Methanol fuel cell model: Anode

An isothermal, steady-state model of an anode in a direct methanol feed, po lymer electrolyte fuel cell is presented. The anode is considered to be a p orous electrode consisting of an electronically conducting catalyst structu re that is thinly coated with an ion-selective polymer electrolyte. The por es are filled with a feed solution of 2 M methanol in water. Four species a re transported in the anode: water, methanol, hydrogen ions, and carbon dio xide. All four species are allowed to transport in the x-direction through the depth of the electrode. Species movement in the pseudo y-direction is t aken into account for water, methanol, and carbon dioxide by use of an effe ctive mass-transfer coefficient. Butler-Volmer kinetics are observed for th e methanol oxidation reaction. Predictions of the model have been fitted wi th kinetic parameters from experimental data, and a sensitivity analysis wa s performed to identify critical parameters affecting the anode's performan ce. Kinetic limitations are a dominant factor in the performance of the sys tem. At higher currents, the polymer electrolyte's conductivity and the ano de's thickness were also found to be important parameters to the prediction of a polymer electrolyte membrane fuel cell anode's behavior in the methan ol oxidation region 0.5-0.6 V vs, a reversible hydrogen electrode. (C) 1999 The Electrochemical Society. S0013-4651(97)12-114-0. All rights reserved.