The behavior of platinum dissolution and deposition in the polymer electrolyte membrane of a membrane-electrode-assembly (MEA) for a proton-exchange membrane fuel cell (PEMFC) was studied using potential cycling experiment and high-resolution transmission electron microscopy (HRTEM). The electrochemically active surface area decreased depending on the cycle number and the upper potential limit. Platinum deposition was observed in the polymer electrolyte membrane near a cathode catalyst layer. Platinum deposition was accelerated by the presence of hydrogen transported through the membrane from an anode compartment. Platinum was transported across the membrane and deposited on the anode layer in the absence of hydrogen in the anode compartment. This deposition was also affected by the presence of oxygen in the cathode compartment.
Substoichiometric titanium oxide
(normalTi4normalO7)
-supported Pt catalysts were prepared and their electrochemical properties, particularly the effects of high-potential conditions on the activity and stability of
Pt∕normalTi4normalO7
catalysts, were compared to those of
Pt∕C
catalyst. Polarization measurements using membrane electrode assemblies revealed that the
Pt∕normalTi4normalO7
cathode shows a similar activity for the oxygen reduction reaction as
Pt∕C
catalyst at
80°C
. A high-potential holding test (
1h
holding at
1.0–1.5V
vs anode) demonstrated that the
Pt∕normalTi4normalO7
catalyst is quite stable against high potential up to
1.5V
. A single cell using a
Pt∕normalTi4normalO7
cathode was operated at
80°C
, and voltage stability for
350h
with
normalH2∕normalO2
was also demonstrated.
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