Impedance analysis on transient behavior of DMFC anodes during preconditioning process

Transient behavior of direct methanol fuel cells (DMFCs) during the preconditioning process has been investigated with a focus on changes manifested in the anode by using an electrochemical impedance spectroscopic analysis. Preconditioning of membrane electrode assembly (MEA) is essential to achieve maximum cell performance, and the time required to accomplish the conditioning may vary depending on the methods that are adopted. Preconditioning temperature substantially influences the behaviors of MEAs, and room-temperature treatment has been found to be more favorable than high-temperature treatment at 90 degrees C. Application of electric load during the preconditioning process accelerates the hydration of electrolyte and thus reduces the time required to reach a maximum performance limit. The anode impedance data of DMFC has been deconvoluted by using an equivalent circuit to investigate three kinds of resistances in the MEA, such as resistance of charge transfer (R-ct), electrolytes (R-e), and pore electrolytes (R-p). The underpinning mechanism which causes the change in performance during the preconditioning process is discussed in terms of the changes in the resistance elements of the anode. (c) 2005 The Electrochemical Society.