Electrode Degradation of Direct Methanol Fuel Cells Evidenced by X-ray Tomography

Abstract

The direct methanol fuel cell (DMFC) offers a promise for portable power applications thanks to the high energy density of methanol, no need for fuel reforming, and an ease of fuel storage and refilling. However, the long-term performance degradation presents a challenge that has hindered DMFC commercialization. The focus of this study is on the degradation of Nafion ® -based membrane electrode assemblies (MEAs) during continuous DMFC operation. The fuel cells in this work were subjected to 100-hour life tests using different methanol feed concentrations at different operating voltages (current densities). X-ray tomography was used to examine structural changes in the MEAs after life tests. DMFC performance degradation was found to be correlated to higher feed concentration of methanol as was the formation of micro-cracks in both the anode and the cathode.

A review on durability issues and restoration techniques in long-term operations of direct methanol fuel cells

“…The presumable reasons for the detachment of electrodes from the membrane include increased mechanical stress at the interface due to swelling and contraction of the membrane [9,61], generation of CO 2 gas at the anode [58], heat generation at the cathode [61], use of concentrated methanol feed [81], and dissolution of Nafion ® ionomer present at the interface [54].…”

“…Generally, diluted methanol solutions are used with concentrations in the range of 0.3e1.0 M in order to minimize the methanol crossover [1,32,41]. Recently, it was [179] reported that the use of concentrated methanol solutions in a 100 h durability test damaged the integrity of both electrodes and led to a severe cracks formation. This resulted in a significant rise of ohmic resistance over time in case of 4.0 M methanol solution.…”

Micro-crack formation in direct methanol fuel cell electrodes

“…Over the past years, significant research efforts have been devoted to DMFC performance degradation during long-term operation [4]. A PtRu black/Nafion ® 117/Ptblack (anode/membrane/cathode) MEA after a DMFC life test exceeding 1000 h was examined by Cheng et al [5].…”

Long‐term Operation of High Temperature Polymer Electrolyte Membrane Fuel Cells with Fuel Composition Switching and Oxygen Enrichment

“…The micro‐computed tomography (μ‐CT) is a non‐destructive method to visualize post mortem defects and structural changes produced during operation , . The tomography represents a revealing extension of the in situ electrochemical characterization .…”