), flow rate of ethanol (0.5–5.0 mL min−1) and air (100–600 mL min−1) on the direct ethanol fuel cell (DEFC) performance. The operations were conducted in three operational modes, namely, passive, semi passive, and active modes, and power generation were measured. Ethanol crossover was indicated by the carbon dioxide (CO2) concentration present at the cathode outlet and measured by using a CO2 analyzer. Results indicated that DEFC performance increased with the increase of ethanol concentration, and ethanol and oxidant flow rate increased with temperature until DEFC reaches the optimum conditions, i.e., concentration and flow rate. Meanwhile, the DEFC performance significantly and proportionally increased with operation temperature and reached values of up to 8.70 mW cm−2 and 85 °C at stable conditions. Furthermore, fuel crossover, that is, ethanol flux, increased in proportion to the ethanol concentration, i.e., 3.71 × 10−4 g m−2 s−1 and 8.79 × 10−4 g m−2 s−1 for 0.5 M and 3.0 M ethanol concentration, respectively. At different modes of operation, the active DEFC system exhibited the highest performance, followed by the semi passive and passive DEFC system. These results indicated that optimizing ethanol, oxidant flow rate and temperature would enhance the mass transport in anodes and cathodes, and hence improve the electrochemical reactions and DEFC performance.