THE INFLUENCE OF THE NAFION CONTENT IN DMFC ANODE CATALYST LAYERS

摘要

The influence of the Nafion content on the electrochemical and structural properties of DMFC anode catalyst layers based on unsupported Pt/Ru was investigated. At potentials ≤ 0.4 V and temperatures ≤ 80 ℃, the highest current densities of methanol oxidation are achieved with a Nafion content of 7 wt%. The highest active platinum surface calculated from hydrogen desorption peaks of CV's is obtained with 10 wt% of Nafion. By filling the catalyst layers with decane and water, both the porosity and the fractions of 'hydrophilic' and 'hydrophobic' pores in the catalyst layers were determined. The smallest porosity of 54 Vol% is reached with 7 wt % Nafion, whereas the highest fraction of 'hydrophobic' pores (80 Vol%) is obtained with a Nafion content of 5 wt%. It turns out, that at moderate current densities, a Nafion content of about 7 wt% provides the best combination of a large active surface area and a fast removal of CO_2, which is favorable for obtaining high performance of the DMFC anode.