Study of Water Retention Elevation on TiO2 /Nafion Membrane By Using Dynamic AFM

Among many technical barriers for the commercialization of proton exchange membrane fuel cells (PEMFC), low working temperature and carbon monoxide poisoning to catalyst have to be solved; however, they are not easy problems because they are related intrinsic properties of per-fluorinated Sulfonic Acid (PFSA) electrolytes such as Nafion. Recently, many groups report that TiO2/Nafion composite membrane shows the high proton conductivity under insufficient hydration on the membrane and high temperature operating condition. They conclude that the performance enhancement under low relative humidity and high temperature of the composite membrane is due to water retention increasing on the membrane. [1-2]

DMAFM, which is called tapping mode or non contact mode AFM measures amplitude and phase shift of specimen surface by amplitude modulation. The amplitude and phase shift are induced from the attraction force variation between tip and sample. The phase shift on the membrane is corresponding mechanical properties on the specimen such as viscosity, elasticity, and viscoelasticity.

We are synthesize the TiO2/Nafion composite membrane for high temperature PEMFC and characterize water retention on the membrane at variation conditions by using dynamic at mode atomic force microscopy (DMAFM). Characterization has done by two steps. Firstly, we simultaneously map topography and phase images of TiO2/Nafion composite membrane and pristine Naion under different humidity and temperature. The phase distributions on the composite membrane under different conditions are characterized. Secondly, the histograms from each image are extracted and statistically analyzed.

References

1. O. Savadogo, Emerging membranes for electrochemical systems Part II. High temperature composite membranes for polymer electrolyte fuel cell (PEFC) applications, Journal of Power Sources 127 (2004) 135–161

2. E. I. Santiago, R. A. Isidoro, M. A. Dresch, B. R. Matos, M. Linardi, and F.C. Fonseca,  Nafion–TiO₂ hybrid electrolytes for stable operation of PEM fuel cells at high temperature, Electrochimica Acta 54, (2009), 4111–4117