Effect of a Proton Conducting Filler on the Physico-Chemical Properties of SPEEKBased Membranes
writer：B. Mecheri ,A.D’Epifanio ,L.Pisani ,F.Chen , E. Traversa ,F.C.Weise , S. Greenbaum
keywords：Composites, Direct Methanol Fuel Cells, Proton Exchange Membranes, Proton Transfer, Methanol Crossove
source：期刊
specific source：Fuel Cells，2009,9(4)，pp372-380
Issue time：2009年
Composite membranes based on sulphonated
polyetherether ketone (SPEEK) having a 60% degree of sulphonation (DS = 0.6)
and containing 23 and 50 wt.-% hydrated tin oxide (SnO2.nH2O) were prepared and
characterised. The lower water uptake (WU) and the higher conductivity values
recorded for the composite membranes with respect to pure SPEEK reference
suggested the involvement of SnO2.nH2O in the proton conduction mechanism.
Pulsedfield-gradient spin-echo (PFGSE) NMR was employed to obtain a direct
measurement of water self-diffusion coefficient in the membranes. Differences
were observed between the unfilled SPEEK and the composites, including
departures from the normal correlation between water diffusivity and proton
conductivity in the case of composites. To better understand the SnO2.nH2O
effect on the proton transport properties of the SPEEK-based membrane, we
employed an analytical model that predicts the membrane conductivity as a
function of its hydration level and porous structure. The comparison of the
model results with the experimental proton conductivity values demonstrated
that the tin oxide phase provides additional paths between the water clusters for
proton transport, resulting in reduced tortuosity and enhanced proton
conductivity. Moreover, the composite showed reduced methanol crossover with
respect to the unfilled membrane.