Development of Nafion/Tin Oxide Composite MEA for DMFC Applications

Nafion composite membranes containing either hydrated tin oxide (SnO2 center dot nH(2)O) or sulphated tin oxide (S-SnO2) at 5 and 10 wt.-% were prepared and characterised. The structural and electrochemical features of the samples were investigated using X-ray diffraction, electrochemical impedance spectroscopy, methanol crossover and direct methanol fuel cell (DMFC) tests. Highest conductivity values were obtained by using S-SnO2 as filler (0.094 S cm(-1) at T = 110 degrees C and RH = 100%). The presence of the inorganic compound resulted in lower methanol crossover and improved DMFC performance with respect to a reference unfilled membrane. To improve the interface of the membrane electrode assembly (MEA), a layer of the composite electrolyte (i.e. the Nafion membrane containing 5 wt.-% S-SnO2) was brushed on the electrodes, obtaining a DMFC operating at 110 degrees C with a power density (PD) of 100 mW cm(-2) which corresponds to a PD improvement of 52% with respect to the unfilled Nafion membrane.