City Research Online

Abstract

This review paper summarises the key aspects of Proton Exchange Membrane Fuel Cell (PEMFC) degradation that are associated with water formation, retention, accumulation, and transport mechanisms within the cell. Issues related to loss of active surface area of the catalyst, ionomer dissolution, membrane swelling, ice formation, corrosion, and contamination are also addressed and discussed. The impact of each of these water mechanisms on cell performance and durability was found to be different and to vary according to the design of the cell and its operating conditions. For example, the presence of liquid water within Membrane Electrode Assembly (MEA), as a result of water accumulation, can be detrimental if the operating temperature of the cell drops to sub-freezing. The volume expansion of liquid water due to ice formation can damage the morphology of different parts of the cell and may shorten its life-time. This can be more serious, for example, during the water transport mechanism where migration of Pt particles from the catalyst may take place after detachment from the carbon support. Furthermore, the effect of transport mechanism could be augmented if humid reactant gases containing impurities poison the membrane, leading to the same outcome as water retention or accumulation.

Overall, the impact of water mechanisms can be classified as aging or catastrophic. Aging has a long-term impact over the duration of the PEMFC life-time whereas in the catastrophic mechanism the impact is immediate. The conversion of cell residual water into ice at sub-freezing temperatures by the water retention/ accumulation mechanism and the access of poisoning contaminants through the water transport mechanism are considered to fall into the catastrophic category. The effect of water mechanisms on PEMFC degradation can be reduced or even eliminated by (a) using advanced materials for improving the electrical, chemical and mechanical stability of the cell components against deterioration, and (b) implementing effective strategies for water management in the cell.

Publication Type:	Article
Publisher Keywords:	PEMFC, water management, degradation, water formation, water transport, flooding, ice, contamination, Pt particles, membrane swelling, corrosion
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology > Engineering
SWORD Depositor:	Symplectic Administrator

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