Abstract:

The oxygen reduction reaction (ORR) activity of Pt/C catalysts was investigated in electrolytes of 0.5 mol/L H₂SO₄ containing varying concentrations of methanol in a half-cell. It was found that the ORR activity was improved notably in an electrolyte of 0.5 mol/L H₂SO₄ containing 0.1 mol/L CH₃OH as compared with that in 0.5 mol/L H₂SO₄, 0.5 mol/L H₂SO₄ containing 0.5 mol/L CH₃OH, or 0.5 mol/L H₂SO₄ containing 1.0 mol/L CH₃OH electrolytes. The same tendency for improved ORR activity was also apparent after commercial Nafion^® NRE-212 membrane was hot-pressed onto the catalyst layers. The linear sweep voltammetry results indicate that the ORR activities of the Pt/C catalyst were almost identical in the 0.5 mol/L H₂SO₄+0.1 mol/L CH₃OH solution before and after coated with the Nafion^® membrane. Electrochemical impedance spectroscopy results demonstrated that the resistance of the Nafion^® membrane is smaller in the electrolyte of 0.5 mol/L H₂SO₄+0.1 mol/L CH₃OH than in other electrolytes with oxygen gas feed. This exceptional property of the Nafion^® membrane is worth investigating and can be applied in fuel cell stacks to improve the system performance.

Key words: Platinum, Carbon, Methanol crossover, Oxygen reduction, Fuel cell