For the decal electrodes, excess
usage of ionomer can also intensify the problem of ionomer
segregation, which adds to mass transport resistance. A
cathode with lower porosity suffers water flooding as well as
poor diffusion of oxygen to the catalyst layer, deteriorating the
MEA performance [29]. The cathodes having ionomer fractions
in amoderate range of 7e10 wt.% perform better and the
highest single-cell performance is obtained for the ionomer
amount of 7 wt.% with a peak power density of 115mWcm2.
This value for peak power density is substantially higher than
the literature reports of decal MEAs for DMFCs with similar or
higher catalyst loadings [23,24]. It implies that the use of
ionomer in the relatively moderate fractions would be
preferred and that an ionomer content of 7 wt.% is appropriate
to maintain a balance between the proton conductivity and
the porosity of decal cathodes in order to ensure a high-performance
operation of decal MEAs in DMFCs