Reversible and irreversible loss in performance in direct methanol fuel cells during freeze/thaw cycles

In this paper, the reversible and the irreversible loss in performance of direct methanol fuel cell (DMFC) single cells induced by freeze/thaw cycling are determined and discussed. The reversible loss in performance is attributed to the decreased activity of electrocatalysts due to the strong adsorption of the intermediates from methanol electro-oxidation at subzero temperatures, while the irreversible loss in performance is due to the damage of membrane electrode assembly (MEA) structure. It is found that the reversible degradation of performance is dominant when the cell operated at low current densities with O-2; the irreversible degradation is more obvious when the cell discharged at high current densities or operated with air. A method, applying a reverse current on the single cell, is put forward to recover the reversible loss in performance. By this method, the voltage of the single cell operated with O-2 at 100 mA cm(-2) drops only about 16 mV after experiencing 100 freeze/thaw cycles between-10 and 60 degrees C. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.