Development of Nafion/Tin Oxide Composite MEA for DMFC Applications

Nafion composite membranes containing either hydrated tin oxide (SnO2 · nH2O) 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 °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 °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.