Strategy to optimize cathode operating conditions to improve the durability of a Direct Methanol Fuel Cell

This study addresses optimal cathode operating conditions to improve the durability of Direct Methanol Fuel Cells (DMFCs). Usually, CO-like adsorbents may poison Pt catalysts and flooding may lead to starvation of the reactant or hindrance of mass-diffusion. Both of these conditions can greatly decrease cell performance; thus, modified operating conditions are needed to lessen the disadvantages. By means of the proposed strategies, including an air on/off condition during the load-off mode, a load on/off interval and an air flow rate during the load-on mode, the degradation rate can be successfully restrained. Resistance R obtained by the individual polarization curve is essential for identifying the main component affecting cell performance. By incorporating Electrochemical Impedance Spectroscopy (EIS), the degradation mechanism can be characterized. The electrochemical surface area (ECA) is employed to investigate the actual chemical degradation, unlike the results in most other reports; the loss in the anode catalyst is discovered to be the main detriment, which is attributed to our modified cathode operating conditions. Notably, a thin metal oxide is found on the surface of the test block after long-term operation, and its influence is also assessed to clarify the actual performance loss of the MEA (membrane electrode assembly). (C) 2011 Elsevier B.V. All rights reserved.