Analysis of a Permselective Membrane-Free Alkaline Direct Ethanol Fuel Cell

A physical model is developed to study the coupled mass and charge transport in a permselective membrane-free alkaline direct ethanol fuel cell. This type of fuel cell is not only free of expensive ion exchange membranes and platinum based catalysts, but also features a facile oxygen reduction reaction due to the presence of alkaline electrolyte. The proposed model is first validated by comparing its predictions to the experimental results from literature and then used to predict the overall performance of the cell and reveal the details of ion transport, distribution of electrolyte potential and current density. It is found that: (1) KOH concentration lower than 1 M notably impairs cell performance due to low electrolyte conductivity; (2) the concentration gradient and electrical field are equally important in driving ion transport in the electrolyte; (3) the current density distributions in the anode and cathode catalyst layers keep nonuniform due to different reasons. In the anode, it is caused by the ethanol concentration gradient, while in the cathode it is because of the electrolyte potential gradient; and (4) at low cell voltage, current density distribution in the catalyst layer shows stronger nonlinearity in the anode than in the cathode.