Abstract
In the present scenario of a global initiative toward a
sustainable energy future, the polymer electrolyte fuel cell
(PEFC) has emerged as one of the most promising alternative
energy conversion devices for various applications. Despite
tremendous progress in recent years, a pivotal performance
limitation in the PEFC comes from liquid water transport and
the resulting flooding phenomena. Liquid water blocks the
open pore space in the electrode and the fibrous diffusion layer
leading to hindered oxygen transport. The electrode is also the
only component in the entire PEFC sandwich which produces
waste heat from the electrochemical reaction. The cathode
electrode, being the host to several competing transport
mechanisms, plays a crucial role in the overall PEFC
performance limitation. In this work, an electrode model is
presented in order to elucidate the coupled heat and water
transport mechanisms. Two scenarios are specifically
considered: (1) conventional, Nafion® impregnated, three-phase
electrode with the hydrated polymeric membrane phase as the
conveyer of protons where local electro-neutrality prevails; and
(2) ultra-thin, two-phase, nano-structured electrode without the
presence of ionomeric phase where charge accumulation due to
electro-statics in the vicinity of the membrane-CL interface
becomes important. The electrode model includes a physical
description of heat and water balance along with
electrochemical performance analysis in order to study the
influence of electro-statics/electro-migration and phase change
on the PEFC electrode performance.